Management of Wisconsin Soils

TOC-FM 10/20/05 10:07 AM Page 1

A3588

Management of Wisconsin Soils

Fifth Edition TOC-FM 10/20/05 10:07 AM Page 2 TOC-FM 10/20/05 10:07 AM Page 3

A3588

Management of Wisconsin Soils

Fifth Edition TOC-FM 10/20/05 10:07 AM Page 4 TOC-FM 10/20/05 10:07 AM Page 5

CONTENTS

Soil formation and Comparison of tillage systems .....34 1 classification Estimating residue cover...... 37 What is soil? ...... 1 Soil crusting ...... 38 Soil formation ...... 1 Soil compaction ...... 38 Factors of soil formation ...... 1 Effect of tillage on nutrient Soil-forming processes ...... 3 availability ...... 39 Weathering...... 3 5 Soil and water conservation Soil classification ...... 4 Runoff and erosion ...... 42 Soil horizons...... 4 Factors influencing erosion ...... 43 Soil name ...... 5 Soil and water conservation Soil maps and mapping reports .....5 practices ...... 43 Soil factors affecting management ...7 Crop rotation ...... 43 Soil slope...... 7 Conservation tillage...... 44 Soil depth ...... 7 Contour tillage ...... 44 Soil drainage ...... 7 Strip cropping ...... 45 Land capability classes ...... 8 Cover crops...... 45 2 Physical properties of soil Terraces and diversions ...... 45 Texture ...... 11 Grass waterways ...... 45 Importance of soil texture.....12 Buffer/filter strips ...... 45 Determining soil texture Wind erosion ...... 46 by feel ...... 13 Tillage translocation...... 47 Structure ...... 14 Conservation incentives ...... 47 Organic matter ...... 15 6 Soil acidity and liming Mineral matter ...... 16 Soil pH ...... 49 Bulk density ...... 18 Importance of soil pH ...... 50 Tilth...... 18 How soils become acidic ...... 51 Color ...... 19 Acid parent material ...... 51 Temperature...... 19 Leaching of basic cations .....51 3 Soil water Crop removal of basic cations...51 Hydrologic cycle ...... 21 Acid-forming fertilizers ...... 52 Evapotranspiration (ET) .....22 Carbonic acid...... 52 Water-use efficiency...... 24 Acid rain ...... 53 How water is held in soil .....24 Oxidation of sulfides ...... 53 Forms of soil water ...... 25 Nature of soil acidity ...... 53 Water movement in soil...... 26 Optimum pH for crops ...... 53 Irrigation scheduling ...... 27 Liming acid soils ...... 55 Benefits of liming ...... 55 4 Tillage Liming materials ...... 58 Purpose of tillage ...... 29 How much lime to apply .....59 Kinds of tillage ...... 29 When to apply aglime ...... 62 Conventional tillage ...... 29 Other factors to consider .....62 Conservation tillage...... 31 Correcting soil alkalinity .....63 TOC-FM 10/20/05 10:07 AM Page 6

7 Biological properties of soil Sources of phosphate...... 87 Soil fauna ...... 66 Methods of phosphorus fertilizer Arthropods ...... 66 application ...... 89 Mollusks ...... 66 Potassium...... 89 Earthworms...... 66 Function in plants ...... 89 Protozoa ...... 66 Reactions in soils...... 90 Nematodes ...... 66 Sources of potassium ...... 91 Mammals ...... 66 Secondary nutrients...... 92 Soil flora...... 66 Calcium ...... 92 Algae ...... 66 Magnesium ...... 93 Bacteria ...... 66 Sulfur ...... 94 Actinomycetes ...... 67 Micronutrients ...... 97 Fungi ...... 67 Boron...... 97 Carbon cycle ...... 67 Manganese ...... 98 Oxygen requirements ...... 68 Zinc...... 98 Symbiotic relationships ...... 68 Copper...... 99 Role of microorganisms in nutrient Iron...... 99 transformations ...... 69 Molybdenum ...... 99 Plant roots...... 69 Chlorine ...... 99 Nickel ...... 99 8 Soil chemistry and plant nutrition Summary of the fate of applied Essential plant nutrients ...... 71 nutrients ...... 100 Non-essential elements ...... 73 Fertilizer analysis ...... 101 Properties of chemical elements, Forms of commercial fertilizer.....101 atoms, ions, and salts ...... 73 Fertilizer grades ...... 102 Sources of plant nutrients in the soil. . 74 Methods of fertilizer application....103 Soil solution ...... 74 Starter or row application.....103 Exchange sites on clay and Broadcast and topdress organic matter ...... 74 applications ...... 106 Complexed or chelated nutrients . 75 Sidedress applications...... 106 Decomposition of organic matter . 75 Injection ...... 106 Low-solubility compounds ....75 Foliar application ...... 106 Soil rocks and minerals ...... 76 Dribble application ...... 107 What constitutes a fertile soil .....76 Fertigation ...... 107 Soil and fertilizer sources 9 10 Soil amendments of plant nutrients Organic amendments ...... 109 Nitrogen ...... 78 Manure ...... 109 Function in plants ...... 78 Biosolids...... 113 Reactions in soils...... 79 Whey...... 114 Sources of nitrogen...... 82 Miscellaneous organic Timing of nitrogen fertilizer amendments ...... 115 applications ...... 85 Inorganic amendments...... 116 Nitrogen fertilizer timing summary 85 Gypsum ...... 116 Phosphorus ...... 86 Non-traditional soil amendments . . 117 Function in plants ...... 86 Soil conditioners...... 117 Reactions in soils...... 86 TOC-FM 10/20/05 10:07 AM Page 7

Mineral nutrient sources.....117 Soil testing, soil test 12 Wetting agents and surfactants . 118 recommendations, and Biological inoculants and plant analysis activators ...... 118 Soil testing ...... 135 Plant stimulants and growth Soil sampling...... 136 regulators ...... 119 Tillage considerations ...... 139 Environmental concerns and Timing and frequency ...... 139 11 Analyzing the soil ...... 139 preventive soil management Interpreting the analytical results 140 practices Soil test recommendations ...... 141 Nitrates in groundwater ...... 121 Nitrogen recommendations ...141 Rate of application ...... 122 Phosphate and potash Methods to improve nitrogen recommendations...... 142 rate recommendations ....123 Aglime recommendations ....145 Nitrogen credits ...... 125 Secondary nutrient Timing of nitrogen applications . 125 recommendations...... 147 Manure management ...... 126 Micronutrient recommendations 150 Irrigation scheduling ...... 126 Soil test report...... 152 Urease inhibitors ...... 127 Plant analysis...... 153 Best management practices ...127 Uses of plant analysis ...... 153 Phosphorus in surface water .....127 Limitations of plant analysis ...154 Rate of application ...... 127 Collecting plant samples.....154 Phosphorus credits ...... 127 Interpretation of plant analyses . 155 Manure management ...... 128 Tissue testing ...... 157 Erosion control ...... 129 Identification of landscape areas Economics of lime and 13 prone to phosphorus loss ...129 fertilizer use Best management practices Returns from aglime ...... 160 for phosphorus ...... 130 Returns from the use of fertilizer ...161 Nutrient management planning ...130 Availability of capital ...... 162 Soil testing...... 130 Price changes ...... 162 Assessment of on-farm Residual carryover ...... 163 nutrient resources...... 130 Substituting fertilizer for land . . 164 Nutrient crediting ...... 130 Calculating the cost of Consistency with the farm’s plant nutrients ...... 164 conservation plan ...... 131 Single nutrient fertilizer .....165 Manure inventory ...... 131 Mixed fertilizer ...... 165 Manure spreading plan .....131 Calculating profits from improved The 590 nutrient management soil management ...... 166 standard ...... 131 Annual costs for long-term capital Non-essential elements...... 131 investments ...... 166 Sources of increased returns ...166 Comparison of net returns ...... 166 Feeding higher crop yields through livestock ...... 167

Index...... 169 TOC-FM 10/20/05 10:07 AM Page 8 TOC-FM 10/20/05 10:07 AM Page 9

“If you are thinking a year ahead, sow seed. If you are thinking 10 years ahead, plant a tree. If you are thinking 100 years ahead, educate the people.” Old Chinese saying

Introduction People look at soils differently. Both grain and livestock farmers need People may view soil in the home as a to produce crops efficiently in order to source of “dirt” or as a good medium succeed economically. And to produce for growing house plants. crops efficiently, they must understand Construction engineers look at soil in and use good soil management terms of its ability to support a practices. building or highway. But Growth of a colony of organisms, agriculturalists look at soil in terms of whether microbes, higher plants, its ability to support the growth of animals, or people, is limited plants. Obviously, this is its most ultimately by exhaustion of the food important function because the soil supply or toxic accumulation of ultimately supports nearly all plant and wastes. As the world population animal life. continues to grow, agriculturalists will Soil appears to be simply an inert be challenged as never before to mixture of different-sized particles. But increase production while managing this certainly is not the case. Living wastes so as to recycle nutrients organisms by the billions, decaying without polluting water supplies. and residual organic matter, a wide Good soil management is a key variety of minerals, and air and water factor in maintaining the quality of interact to form a dynamic and our water resources. Protecting our exceedingly complex biological, surface water supplies requires that we physical and chemical system. For follow a good soil and water example, a teaspoon of soil may conservation program. Runoff water contain as many microorganisms as and soil erosion losses account for there are people on the earth. This much of the nitrogen and phosphorus same teaspoon of soil contains more entering our lakes and streams from chemical atoms than there are drops of rural areas. To protect groundwater we water in Lake Superior and Lake must develop nutrient management Michigan combined! programs that support productive The various chemical, physical, cropping systems and simultaneously and biological processes taking place in reduce leaching of nutrients. If we are the soil are complex and sometimes interested in agricultural sustainability not easily understood. But for farmers and environmental protection, we and land managers to make wise must develop a conservation ethic and decisions in the future, they must truly become “stewards of the soil.” understand these processes. In this age of rapid technological change, we need Emmett E. Schulte to know why things happen—knowing Leo M. Walsh only what to do is often inadequate. TOC-FM 10/20/05 10:07 AM Page 10 C-1 10/18/05 11:06 AM Page 1

CHAPTER 1 1 Soil formation and classification

What is soil? Parent materials that make Soil is the upper layer of earth up Wisconsin’s soils are (1) bedrock which may be tilled and cultivated. weathered in place, (2) deposits left by More specifically, soils are the glaciers, (3) materials deposited by “Soil is a living entity: the unconsolidated (loose) inorganic and wind or water, and (4) decaying plant material. crucible of life, a seething organic materials on the surface of the earth which support the growth of The bedrock geology of an area foundry in which matter and plants. Weathered rocks and minerals often directly or indirectly influences soil formation. Soils in the west central energy are in constant flux make up the inorganic fraction of the soil and can supply all essential plant and central parts of the state are the and life is continually created nutrients except nitrogen. Virtually all result of direct influence of bedrock. In these areas the weathering of the and destroyed.” of the nitrogen, as well as a portion of several other essential plant nutrients, is sandstone bedrock left predominately stored in the organic matter. sandy soils. The bedrock has indirectly D. Hillel, Out of the Earth, 1991 influenced those soils formed in glacial till. In northern and north central Soil formation Wisconsin the glacial till is acid because the till was derived from the weathering Soils are formed from many kinds of acidic granitic rock in northern of materials exposed on the land surface Wisconsin; whereas, calcareous glacial known as parent materials. Physical and till was developed in the southern and chemical weathering processes gradually eastern parts of the state where the change rocks, glacial deposits, and wind predominant bedrock is limestone. The or water deposits into soil over long map, Bedrock Geology of Wisconsin, periods of time. These processes are shows the location of the different kinds influenced by variations in climate, of bedrock throughout the state. See plants and animals, and topography. the back side of the map for additional Factors of soil formation information on Wisconsin bedrock. Parent material, climate, living Glacial deposits and the action of organisms, topography, and time are glaciers in altering the landscape have the five factors of soil formation. Some profoundly influenced the formation of would include humans as a sixth factor, most soils in Wisconsin. Many soils are for our activities can markedly change formed partially or entirely out of the formation of many soils. The type glacial “drift” or till. In these areas the of soil developed depends on the soils have taken on many of the amount of time a parent material in a physical and chemical characteristics of specific topography is exposed to the the till. Acid soils are formed from acid effects of climate and vegetation. till; stony soils are formed from stony C-1 10/18/05 11:06 AM Page 2

2 MANAGEMENT OF WISCONSIN SOILS

till; red-colored soils are formed from Climate is defined as weather as it grow on soils where the climate is red-colored till, etc. The Ice Age Deposits exists over a long period of time. relatively dry while trees tend to grow of Wisconsin map shows the glacial Climate changes with time, and soils in the more humid climates. deposits in Wisconsin. The back side often reflect the effects of past climates. Living organisms, plants and contains additional information on the Precipitation and temperature animals, play an important role in soil ice age in Wisconsin. changes both help form soil. Water formation. Plants extract nutrients Materials deposited by wind and from rain and melting snow dissolves from the subsoil as they grow. These water have been important in the for- some soil minerals. Freezing and nutrients are subsequently deposited on mation of many soils in the state. The thawing break rocks and large soil the soil surface when the plants die. wind-blown or aeolian silts (loess) are particles into smaller pieces. Soil differences frequently can be quite deep in the unglaciated area in High temperatures and high levels related to the type of plants grown on western and southwestern Wisconsin. A of precipitation often speed weathering. them over long periods of time. In parts silt cap of more than 4 feet is common The effect of climate can be seen best of southern Wisconsin, tall prairie near the Mississippi River. The silt cap by comparing soils over large areas. For grasses growing on soil produced a or loess becomes progressively thinner instance, the more intensive weathering thick black layer of surface soil high in as one moves in a northeasterly in southeastern United States has humus. Much of this humus came direction. Little, if any, silt cap exists on resulted in the development of from the decay of grass roots. Trees, on the soils in the eastern and northeastern extensive areas of brick-red colored soil the other hand, deposit their leaves, parts of the state. Soils with a deep silt containing relatively low amounts of needles and twigs on the top of the soil, cap are very productive because they are organic matter and high levels of and tree roots do not die each year as usually well-drained and store relatively oxidized iron. In contrast, most soils in most grass roots do. Therefore, most large quantities of available water. Also, the Midwest contain much more forest soils do not have thick black they are generally easy to work and free organic matter and lower amounts of surface layers. from stones. oxidized iron. Soils in the northern Fire has also played an important Alluvial soils have been formed as a Great Plains differ from soils in the role in determining the native result of materials being deposited by north central region mainly because vegetation growing on our soils. For water. These soils are commonly found they developed in a drier climate. Soils example, in southern Wisconsin the on stream terraces and range from silty formed in drier climates typically have prairies burned frequently. Fire to very sandy, and from well-drained to a relatively high pH and more plant prevented the development of forests; very poorly drained. nutrients due to less leaching. thus, in these areas only a few large oak Decaying plant material in bogs Even within Wisconsin there is trees growing in fields of grass survived. and low-lying areas is the parent enough climatic difference from the Bacteria and fungi, which are material of organic soils. The lack of north to the south to produce microscopic plants, are a vital part of oxygen in these saturated soils prevents noticeable variation in the soils. the soil. They decompose organic decomposition, allowing organic Northern Wisconsin’s cooler climate matter and produce materials that bind material to accumulate. Generally, slows decomposition of organic matter soil particles together in aggregates, and organic soils contain at least 20% of on the surface of the soil. This slowly they help make certain nutrients organic matter (by weight), and this decomposing organic matter produces available for plants. organic layer is more than 1 foot thick. organic substances that promote Animals have a lot to do with soil Organic soils occupy approximately leaching of minerals and nutrients from formation. Earthworms burrow through 7.5% of Wisconsin’s surface and are the soil. Northern Wisconsin soils are, the soil making large holes that improve often referred to as mucks or peats. therefore, more leached and tend to be both water and air movement in the Mucks are more highly decomposed less fertile than those further south. soil. They also consume large amounts than peats to the extent that the kind of Climate also influences the kinds of dead organic matter and often carry plants from which they formed is not of plants and animals that will grow in plant material from the surface down easily identified. Mineral soils contain and on the soil. For instance, under several inches into the soil. This hastens less than 20% organic matter. natural conditions grasses and shrubs decomposition of organic matter and C-1 10/18/05 11:06 AM Page 3

Chapter 1. Soil formation and classification 3

tends to thicken the dark surface soil. Soil-forming processes salinization—accumulation of soluble Other small animals living in the soil Many complex physical, biological, salts (usually sulfates or chlorides of also eat and partially decompose organic and chemical transformations occur in calcium, magnesium, potassium and matter from leaves, grass blades, and soils. Any set of events that intimately sodium). Usually found in semi-arid other plant materials. affects the soil in which it operates is a regions. Humans have had an extremely soil-forming process. There are many More than one soil-forming important effect on soil formation— soil-forming processes active in soil. process can be active simultaneously or both beneficial and destructive. They Only the more important processes will sequentially. It is the net effect of the can cause erosion, compaction and be discussed here. Not all processes are active processes that give a soil its depletion of essential nutrients, or they active in every soil. Some processes unique characteristics. can improve the physical and chemical predominate in one soil, others in conditions in soil by using sound tillage another soil. The terms defined below Weathering practices and by adding lime, fertilizer, identify several of the more important Weathering transforms parent manure, and crop residues. soil-forming processes. materials in the process of soil formation. This weathering may be Topography refers to the lay of decomposition—breakdown of a mineral physical, chemical, or both. Chemical the land—the patterns of hills, valleys, or organic matter into its weathering is not very significant in and plains. It strongly influences water components. flow across and through soils, and this large rocks because there is relatively has a major influence on soil formation. eluviation—downward movement of little surface area exposed. Physical For instance, soils may be very shallow solid material, usually clay particles, weathering is more important. or “thin” where slopes are steep and within a soil profile. Physical weathering involves serious erosion has occurred. In the erosion—loss of material from the natural forces that break rocks into eastern part of the state the topography surface layer of soil by the action of smaller pieces. These forces include has been strongly influenced by the water or wind. temperature, wind, water, ice, and glaciers. Many low-lying soils—peats gleization—reduction of iron under plant roots. Rapid temperature changes and mucks, for example—occur in bogs waterlogged soil conditions, giving can cause rocks to crack. Rocks are and poorly drained depressions. subsoils a blue-grey color. made up of two or more minerals, each Topography becomes especially mineral expanding and contracting humification—transformation of raw important when soils are farmed. Steep differently in response to temperature organic matter into humus. slopes require excellent soil conservation changes. Some early pioneers built fires practices, while low-lands and illuviation—the accumulation of fine on large rocks, then doused them with depressional areas need surface or tile soil particles which move from upper cold water to break them into smaller drainage for optimum crop production. layers of soil to the subsoil. rocks that could be hauled away. Time, measured in thousands of laterization—chemical migration of Wind strong enough to carry sand years, is the final element in soil silica out of the soil profile and particles can sandblast rock surfaces. development. Most Wisconsin soils concentration of oxides and Moving water, especially that carrying have formed since the glaciers retreated. hydroxides of iron and aluminum. sediment, is also abrasive. Pebbles on the With the exception of southwestern Occurs in tropical regions. bottom of a stream tend to be rounded Wisconsin, most of the state has been or smooth as a result of the tumbling leaching—movement of soluble covered by glaciers within the last action of the water. Water freezing in material through the soil in 30,000 years, and much of the eastern, cracks and crevices also causes percolating water. central and northern parts of the state disintegration by expansion. In were covered by ice or water within the mineralization—conversion of organic Wisconsin, glacial activity broke rocks last 8,000 to 15,000 years. Because of compounds into inorganic elements. into smaller fragments and ground some leaching and the weathering process, rocks to silt-sized particles. Plant roots older soils tend to be less fertile than growing into cracks in rocks can also soils of relatively recent origin. cause cracking and breaking. C-1 10/18/05 11:06 AM Page 4

4 MANAGEMENT OF WISCONSIN SOILS

Chemical weathering becomes (CaSO4) results in gypsum part of the oxygen from iron and significant once physical weathering (CaSO4•2H2O), with two water manganese oxides makes them more reduces parent materials to the size of molecules bound to each calcium soluble, allowing them to be leached. sand or smaller particles. The most sulfate molecule. Complexation refers to the important chemical reactions are Hydrolysis is a form of surrounding of metallic ions by groups solution, hydration, hydrolysis, decomposition in which the hydrogen- of anions or neutral molecules. decomposition, and complexation. hydroxyl (H-OH) bond in water is Ammonia, for example, forms a Solution refers to the dissolving of a split, and the resulting ions combine complex with copper by surrounding a solid in a liquid. Water is the liquid in with a reactant. For example, feldspar copper ion with four ammonia soils and is considered a universal (KAlSi3O8) and water (H2O) react to molecules. Organic molecules can form solvent. Every solid is soluble in water form silicic acid (HAlSi3O8) and complexes with metallic ions. Some to some extent. Most rocks and potassium hydroxide (KOH). large organic molecules form two or minerals are negligibly soluble. Most Decomposition involves the more bonds with the same metallic chloride and nitrate salts are highly breakdown of a substance into its ions. These are known as chelates soluble; whereas many phosphate component parts. Organic matter, for (Greek: chele = claw). Some chelates, compounds are only slightly soluble. example, is broken down into carbon such as ZnEDTA, make good fertilizers When the solubility of a dissolved dioxide and nutrients which can be because they prevent precipitation of substance is exceeded, it precipitates or recycled for new plant growth. the metallic ion, keeping it more solidifies and drops out of solution. For Oxidation, a form of decomposition, available to plants. In chemical example, when hard water is heated, is the combination of oxygen with a weathering, chelates help make the calcium carbonate precipitates to form substance, as in burning. Organic metals in rocks and minerals slightly lime on the walls of a teakettle. Also, matter decomposes (oxidizes) in soils. more soluble. some dissolved materials may be Also, some elements such as nitrogen, adsorbed or attached onto the surfaces sulfur, iron, and manganese undergo of existing soil particles. oxidation in well-aerated soils. Under Soil classification Hydration is the addition of water waterlogged conditions, reduction— The factors and processes of soil to a substance. For example, the the reverse of oxidation—can occur. formation discussed above have addition of water to dry calcium sulfate Under these conditions, the removal of produced many kinds of soil in Wisconsin. Soils vary considerably SOIL BODY from place to place, sometimes even within a small field. Soils are classified in a manner similarly to how plants and animals are classified. Instead of genus and species, however, the lowest A horizon or most specific unit of soil E horizon classification is the soil series. Higher 1' levels of classification include the 2' family, subgroup, great group, B horizon suborder, and order. The classification 3' system implies that one soil differs C horizon from another sufficiently to make 4' (parent material) classification meaningful. Bedrock Soil horizons A body of soil is three-dimensional SOIL PROFILE (figure 1-1). The depth is the lower Figure 1-1. Relationship of soil horizons and profile to soil body. limit to which native perennial plant Source: F.D. Hole, UW-Madison. C-1 10/18/05 11:06 AM Page 5

Chapter 1. Soil formation and classification 5

Soil scientists designate horizons A mineral horizon containing a high proportion of finely alphabetically: A for the surface layers, divided organic matter, and consequently dark in color. B for subsoil, C for parent material, E for eluvial (loss of clay, iron, or A aluminum), and R (sometimes D) for A layer lighter in color and lower in organic matter than the bedrock. These horizons may be overlying A whose main feature is loss of silicate clay, iron, subdivided. The horizon sequence E aluminum, and leaving a concentration of sand and silt particles of quartz or other resistant minerals. typical for a cultivated soil is presented in figure 1-2. The kind and arrange- EB Transitional layer ment of soil horizons is used as a basis Transitional layer BE for soil classification. Soil name The name of a soil is a combina- Illuvial or residual concentration of silicate clays, B sesquioxides, humus, etc, and/or development of structure tion of its series and type. The series is if volume changes accompany changes in moisture content. a geographical name taken from the area in which the soil was first described and mapped. The type is the textural class (e.g., sandy loam, silty BC Transitional layer clay loam, clay). Thus, we have such soil names as Fayette silt loam, Plainfield sand, and Kewaunee silty C Parent material; this layer may be considered to be similar clay loam. The same soil type can be to the original appearance of the parent material where found in neighboring states (Fayette, there are obviously no geologic nonconformities. for example, is named after Fayette, Iowa). In all, there are more than 730 soil names recognized in Wisconsin R and more than 20,000 in the United Bedrock States and affiliated territories. Nevertheless, these soils can be grouped Figure 1-2. A hypothetical profile for a cultivated soil with all together into several major soil regions. master horizons and some transitional horizons. The thickness of the horizons varies as indicated. Adapted from Foth, 1988. The map on the following page, Soil Regions of Wisconsin, shows the locations of these major soil regions. roots extend. In Wisconsin, soil depth Accumulation of organic matter under The soils in each of the major soil usually ranges from 1 foot in shallow prairie, for example, results in dark- regions are described in general terms soils over bedrock to about 7 feet. The colored surface soil. In contrast, soils on the back side of the map. surface area may be less than an acre to formed under forests are much lighter more than 100 acres. Usually we view in color. Regardless of original only the soil surface or the depth to vegetation, the downward movement of Soil maps and which the soil is tilled. In ditches and clay and iron oxides results in the along road cuts one can see the vertical formation of subsoil horizons that are mapping reports dimension. A vertical section of soil is more dense than the surface soil. The The following map shows the areas called a soil profile. This profile depths at which the different horizons of the state that have roughly the same typically has distinct layers called occur depends on the intensity of the kinds of soils. However, to find out horizons. Horizons are the result of predominant soil-forming factors what soils occur on a small tract of various soil-forming processes acting on a particular soil. land—such as a farm—a much more occurring in a particular soil. detailed soil map is necessary. C-1 10/18/05 11:06 AM Page 6

6 MANAGEMENT OF WISCONSIN SOILS

The Natural Resources Conservation Service (NRCS) makes detailed maps to assist farmers in developing soil and water conservation plans. A detailed soil map, drawn on an aerial photograph, is a very important part of a soil and water conservation plan. It shows the extent of erosion, the need for and possibilities of drainage, and gives an indication of what yields can be expected from the soils shown on the map. The NRCS also suggests soil and crop management practices to keep soil loss at or below tolerable levels. Figures 1-3 and 1-4 show an aerial photograph used for mapping and the detailed soil map drawn from the photograph. NRCS publishes soil maps and detailed reports for each county. Upon request, NRCS and other conservation agencies can prepare individual farm Figure 1-3. Aerial photograph used for detailed plans using the county soil survey report. mapping of a 160-acre tract of land. Soil survey reports can often be obtained free from senators or congressional representatives from Wisconsin. They may also be purchased from county land conservation departments or NRCS offices. Many libraries also have a copy of the local survey report. The soil survey provides much useful information in addition to the detailed soil maps. Use and management of the soils for different purposes is explained. Expected yields of crops are given for each soil, as is information on woodland management and productivity. Engineering properties and suitability for recreation and wildlife are listed. History, geology, climate, topography, soil formation, and more are also included.

Figure 1-4. Detailed soil map drawn on the aerial photograph. Symbols indicate soil type, slope, and degree of erosion. For example, DuD2 means a Dunbarton silt loam (Du) on a slope of 12 to 20% (D) and a moderate degree of erosion (2). (NRCS photo) C-1 10/18/05 11:06 AM Page 7

Chapter 1. Soil formation and classification 7

Soil depth Open-ditch drainage systems Soil factors The depth of soil favorable for root are very effective on flat, low-lying soils affecting development is more important now such as peats and mucks that are than it has been in the past. This is normally saturated to near the surface. management because better production and Such soils frequently have seepage Soil slope management practices are increasing zones and springy areas that require Slope has a great deal of influence yields year by year. As a result, water tiling as well as ditching. However, on soil management and crop more often becomes the factor which because of regulations to protect production. Three important limits yields. Plants growing in deep wetlands, a permit must be obtained characteristics are steepness, length, and soil will have a greater volume of soil from the Department of Natural direction. from which to extract water than will Resources (DNR) before any new or Cultivated land with a slope of plants growing in soil with a restricted improved drainage systems can be greater than 2% is usually subject to root zone. installed in wetland soils. erosion. The velocity and amount of Soils with 4 to 5 feet of medium- Tile drainage removes excess the collecting runoff water increases textured subsoil will provide the best water from the soil through a with steepness or length of the slope. A conditions for plant roots. Poor soil continuous line of tile or plastic tubing. larger quantity of water moving at a conditions such as very dense, heavy Tiling is designed to keep the water greater speed has much more energy to subsoils, claypans and plow pans, very table below the root zones of plants. carry soil away. If sloping soils are not high acidity, and excessive wetness will The excess water enters through tile properly managed, serious erosion can restrict root growth. In most cases, only joints or holes in the plastic tubes and occur. Runoff water coming from a excessive wetness, which can often be flows out by gravity. Water will enter a steep to gentle slope undergoes an overcome by proper drainage, can be tile line only when the soil around the abrupt decrease in velocity. The sudden corrected economically. Sometimes tile becomes saturated. change of speed allows sediment to crop growth can be improved on soils Tiling is highly effective on peats, drop out of the water. with unfavorable subsoils by liming mucks, and other soils that are Extremely long slopes (300 to and fertilizing the surface soils normally saturated to near the surface. 500 feet) concentrate a great deal of adequately. These soils frequently have seepage zones and springy areas that make tiling water near the bottom. These long Soil drainage an absolute must. Some mineral soil slopes often need to be broken up by Drainage is often essential to good types, especially those with deep, fine- the use of terraces, diversions, and strip soil management. Successful use of textured subsoils such as the red clays, cropping. Short, choppy slopes present some of the most productive land in have been tiled satisfactorily. On some management challenges. The uneven Wisconsin is dependent upon proper soils “land-forming” will increase the surface makes it difficult to install soil drainage. Agricultural drainage is the efficiency of tile. Soils with impervious conservation practices on them and removal of excess water by artificial layers in the subsoil and most wet crops may mature unevenly. Short means from the soil profile to enhance sandy soils are unsuited to tiling. Such irregular slopes may require a drainage agricultural production, or more soils occur mainly in central and north- system and soil conserving practices on specifically, the removal of excess central Wisconsin. the same field. gravitational water from the soil. The direction that a slope faces, or Surface drainage systems aspect, can also influence plant growth. (usually referred to as “land forming”) In the northern hemisphere, south- and are designed primarily to remove west-facing slopes are generally warmer surface water that has not entered the and drier than north- and east-facing soil profile. This is done by shaping the slopes. This temperature and moisture slope of the land to allow excess water difference can affect both agricultural to flow slowly to a system of shallow crops and trees. field waterways which empty into larger drainage systems. C-1 10/18/05 11:06 AM Page 8

8 MANAGEMENT OF WISCONSIN SOILS

Class II land can be cultivated Class VIII land is not suited to Land capability regularly, but certain physical economic crops. Usually it is very classes conditions give it more limitations than severely eroded or is extremely sandy, Class I land. Some Class II land may be wet, arid, rough, steep, or stony. Much Land capability classes are practical gently sloping so it will need moderate of it is valuable for wildlife food and groupings of soil limitations based on erosion control. Other soils in this class cover, for watershed protection, or for such characteristics as erosion hazard, may be slightly droughty, slightly wet, recreation. Class VIII land is colored droughtiness, wetness, stoniness, and or somewhat limited in depth. This purple. response to management. Soil maps class is colored yellow on soil maps. These capability classes, as prepared by NRCS farm planners are Class III land can be cropped summarized in table 1-1, indicate the colored to show different land regularly but has a narrower range of limitations of land and the hazards capability classes. Each color on the soil safe alternative uses than Class I or II associated with its use for agriculture map indicates one of eight land land. This land usually requires and forestry. Land use recommendations capability classes. These classes reflect extensive use of conservation practices in soil and water conservation plans the land’s relative suitability for crops, to control erosion or provide drainage. take these hazards into account and are grazing, forestry, and wildlife. For a This class is colored red on soil maps. based primarily upon the needs for summary of the limitations and the Class IV soils should be cultivated erosion control and good water manage- recommended management practices, only occasionally or under very careful ment rather than upon practices such as see table 1-1. management. Generally, it is best fertilizer application and weed control. Land classes are designated using adapted for pastures or forests. This roman numerals I through VIII. The class is colored blue on soil maps. classes are divided into subclasses and Class V land is not suited to units. Subclasses are designated by ordinary cultivation because it is too letters and numbers. The letter “e” wet or too stony, or because the stands for an erosion hazard, “w” for a growing season is too short. It can wetness hazard, and “s” for a produce good pasture and trees. This permanent soil limitation such as class is white. shallow depth and/or droughtiness. Class VI or VII land use is severely Class I land has the widest range of limited because of erosion hazards. use with the least risk of being damaged. Some kind of permanent cover should It is level or nearly level, well-drained, be kept on these soils. With very special and productive. Land in this class can management, including elaborate soil be cultivated with almost no risk of and water conservation practices, erosion and will remain productive if improved pastures can in some managed with normal care. This class is instances be established by renovation. colored green on soil maps. Class VI is colored orange, and Class VII is colored brown. C-1 10/18/05 11:06 AM Page 9

Chapter 1. Soil formation and classification 9

Table 1-1. Description of land capability classes and the conservation practices needed for each.

Land capability class Map Conservation practices (degree of limitations) color (organized by subclass)a

Suited for cultivation I Few limitations. Very good Green Practice good soil and crop management. land from every standpoint.

II Moderate limitations or risks Yellow e Use contour strip cropping, terraces, of damage when used for crops. grass waterways, and conservation tillage.

w Protect from flooding, use drainage.

s Maintain good soil structure.

III Moderate to severe risk of damage Red e Use contour strip cropping, grass waterways, or limitations. Regular cultivation terraces, diversions, and conservation tillage. possible if limitations are observed. w Install surface and/or tile drainage, diversions.

s Practice moisture conservation, control wind erosion, and irrigate.

IV Severe limitations. Can be Blue e Use contour strip cropping, grass waterways, cultivated with special diversions, terraces and conservation tillage, or management. manage as permanent pasture or woodland.

w Protect from flooding, use surface drainage.

s Practice moisture conservation and control wind erosion.

Not suited for cultivation V Too wet or stony for cultivation. White Grazing, forestry, recreation

VI Too steep, stony, wet, or droughty. Orange Grazing, forestry, recreation Moderate limitations for grazing. or forestry

VII Very steep, rough, wet, or sandy. Brown Grazing, forestry, recreation Severe limitations for grazing or forestry.

VIII Extremely rough, swampy, etc. Purple Wildlife, watershed protection, or recreation

a Abbreviations: e=erosion hazard; w=wetness hazard; s=permanent soil limitation such as shallow depth and/or droughtiness. C-1 10/18/05 11:06 AM Page 10

10 MANAGEMENT OF WISCONSIN SOILS

Questions 1. The soils of southwestern 8. What is the difference between Wisconsin are considerably older physical weathering and chemical than those of northeastern weathering? Wisconsin. Explain why. 9. Explain how “horizons” form in 2. Why are the soils of north-central soil.What is the difference between Wisconsin consistently more acid the A and B horizons in a soil? than the red clay soils in eastern 10.How are soils named? Give an Wisconsin? example of a soil name and explain 3. What are aeolian deposits, and the meaning of each part of the what is their importance in terms name. How can you find out the of the soils in Wisconsin? names of soils on a particular farm and the yields of crops that these 4. The parent materials having the soils are capable of producing? most effect on the soils of Wisconsin are the bedrock, glacial 11.A soil map in a soil and water deposits, and aeolian deposits. conservation plan shows a field Explain what effect, if any, each of with some land in Land Capability these parent materials have had on Subclass IIIe and some in Subclass the soils in your local area. IIIw. What land use practices would apply to these land 5. What are alluvial soils? Name some subclasses? important areas of alluvial soils in Wisconsin, elsewhere in the United States, and in other countries. 6. Why are soils developed from sandstone inherently less fertile than soils developed from limestone? 7. In southwestern Wisconsin, prairie soils developed on the broad, flat hilltops while forested soils predominate on the hillsides and in the valleys. Explain why. C-2 10/18/05 11:07 AM Page 11

CHAPTER 2 11 Physical properties of soil

Spectacular advances in the use of Texture fertilizers, pesticides, and other In its broadest sense, soil texture agricultural chemicals since the 1950s refers to the “feel” of the soil; that is, its have placed a great deal of emphasis on coarseness or fineness. Soils are often There is a widespread agricultural chemistry. In the process, referred to as being coarse-textured, the importance of the physical medium-textured, or fine-textured. popular acceptance of the properties of soils and their effects on More specifically, soil texture is defined importance of the physical plant growth have often been as the relative proportion of sand, silt, overlooked. For example, heavier and clay in the soil. The textural properties of soil to plant equipment makes soil compaction an triangle in figure 2-1 shows the ranges growth, but a large increasing problem. Also, few people in the percentage of sand, silt, and clay understand the physical forces that proportion of the statements associated with different textural control water retention and movement classifications. A soil containing equal commonly made on this in soils. As a result, water is frequently percentages (33.3%) of sand, silt, and the most mismanaged of all growth clay would be classified as a clay loam, subject are vague, qualitative factors. Figure 2-1. Ranges in sand, silt, and clay and frequently unsupported for the different textural classes. by factual evidence.”

B.T. Shaw, Soil Physical Conditions and Plant Growth, 1952

1 inch

millimeters Size range in millimeters (mean diameter) 75 2 1 .5 .25 .1 .05 .02 .005 .002 .0002 .0008

GRAVEL SAND SILT CLAY very coarse mediumfine very coarse mediumfinecoarse medium fine coarse fine C-2 10/18/05 11:07 AM Page 12

12 MANAGEMENT OF WISCONSIN SOILS

not as a loam which many would guess. Another way of visualizing the size also a serious problem on these soils There is a tremendous difference in size of various soil particles is to look at when they are bare. Some plant between sand, silt, and clay particles. their rate of sedimentation, or the rate nutrients rapidly leach through sandy This is shown on the scale on the at which they settle out of a suspension. soils. Clay soils are often hard to work bottom of figure 2-1 and in the If soils are dispersed by shaking them in up into a good seedbed. Water often illustration of relative sizes presented in water with a dispersing agent, the sand- moves through clay soils very slowly, figure 2-2. sized particles will settle out of the making them excessively wet. Medium- suspension in about 40 seconds. The textured soils, which are between sandy silt-sized particles will settle out in and clayey soils, are usually the best

approximately 7 hours. Because of their suited for crop production. Fine ➞ sand extremely small size, most clay particles The amount of surface area that will remain in suspension for a very soil particles have is very important. long period of time. Surface area determines the amount of

available water and plant nutrients that Medium silt➞ Importance of soil texture a soil can hold. Clay particles, being

Soil texture is important because it extremely small, have a very high ➞ affects physical and chemical properties surface area in proportion to their Coarse clay • that influence crop growth. Soil volume. These particles are usually structure, organic matter, aeration, bulk broad and flat, like flakes of mica. Most density, tilth, water movement and of them are composed of millions of storage, weathering of minerals, and thin layers, each separated by layers of nutrient supply are all influenced water. The internal surface along these directly or indirectly by soil texture. layers is much larger than the outside Figure 2-2. Relative sizes of fine Clay soil may be termed “heavy”—even surface. In fact, an acre of clay 7 inches sand, medium silt, and coarse though it weighs less per cubic foot clay particles enlarged 500 deep has a surface area equivalent to than a sandy soil—because it is harder times. Coarse sand is about 1⁄25 25,000,000 acres (table 2-1). It is this to pull a tillage implement through of an inch or 1 millimeter in vast surface area that causes a small diameter. clayey soil than through silty or sandy amount of clay to have such a great soil. effect on both the physical and the Soil texture has a substantial effect chemical properties of soils. The clay in on the growth of crops. Sandy soils have most soils accounts for the bulk of the large pores that hold little water and are, surface area that holds plant nutrients. therefore, droughty. Wind erosion is

Table 2-1. Properties of sand, silt, and clay-sized soil particles.

Surface area of soil particles in an acre Particle sizes Physical properties plowed 7 inches deep

Coarse sand Loose, non-sticky, gritty 500 acres

Fine & very fine sand Loose, not sticky 5,000 acres

Coarse, medium, fine silts Smooth and floury, slightly sticky 50,000 acres

Coarse, medium, fine clay Sticky and plastic when wet; hard 25,000,000 acresa and cohesive when dry

a Includes both external surfaces and surfaces between crystal plates. C-2 10/18/05 11:07 AM Page 13

Chapter 2. Physical properties of soil 13

Determining soil sand, silt, and clay. While soils rarely example, clay moistened to the texture by feel consist entirely of one particle size consistency of workable putty feels like A precise determination of soil range, learning the characteristic feel of smooth satin, while dry clay feels rough texture requires laboratory analysis. For each particle size helps in identifying and gritty. Organic matter makes clay most practical purposes, the texture can the different size fractions (table 2-2). feel less sticky and sand feel less gritty. be estimated accurately enough by Mastering this method requires Organic matter is also an important hand texturing. In a mineral soil, the knowing how each soil texture feels. coloring agent in soil; however, soil feel of the soil when rubbed between However, moisture and organic matter color is not an indicator of texture. the thumb and forefinger is dependent can change the feel of the different size primarily on the relative amount of fractions and thus the soil itself. For

Table 2-2. Textural properties of mineral soils.

—————————————Feel and appearance of soila —————————————— Soil class Dry soil Moist soil

Sand Loose single grains that feel gritty. Squeezed in the hand it forms a cast Squeezed in the hand the soil mass falls or mold that crumbles when touched. apart when the pressure is released. Does not form a ribbon.

Sandy loam Aggregates are easily crushed; very faint Forms a cast requiring careful handling velvety feeling initially but as rubbing is to keep it from breaking. Does not form a ribbon. continued the gritty feeling of sand soon dominates.

Loam Moderate pressure crushes aggregates; Cast can be handled quite freely without clods can be quite firm. Pulverized loam breaking. Very slight tendency to ribbon. has a velvety feel that becomes gritty Rubbed surface is rough. with continued rubbing.

Silt loam Aggregates are firm but may be crushed Cast can be freely handled without breaking. under moderate pressure. Clods are firm to Slight tendency to ribbon with rubbed surface hard. Smooth, flour-like feel dominates having a broken or rippled appearance. when soil is pulverized.

Clay loam Very firm aggregates and hard clods are Cast can bear much handling without breaking. difficult to crush by hand. Pulverized clay Pinched between the thumb and forefinger it loam feels somewhat gritty due to the forms a ribbon. The ribbon’s surface tends to feel harshness of the tiny remaining aggregates. slightly gritty when dampened and rubbed. Soil is plastic, sticky, and puddles easily.

Clay Aggregates are hard and clods are extremely Casts can bear considerable handling without hard to crush by hand. Pulverized clay has a breaking. Forms a flexible ribbon and retains gritty texture due to the harshness of its plasticity when elongated. Rubbed very smooth, numerous very small aggregates. surface has a satin feeling. Sticky when wet and easily puddled.

a The properties described for the clayey soils refer to those found in the temperate regions. C-2 10/18/05 11:07 AM Page 14

14 MANAGEMENT OF WISCONSIN SOILS

Granular soils work up easily into a 129 bu/a to 98 bu/a the first year and Structure good seedbed. This is particularly true from 167 to 156 bu/a the second year The arrangement of primary soil when the granules are well-cemented (table 2-3). Alfalfa yields were reduced particles (sand, silt, clay) into together and are fine. Many surface by 0.97 and 0.81 ton/a in the first and aggregates of definite shape is known as soils in Wisconsin were originally second year, respectively. soil structure. Soil structure affects granular. Intensive row cropping, poor When surface soils have been water movement into and through soil, management, and erosion have poorly managed, the natural aggregates root penetration, porosity or aeration, destroyed much of this granular in the surface soils are destroyed and and bulk density. In all soils other than structure. The impact of raindrops can large, hard, irregularly shaped clods are sands, soil particles tend to stick also break down aggregates near the soil formed. Restoring good soil structure together. The pieces that are formed are surface. Moreover, the use of heavy involves growing sod crops such as called structural aggregates or peds equipment and excessive tillage when native grasses and grass-legume (figure 2-3). The major materials the soil is too wet can destroy soil mixtures, returning barnyard manure cementing soil particles together into structure. With modern four-wheel- and crop residues to the soil, peds are clay, organic matter, various drive tractors, fields can be tilled when controlling erosion, and minimizing bacterial gums, iron and aluminum they are too wet. The resulting tillage and traffic over the field with oxides, silica, and lime. Root hairs and compaction stunts crop growth by heavy equipment. The expansion and fungal mycelia also help stabilize soil reducing aeration, restricting root contraction caused by wetting and aggregates. growth, and inducing nutrient drying or freezing and thawing in Some soils, such as sands, have no deficiencies. Plant roots will tend to Wisconsin winters will also help to structure and are described as single- grow horizontally when they encounter restore soil structure. If excessively grained. Another kind of structureless a compacted layer of soil. heavy loads cause deep compaction, soil is one in which the structure has In a Wisconsin study on a Plano freezing and thawing might not suffice been physically destroyed or puddled silt loam, researchers compacted the to undo the damage, and deep chiseling when wet. The soil in the rut of a soil by driving a loaded tractor with a or subsoiling may be needed. tractor that has been stuck in the mud 14-ton axle weight over plots in the Many subsoils in Wisconsin have is an example of such a structureless or spring before planting. Corn yields on blocky or prismatic structure. Both of massive soil. the compacted plots were reduced from these kinds of peds aid the movement

Table 2-3. Effect of soil compaction on the yield of alfalfa and corn in Plano silt loam at Arlington, WI.

Compaction ———— Alfalfa ———— ———— Corn ———— (axle weight) Year 1 Year 2 Year 1 Year 2

tons —— ton/a —— —— bu/a ——

Less than 5 2.27 4.13 129 167

14 1.30 3.32 98 156

Source: Wolkowski, R.P., and L.G. Bundy. 1990. Proc. 1990 Fert., Aglime & Pest Mgmt. Conf. 29:29-37. Wolkowski, R.P., and L.G. Bundy. 1992. New Horizons in Soil Sci. No. 3; Dept., of Soil Sci., UW-Madison.

Figure 2-3. The most common shapes for peds.

prisms or columns blocks plates granules six-sided and roughly cubical long, broad, roughly spherical columnar shapes shapes and flat shapes shapes found in the A horizon

Adapted from Soil Survey Manual, USDA Handbook No.18, 1951, p.227. C-2 10/18/05 11:07 AM Page 15

Chapter 2. Physical properties of soil 15

of water, air, and plant roots through incorporation of 6,000 pounds of crop the subsoil. Organic matter residues into the soil results in about Platy structure is the least The organic portion of the soil is 90% of this dry matter returned to the desirable. Water and roots have to go extremely important. It stores plant air as carbon dioxide through microbial back and forth to get between the nutrients and improves the water- respiration or reduced to simple plates, slowing their downward holding capacity of soil. On the surface chemical salts and water. Only 600 movement. Platy structure occurs as a mulch, organic matter shades the pounds will remain as stable organic naturally in some soils. It can also be soil and reduces the harmful effect of matter or humus. Since the soils of created by farming. Use of the raindrop impact on soil structure. Wisconsin commonly contain 30,000 moldboard plow when the soil is too Organic matter improves soils for the to 80,000 pounds/acre of organic wet and plowing at the same depth year growth of plants by promoting soil matter (1.5 to 4.0%), adding a few after year tend to create a platy aggregation, thus improving soil hundred pounds per acre will have very structure (plow pan) just below the structure and tilth. little effect on the total organic matter plowed layer of surface soil. Plow pans The plants and animals living in content. It is not possible to quickly can be eliminated by varying the depth soil feed on organic matter. Frequent change the organic matter content of of plowing occasionally, by using a additions of fresh organic matter are the soil in the same way that the chisel plow or subsoiler, and by not needed to maintain large and vigorous content of available phosphorus or working the soil when it is too wet. populations of bacteria, earthworms potassium can be modified by Sometimes farmers attempt to and other soil organisms. Organic fertilization. Some typical organic improve poorly drained, tight subsoils matter also helps soil retain plant matter contents of the plow layers of by deep tillage. Deep tillage may nutrients. This is most noticeable in various kinds of Wisconsin soils are provide some temporary benefit, but it sandy soils but is important in all soils. given in table 2-4. won’t give long-term improvement on While adding fresh organic matter is Soils tend to have a natural soils that have drainage problems or in very beneficial, it does not significantly equilibrium level of organic matter. cases where improper management is increase the residual organic matter or This level is regulated mainly by soil not corrected. humus content. For example, the temperature, moisture, aeration, pH,

Table 2-4. Approximate amounts of organic matter in various Wisconsin soils.

Soil color and texture Approximate % organic matter

Light- and dark-colored loamy sands 0.4 – 1.2

Light-colored sandy loam 1.2 – 2.0

Dark-colored sandy loams and light-colored silt loams and loams 2.0 – 3.5

Moderately dark and dark-colored silt loams, loams and clay loams 3.5 – 5.5

Imperfectly drained soils 5.5 – 9.0

Poorly drained and very poorly drained soils 9.0 – 20.0

Peats and mucks > 20.0 C-2 10/18/05 11:07 AM Page 16

16 MANAGEMENT OF WISCONSIN SOILS

carbon:nitrogen ratio, and nutrient management and returning crop the earth’s interior. Secondary minerals supply. These factors influence the residues to the soil, organic matter can are formed from pre-existing minerals microbial process that decomposes be maintained or slightly increased. For by weathering. organic matter. Organic matter example, corn was grown continuously Silicate minerals make up about accumulates in swamps and poorly on Plano silt loam at Arlington, WI, 80% of the earth’s crust (table 2-6). In drained soils because aeration is since 1958. At that time the organic this group, the most abundant class of restricted. It also accumulates in arctic matter varied from 3.0 to 3.5%. In minerals are the framework silicates, soils, as in Alaska, because 1990, as a result of incorporation of the typified by feldspar and quartz. Quartz accumulation during the short growing corn stover, the organic matter content is silicon dioxide, a combination of season exceeds decomposition during had increased to 3.5 to 4.0%. silicon and oxygen (SiO2), the two the rest of the year. most abundant elements on earth. Tillage accelerates organic matter Quartz contains no plant nutrients. decomposition by aerating the soil. A Mineral matter Feldspars contain potassium, calcium, 30-year study of the effect of tillage on Many kinds of minerals occur in magnesium, copper, iron, manganese, organic carbon in a Wooster silt loam soils. A mineral is a naturally occurring and zinc. The ferromagnesium silicates soil in Ohio showed that organic inorganic substance whose chemical are high in iron and magnesium. The matter decreased by 64% after 30 years composition varies only within layer silicates are usually found in the of continuous corn (table 2-5.). The prescribed limits and which has definite clay fraction of soil, although mica can drop in organic matter was physical properties. Some of these be found in large pieces several inches proportional to the number of years in minerals contribute little to plant across in rocks. (A rock is a complex corn, although there was some loss growth. Others provide the main combination of two or more minerals.) (37%) even with continuous oats or sources of many plant nutrients. Oxides of iron, manganese, wheat. Some tillage is involved in Primary minerals are formed by the aluminum, and magnesium are seeding these crops. With good soil solidification of molten magma within commonly found in the clay fraction of

Table 2-5. Decrease in soil organic matter in a Wooster silt loam after 30 years under several cropping systems.

Organic Organic Decrease in Cropping system carbon matter organic matter

%% %

Initial 2.04 3.52 —

Continuous corn 0.74 1.28 64

Continuous oats or wheat 1.28 2.22 37

Corn-wheat-clover 1.16 2.00 43

Corn-oats-wheat- 1.55 2.67 24 clover-timothy

Source: Salter and Greene, 1933. J. Amer. Soc. Agron., 25:622–23. C-2 10/18/05 11:07 AM Page 17

Chapter 2. Physical properties of soil 17

soils. They are important sources of Wisconsin soils have no native sources quartz. These minerals contain magnesium, boron, copper, iron, of gypsum (calcium sulfate). potassium, iron, zinc, copper, manganese, molybdenum, and zinc. The kinds of minerals in magnesium, manganese, and other Some of these nutrients are adsorbed Wisconsin soils vary somewhat from elements essential for plants. (bonded) onto the surfaces of these place to place throughout the state. Some essential plant nutrients such oxides. They also vary greatly among the as potassium and magnesium are Dolomite is the predominant different particle sizes in each soil. Sand structural components inside clay carbonate mineral found in Wisconsin; and coarse silt particles are mostly particles, but clay minerals also hold dolomitic limestone is the rock quartz, a colorless mineral which these and other essential elements in an formation quarried for use as aglime. It contains no elements essential for available form on their surfaces by is a source of both calcium and plants. Medium and fine silt often means of an electrical charge. This is magnesium. Apatite is the original contain significant amounts of one reason why clay is a very important source of native phosphorus in soils. feldspars and micas in addition to part of the soil.

Table 2-6. Minerals common in Wisconsin soils.

Class of minerala Examples Associated plant nutrients

Silicates (80% of earth’s crust) Ferromagnesium (16%) Amphibole Calcium, magnesium, iron, boron Pyroxene Calcium, magnesium, iron Olivine Iron, magnesium

Framework (60%) Feldspar Potassium, magnesium, copper, zinc, manganese Quartz None

Layer silicates (4%) Montmorillonite Calcium, potassium, magnesium Vermiculite Calcium, potassium, magnesium Mica Potassium, magnesium, iron, manganese Kaolinite Calcium, potassium, magnesium

Oxides of aluminum, iron, Hematite Iron, trace element impurities magnesium, and manganese (13%) Goethite Iron, trace element impurities Limonite Iron, trace element impurities Magnetite Iron, trace element impurities Gibbsite Trace element impurities Pyrolusite Manganese, trace element impurities Brucite Magnesium, trace element impurities

Carbonates (<5) Dolomite Calcium, magnesium Calcite Calcium

Other (trace) Apatite Phosphorus Tourmaline Boron

a The percentages indicate the approximate amount of each of the minerals in soil. C-2 10/18/05 11:07 AM Page 18

18 MANAGEMENT OF WISCONSIN SOILS

As previously mentioned, clay particles are layer-like crystals, with Bulk density each layer separated by water. The exact Bulk density is the dry weight of a kind of clay mineral found in soils given volume of soil. The bulk density depends upon the degree and length of of water is 62.4 pounds per cubic foot weathering. Montmorillonite, the or 1.0 grams per cubic centimeter. dominant clay mineral in Wisconsin Mineral soils have a bulk density Silica sheet soils, is composed of crystal units heavier than water, but most organic Alumina sheet Crystal unit containing a layer of alumina soils are lighter than water. Bulk sandwiched between two layers of silica density is inversely proportional to pore Silica sheet (figure 2-4). Water separates each space (table 2-7). That is, the greater crystal unit. The changing water

➡ the soil bulk density, the lesser the soil ➡ Variable distance content causes the clay to swell when pore space. Silica sheet the soil is wet and shrink or contract when the soil is dry. Collapse of the Alumina sheet Crystal unit crystal units of the clay particles is, in Tilth part, responsible for the cracking of soil Silica sheet Tilth is a description of the during dry weather. physical condition of soil as related to Figure 2-4. Schematic repre- its ease of tillage, fitness as a seedbed, sentation of montmorillonite, a and its impedance to seedling common layer silicate mineral. emergence and root penetration. It is a descriptive term that is difficult to quantify.

Table 2-7. Relationship between soil texture, bulk density, and pore space.

Bulk Pore Soil texture density space

g/cc %

Sand 1.6 39

Loam 1.3 50

Silt loam 1.2 54

Clay 1.1 58

Muck 0.9–1.1 Variable

Peat 0.7–1.0 Variable C-2 10/18/05 11:07 AM Page 19

Chapter 2. Physical properties of soil 19

tillage and good drainage, the reduced corn planted with conventional tillage Color iron slowly oxidizes, and the color turns and that planted no-till has been attri- Soil color is determined mainly by yellowish-brown. Many tropical soils buted to slightly cooler soil (2° to 4°F) the iron and organic matter in soil and are brick-red because intense under no-till. the oxidation state of the iron. Soil weathering results in accumulation of Although we cannot control the minerals are mostly whitish to grayish iron oxides. The pinkish-red soils of weather, some management practices in color when the iron and organic eastern Wisconsin are young; the iron will affect soil temperature. It takes five matter are removed. Humus and iron oxide was removed from iron deposits times as many calories to heat a pound oxide are the principal pigments in soil, by glacial activity and ground and of water than it does to heat a pound of and like paint, a little goes a long way. mixed with the parent material that dry soil. Consequently, wet soils remain Color bears little relationship to soil formed these soils. Soils that are cold much longer than well-drained fertility, although it may give some subjected to alternate periods of wet soils. Proper drainage, therefore, will useful clues to the nature of soils. A and dry conditions often have reddish- facilitate soil warming in the spring. black or dark soil usually is high in yellow mottles in the subsoil because Also, surface residue shades the soil organic matter. Yet a peat with 60% the oxidation and reduction of iron from direct solar radiation and tends to organic matter will not be as dark as a oxide is a slow process. While the color keep the surface soil moist. At 4 inches muck with only 30% organic matter of a soil gives some clues to its organic deep, soil temperatures of fields with because the peat is less decomposed. matter content and state of iron substantial surface residue typically are The reddish soils of eastern Wisconsin oxidation, it is not a reliable indicator a few degrees cooler than under bare are red because of the presence of iron of soil fertility. soil. However, the advantage of a oxide coatings. This pigment coats the warmer soil must be weighed against silt, clay, and humus and masks the the erosion potential of a bare soil. dark pigmentation of the latter. Temperature North slopes are cooler than south Highly oxidized iron oxide is red. The temperature of the soil is slopes (in the northern hemisphere). Iron that’s been exposed to both water important for both root growth and Sometimes the difference is great and oxygen, called hydrated iron oxide, microbial activity. Little microbial enough to result in differences in is yellowish. Iron in an oxygen-scarce activity occurs below 45°F or above cropping and native vegetation. In environment (such as waterlogged soils), 90°F. A temperature difference of only southern Wisconsin, for example, called reduced iron oxide, is blue-gray. a few degrees can be important when a apples are often grown on northern Thus, when a wet mineral soil is crop is near the threshold temperature slopes because the temperature drained and cultivated, the subsoil will required for growth. For example, the fluctuates less, lessening the risks of have a blue-gray color. In time, with difference in early season vigor between premature bloom and subsequent frost damage. C-2 10/18/05 11:07 AM Page 20

20 MANAGEMENT OF WISCONSIN SOILS

Questions 1. What is meant by the texture of a 5. Why is a sandy soil that weighs soil? How is soil texture measured? 100 pounds per cubic foot easier to Which soil texture offers ideal plow than a silty clay loam that growth conditions for plants? weighs only 72 pounds per cubic Why? foot? 2. The percentages of sand, silt, and 6. Explain why tilling silty or clayey clay are given below for several soils when they are too wet reduces soils. What would be the textural crop yields. classification of each of these soils? 7. Discuss five reasons why organic sand silt clay matter is an important component ———— % ———— of soil. a. 65 25 10 8. It is much easier to lose organic b. 50 20 30 matter from soil than to increase c. 40 40 20 soil organic matter. Why? d. 30 40 30 9. Why do cracks form in silt loam e. 15 50 35 soils during periods of drought but not in sandy soils? 3. Why is soil structure important? What are some factors that 10.What can you tell about a soil contribute to the breakdown of soil from its color? structure? 11.Why do dry soils warm up faster 4. How can the structure and tilth of than wet soils? a soil be maintained when the land is cropped to continuous corn? C-3 10/18/05 11:08 AM Page 21

CHAPTER 3 21

Soil water

Water is the most limiting factor within the plant are translocated. In affecting plant growth throughout fact, all of the biochemical reactions much of the world. The amount and within the plant and the chemical frequency of rainfall received during reactions of the soil take place in an “In a majority of seasons, the growing season is as important as aqueous system. However, all of these the total annual precipitation. functions demand only a very small deficiency of moisture [is] a Wisconsin receives an average of percentage of the water absorbed by marked limiting factor of 31 inches of precipitation annually, plants; most of the water is lost to the with about two-thirds coming during atmosphere by transpiration. yield.” the growing season. F.H. King, The Soil, 1895 Water is the plant’s source of hydrogen, which is incorporated into Hydrologic cycle carbohydrates by photosynthesis. It The cycling of water from the serves as the medium in which atmosphere to the ground and back nutrients are taken up and distributed again is known as the hydrologic cycle within the plant and through which (figure 3-1). Water travels along one of materials that have been synthesized many paths before returning to the

Figure 3-1. The hydrologic cycle.

cloudcloud formation formation

rain clouds evaporation

from ocean

while falling

from soil

from streams transpiration surface runoff

infiltration

soil

ocean

ground water Source: Reproduced by permission of Deere & Co. C-3 10/18/05 11:08 AM Page 22

22 MANAGEMENT OF WISCONSIN SOILS

atmosphere through evaporation. It greater capillary movement than sands Figure 3-2 depicts a soil water may remain on the earth’s surface, or peats, so they lose more water by budget for a crop grown on a sandy infiltrate the soil, or run off into evaporation. loam soil. The graph shows how the swamps, streams, lakes, or reservoirs. Transpiration is the process of amount of stored soil water changes Water entering the soil may be stored plants pulling water from the soil daily with evapotranpiration, drainage, in the soil, used by plants, or continue through their roots to replace the water and rainfall. At the start of day 1 all of moving downward through the vadose that is lost by evaporation from their the gravitational water has drained (unsaturated) zone to the groundwater. leaves. The amount of water plants can away and the available water is at Groundwater moves laterally to lakes, transpire depends on length of growing 1.4 inches, nearly its maximum springs, streams, and rivers where it season, plant density, depth of rooting, (1.6 inches in this example). Daily eventually returns to the surface. Water rainfall distribution, temperature, and evaporation removes some water from at the surface of soil or water bodies humidity. Early in the season, the the storage (0.12 to 0.32 inches), as is evaporates and returns to the amount of water lost by transpiration easily seen on days 1 through 4. Rain atmosphere where it may form clouds depends on the amount of leaf surface on day 5 refills the available water, and and eventually return to the surface as exposed. When the soil is reasonably because it is cloudy only a small precipitation. wet and the sun is shining there is a amount evaporates. On day 6, however, steady flow of water into roots, up the it rains too much for the soil to hold, plant stem, and into the leaves. and after the 1.6 inches of available Evapotranspiration Increasing the plant population beyond water capacity is saturated, the (ET) that required to form a closed canopy remainder drains. Because the soil was Evapotranspiration is a does not increase transpiration. Once completely saturated on day 6, much of combination of water loss from the soil is completely shaded by the day 7 rain also drains. During the evaporation of the soil surface plus vegetation, most of the water loss is by rain-free period of days 8 and 9 transpiration from plants. It is transpiration rather than evaporation evaporation again steadily depletes the estimated that roughly two-thirds of from the soil surface. Depth of rooting available water. Another rain on day 10 Wisconsin’s 31-inch average annual is important because it determines how refills the soil’s reserve for available precipitation returns to the atmosphere much water is available. Deep-rooted water. through evapotranspiration. The plants continue transpiring after remainder either percolates through the shallow-rooted plants wilt for lack of soil profile to the water table or runs moisture. Rainfall distribution off the land surface. determines the amount of time the The amount of water lost from the exposed surface soil is wet, and it soil by evaporation depends on many influences the depth of rooting. Longer factors, including soil moisture, periods of time between rains result in temperature, vegetation, and soil deeper rooting. Table 3-1 compares texture. On moist soil, heat determines amounts of evapotranspiration from the amount of evaporation. Wet soils different kinds of vegetation over a year stay cold longer in the spring because it and over the length of their growing takes more heat to warm the water in season. soil pores than it does to warm the air or soil particles. However, when the soil surface is dry, evaporation also depends on the rate of water movement through capillary flow to the surface, not on heat alone. Fine-textured soils have C-3 10/18/05 11:08 AM Page 23

Chapter 3. Soil water 23

Table 3-1. Evapotranspiration losses of water as affected by various uses of land in Wisconsin.

— Evapotranspiration (inches) — Land use Growing season Annual Growing season

Water (lake or stream) — 29–32 —

Forest April–October 26–29 26–29

Alfalfa-bromegrass April–September 22–26 19–23

Corn mid-May–September 18–22 11–15

Grain (with seeding) April–June 18–22 9–13

Bluegrass April–June 12–18 10–16

Bare soil — 12–18 —

Figure 3-2. A soil water budget for a crop growing in a sandy loam soil.

1.6 plant-available 1.2 water

0.8 precipitation 0.4

0.0

–0.4 evapotranspiration drainage

Water gains and losses (in) –0.8

1 2 3 4 5 6 7 8 9 10 — Day — C-3 10/18/05 11:08 AM Page 24

24 MANAGEMENT OF WISCONSIN SOILS

amount of dry matter. Improving soil is attracted to the surface of soil Water-use fertility to produce optimum crop particles and held there by adhesion in efficiency yields also gives the highest water-use thin films around each particle. This efficiency (figure 3-3). The more- water is bound so tightly that plants The amount of water (from the vigorous root system of plants in a well- cannot extract it. It can be removed by soil, precipitation, and irrigation) fertilized soil enables the plants to heating. Water molecules are polar; that needed to produce dry matter is known extract more water and nutrients from is, each molecule has a negative side and as water-use efficiency and varies the soil than can plants in a soil of a positive side. This polarity makes the depending on the crop. For instance, lower fertility. molecules stick together by cohesion. corn requires less water to produce a The size of the space between soil ton of dry matter than does alfalfa. The particles (soil pores) determines whether difference is due to the fact that alfalfa water will remain in the soil or continue uses water from April until the first How water is to move downward. If the soil pores are killing frost in the fall; whereas corn held in soil small enough, adhesion and cohesion has a shorter period of growth. Gravity moves soil water work together to hold the water in Factors limiting plant growth, such downward. However, the attractive place. If the pores are too large, as in as poor soil fertility, markedly lower a forces between water molecules and soil sand, the cohesive force is not great plant’s water-use efficiency. That is, particles (adhesion), and between one enough to hold the water molecules plants subjected to these conditions water molecule and another (cohesion) together, and the water drains. require more water to produce a given counteract the gravitational force. Water

Figure 3-3. Fertilization and water-use efficiency.

147 bu/a yield

91 bu/a yield 7.4 bu/inch of water

4.9 bu/inch of water

18.6 inches of 19.9 inches of soil water used soil water used

Low fertility High fertility

Source: Adapted from Potash & Phosphate Institute. C-3 10/18/05 11:08 AM Page 25

Chapter 3. Soil water 25

When all soil pores are filled with that lost by transpiration. Without Forms of water, the soil is said to be saturated. additional water, the plant will wilt and soil water The excess water, often called eventually die. The amount of water in gravitational water, drains from the the soil at this point is called the Plant growth requires soils large pores within a few days due to the permanent wilting percentage. Available containing water and air. On a volume force of gravity. Only excess water (that water, then, is the amount of moisture basis, “ideal” soils should have about which cannot be held in the large soil held in the soil between field moisture 50% pore space and 50% solids. The pores) drains out of the soil profile; this capacity and permanent wilting ideal composition of a surface soil in drainage takes place much faster in percentage. Water is held in soil much good physical condition would be sandy or well-aggregated soils than in as it is in a sponge. If a sponge is about 25% air, 25% water, 45% clayey or poorly aggregated soils. saturated with water, a certain amount mineral matter and 5% organic matter Once the gravitational water drains will drain by gravity. The water (figure 3-4). The percentages of water away, the soil is at field moisture remaining in the sponge is analogous to and air will fluctuate considerably, and capacity. At this point, water is held in field moisture capacity. If you wring lack of either water or air will severely the small pores and as a thin film on out the sponge, more water, analogous limit plant growth. soil particles, while the large soil pores to available water, will be released; but Sandy soils have few pores but contain air. At field moisture capacity, there will be some water left that these pores are relatively large. Medium- plant roots can absorb approximately cannot be wrung out (permanent textured soils such as loams and silt half of the water in the soil. The water wilting percentage). loams and well-structured clay soils films become thinner as water The amount of water available to have both large and small pores. Poorly evaporates or is taken up by plants. plants depends on the soil texture. The structured clay soils have many very Eventually the water films become so smaller the soil pores, the more tightly small pores. When water fills all of the thin and are so tightly held by the soil the water is held. That is why a clay pores, silty and clayey soils hold more particles that the plant roots can no loam contains slightly less available total water than sandy soils simply longer remove enough water to replace water than a silt loam. As shown in because they have so many more pores.

Figure 3-4. Typical volume composition of the surface layer (A horizon) of a silt loam soil. The percentages of air and water vary considerably, as the soil pores are filled with either air or water.

Water 25% Air 25%

Organic 5%

Mineral 45% C-3 10/18/05 11:08 AM Page 26

26 MANAGEMENT OF WISCONSIN SOILS

Figure 3-5. Water availability relative to soil texture.

60 Field moisture capacity 50 Available 40 water Permanent wilting percentage 30

Soil water, % Soil water, 20

10

0 Loamy Loamy Sandy Loam Silt Silty Muck Peat sand fine loam loam clay sand loam

Soil texture Source: Potash & Phosphate Institute.

figure 3-5, a silty clay loam holds about nutrients. Most plants suffer supply a significant percentage of the the same amount of water as a silt permanent damage and yields are crop’s moisture requirement. loam, but it holds the water more severely reduced if a soil is ponded for Layering of different soil textures tightly so slightly less is available to more than 1 to 3 days in the growing impedes water movement through soils. crops. (Silty clay loams hold 2.6 inches season. If a layer of fine-textured soil lies above of available water per foot compared to a coarser layer (such as silt over sand), 2.8 inches for a silt loam.) the fine pores in the upper layer will Poorly drained soils hold excess Water movement hold moisture from the lower layer water in the soil pores, sometimes in soil until the upper layer becomes almost permanently, either because Water molecules try to equalize saturated. Only then will moisture internal drainage is impeded by clay moisture tension, or even out the soil move downward by gravity. This layers or hardpans or because the soil is moisture. Water moves to areas where situation is known as a perched water situated in a low area in the landscape. the moisture content is lowest (highest table. The coarser lower layer does not When there is too much water, not moisture tension). For example, water have enough fine capillaries to “pull” enough pore space remains for good absorption by plants reduces the moisture from the fine upper layer. exchange of carbon dioxide and oxygen amount of water near the roots, raising When the reverse occurs—a layer between soil air and the external the moisture tension in that part of the of coarser-textured soil over a finer- atmosphere. Carbon dioxide soil. Water moves toward the roots by textured soil, such as a loam over a accumulates and the oxygen supply capillary action to equalize the tension. clay—another type of perched water diminishes as plant roots and Unlike gravitational water, which only table is formed. In this example, water microorganisms respire. This moves downward, capillary water can moves fairly fast through the loam, but combination—insufficient oxygen and move in any direction. If the water very slowly through the clay. As a excess carbon dioxide—impairs root table is within 40 inches of the soil result, water again accumulates in the growth and absorption of plant surface, capillary rise of water can upper layer. C-3 10/18/05 11:08 AM Page 27

Chapter 3. Soil water 27

textures take to reach the permanent Excess water from over-irrigation is Irrigation wilting point. not only wasteful, it can also leach scheduling Crops begin to wilt (incipient wilt) nitrates and other nutrients as well as when about 45% of the available water pesticides into the groundwater. A good Most crops could benefit from has been depleted. This first happens in irrigation scheduling program lessens additional water during parts of the the early afternoon on warm, bright these problems by evaluating different growing season. Even so, economics and days after several days without rain, but factors to determine the timing and the availability of water limit irrigation the plants recover when the rate of amount of water needed. These factors in Wisconsin mainly to sandy soils. evapotranspiration drops toward include the water-holding capacity of How often should a soil be evening and overnight. Nevertheless, the soil, stage of growth of the crop, irrigated if it doesn’t rain? The answer the stomata (leaf pores) close when the evapotranspiration, and water supplied depends on the amount of available plant wilts. As a result, carbon dioxide through rainfall and previous water stored in the soil, the rooting can no longer enter the leaves, and irrigations. depth of the crop and rate of photosynthesis and other growth Irrigation scheduling tools can be evapotranspiration. On a hot summer processes slow down. To prevent as simple as a notebook or as intricate day, the rate of evapotranspiration is damage and to maximize crop as a computer software program. Both about 0.25 inches of water per day. production, irrigation should begin as approaches track the various water use Over the growing season, the average soon as plants start to wilt—long factors described above and calculate rate is about 0.15 inches per day. before they’ve reached the permanent irrigation needs. When the calculations Figure 3-6 shows an example of how wilting point. show that the available water supply is long plants growing in different soil low, irrigation water should be applied to restore soil water back to desired Figure 3-6. Time required at different rates of evapotranspiration (ET) for plants to begin wilting and to reach permanent wilt with levels. Reasonably accurate the soil initially at field moisture capacity (rooting depth, 3 ft). evapotranspiration values are critical to any irrigation scheduling system. Evapotranspiration estimates for crop Permanent wilt ET rate production areas in Wisconsin and Incipient wilt (inch/day) Minnesota can be viewed by accessing 60 the Wisconsin-Minnesota Cooperative Extension agricultural weather page at 50 .15 www.soils.wisc.edu/wimnext/et/wimnet .html. An example of a checkbook-style irrigation scheduling method from the 40 University of Minnesota–Extension Service can be found at 30 .25 www.extension.umn.edu/distribution/

Time, days cropsystems/DC1322.html. 20 .15

.25 10

0 Loamy Sandy Loam Silt Silty sand loam loam clay loam

Soil texture C-3 10/18/05 11:08 AM Page 28

28 MANAGEMENT OF WISCONSIN SOILS

Questions 1. Approximately two-thirds of the 5. Define the following: rainfall received in Wisconsin is a. field moisture capacity returned to the atmosphere by way b. permanent wilting percentage of evapotranspiration. What useful purpose(s) does evapotranspiration c. available water serve? What would happen if only d. gravitational water one-third of the rainfall received e. evapotranspiration returned to the air by evapotranspiration? 6. Corn sometimes curls in mid- afternoon due to moisture stress but 2. Why is less water lost by recovers by the next morning even evapotranspiration from land though there was no rain or dew. cropped to corn than from forested Explain. land? 7. A farmer has difficulty establishing 3. Explain why a well-fertilized crop alfalfa on a soil containing 8.0% uses less water to produce a pound organic matter while the same crop of dry matter than does a crop on an grows very well on another soil infertile soil. containing 3.0% organic matter. 4. A farmer has a field containing three What is the most likely reason for kinds of soil: (a) a uniform loamy the poor alfalfa growth and survival sand several feet deep, (b) a silt loam on the soil containing high organic several feet deep and (c) a clay matter? several feet deep. Identify where in 8. What is a perched water table? the field you’d expect to see the Under what conditions is a perched following characteristics: water table possible? a. Plants showing the first signs of 9. If corn is growing on a silt loam soil water shortage. 3 feet deep which contains 2 inches b. Plants showing deficiency of available water per foot of soil, symptoms of nitrogen and and if 0.15 inches of water is lost per potassium if no fertilizer was day by evapotranspiration, about used. how many days can this crop grow c. Soil that works up into a fine without rain before showing granular seedbed most readily. incipient wilt? Permanent wilt? d. Water ponding after a heavy rain. C-4 10/18/05 11:09 AM Page 29

CHAPTER 4 29

Tillage

Soil scientists have long production and accelerate erosion by appreciated the physical effect of destroying soil structure. Depending tillage. F.H. King, UW Professor of upon the previous crop it may be Agricultural Physics, in his book The advantageous to incorporate or move “But Nature neither plows, Soil, published in 1895, gives us an some crop residue so that the soil will insight that many have overlooked to warm more quickly in the spring. harrows, nor hoes her fields, this day when he stated: Tillage to manage crop residue and yet where water is When we reflect upon Nature’s following corn is common, whereas methods, we see plainly that they are residue may not be a consideration abundant and the temperature quite different from those adopted by where a crop is planted after soybean. right, the grasses thrive, the thrifty husbandry. In the first place, Ideal conditions for a rootbed are by Nature’s methods, not one seed in considerably different than for a flowers bloom and fruit, and many hundreds ever germinates and seedbed. A field serves as a rootbed tree and shrub vie with one comes to maturity, but in farming no throughout 95% of the growing season, such chances can be taken. In the so the primary emphasis should be on another for occupancy of the second place, by Nature’s methods, rootbed preparation. A good seedbed whole surface of the earth.” almost all fields bear a mixed requires fine, grain-like soil aggregates vegetation, …but in agriculture that will be in firm contact with the F.H King, The Soil, 1895 certain crops must occupy the field seed. This ensures good moisture for the season to the exclusion of all movement to the seeds to speed others, and in these…(fields) we find germination. However, a good rootbed the chief needs for, and the great requires a loose and porous soil with importance of, good (soil) tilth... some residue being maintained on the soil surface. Such a soil improves root growth and absorbs water rapidly, Purpose of tillage reducing runoff and erosion. Hence, The main purposes of tillage are to only the seedbed area should be prepare a seedbed, prepare a rootbed, thoroughly tilled and compacted. eliminate competing vegetation, and Preparing the entire field as a seedbed manage previous crop residue. The for row crops wastes time and money. seedbed is that small volume of soil in the immediate vicinity of the germinating seed; whereas the rootbed Kinds of tillage is the much larger volume of soil in Tillage systems are sometimes which roots develop. Tillage loosens defined according to their objective and aerates the soil if done at the (reduced, conventional, conservation) proper moisture stage. Over-aggressive or according to the principal tillage soil preparation can hurt crop implement employed (moldboard plow, C-4 10/18/05 11:09 AM Page 30

30 MANAGEMENT OF WISCONSIN SOILS

chisel plow, no-till). Another way to leaving at least 30% residue. Tillage more passes with a secondary tillage define a tillage system is by describing practices have changed in the past implement, such as a disk, field the amount of crop residue left decade because of improvements in cultivator or springtooth harrow. following tillage. Measurements are pest management, hybrid and variety Primary tillage is the initial, major soil made after planting since any tolerance, and tillage implements. manipulation operation intended to manipulation of the soil, no matter Figure 4-1 shows the changes in tillage loosen soil and manage crop residue, how slight, will affect residue coverage. systems in Wisconsin between 1990 either by burial or movement away The Conservation Technology and 2002. There are still numerous from the future row area. Secondary Information Center at Purdue acres that have less than 15% residue, tillage is intended to create a seedbed University conducts an annual “Crop but many of these are likely first-year that is suitable for planting. Residue Management Survey” for the corn following soybean where any Primary tillage in a United States. This survey defines three tillage will bury a substantial amount of conventional system uses a moldboard types of tillage: residue. The greatest change in residue plow, which greatly benefits the soil 1. Conventional tillage = <15% residue; management over this period has been when used properly. It lifts, turns, in soybean where in 2002 nearly 60% aerates, and loosens the soil and 2. Reduced tillage = 15–30% residue; of the crop was grown in a conservation incorporates organic matter. and, tillage system. Moldboard plowing does not compact 3. Conservation tillage = >30% residue. the soil when used properly and is one Conventional tillage Conservation tillage is further of the few implements that can move Conventional tillage is commonly broken down into no-till or mulch-till. soil uphill. However, if a soil is plowed conducted with a moldboard plow The latter being full width tillage at the same depth every year, a plow (primary tillage) followed by one or

Figure 4-1. Changes in Wisconsin tillage systems, 1990–2002.

—— Corn —— — Soybean — — Forage — 90 1990 2002 1990 2002 1990 2002

80

70

60

No-till 50 Mulch-till Reduced-till 40

acres, % Conventional-till 30

20

10

0

Source: Conservation Technology Information Center (CTIC) residue management survey, 2002. C-4 10/18/05 11:09 AM Page 31

Chapter 4. Tillage 31

sole or compacted zone just below the ■ Draft (power) requirements increase it is for seedling emergence and root plow layer can develop. This layer can greatly. penetration. Good tilth is essential for impede root growth and water ■ Plowing well-managed soils deeper good plant growth. It improves movement through the soil. than 8 inches generally does not drainage, increases water storage Fall plowing should be limited to improve yields. capacity, and decreases the danger of fine-textured, non-erosive soils. Spring Moldboard plowing’s primary soil crusting or packing. plowing may be unsatisfactory on these disadvantage is that it leaves insufficient Care must be taken not to over-till soils. Freezing and thawing, wetting surface residue—often less than 5%. the soil. Both disks and spring-tooth and drying, and rain need time to This results in soil surface sealing harrows have a tendency to separate break down clay lumps. In addition, a (crusting), less infiltration, more larger clods from fine particles rather good job of plowing high-clay soils in runoff, and greater problems with soil than mix all particle sizes uniformly the fall can improve drainage in the erosion than in conservation tillage throughout the tilled layer. The fine plow layer temporarily, which could systems that maintain 30% or more particles accumulate near the bottom of permit earlier spring tillage and residue cover. the operating depth of the tool. planting. Secondary tillage in a Tandem disks, due to their weight, A 6- to 8-inch depth is sufficient conventional system usually involves pack the soil below the cutting depth when plowing well-drained and well- use of a tandem disk, field cultivator, more than any other secondary aerated soils. In contrast, deeper spring-tooth harrow, or combination implement. Many modern planters are plowing may benefit soils with implement to smooth the soil surface. designed to plant in rough ground. naturally tight layers or soils packed by Weather, soil and crop type, and Conservation tillage vehicle traffic. Before undertaking deep implement used all play a role in The Natural Resources plowing, consider the following points: determining when secondary tillage Conservation Service (NRCS) defines ■ Ordinary 16-inch plows will not should occur. Lumps and clods break conservation tillage as “any tillage and turn a good furrow if operated more up most easily when the soil is slightly planting system that maintains at least than 8 inches deep. moist (table 4-1). Working the soil 30% of the soil surface covered by ■ Deep plowing is not practical in when it is at the proper moisture residue after planting to reduce soil rocky soils. content and incorporating organic erosion by water.” Conservation tillage matter maintains or even improves soil ■ If the subsoil is acid, deep plowing is designed to increase infiltration and tilth. Tilth describes the physical will require a larger application of reduce water runoff and erosion by condition of soil—how easy it is to till, lime to neutralize the furrow slice. maintaining soil surface residue which its fitness as a seedbed, and how suited

Table 4-1. The effects of tillage on the tilth of soil at various moisture levels.

Soil moisture Appearance Effect

Dry Dusty, usually hard. Tilth building impossible.

Moist Crumbly, not pliable Moisture lubricates and and not slick, forms softens clods. Tilth weak ball. building easy.

Slightly wet Moist soil forms Soil packing likely; tilth pliable, sticky ball. building impossible.

Muddy Water oozes from ball. You are stuck! C-4 10/18/05 11:09 AM Page 32

32 MANAGEMENT OF WISCONSIN SOILS

absorbs the energy of raindrops and conservation tillage methods. Two only a few degrees, it is enough to delay impedes overland flow. In addition to passes with the same implement do not early growth of crops. Corn planted in soil conservation, this system conserves bury twice as much residue as a single plots with substantial surface residue moisture, energy, labor, equipment, pass because the second pass brings typically germinates 4 to 7 days later and stored carbon to reduce the some residue back to the surface. In than corn planted in moldboard- emission of CO2, a greenhouse gas. fact, a tandem disk followed by a field plowed plots. Conservation tillage implements cultivator leaves more residue (32%) The slightly higher moisture levels include the no-till planter, ridge-till than two passes with a tandem disk in residue-covered fields are a definite planter, strip-tillage tools and planter (23%). Nevertheless, avoid tilling more advantage in dry years but a attachments, and various mulch tillage than necessary. Shredding stalks prior disadvantage in cool, wet years. The implements. to tillage will lower residue coverage higher moisture plus higher bulk The amount of residue remaining because the smaller-sized material is density under reduced tillage means after tillage depends on the previous more easily covered by soil. One study there are fewer large pores and more crop, soil conditions, tractor speed, showed that stalk shredding followed water-filled pores. Thus, aeration is depth of tillage, and the tillage by chisel plowing resulted in 42% reduced. Table 4-3 shows how tillage implement. Approximately 80 to 95% residue, whereas 58% residue was left affects surface residue, soil temperature of the soil surface will be covered with on the surface when stalks were not at 2 inches, and soil moisture. The residue in the spring following corn shredded. moisture differences persisted harvest assuming that the residue is Residue on the surface keeps the throughout the growing season, but well distributed by the combine. Table soil wetter and cooler than bare soil. temperature differences were slight after 4-2 shows the different amounts of Although the temperature difference a complete canopy covered the soil. corn residue cover following different between bare and residue-covered soil is

Table 4-2. Corn residue cover following various tillage methods on farms in southern Wisconsin.

Average Expected Tillage implement(s) cover range

%%

No-till 70 65–80

Chisel plow 37 30–70

Chisel plow and field cultivator 34 30–65

Chisel plow and soil finisher 31 25–50

Chisel plow and tandem disk 27 20–40

Chisel plow and field cultivator (two passes) 30 25–50

Chisel plow and tandem disk (two passes) 23 15–35

Chisel plow, tandem disk, and field cultivator 32 25–50

Source: Adapted from Enlow et al. Proc. 1992 Fert., Aglime & Pest Mgmt. Conf. 31:136–144. C-4 10/18/05 11:09 AM Page 33

Chapter 4. Tillage 33

Table 4-3. Effect of tillage on residue cover, soil temperature at 2 inches, and soil moisture (Lancaster, WI, 1979).

Residue ——— Soil temperature ——— — Soil moisture — Tillage system cover May 25 May 28 May 30 May 28 May 30

% ——————— °F ——————— — % water by weight —

Moldboard plow 5 67.8 75.6 78.1 19.3 17.4

Chisel plow 26 66.2 73.6 77.0 19.7 18.2

No-till 60 63.3 69.3 72.7 20.6 19.2

Source: Moncrief, J.F. and Schulte, E.E. 1980. Proc. 1980 Fert., Aglime, and Pest Mgmt Conf. 19:134–144.

There has been some concern previous crop is sometimes chopped, ridges flattened during planting and about the stratification of nutrients and but this is not necessary for well- removes weeds between rows. organic matter in conservation tillage designed equipment. In fact, drills and Strip-till systems have row crops systems. Some advocate the use of a planters often perform better when the planted on the small ridges formed moldboard plow every 5 to 10 years to residue is standing and attached to the following harvest of the previous crop redistribute nutrients and organic soil. Chopped residue sometimes forms either in the fall or the following matter, to incorporate lime and a wet mat which is more difficult to spring. A variation of this method is fertilizer, and to aerate the soil. penetrate. Herbicides are used to known as row-clearing. Row clearing is However, long-term tillage studies in control weeds and to kill the previous most often accomplished with planter Minnesota indicate that after about crop if it was a perennial (e.g., a forage attachments mounted ahead of the 4 years the soil bulk density decreases legume). The use of glyphosate- seeding unit. These are designed to while the size of the pores and resistant crops has increased the move residue from the future row area aggregates increase in conservation adoption of high-residue systems due using finger coulters, disks, or brushes. tillage systems. These changes result to the ease of weed control. Similar to ridge-till, this system leaves from the buildup of earthworm and Ridge-till systems have row crops 40 to 65% surface residue, that may burrowing insect populations, which planted on the ridges formed during not be distributed uniformly. The bare aerate the soil and incorporate organic cultivation of the previous crop. soil in the cleared strip warms up faster matter. Hence, it is doubtful that Residue covers the soil until planting. in the spring than the covered soil periodic use of the moldboard plow is During planting, residue on the ridge is between rows. These smaller ridges necessary or even desirable. If the removed or falls into the valleys should be 2 to 4 inches higher than the surface soil acidifies, some tillage to between ridges. This leaves 40 to 65% valleys. Fertilizer is often banded- incorporate lime is advisable. (See of the soil surface covered with residue, applied during tillage to replace the chapter 6.) although it is not distributed need for starter fertilizer applied with No-till means that crops are uniformly. The bare soil in the ridge the planter. planted in untilled fields using special warms up faster in the spring than the Mulch till systems use a variety of planters or drills designed to cut covered soil between rows. The ridges tillage implements, including the chisel through crop residue. This technique should be 6 to 8 inches higher than the plow, offset disk, tandem disk, field uses a disk or knife opener to insert the valleys, with round or flat tops to cultivator, and soil finisher. The tool seed, while a second opener is used to facilitate planting the following year. that is selected depends somewhat on apply row fertilizer. Residue from the The ridge-till cultivator reforms the the nature of the existing crop residue. C-4 10/18/05 11:09 AM Page 34

34 MANAGEMENT OF WISCONSIN SOILS

The chisel plow is the most commonly result, it usually does not leave enough used of these implements in Wisconsin. residue to qualify as conservation tillage Comparison of The chisel plow, disks, and field for compliance with government soil tillage systems cultivator may be used alone or in conservation programs. On wet fields, Different tillage implements are combination with each other. Soil the offset disk can compact the soil compared in table 4-5. What works finishers are commonly used in beneath the blades. well on one farm under a given set of combination with a chisel plow or disk A tandem disk used in a single pass conditions might not work as well on to incorporate herbicides. to prepare a seedbed following chisel another farm with different One pass with a chisel plow leaves plowing leaves 20 to 40% of the surface management and conditions. For each 30 to 70% of corn residue on the soil covered with residue; two passes leave system, evaluate differences in soil surface; however, the actual amount 15 to 35%. Sometimes a soil finisher is conservation, as well as cost of remaining is greatly influenced by the attached behind the disk to smooth the equipment, pesticide, fuel, and labor type of point used on the plow. See field and prepare it for planting by requirements. Tables 4-6 and 4-7 table 4-4 for a comparison of three making a single pass. estimate fuel and labor requirements chisel types and their effect on residue. To increase surface residue and for five tillage and planting systems. Twisted shovels bury more residue than ensure compliance with soil do straight shanks or sweeps. In heavy conservation programs, follow these or wet residue, light disking or stalk recommendations: shredding is sometimes used to reduce ■ Replace twisted shovels with points clogging. Most units have coulters or or sweeps. disks mounted ahead of the chisels for ■ Limit tandem disking to a single this purpose. Chisel plowing in the fall pass. loosens the soil and may provide better erosion control over winter. Some ■ Replace tandem disks with additional tillage is often needed to implements equipped with sweeps prepare a good seedbed in the spring. (field cultivator, soil finisher) Another advantage of using a disk, field ■ Avoid shredding crop residue. Use cultivator, or combination implement equipment that can handle corn in the spring is that they incorporate stover without shredding. some of the fertilizer and pesticides on fields chiseled in the fall. Offset disks have long been used in the Great Plains for primary tillage, but Table 4-4. Effect of implement shape on surface they’re not very popular in Wisconsin. residue following fall chisel plowing (one pass). An offset disk uses large blades Residue (22 inches or more) for deep tillage. It Tool cover (%) buries considerable residue, leaving only 5 to 40% on the surface. As a 3-inch concave twisted shovel 53

2-inch chisel point 60

16-inch medium crown sweep 66

Source: Johnson, R.R. 1988. Soil Sci. Soc. Amer. J. 53:237–243. Reprinted with permission of the Soil Science Society of America, Inc., Madison, WI. C-4 10/18/05 11:09 AM Page 35

Chapter 4. Tillage 35

Table 4-5. Typical tillage field operations.

System Typical field operations Major advantages Major disadvantages

Moldboard plow Fall or spring plow; one or Suited to most soil and Excessive soil erosion. High two spring diskings or field management conditions. soil moisture loss. Must be cultivations; plant; cultivate. Suitable for poorly drained timed carefully. Highest soils. Excellent incorporation. fuel and labor costs. Soils warm up early.

Chisel plow Fall chisel; one or two spring Less erosion potential than Multiple passes cause excessive diskings or field cultivations; fall plow or fall disk. Well soil erosion and moisture loss. plant; cultivate. adapted to all soils, including In heavy residues, may need those that are poorly drained. to shred stalks to keep chisels Good to excellent incorporation. from clogging.

Disk Fall or spring disk; spring Less erosion than from cleanly Multiple passes cause disk and/or field cultivate; tilled systems. Well adapted for excessive soil erosion and plant; cultivate. lighter to medium textured, well- moisture loss. Disking wet drained soils. Good to excellent fields compacts soils. incorporation.

No-till Spray; plant into undisturbed Maximum erosion control. Soil No incorporation. Increases surface; postemergent spray moisture conservation. Lowest dependence on herbicides. as necessary. fuel and labor costs. Not well suited for poorly drained soils.

Ridge-till Shred stalks; plant on ridges; Excellent erosion control on No incorporation. May be cultivate for weed control contour fields. Well adapted to all difficult to create and maintain and to rebuild ridges. soils. Ridges warm up and dry out ridges. Not well suited to quickly. Low fuel and labor costs. narrow-row corn or soybeans.

Strip-till Fall strip-till; spray; plant row Clears residue from row area to Cost of preplant operation. crops on cleared strips; post- allow preplant soil warming and Strips may dry too much, emergent sprays as needed. drying. Injection of nutrients crust, or erode without residue. directly into row area. Well suited Potential for nitrogen fertilizer for poorly drained soils. losses.

Source: Reeder et al., 2000. Reproduced with permission from Conservation Tillage Systems and Management, MWPS-45, 2nd edition, Midwest Plan Service, Ames, IA 50011-3080. C-4 10/18/05 11:09 AM Page 36

36 MANAGEMENT OF WISCONSIN SOILS

Table 4-6. Typical diesel fuel requirements for various tillage and planting systems.

————————————— Fuel use, gal/a ————————————— Operation Moldboard Chisel Disk No-till/Strip-till Ridge-till

Chop stalks 0.55

Moldboard plow 2.25

Chisel plow 1.05

Fertilize, knife 0.60 0.60 0.60 0.60 0.60

Disk 1.48a 0.74 1.48a

Plant 0.52 0.52 0.52 0.60 0.68

Cultivate 0.43 0.43 0.43 0.86a

Spray 0.23a

Total 5.28 3.34 3.03 1.43 2.69

aTwo passes. Source: Reeder et al., 2000. Reproduced with permission from Conservation Tillage Systems and Management, MWPS-45, 2nd edition, Midwest Plan Service, Ames, IA 50011-3080.

Table 4-7. Typical labor requirements for various tillage and planting systems.

————————————— Labor, hr/aa ————————————— Operation Moldboard Chisel Disk No-till/Strip-till Ridge-till

Chop stalks 0.17

Moldboard plow 0.38

Chisel plow 0.21

Fertilize, knife 0.13 0.13 0.13 0.13 0.13

Disk 0.32b 0.16 0.32b

Plant 0.21 0.21 0.21 0.25 0.25

Cultivate 0.18 0.18 0.18 0.36b

Spray 0.11b

Total 1.22 0.89 0.84 0.49 0.91

aHours per acre assumes 100 hp tractor and matching equipment for average soil conditions. bTwo passes. Source: Reeder et al., 2000. Reproduced with permission from Conservation Tillage Systems and Management, MWPS-45, 2nd edition, Midwest Plan Service, Ames, IA 50011-3080. C-4 10/18/05 11:09 AM Page 37

Chapter 4. Tillage 37

Figure 4-2. Appearance of soil with different amounts of corn or Estimating soybean residue. Photos courtesy USDA Natural Resources Conservation Service. residue cover Corn Soybeans With experience, the amount of crop residue on the soil surface can be approximated by inspection. Figure 4-2 shows how 15, 30, and 50% corn and soybean residue cover appear. A more exact measurement can be made by the line-transect method. This procedure involves stretching a line diagonal to the crop rows and recording whether or not residue intersects the line at Field view, 30% cover Field view, 30% cover specified points. The line can be a wire cable with tabs attached at fixed spacings, a knotted rope, or a tape measure. It should be 100 feet long with markings at 1-foot intervals or 50 feet long with markings every 6 inches. Anchor both ends of the line. Walk along the line and look straight down at each recording point (tab, knot, etc.). Record the number of points that are directly over a piece of 15% ground cover 15% ground cover residue. Always look at the same side of the line and avoid moving the line while counting. Stones should not be counted, but manure should be counted as residue. The number of intersections with residue out of the 100 recording points is the percent residue cover. Repeat the procedure at five randomly selected locations in the field, and take the average of the five results. For more details, see Extension publication Estimating Residue Using 30% ground cover 30% ground cover the Line-Transect Method (A3533).

50% ground cover 50% ground cover C-4 10/18/05 11:09 AM Page 38

38 MANAGEMENT OF WISCONSIN SOILS

clay get washed into larger pores, Another way to reduce compaction Soil crusting increasing the bulk density of the soil. is to control traffic. All vehicle and Raindrop impact on bare soil Residue on the surface protects soil implement wheels are spaced to run dislodges individual sand, silt, clay, and structure from this effect of raindrop centered between rows. Many tillage, organic matter particles from soil impact. planting, spraying, and harvesting aggregates. When pools of water Moisture is usually the operations can use the same tracks. In develop, the sand settles to the bottom, determining factor in compaction. continuous row crops, this system the silt rests on top of the sand, and the Before doing any field work, check soil works well with ridge-till, strip-till, and clay on top of the silt—if it is not moisture, not only at the surface but to no-till where the same tracks are used carried away with organic matter the depth of tillage and immediately year after year. Traffic, and therefore particles in the runoff water. When the below. The most serious damage occurs compaction, is confined to a small water dries, a surface crust about when tillage, planting, cultivating, or percentage of the soil between rows. 1⁄4-inch thick is formed. This crust can harvesting operations are done when Compaction is thereby managed, not prevent seedling emergence, reduce air the soil is wet. For example, in one eliminated. exchange, limit water infiltration, and study on a clay loam soil, three passes A common management response increase water runoff. with a tractor packed the plow layer to to compaction is subsoiling or deep Crop residue on the surface retards the same bulk density as the subsoil. tillage. Recent research showed that the crust formation by absorbing the It is a good practice to return as type of subsoiler that is used can energy of the raindrop and limiting the much fresh organic matter (crop influence yield. A straight-shanked amount of dislodged soil particles. residue, manure) to the soil as possible. subsoiler following either corn or Coarse, sandy soils do not form crusts, All soil compaction problems become soybean was found to increase crop nor do well-granulated clays. Most more severe as organic matter is yield when compared to a more clayey soils will shrink enough on depleted. Humus (decomposing aggressive subsoiler that lifted and drying to break up crusts. Sandy loam organic matter) acts as a cementing shattered the entire soil volume. and silt loam soils low in organic material to give stability to soil Researchers have noted that intensive matter seem to produce the densest and aggregates, thus maintaining soil subsoiling destroys the bearing strength thickest crusts. Sometimes these crusts structure. and natural channels in the soil such can be broken up with a rotary hoe. Most compaction is the result of that it can be recompacted to a worse wheel traffic. Large rubber tires cause condition. Before subsoiling, less surface compaction than small tires compaction should be diagnosed. The Soil compaction because of their larger “footprint.” most common tool is a cone Compacted soil reduces water Radial-ply tires have a larger footprint penetrometer that is pushed into the infiltration at the surface and decreases than bias-ply tires. Depth of soil at a constant rate. Be sure to note permeability at lower levels, reduces compaction depends on the total load both the intensity and depth of the aeration, and physically restricts plant on the tire. Deep compaction is not resistance. Subsoiling points should run shoot emergence and root affected by slippage of a driving tire, 1 to 2 inches below the compacted development. Three forces compact but it is increased by liquid in the tire layer. Be sure to take penetrometer soil: gravity, rain, and traffic. If the soil and wheel weights. Wheel weights measurements in affected and surface is bare, raindrop impact tends should be removed when they are not unaffected areas because the resistance to dislodge silt and clay particles from needed for traction. to penetration is relative to the aggregates at the surface. The silt and moisture content of the soil. C-4 10/18/05 11:09 AM Page 39

Chapter 4. Tillage 39

For nitrogen, reduced air space Reduced air space also plays a role Effect of tillage provides conditions conducive to the in potassium availability. The on nutrient conversion of nitrate-nitrogen to concentration of potassium in plant atmospheric nitrogen (denitrification) root cells is about 2,000 times higher availability resulting in less plant-available nitrogen. than the concentration of potassium in Wisconsin research shows that Studies of seven soils across the U.S. the soil solution. Plants must exert tillage has little influence on have shown a much higher population energy to take in potassium against this phosphorus (P) availability, but it of denitrifying microorganisms in no- high concentration gradient. This strongly influences the availability of till plots compared to moldboard- energy comes from respiration of sugars nitrogen (N) and potassium (K). plowed plots. Wisconsin research shows translocated to the roots from the Nutrient availability is linked to tillage that, in wet years, nitrogen is less leaves where it was manufactured. because of changes in soil moisture and available in no-till plots compared to Respiration requires oxygen, so when air space. Reduced tillage increases moldboard or chisel-plowed plots. aeration is reduced, the plant has less moisture and reduces air space. Figure However, in dry years the no-till plots energy to extract potassium (and other 4-3 shows how various tillage systems had better yields than moldboard or nutrients). affect moisture content and air space. chisel-plowed plots.

Figure 4-3. Influence of tillage on soil bulk density and pore space occupied by air or water (upper 3 inches of soil).

Chisel

Air 31.7% Solids 43.0%

Water 25.3%

No till Moldboard

Air 10.8% Air 30.4% Solids Solids 53.6% 43.4% Water 35.6% Water 26.2%

Adapted from Moncrief, J.F. 1981. Ph.D thesis, UW-Madison. C-4 10/18/05 11:09 AM Page 40

40 MANAGEMENT OF WISCONSIN SOILS

Compacting a Plano silt loam Potassium is less readily available using a payloader with a 14-ton axle under reduced tillage than in Questions weight reduced the concentration of conventionally tilled fields. The best potassium in whole corn plants at the way to correct potassium deficiency is 1. One reason for tilling the soil is to eight-leaf stage and in alfalfa at harvest to include potassium in row (starter) remove vegetation that competes (figure 4-4). The reduction in fertilizer and ensure that soil test with crops. With herbicides that potassium concentration resulted in potassium is in the optimum range. reason is no longer of primary reduced yields of both crops. importance. Discuss other reasons for tillage, as well as disadvantages of tillage. Figure 4-4. Effect of soil compaction on potassium 2. Under what conditions should soils concentrations in corn (eighth leaf stage) and alfalfa. be plowed deeper than 8 inches? Why is deep plowing not ordinarily Compaction level: None 14 tons 5.0 recommended? —— Corn —— ——— Alfalfa ——— 3. What percent residue cover is 4.5 needed to meet the requirements of a conservation plan that calls for 4.0 residue management? 4. Describe a method of measuring soil 3.5 residue cover. 5. What kinds of soil are most prone to 3.0 crusting? What can be done to

Potassium concentration (%) reduce crust formation on these soils? 2.5 6. Why is soil compaction becoming an increasing problem in Wisconsin? 2.0 1988 1989 1990 Cut 1 Cut 2 Cut 1 Cut 2 What can be done to minimize soil — 1991 — — 1992 — compaction? Source: Wolkowski, R.P. and L.G. Bundy. 1992. New Horizons in Soil Science. 7. The soil in no-till fields usually No. 3, Dept. of Soil Sci., UW-Madison. contains somewhat more moisture than soil in plowed fields. Under what conditions is the extra moisture an advantage? A disadvantage? 8. A tillage trial comparing no-till with moldboard plowing is conducted on a field of corn. The no-till corn shows potassium deficiency; the conventional tillage does not. Explain why. C-5 10/18/05 11:10 AM Page 41

CHAPTER 5 41 Soil and water conservation

Soil erosion affects everyone, and higher than the soil from which they we all contribute to the problem. came. Exchangeable potassium was Erosion occurs at construction sites, more than six times higher. With along roadsides, in parks and forests, conservation tillage, phosphorus and “The nation that destroys its along stream banks, on hiking trails potassium tend to be concentrated on and bicycle paths, and on agricultural the soil surface. As a result, the soil destroys itself. The soil is land. It scars the landscape, causes concentration of these nutrients in indispensable. Heedless siltation in drainage ways, sewers, runoff and sediments is often higher as reservoirs and lakes, degrades water well. Even so, the total loss of wastage of the wealth which quality, and reduces soil productivity. phosphorus and potassium is less from nature has stored in the soil The Natural Resources Conservation conservation tillage fields because these Service (NRCS) estimates in its 2001 systems reduce sediment loss. cannot long continue national resources inventory that the Most soil conservationists feel that without the effects being felt nation’s cropland is losing 1.8 billion erosion cannot be stopped; it can only tons of topsoil per year. Average erosion be controlled. Soil loss from sheet and by every member of society.” rates are estimated to be 2.7 tons per rill erosion is estimated through the use acre per year from water (sheet and rill) of the Revised Universal Soil Loss Henry A. Wallace, erosion and 2.1 tons per acre per year Equation 2 (RUSLE2) software model. U.S. Secretary of Agriculture, 1936 from wind erosion. Soil erosion by The RUSLE2 model is the latest in a water is a natural process that occurs series of predictive tools (including whenever rain falls on sloping land. USLE and RUSLE) for estimating long- Erosion produced the sediment that term, average annual soil loss caused by gave rise to the fertile delta soils of the rainfall. Model inputs include slope great rivers of the world long before length and steepness, rainfall factors people began to till the soil. But human (intensity and duration), soil activities have often accelerated erosion erodibility, cropping practices, and beyond acceptable limits. presence of soil conservation practices Organic matter and clay erode for a given field. Results are compared more easily than silt and sand because to tolerable soil loss (T) values. Values the particles are lighter or smaller and for “T” are defined for a given soil as are more easily suspended in runoff the soil loss rate that is, in theory, equal water. These particles hold more to the rate of soil formation. Hence, at available nutrients than sand or silt. T, equilibrium between soil loss and Hence, the most fertile part of the soil gain is reached. T values typically range is lost. In one study using conventional from 3 to 5 tons per acre per year for tillage, the organic matter, total most crop, pasture, and forest lands. nitrogen, and available phosphorus in On western rangeland, T values are eroded sediments were about 33% typically much lower (2 tons per acre C-5 10/18/05 11:10 AM Page 42

42 MANAGEMENT OF WISCONSIN SOILS

per year) because soil formation in arid water passes over the soil and carries 3) Rill —water moving across the soil and semi-arid climates is much slower some of it away. Sand, silt, and coarse surface cuts many small channels or than in more humid environments. clay particles are deposited when water ditches, usually only a few inches Comparing predicted soil loss estimates movement slows sufficiently, but fine wide and deep (figure 5-2). from RUSLE2 to soil T values allows clay can be suspended and carried off 4) Gully—water flows through one conservation planners to develop to surface water. channel long enough to cut large management plans for effective erosion Water erosion may be divided into gullies. This is the most dramatic control. Conservation efforts should be four basic categories: type of erosion and receives the most concentrated on the soils with the 1) Splash—raindrop impact on the notice, but the other types can greatest erosion potential. soil surface breaks soil aggregates remove just as much soil. Ephemeral into particles that can then be gullies are small channels that can be carried by running water (figure 5-1). filled by normal tillage, but are likely Runoff and 2) Interrill/sheet—continuous to reform again in the same location. erosion splash erosion causes interrill Classical gullies are channels too Water erosion is a three-step erosion; water moving across the soil wide and deep to be obliterated with process that involves detachment, carries thin sheets of soil downhill. normal tillage operations (figure 5-3). transport, and deposition of soil Interrill erosion is usually slow and The obvious solution to water particles. Erosion begins when imperceptible, so its occurrence is erosion is to control water movement. raindrops or running water detach soil not recognized immediately. The erosive power of water is dictated particles for aggregates and flowing by the volume and velocity of water

Figure 5-1. Raindrop splash. Figure 5-3. Gully erosion.

Source: USDA-NRCS

Figure 5-2. Rill erosion.

Source: USDA-NRCS Source: USDA-NRCS C-5 10/18/05 11:10 AM Page 43

Chapter 5. Soil and water conservation 43

moving over the soil surface. The greater the volume and velocity, the greater the amount of sediment that can be carried by runoff. Slowing the water allows more time for it to soak in rather than run off and reduces its capacity to carry sediment. Furthermore, in a dry year the additional water held in the soil can make the difference between a good and poor crop. An extra inch of stored moisture during a drought period will give a significantly better crop yield.

Factors Source: USDA-NRCS influencing erosion holding aggregates together and The most important factors stabilizing them against erosion. Soil and water influencing erosion are the intensity The steepness and length of slope conservation and duration of rainfall, the erodibility are extremely important. Water on a of the soil, length of slope, slope angle, level field has much more time to soak practices soil cover, and erosion control practices. in than water on a steep slope. Conservation practices help A light steady rain that falls slower Doubling the steepness more than growers retain the soils’ productivity than it’s absorbed by the soil causes doubles the amount of soil loss. Soil while making the best use of resources very little erosion. Most erosion is loss increases rapidly as slope length (land, labor, and capital). This section caused by heavy rains and by rapid increases up to about 400 feet, then describes the most commonly used soil melting of snow when the soil begins to more gradual increases in erosion occur conservation practices. Erosion and thaw. Erosive rain storms occur most at longer slope lengths. However, slopes runoff control practices range from often in late spring or summer. Erosion that are nearly level are not immune to changes in agricultural land control practices must be designed for soil erosion. A long, relatively flat slope management (such as crop rotation, these intense storms and rapid snow with a lot of water flowing over it can conservation tillage, contour tillage, melts. An inch of rain over an acre transport as much sediment as a steep strip cropping, and cover crops) to the weighs 226,000 pounds and carries slope having only a little runoff. installation of structural practices such considerable energy when flowing over Soil cover varies in its effectiveness as terraces, diversions, and waterways. the landscape. A raindrop strikes the to reduce raindrop impact and soil loss. Crop rotation soil surface at a velocity of 20 mph. Vegetation or residue that covers the Crop rotation is the practice of This is enough force to splash soil as soil during intense storms is more growing different crops in recurring much as 2 feet high and 5 feet away effective than land use that leaves the succession on the same field. Perennial from the point of impact. soil exposed during critical times. forage crops provide year-round soil Some soils erode more easily than Forage legumes and grasses are more coverage and, therefore, greatly reduce others. The composition of the soil, effective than row crops because part of erosion compared to row crops. By particularly the soil structure, makes a the soil surface under row crops is bare combining conserving practices, such big difference in the ease with which from the time the soil is tilled until a as terraces or contour strips with rainfall can detach particles and get complete canopy covers the surface. conservation tillage, rotations can often them moving with running water. This means the soil is bare when many be used with more corn and small grain Organic matter is very important in intense rainstorms occur. and less forage. These more intensive C-5 10/18/05 11:10 AM Page 44

44 MANAGEMENT OF WISCONSIN SOILS

rotations are usually more profitable on conservation tillage is used. If Contour tillage cash crop farms and those with hog or recommended amounts of lime and Contour tillage follows the shape beef enterprises. fertilizer are applied and if weeds, of the land to till and plant. The Corn grown in rotation with insects and disease are controlled, high effectiveness of contour tillage is alfalfa, soybeans, or other crops yields can be maintained. County Land dependent largely on the ridges typically out-performs continuous Conservation Department (LCD) produced by tillage implements. By corn. As shown in table 5-1, the personnel and NRCS conservationists cutting across the natural flow of runoff maximum yield of continuous corn was can help farmers develop a cropping water, contour tillage builds small 141 bushels/acre when 200 pounds/acre system that best fits their farming impediments to flow that reduce the of nitrogen was applied. In contrast, program and land. speed and amount of runoff, which in first-year corn following alfalfa yielded turn reduces soil loss. Conservation tillage 157 bushels/acre with no added Contour tillage is most effective at Any tillage practice that leaves nitrogen. Legumes in the rotation reducing soil loss on slopes below 8%. residue on the soil surface aids in soil provide more than just nitrogen. The On steeper slopes, ridges lose their and water conservation. Conservation improved productivity (added yield) ability to hold and retard water flow. or mulch tillage systems can be defined that occurs with rotated corn as Contour tillage on slopes of 3 to 8% as those that result in the least amount compared to continuous corn is reduces soil loss by 50% compared to of tillage necessary to provide a good sometimes referred to as the “rotation up-and-down-slope tillage. seedbed. They can also be defined as effect.” Rotations help break the life Slope length also influences the restricting the number of cultural cycles of insects and diseases that build effectiveness of contour tillage. There is operations to those that are properly up in monocropping. a limit to the length of slope that can timed and are essential to produce an Another recent adaptation of crop be contoured without supplementary ideal seedbed and rootbed. Generally, rotations is the practice of keeping hilly practices. Runoff from the upper part those systems that leave at least 30% fields in permanent alfalfa and grass of the slope combines with runoff from residue cover are considered to be and growing corn and soybeans on the lower part. The additional water on conservation tillage. See chapter 4 for nearly level fields. Corn can be grown the lower part of the slope increases the additional information on conservation for grain on such fields for several years rate of erosion. Most of the severe tillage systems. with no damage to soil structure if cutting from water erosion occurs on

Table 5-1. Effect of alfalfa or soybeans on the yield of corn grown on a Rozetta silt loam soil (Lancaster, WI), 1995–2004.

——————————— Cropping sequence ——————————— Second-year First-year First-year Nitrogen Continuous corn after corn after corn after applied corn alfalfa alfalfa soybean

lb/a ——————————————— Corn yield, bu/a —————————————

0 57 96 157 102

50 88 130 167 134

100 128 145 170 157

200 141 155 173 164 C-5 10/18/05 11:10 AM Page 45

Chapter 5. Soil and water conservation 45

the lower parts of the field where Cover crops on sandy soils, minimized by slowing the water and running water will have the most especially irrigated sands, help reduce directing the flow. energy. On 3 to 8% slopes longer than early spring wind erosion. They are also Diversions are similar to terraces 300 feet, contour tillage needs to be extremely beneficial when the principal but do not have standard spacings. augmented with terraces or other crop is harvested early. Cover crops, Each diversion handles runoff from its conservation practices to prevent such as winter rye, are being used drainage area. Diversions are effective erosion. following the harvest of corn for silage. under the following conditions: This crop actively grows until early Strip cropping ■ to reduce slope length on long winter and then initiates regrowth in Strip cropping is the practice of slopes, making strip cropping more early spring. It is important that it be growing row or grain crops in alternate effective, managed by herbicide or clipping the contour strips with sod crops (grasses ■ to protect gullied areas, following season to prevent or legumes). The grass strips should competition with the succeeding crop. ■ to divert surface water away from cover at least 20% of the field. The low-lying lands, and dense sod cover slows runoff and holds Terraces and diversions ■ any soil carried from the clean-tilled Terraces and diversions, when to divert water away from barnyards, crop. properly installed and maintained, are buildings, and roadways. Certain conservation measures very effective mechanical practices for Grass waterways improve the effectiveness of strip controlling erosion. Recent Grass waterways are wide, shallow, cropping. Contour tillage, an integral modifications have made them even vegetated channels. They are usually part of strip cropping, helps control more effective and easier to use. designed to carry peak runoff following erosion. Grass waterways are essential Formerly, irregular terraces left severe rainstorms. A plow, grader, to carry concentrated runoff. On long many hard-to-handle point rows (areas bulldozer, or scraper can be used to slopes, diversions or terraces are of planter overlap due to field shape the channels. essential to redirect and remove excess boundaries that are not square) in the Functional grass waterways require runoff slowly and to prevent gullies. field. But the use of parallel terraces has well-established, “heavy-duty” Unfortunately, many fields do not have substantially reduced the acreage of vegetative cover. The sod grown in the an adequate system of grass waterways point rows. The second modification is water course needs special care during as these are often removed by tillage or the construction of terraces that use establishment to help it withstand the herbicide application. drainage tiles to remove excess water. added hazard of flowing water. Avoid Alternatively, the terraces may be Cover crops any practices that would hurt the graded or sloped towards one end, and Cover crops provide interim quality or quantity of the grass in the excess water is removed via a grass protection to the soil between regular waterway, such as using it as a farm waterway. Graded terraces that use cropping intervals. They protect the road. Also, use herbicides very carefully grass waterways are cheaper to soil surface from the impact of near grass waterways; otherwise, runoff construct than those that use tile raindrops and wind erosion, add water can carry the herbicide into the drainage, but they require more organic matter, and minimize loss of waterway and kill the grass. Only maintenance. nutrients by leaching. Water is conscientious management and Surface drainage is required for absorbed more readily because the pore maintenance will keep this important some poorly drained soils that cannot space on the surface of the soil is kept conservation structure operating be tiled, such as those in north central open. Thus, cover crops aid in the effectively. Wisconsin. The soil landscape is conservation of water, in the control of smoothed with a large land leveler Buffer/filter strips wind and water erosion, weed control, between shallow, graded terraces. This Buffer or filter strips are areas of and the maintenance of soil system allows excess water to run off grass or other vegetation planted either productivity. Several crops can be used the land slowly to the terrace, and then in a field or along a field edge, often for cover crops, among them rye, oats, into a surface outlet. Erosion is near a stream or other surface water wheat, barley, domestic ryegrass, hairy feature. These act like the silt fences vetch, and sweet-clover. C-5 10/18/05 11:10 AM Page 46

46 MANAGEMENT OF WISCONSIN SOILS

that are commonly placed around Coarse sand grains are too heavy to construction sites. As runoff flows Wind erosion be lifted by most winds, but they can through the filter strip, its velocity is Wind, like water, can cause be rolled short distances and “creep” slowed by the vegetation and sediment erosion. In addition to removing along the soil surface (figure 5-5). Most drops out of the runoff. Water volume topsoil, wind erosion can damage soil is moved by a process known as moving across the slope decreases as young seedlings by a sandblasting saltation which lifts and bounces runoff infiltrates reducing the sediment effect. Airborne particles contribute to particles along. In another type of wind load. air pollution, poor visibility, and erosion, suspension, wind blowing over A contour buffer strip is typically allergies. soil surfaces exerts a lifting force like 12 to 15 feet wide and is planted in the For wind to lift and move a soil that on an airplane wing as it flies upland on the contour between particle, the wind must be stronger through the air. Once airborne, the soil contour strips. Normally, a cool-season than the forces holding the particle to is moved along with the wind for some grass such as timothy or bromegrass is the ground (gravity and adhesion). distance and then lifted again. used. This grassy forage can be Clay and silt-sized particles may be Wind erosion is influenced by the harvested occasionally for hay. lifted high in the air and carried great erodibility of the soil, climate (wind Riparian filter strips are planted distances (figure 5-4). Silt from the velocity and duration, soil moisture, near bodies of surface water and are Great Plains and glacial floodplains in etc.), field roughness, field length and typically 50 to 60 feet wide. Their the Mississippi River valley was carried orientation to wind, and the amount of major function is to remove sediment, eastward across much of Wisconsin vegetative cover. Long-term, average, but they also serve to stabilize stream following the glaciers that receded annual soil losses from wind erosion are banks and provide habitat for wildlife. thousands of years ago. Roughly two- estimated by the Wind Erosion While some are planted to a cool- thirds of the state is still covered by this Equation (WEQ) model which season grass, native warm-season grasses loess or wind-blown silt. The great dust includes all these parameters. The most such as switchgrass are more effective storms of the 1930s were a result of serious wind erosion problem in because they have stiffer stems and wind erosion. Beautiful sunsets are Wisconsin is in the Central Sands area remain erect when dormant. They also caused by different wavelengths of where windbreaks have been removed produce more vegetation and can visible light being reflected from dust to make way for quarter-section center- absorb larger quantities of nutrients. in the atmosphere. pivot irrigation systems. Wind erosion The use of buffer strips can be controversial because they are typically installed in the tillable portion of a field Figure 5-4. Wind erosion. and, subsequently, remove land from production. Filter strips should not be used as roads to outlying fields and need to be clipped occasionally to eliminate undesirable vegetation, remove excess nutrients from the riparian area, and maintain the vigor of the plants. Cutting is often done in mid-summer to protect the nests of grassland birds. Riparian filter strips serve as a “last line of defense” for the protection of surface water and should be used in conjunction with the other upland conservation practices described in this section. Source: USDA-NRCS C-5 10/18/05 11:10 AM Page 47

Chapter 5. Soil and water conservation 47

Fig. 5.5. Types of soil movement by wind. Conservation wind incentives The greatest incentive to practicing soil conservation should be a moral suspension one, a conviction that one has a responsibility to take the best possible care of soil that has been entrusted to saltation us so that future generations may continue to reap the benefits derived rolling or sliding (creep) from productive soil. Secondly, farmers who live on the land they till take pride in managing it well and passing it on to future generations in a more productive is most severe on bare, dry soil. Cover condition than when they acquired it. crops and windbreaks should be used in Tillage Soil stewardship along with economic areas prone to this type of erosion. translocation benefits become yardsticks by which There are chemicals available to Another type of soil movement some managerial decisions are made. spray onto soils prone to wind erosion that is often overlooked is tillage Several federal, state, and county that create a short-lived crust to help translocation, or the movement of soil agencies provide farmers with control erosion. However, they are by the action of various tillage information and technical and financial costly and, once applied, cannot be operations. It is not difficult to visualize assistance to implement soil disturbed by tillage. If applied early in tillage translocation. When an conservation practices. Federal agencies the spring, they will not protect the implement is moving upslope and then include the Natural Resources crop after tillage and planting. If downslope, or across a steep slope, it is Conservation Service (NRCS) and the applied after planting, the soil is not expected that there will be a net Farm Service Agency (FSA). Wisconsin protected early. movement of soil in the downslope agencies include the Department of The best way to prevent wind direction. Tillage translocation has a Agriculture, Trade and Consumer erosion is by keeping the soil covered as leveling effect and it is likely that Protection (DATCP) and the much as possible and by tilling as little eroded knolls within fields are caused, Department of Natural Resources as possible. To do this, cover crops can in part, by this mechanism. When (DNR). These agencies work closely be sown into standing crops or planted combined with the effects of water with county Land Conservation after harvest and allowed to grow until erosion, a significant amount of soil Departments (LCDs) and the county the next crop is planted in spring. can be moved within the field. Actual Land Conservation Committees Cover crops can be killed using a sediment loss from the field is minimal, (LCCs) that supervise the LCDs. herbicide, and the crop can be no-till however, because physical boundaries The county LCDs provide planted in the spring. The residue from such as fences, roads, and ditches can planning, financial, and technical the cover crop continues to reduce stop the movement of soil from tillage assistance to private landowners and wind erosion and protect the soil. An translocation. Speed and intensity of local units of government for soil and additional benefit is that the cover crop tillage operations contribute to the water conservation practices. The takes up nitrogen that might otherwise effects of tillage translocation. Over DATCP administers the conservation leach over winter. This nitrogen is long periods of time tillage translocation provisions of the Farmland Preservation released gradually as the cover crop will reduce productivity in upper Program. They also support soil decomposes. portions of a field though the loss of conservation programs at the county nutrients, organic matter, and topsoil. and state level, and provide cost-sharing C-5 10/18/05 11:10 AM Page 48

48 MANAGEMENT OF WISCONSIN SOILS

to participants. The DNR administers Wisconsin non-point source water Questions pollution abatement programs, which are implemented locally by LCDs in 1. Apart from the loss of precious selected watersheds. University of topsoil, why is soil erosion Wisconsin-Extension and other undesirable? institutions within the university 2. How much soil loss is permissible? system conduct educational programs and do research in support of soil and 3. Describe four different kinds of water conservation programs. water erosion. Which causes the The NRCS assigns full-time greatest soil loss in your area? professional technicians to Wisconsin 4. Name three factors that affect soil counties to assist LCDs in developing erosion. Explain the importance of and carrying out conservation each factor. programs. These specialists assist landowners in developing resource 5. Explain how a surface mulch of conservation plans. They provide crop residues reduces soil erosion. specifications, standards, and guidelines 6. If all rainfall could be held on the for selection, design, layout, soil long enough to eliminate installation, and maintenance of runoff, soil erosion by water would management practices and engineering be eliminated as well. Why is this measures to control runoff, soil erosion, not practical? and sedimentation. They also help plan and design animal waste management 7. What soil conservation measures systems. The FSA administers federally can be used to counteract the funded programs which provide cost effects of long, steep slopes on soil sharing and incentive payments to erosion? farmers to encourage the use of 8. “Water conservation equals soil practices that will reduce soil erosion conservation.” Explain. and water pollution. 9. Under what conditions might wind erosion be a problem? How can it be reduced? 10.List each federal, state, and county agency involved in conservation programs. What role does each play? C-6 10/18/05 11:11 AM Page 49

CHAPTER 6 49 Soil acidity and liming

The late Professor Emil Truog once Sulfuric acid ionizes (dissolves) remarked that if you could have but completely; that is, it goes to the right one soil test run on a field, that test in the reaction above. It is a strong acid should be pH. Soil acidity, which is because it contains more hydrogen ions + – “So without question, the determined by measuring soil pH, (H ) than hydroxyl ions (OH ). reduces productivity of all crops and When lye (sodium hydroxide) is most important single eliminates the possibility of growing mixed with water, it ionizes, forming chemical characteristic of a acid-sensitive crops. Aglime added to excess hydroxyl ions. This results in a acid soils raises the pH by neutralizing strongly alkaline or basic solution: soil as regards its suitability soil acidity. On the other hand, NaOH + HOH <——> Na+ + H+ + 2OH– for plant growth is its lowering the pH of alkaline soils is sodium hydroxidewater sodium hydrogenion hydroxyl ion ion seldom required and usually is not reaction or pH status.” practical on a large scale.

Emil Truog, Mineral Nutrition of Plants, 1951 Soil pH Soil pH, a measure of acidity or Pure water contains an equal alkalinity, affects many chemical and amount of hydrogen and hydroxyl ions biological reactions taking place in the and, therefore, is neutral. soil. Before discussing these reactions, it HOH <——> H+ + OH– is necessary to understand what the pH measurement means and the chemical The concentration of hydrogen nature of acids and bases. ions in pure water has been found to be Stated simply, an acid is a 0.0000001 moles per liter of water substance with an excess of hydrogen (1 mole = 1.008 grams of H+). The pH + ions (H ), and a base is a substance scale is a convenient way to express – with an excess of hydroxyl ions (OH ). such small numbers. The pH is defined A common example of an acid is as the logarithm of the reciprocal of the sulfuric acid (the solution in car hydrogen ion concentration (pH = log batteries). Sodium hydroxide (lye) is an 1/H+). For example, the concentration example of a base. When sulfuric acid of 0.0000001 moles of hydrogen per is mixed with water, the following liter of water is converted into a pH of reaction occurs (in chemical equations 7 as follows: the symbol HOH is often used for pH = log 1/0.0000001 water instead of H2O): = log 10,000,000 + = – H2SO4 + HOH <——> 3H + SO4 + OH (reciprocal number) sulfuric acidwater hydrogensulfate ion ionhydroxyl ion = 7 C-6 10/18/05 11:11 AM Page 50

50 MANAGEMENT OF WISCONSIN SOILS

Table 6-1. Hydrogen and hydroxyl concentrations and as microorganisms decompose the interpretations at common pH levels. organic matter. The optimum pH for most soil microorganisms is pH 6.0 to H+ OH– 7.5. Also, Rhizobium bacteria are most concentration concentration pH Interpretation active in converting atmospheric —————— moles/liter —————— nitrogen into plant-usable nitrogen in this pH range. The Rhizobium bacteria 0.00000001 0.000001 8 strongly alkaline associated with alfalfa are most active at pH 6.8 and higher. Nitrogen fixation 0.0000001 0.0000001 7 neutral by Rhizobia associated with other 0.000001 0.00000001 6 slightly acid legumes, such as red clover and birds- foot trefoil, is less dependent on pH. 0.00001 0.000000001 5 strongly acid Phosphorus is most available between pH 6.5 and 7.5. Below pH 0.0001 0.0000000001 4 extremely acid 6.0, phosphorus reacts with iron and aluminum oxides to form insoluble The concentration of hydrogen microbial activity. The relationship phosphates. Above pH 7.0, phosphorus and hydroxyl ions at pH levels between soil pH and nutrient reacts with calcium compounds to commonly observed in Wisconsin soils availability is illustrated in figure 6-1. form insoluble calcium phosphates. is presented in table 6-1. Note that as In this graph, the wider the bar, the The influence of pH on the availability acidity increases, the pH number greater the relative availability of the of potassium, calcium, and magnesium decreases. Another important point is nutrient. is due principally to competition that for each one unit change in the pH The effect of pH on nitrogen between these cations (positively value, there is a 10-fold change in the availability is due mainly to its charged ions) and hydrogen ions for concentration of hydrogen ions. For influence on microbial activity. exchange sites. (For more details about instance, when the pH decreases from Nitrogen in soil is stored in humus or chemical reactions, see chapter 8.) In 5.0 to 4.0, the concentration of organic matter and becomes available hydrogen ions increases 10 times from 0.00001 to 0.0001 moles/liter. Figure 6-1. Relationship between soil pH and nutrient availability. Importance of soil pH The width of the bar represents relative nutrient availability. Soil pH is important because it affects both chemical and biological Nitrogen reactions, including the following: Phosphorus ■ availability of most of the essential Potassium nutrients, Sulfur ■ activity of microorganisms, Calcium ■ ability of soil to hold positively Magnesium charged nutrients (cations), ■ solubility of non-essential elements, Iron including heavy metals, and Manganese ■ performance of some herbicides. Boron

The soil pH directly affects the Copper, Nickel, Zinc availability of some nutrients, but it Molybdenum often indirectly affects nutrient

availability through its influence on 4.0 5.0 6.0 7.0 8.0 9.0 10.0 Soil pH C-6 10/18/05 11:11 AM Page 51

Chapter 6. Soil acidity and liming 51

addition, calcium and magnesium are of these organisms do better outside of ■ use of acid-forming fertilizers added when dolomitic lime is applied. these ranges. Some plant diseases can ■ carbonic acid from microbial and Sulfur availability is related to pH be controlled by controlling soil pH. plant respiration in much the same way as is nitrogen Potato scab, for example, is controlled ■ acid rain availability. In acid soils, most of the by maintaining soil pH at 5.3 or below. sulfur is a component of soil organic In contrast, club root disease of ■ oxidation of sulfide matter. It becomes available as cabbage and cauliflower can be ■ organic acids secreted by plant roots microorganisms decompose or controlled by growing these crops in a mineralize organic matter. In some soil with a pH of 7.2 or above. Acid parent material alkaline soils, sulfur accumulates as The cation exchange capacity Some soils were formed from sulfate salts. The solubility of these salts (CEC) of soil (to be discussed in acidic parent material, such as granitic is not greatly affected by pH. Sulfate- chapter 8) increases as soil pH increases till, and have always been acid. Soils in = north-central Wisconsin (as shown on sulfur (SO4 -S) is usually not held by due to the removal of hydrogen ions the clay minerals in soils. However, from potential cation exchange sites on the soil map in chapter 1) are examples under very acid conditions (pH less clay minerals and organic matter. of such soils. than 5.5), clays can retain fairly Increasing the pH of Wisconsin soils by Leaching of basic cations substantial amounts of sulfate sulfur. one full pH unit increases the CEC of Some soils were originally neutral This can be an important source of its organic fraction by about 25% and or alkaline, but over thousands of years sulfur in areas where the subsoils are the clay fraction by 8%. Overall, soil they have become acid due to leaching fine-textured and strongly acid, such as CEC increases by about 12% for each of basic cations (calcium, magnesium, north-central Wisconsin. unit increase in pH. potassium, sodium). When soluble Manganese, zinc, iron, and nickel anions are leached, such as nitrates and availability decreases as soil pH chlorides, an equivalent amount of increases because of the formation of How soils cations, such as calcium and insoluble hydroxides of these metals. become acidic magnesium, must leach as well in order The availability of boron and copper Soils are acidic because of one or to maintain electro-chemical neutrality. also decrease as pH increases. Boron more of the following reasons: becomes more strongly adsorbed in an Crop removal ■ insoluble form by organic matter and acidic parent material of basic cations clay as the pH increases above 6.5. ■ bases removed by leaching Harvesting crops also acidifies soils Similarly, copper is strongly bound by ■ bases removed by crops by removing cations. If the harvested soil organic matter. Unlike most of the other Table 6-2. Amount of pure calcium carbonate (CaCO3) needed to replace the basic cations in several crops. micronutrients, the availability of molybdenum increases as pH increases. CaCO3 equivalent of Liming alone is often sufficient to Crop Yield excess basic cations overcome molybdenum deficiency. Chlorine exists in soil as a soluble salt Corn grain 150 bu/a 20 lb/a and is unaffected by pH. Corn silage 8 ton/a 200 lb/a As noted earlier, soil pH influences the activity of microorganisms. Fungi Oats 75 bu/a 5 lb/a do well in acid soils; bacteria generally thrive best at pH 6.0 to 7.5; and Soybean 45 bu/a 95 lb/a actinomycetes usually reproduce most Alfalfa 4 ton/a 515 lb/a rapidly in alkaline soils. (See chapter 7 for a description of microorganisms.) Source: Pierre, W.H., and W.L. Banwart, 1973, Agron. J. 65: 91–96. Reproduced with These are generalizations; some species permission from the American Society of Agronomy, Inc., Madison, WI. C-6 10/18/05 11:11 AM Page 52

52 MANAGEMENT OF WISCONSIN SOILS

portion contains more cations The effect of nitrogen fertilization acid present depends on the amount of (calcium, magnesium, potassium, on the pH of a Plano silt loam soil is carbon dioxide (CO2) in the soil sodium) than anions (phosphate, presented in table 6-3. The pH drop atmosphere (pore spaces). The source sulfate, nitrate, chloride), then there would be even greater in a soil with less of carbon dioxide in soil is that released will be a net loss of basic cations from clay and organic matter, or in the from plant roots due to respiration, the soil. Leguminous crops (alfalfa, surface of a no-tilled soil. When that given off by soil microorganisms soybeans) remove more basic cations 200 pounds of nitrogen per acre was during the decomposition of organic than cereals. Harvesting corn for silage applied each year for 5 years (1,000 matter, and a small amount directly removes more basic cations than pounds total), the pH dropped from from the atmosphere. The concentration harvesting it for grain. Table 6-2 lists 6.11 to 5.68. To raise the pH back to of carbon dioxide in the soil is often 10 the amount of pure calcium carbonate 6.11 would have required 2.7 tons per to 100 times that found in the (CaCO3) that would be required to acre (5,400 pounds) of aglime atmosphere. replace harvested cations and prevent (equivalent to 5.4 pounds of aglime per The carbon dioxide in soil air an increase in soil acidity. 1 pound of nitrogen). In this example, readily reacts with water to form nitrogen was applied as ammonium carbonic acid: Acid-forming fertilizers nitrate. Thus, half of the nitrogen was CO + H O <——> H CO Another significant means by 2 2 2 3 applied as ammonium and half as carbon dioxidewater carbonic acid which soils become acidic is through nitrate. Therefore, 10.8 pounds of the use of fertilizers containing aglime would have been needed to ammonium nitrogen. Ammonium neutralize the acidity produced by accounts for half of the nitrogen in 1 pound of ammonium nitrogen. ammonium nitrate, three-quarters of The carbonic acid in turn ionizes the nitrogen in urea-ammonium nitrate Carbonic acid to form the acidic hydrogen ion and (UAN) solutions, and all of the Displacement of calcium, the bicarbonate ion (HCO –): nitrogen in ammonium sulfate, magnesium, potassium, and sodium 3 + – diammonium phosphate, from soil exchange sites is due, in part, H2CO3 <——> H + HCO3 carbonic acid hydrogen ionbicarbonate ion monoammonium phosphate, to the hydrogen ion derived from anhydrous ammonia, and urea. Some carbonic acid (H2CO3) present in the nitrogen carriers, such as anhydrous soil solution. The amount of carbonic ammonia and urea, raise soil pH temporarily. But, their long-term effect Table 6-3. The effect of nitrogen fertilizer application is to lower the pH because the on the pH of Plano silt loam (Arlington, WI). ammonium form of nitrogen is Nitrogen applied each Soil pH Aglime needed to converted ultimately to the nitrate year for 5 yearsa after 5 years return soil pH to 6.1 form by soil bacteria, with the production of hydrogen ions, as shown lb/a ton/a below: 0 6.11 0.00

+ – + 2NH4 + 3O2 ——> 2NO2 + 2H2O + 4H 40 6.10 0.31 ammonium oxygen nitrite water hydrogen 80 6.02 0.65

120 5.98 0.96

160 5.81 2.03 – – 2NO2 +O2 —— > 2NO3 nitrite oxygen nitrate 200 5.68 2.72

a Nitrogen was applied as ammonium nitrate and incorporated by plowing to a depth of 7 inches. Source: Walsh, L.M. 1965. Proc. Wis. Fert. and Aglime Conf. C-6 10/18/05 11:11 AM Page 53

Chapter 6. Soil acidity and liming 53

The hydrogen ion readily reacts a precipitate of iron sulfide (FeS or acidity) even though only a few cups of with soil particles to displace adsorbed pyrite). If the swamp is drained, the water (comparable to active acidity) are calcium (and other cations) to the soil iron sulfide will slowly oxidize to iron accessible at any one time. The level of solution. The result is that hydrogen oxide (rust) and sulfuric acid. In some accessible water in the drinking trough ions are preferentially adsorbed by the cases, the pH will drop by two to three cannot be reduced significantly until soil, making it more acid, and calcium full units if these soils are drained, so the reserve is depleted. Similarly, the bicarbonate [Ca(HCO3)2] is formed. the cost of liming may be prohibitive active acidity in soil solution cannot be This is a moderately soluble salt which and should be considered before neutralized by lime until the reserve can be leached from the soil. attempting to farm these soils. acidity is depleted. Aluminum ions (Al+++) in soil are Acid rain another source of acidity at low pH Acid rain contributes to soil Nature of levels (below 5.2). Aluminum is not an acidity, although the effect is small essential element, but it is taken up by compared to other sources of acidity. soil acidity plants if it is present in the soil The pH of rainwater in equilibrium Soil acidity is comprised of active solution. In very acid soils, it can be with carbon dioxide from the and reserve acidity. Active acidity refers + present in toxic concentrations. Excess atmosphere is about 5.6. Rain more to the free hydrogen ions (H ) present aluminum interferes with cell division in acid than this is considered acid rain. in the soil solution. Reserve acidity plant roots, decreases root respiration, The sources of this additional acidity arises from neutralizable hydrogen ions + increases cell wall rigidity, interferes are sulfur dioxide (SO ) from the (H ) and aluminum chemically bound 2 with certain enzymes involved in the burning of fuel and volcanic activity; to organic matter and clay particles. deposition of polysacharides in cell oxidation of hydrogen sulfide (H S) The reserve acidity accounts for 2 walls, and interferes with the uptake of from pulp mills, swamps, and oceans; virtually all the acidity in soil. In fact, calcium, magnesium, phosphorus, and and nitrous and nitric oxides from less than 5 ounces of limestone per acre water by plants. Most Wisconsin soils thunderstorms and emissions, from would be required to completely do not contain large amounts of internal combustion engines, and from neutralize the active acidity in a soil aluminum ions. conversion of soil nitrate. with a pH of 5.5. Although active and reserve acidity Oxidation of sulfides are separable by definition, they are Under prolonged water-logged interrelated through chemical Optimum pH conditions, as in a marsh, sulfur is equilibrium. Thus, neutralization of for crops reduced to hydrogen sulfide (H2S). If acidity contained in the soil solution Most crops have a range in pH in ++ there is reduced iron (Fe ) present, it (active acidity) triggers the release of which they grow best. In general, will react with hydrogen sulfide to form more hydrogen ions from soil particles leguminous crops do better at a pH (reserve acidity) to replenish the acidity above 6.3. Research in Wisconsin of the soil solution. When a soil is indicates that the most economical pH limed, this cycle is repeated for alfalfa is 6.8. The pH for which continuously until the liming material lime recommendations are made for Reserve is completely consumed in the Wisconsin crops is shown in table 6-4. acidity neutralization reaction or until the Because most crops in Wisconsin are reserve acidity has been neutralized and grown in rotation, the soil should be the pH is raised. limed to the optimum pH for the most The concept of an interacting acid-sensitive crop in the rotation. Active acidity reserve and active acidity is quite These optimum pH values are based on simple and can be compared to a research from lime plots in Wisconsin poultry drinking fountain (figure 6-2). where data are available or from Figure 6-2. Active and reserve The fountain may contain several information in the literature under acidity in soil compared with a gallons of water (comparable to reserve conditions as close as possible to poultry watering fountain. C-6 10/18/05 11:11 AM Page 54

54 MANAGEMENT OF WISCONSIN SOILS

Table 6-4. Optimum pH for Wisconsin crops growing in mineral and organic soils.

Lime recommendation Lime recommendation ——— Target pH ——— ——— Target pH ——— Common name Mineral Organic Common name Mineral Organic

Alfalfa 6.8 — Pea, canning 6.0 5.6 Alfalfa seeding 6.8 — Pea (chick, field, cow) 6.0 5.6 Asparagus 6.0 5.6 Pepper 6.0 5.6 Barley 6.6 5.6 Popcorn 6.0 5.6 Bean, dry (kidney, navy) 6.0 5.6 Potato 5.2/6.0 5.2/5.6 Bean, lima 6.0 5.6 Pumpkin 6.0 5.6 Beet, table 6.0 5.6 Reed canarygrass 6.0 5.6 Brassica, forage 6.0 5.6 Red clover 6.3 5.6 Broccoli 6.0 5.6 Rye 5.6 5.4 Brussels sprout 6.0 5.6 Snapbean 6.8 5.6 Buckwheat 5.6 5.4 Sod 6.0 5.6 Cabbage 6.0 5.6 Sorghum, grain 5.6 5.4 Canola 5.8 5.6 Sorghum-sudan forage 5.6 5.4 Carrot 5.8 5.6 Soybean 6.3 5.6 Cauliflower 6.0 5.6 Spinach 6.0 5.6 Celery 6.0 5.6 Squash 6.0 5.6 Corn, grain 6.0 5.6 Sunflower 6.0 5.6 Corn, silage 6.0 5.6 Tobacco 5.8 5.6 Corn, sweet 6.0 5.6 Tomato 6.0 5.6 Cucumber 5.8 5.6 Trefoil, birdsfoot 6.0 5.6 Flax 6.0 5.6 Triticale 6.0 5.6 Ginseng — — Truck crops 6.0 5.6 Lettuce 5.8 5.6 Vetch, crown, hairy 6.0 5.6 Lupin 6.3 5.6 Wheat 6.0 5.6 Melon 5.8 5.6 Miscellaneous — — Millet 5.6 5.4 Applec 6.0 — Mint, oil — 5.6 Blueberry 4.5 4.5 Oat 5.8 5.6 Cherryc 6.0 — Oatlagea 6.8 — Cranberry 4.5 4.5 Oat–pea–foragea 6.8 — Raspberry 6.0 5.6 Onion 5.6 5.4 Strawberry 6.0 5.6 Pasture, unimproved 6.0 5.6 CRP, alfalfa 6.6 — Pasture, managedb 6.0 5.6 CRP, red clover 6.3 5.6 Pasture, legume–grass 6.0 — CRP, grass 5.6 5.4 — = no data available a Assumes alfalfa underseeding. b Includes bromegrass, fescue, orchardgrass, ryegrass, and timothy. c Lime recommendations for apples and cherries apply only to preplant tests. Adjustment of pH is impractical once an orchard is established. C-6 10/18/05 11:11 AM Page 55

Chapter 6. Soil acidity and liming 55

Wisconsin’s soils. Organic soils are not Table 6-5. Increases in yield and protein concentration of alfalfa limed above pH 5.6 because the due to liming an acid Withee silt loam soil (Marshfield, WI). amount of lime needed would be Dry matter Protein Protein uneconomical and aluminum and pH yield (2 cuts) concentration yield manganese toxicity are not problems in organic soils. ton/a % lb/a 5.4 1.35 16.2 437

Liming acid soils 6.0 2.59 18.9 977 Acid soils can be neutralized by the addition of aglime. Soils should be 6.9 2.66 20.1 1069 limed to the optimum pH for the crop Source: Schulte, E.E. 1983. Unpublished data. in the rotation having the highest pH requirement. Thus, in a corn-oats- calcium, magnesium, sulfur, and ■ It adds calcium and magnesium, alfalfa rotation, lime needs should be molybdenum. both essential nutrients. based on alfalfa, but in a corn-soybean rotation, liming for soybeans to pH of ■ It increases nitrogen fixation of ■ It improves the performance of some 6.3 is adequate. leguminous crops, which increases herbicides. protein content. Liming acid soils markedly Benefits of liming ■ It reduces the toxicity of aluminum, improves the yield of most crops, Liming to raise soil pH benefits manganese, and heavy metals. especially alfalfa. Liming increases the both biological and chemical reactions protein content of leguminous crops by ■ It creates a favorable environment in the soil: providing a more favorable for microorganisms to break down ■ It increases yields. environment for nitrogen fixation by crop residue and recycle plant Rhizobium bacteria in their root ■ It improves the availability of nutrients. nitrogen, phosphorus, potassium, nodules. Liming an acid (pH 5.4) Withee silt loam soil to pH 6.9 nearly Figure 6-3. Effect of soil pH on the dry matter yield of four cuttings doubled the dry matter yield (table 6-5) of legume forages grown in Withee silt loam (Marshfield, WI). while increasing the protein concentration from 16.2% to 20.1%. Alfalfa Red clover Birdsfoot trefoil 6 As a result, protein yield increased 145%. Figure 6-3 shows the differences in 5 yields for alfalfa, red clover, and birdsfoot trefoil relative to soil pH. All three crops responded to liming, but 4 alfalfa gave the greatest response. Although red clover and birdsfoot trefoil perform fairly well on strongly 3 acid soils (pH 4.8 to 5.2), liming increased their yields as well. In Dry matter yield, ton/a 2 addition to improving yield, liming to pH 6.0 markedly increases both establishment and survival of alfalfa 1 (figure 6-4). 4.5 5.0 5.5 6.0 6.57.0 7.5 Corn does not always respond to Soil pH increasing pH. Response is most likely Source: Schulte et al. 1981. Proc. 1981 Fert., Aglime & Pest Mgmt Conf. 20:77–85. C-6 10/18/05 11:11 AM Page 56

56 MANAGEMENT OF WISCONSIN SOILS

Figure 6-4. Effect of soil pH on establishment and persistence of to occur in areas where soil acidity can alfalfa in Withee silt loam (Marshfield, WI). cause a manganese toxicity and in areas Adapted from Proc. 1981 Fert., Aglime & Pest Mgmt Conf. 20:77–85. where the acidity ties up marginal levels Survival % of available phosphorus. Corn yields 12 40 can also be influenced by the indirect effects of soil pH. For example, in a continuation of the study represented 10 in figure 6-4, the alfalfa was plowed Survival down, and the field was planted to corn Crowns, (over 2 years) 30 year 1 the next 2 years. In the second year of 8 corn, yields were improved substantially as the pH increased. As shown in figure 6-5, yields were 6 20 increased about 21 bushels per acre for every unit increase in pH. The

4 herbicide used on these plots was more effective as the soil pH increased, as a Alfalfa crowns, no./sq. ft. Alfalfa crowns, 10 Crowns, result, some of the yield increase was year 2 2 due to improved weed control. Also, the improved yield and survival of alfalfa at the higher pH levels (figures 0 0 6-3 and 6-4) probably resulted in more 4.9 5.2 5.5 6.0 6.9 7.1 carry-over organic nitrogen being Soil pH released during the second year of corn. Additional research has shown that corn matures more quickly when soil is Figure 6-5. Effect of soil pH on the yield of second-year corn following alfalfa grown in Withee silt loam (Marshfield, WI). adequately limed. Source: Schulte, E.E. 1983. Unpublished data. Other crops also respond to lime. In soybean, the protein concentration 100 increased as well as the yield where lime • was applied (figure 6-6), and on 90 snapbeans grown on a Plainfield loamy sand at Hancock the yield more than • 80 tripled as the soil pH increased from 5.1 to 7.2 (figure 6-7). Part of the 70 snapbean yield increase was attributed • to the effect of pH on root rot organisms. These organisms markedly 60 • reduced the stand when grown in very Corn yield, bu/a acid soils. 50 • • Liming reduces toxic • concentrations of manganese, 40 aluminum, and iron that are possible at • low pH. The concentration of 30 manganese in alfalfa tissue dropped 4.5 5.0 5.5 6.0 6.5 7.0 from 950 ppm at pH 4.9 to 61 ppm at Soil pH pH 7.1 (figure 6-8). The C-6 10/18/05 11:11 AM Page 57

Chapter 6. Soil acidity and liming 57

Figure 6-6. Effect of soil pH on soybean yield and protein (Marshfield, WI). Source: Gritton et al., 1985. Proc. 1985. Fert., Aglime & Pest Mgmt. Conf. 24:43–48. 40

✱ 42 36 Yield ✱ ✱ ✱ • • 32 • • 38 28 Protein ✱• • • ✱ 24 ✱ Yield, bu/a Yield, 34

20 ✱ Protein concentration, % Protein

16 30 4.8 5.2 5.6 6.0 6.4 6.8

Soil pH Figure 6-7. Relationship between soil pH, snapbean yield, and root rot (Hancock, WI). Source: Schulte, E.E. 1987. Proc. Processing Crops Conf. Dept. of Hort., UW-Madison.

7000 Root rot ✱ 70 • • • • ✱ 50 5000 • • ✱ 30 Yield ✱ Yield, lb/a Yield, 3000 ✱✱ • ✱ 10 • % Plants affected, 1000 5.0 5.5 6.0 6.5 7.0 7.5

Figure 6-8. The influence of soil pH on the concentration of Soil pH manganese in alfalfa tissue (Marshfield, WI). Source: Schulte, E.E. 1982. Unpublished data. 1000

800

600

400

200 Concentration of Mn, ppm 0 4.8 5.2 5.8 6.8 7.2 Soil pH C-6 10/18/05 11:11 AM Page 58

58 MANAGEMENT OF WISCONSIN SOILS

concentrations of iron and aluminum Table 6-6 is a list of liming Wisconsin because soils are already did not decrease as dramatically, but materials used to raise soil pH, along high in magnesium. Research has not both were less than one-half of the level with their calcium carbonate (CaCO3) shown this to be true. See chapter 9 for observed at pH 4.9. equivalent. The calcium carbonate a discussion on calcium to magnesium equivalent of a liming material is a ratios. Liming materials measure of the amount of acid a given Hydrated lime and air-slaked lime A liming material in the broadest weight of the material will neutralize are made by heating dolomitic or sense is anything that neutralizes excess compared to pure calcium carbonate. It calcitic limestone in a furnace to drive hydrogen ions and raises the soil pH. is expressed as a percent, with pure off the carbon dioxide. Hydrated lime As such, it must be a base. There is a calcium carbonate being 100%. is burnt lime reacted with water to popular misconception that any Limestone deposits in this state form calcium hydroxide [Ca(OH) ]. calcium compound is a liming material. 2 were laid down 100 to 400 million Upon reaction with carbon dioxide While it is true that most common years ago, when much of Wisconsin from the air, hydrated lime will form liming materials contain calcium, not was covered by a shallow sea. The most air-slaked lime, a mixture of calcium all calcium compounds are liming common and least expensive liming hydroxide and calcium carbonate. materials. material in Wisconsin is dolomitic Hydrated and air-slaked lime are very Gypsum (CaSO ), for example, is 4 limestone. It contains calcium and soluble compared to dolomitic not a liming material. Gypsum is a salt magnesium in roughly the proportions limestone, so it’s possible to overlime of calcium hydroxide [Ca(OH) ] and 2 needed by most crops. In states where with these materials, especially in sandy sulfuric acid (H SO ). Adding gypsum 2 4 calcitic lime (calcium carbonate) is the soils. to soil will actually lower soil pH principal liming material, magnesium Marl is a mixture of calcareous slightly (about 0.3 pH unit) because deficiency is a potential problem. Some shells and mud deposited in wetlands the calcium ions (Ca++) will force some agri-businesses have suggested that where mollusks were active when these hydrogen (H+) ions held on the surface calcitic lime should be used in soils were formed. The composition of soil particles into soil solution.

Table 6-6. Liming materials and their calcium carbonate (CaCO3) equivalent.

CaCO3 equivalent Liming material Neutralizing agent of pure material (%)

Dolomitic limestone CaCO3•MgCO3 110–118

Paper mill lime sludge Mainly CaCO3 *

Marl Mainly CaCO3 variable

Calcitic limestone CaCO3 100

Water treatment lime waste CaCO3 variable

Wood ash K2CO3, CaCO3, MgCO3 20–90

Fly ash CaO, Ca(OH)2, CaCO3 variable

Hydrated lime Ca(OH)2 135

Air-slaked lime Ca(OH)2 + CaCO3 100–135

* According to the Wisconsin Lime Law, 1 cubic yard of papermill lime sludge is equivalent to 1 ton of aglime having a neutralizing index of 60–69. C-6 10/18/05 11:11 AM Page 59

Chapter 6. Soil acidity and liming 59

depends on the amount of silt and clay estimated that the United States How much lime to apply mixed with the shells. produces 100 million tons of fly ash The amount of lime needed to Papermill lime sludge is a annually. Ash from coal containing raise soil pH to a given level depends byproduct of the paper industry. Finely lime will also contain lime. Western on the quality of the liming material ground lime is used in the papermaking coals tend to be relatively high in lime, and the lime requirement of the soil. process. The lime is recovered from whereas southern coals are low. Fly ash Lime quality is judged by how storage pits where excess moisture is made up of silt-sized particles. effectively it raises soil pH to a drains away. It is handled and spread Because of its fine size, fly ash reacts desirable level within 3 years. Two while still moist. Since the moisture quickly, but it is difficult to spread. properties of lime govern its quality: content varies, it is sold and applied on Some fly ash can be moistened to ■ purity (% CaCO equivalent) a volume basis with 1 cubic yard of improve spreadability, but others set up 3 ■ papermill lime sludge equivalent to like concrete when moistened. In fact, fineness (particle size) 1 ton of aglime having a neutralizing most of the fly ash generated by the The time required to neutralize an index of 60–69. Columbia Power Facility near Portage, acid soil depends largely on the size of Wood ash was one of the first Wisconsin is sold as a cement replacer. the lime particles. Particle size is liming materials used. In addition to In addition to its liming potential, fly measured using mesh screens: the larger carbonates, it contains a significant ash contains significant amounts of the mesh number, the smaller the amount of potash (5 to 30%). The boron, sulfur, and molybdenum. Alfalfa particle that can pass through it. As composition depends on the tree has relatively high requirements for shown in table 6-7, particle sizes species and temperature of combustion. these three nutrients, making fly ash between 8 and 20 mesh are 20% as Some potassium, chlorine, and sulfur ideally suited for alfalfa production—if effective as particles smaller than 60- vaporize at high temperatures. Analysis the spreading problem could be mesh. It takes 5 tons of 8- to 20-mesh of wood ashes from 14 fireplaces in resolved. aglime to make the same pH change as Madison showed calcium carbonate Kiln dust is a byproduct of the 1 ton of less than 60-mesh material. To equivalents ranging from 27 to 93% cement industry, having a calcium give a sense of particle sizes, a window screen is 12- to 14-mesh. So particles and potash (K2O) concentrations from carbonate equivalent of 40 to 100%. 4.6 to 16.3%. If a high-potash wood Like fly ash, the fine particles make fitting through a 60-mesh screen would ash (e.g., 10%) were applied at a spreadability a problem. be about one-fifth the size of the space normal rate for a liming material (e.g., Various municipal water treatment in a window screen. 4 tons per acre), the potash addition plants use lime to purify water. Adding Since purity and fineness are the would be 800 pounds per acre. Thus, slaked lime to the water raises the pH primary factors in determining wood ash should be applied on the above 11, high enough to kill limestone quality, its relative basis of its potash content, not pathogens. Waste lime and other by- effectiveness in changing soil pH can primarily as a liming material. products from treatment plants have be reduced to a single numerical figure. Fly ash is the ash from the exhaust variable compositions, so they need to This figure is called the neutralizing stream of coal-burning plants. It is be tested before use. index (NI). A smaller number indicates a less efficient liming material. The NI

Table 6-7. Lime effectiveness over 3-year period.

————— Particle size (mesh) ————— Coarser Finer than 8 8–20 20–60 than 60

———— % of lime reacted ————

Percent effectiveness 0 20 60 100 C-6 10/18/05 11:11 AM Page 60

60 MANAGEMENT OF WISCONSIN SOILS

for most Wisconsin aglime ranges in When comparing the relative soil Lime recommendations need to be value from 40 to over 100 and is neutralizing ability of the two lime adjusted to account for differences in calculated using the following materials in the examples above, lime A lime quality. Use the aglime conversion equation: (NI = 53.2) is less efficient than lime B data in table 6-8 to determine how NI = [(% 8–20 mesh x 0.2) + (NI = 60.3) even though lime A has a much to apply. For example, if you (% 20–60 mesh x 0.6) + (% less higher calcium carbonate equivalent receive a recommendation from a soil than lime B (95% vs. 90%). Therefore, test report for 4.0 ton/a of 60–69 than 60 mesh x 1.0)] x % CaCO3 equivalent. it would take more of lime A to raise aglime, you would need 4.7 ton/a of the soil pH to the desired level in the 50–59 lime, or 3.5 ton/a of 70–79 Two examples follow: same period of time. lime. Usually the price of lime increases as the neutralizing index increases Example I: Lime A (95% calcium carbonate equivalent). because more energy is required to grind limestone finer. The cost of 4.7 Screen size Screen analysis Effectiveness factor tons of 50–59 lime, for example, may

% be the same or less than 4.0 tons of 60–69 lime. The 50–59 lime will give greater than 8 mesh 10.0 x 0.0 = 0.0 the same soil pH as the 60–69 and— because it has larger particles—will 8 to 20 mesh 30.0 x 0.2 = 6.0 continue to neutralize soil acidity 20 to 60 mesh 25.0 x 0.6 = 15.0 beyond 3 years. Lime requirement in Wisconsin less than 60 mesh 35.0 x 1.0 = 35.0 soil testing labs is calculated from estimates of reserve acidity, using soil Total = 56.0 organic matter and buffer pH. Organic NI = 56.0 x 95% = 53.2 matter is estimated by loss of weight when a soil sample is heated to 360°C. The buffer pH is a measurement of Example 2: Lime B (90% calcium carbonate equivalent). how much the soil reduces the pH of a solution that is buffered at pH 7.5. Screen size Screen analysis Effectiveness factor (Reserve acidity lowers the pH of the % soil-buffer mixture.) The pH of the soil in water (water pH or active acidity) is greater than 8 mesh 5.0 x 0.0 = 0.0 also measured to determine whether aglime is needed in the first place and, 8 to 20 mesh 25.0 x 0.2 = 5.0 if so, how much the soil pH must be 20 to 60 mesh 20.0 x 0.6 = 12.0 raised for the crops to be grown. An accurate lime recommendation cannot less than 60 mesh 50.0 x 1.0 = 50.0

Total = 67.0 NI = 67.0 x 90% = 60.3 C-6 10/18/05 11:11 AM Page 61

Chapter 6. Soil acidity and liming 61

Table 6-8. Aglime conversion table for different neutralizing index zones.

Lime Zones of lime quality according to neutralizing index values recommendationa 40–49 50–59 60–69 70–79 80–89 90–99 100–109+

(ton/a) ——————————————— ton/a lime to apply —————————————

1 1.4 1.2 1.0 0.9 0.8 0.7 0.6

2 2.9 2.4 2.0 1.7 1.5 1.4 1.2

3 4.3 3.5 3.0 2.6 2.3 2.1 1.9

4 5.8 4.7 4.0 3.5 3.1 2.7 2.5

5 7.2 5.9 5.0 4.3 3.8 3.4 3.1

6 8.7 7.1 6.0 5.2 4.6 4.1 3.7

7 10.1 8.3 7.0 6.1 5.4 4.8 4.3

8 11.6 9.5 8.0 6.9 6.1 5.5 5.0

9 13.0 10.6 9.0 7.8 6.9 6.2 5.6

10 14.4 11.8 10.0 8.7 7.6 6.8 6.2

a Soil test recommendations are made for lime having a neutralizing index zone of 60–69. To convert a recommendation to a liming material with a different grade, read across the table to the appropriate column.

be made with a water pH measurement More explanation of how the lime Table 6-9. Multipliers used to alone because it only measures the requirement is calculated for several adjust lime recommendations based on tillage depth. active acidity. Water pH does not target pH levels is given in Extension measure reserve acidity; that is, the publication Soil Test Recommendations Tillage depth hydrogen bonded to clay and organic for Field, Vegetable and Fruit Crops (inches) Multiplier matter. (A2809). The lime requirement is calculated Standard recommendations are <7.1 1.00 using loss of weight on heating to based on liming the soil to a depth of 7 7.1–8.0 1.15 360°C, buffer pH, and water pH. As inches or less. If tillage is deeper than 7 an example, the amount of aglime (NI inches, more lime will be needed to 8.1–9.0 1.31 of 60–69) needed to raise the water pH neutralize the entire tilled layer. To from 5.8 to 6.3 in a soil with a weight calculate how much more lime to add, >9.0 1.46 loss upon heating of 3.3% and a buffer use the appropriate multiplier pH of 6.0 would be as follows: (table 6-9) to adjust the formula.

Lime required = 1.75 [1.20(6.3 – soil pH)(% weight loss) + 0.030 (buffer pH)]

= 1.75 [1.20(6.3–5.8)(3.3) + 0.030(6.0)]

= 1.75 [1.98 + 0.18] = 4 ton/a C-6 10/18/05 11:12 AM Page 62

62 MANAGEMENT OF WISCONSIN SOILS

When to apply aglime Method of tillage. Where lime Soil. Aglime can be applied any The proper time to apply aglime is incorporation is not possible, such as in time the soils are physically fit and determined by five factors: the crops to no-till grass-legume pastures, apply as spreading equipment doesn’t damage be grown, tillage method, lime particle fine a grade as possible at least 1 year soils or crops. Sample your soils every size, soil type, and convenience. before the seeding. 4 years to determine whether lime is Crops to be grown. In Lime particle size. Wisconsin needed. If required, apply aglime, disk, Wisconsin, soil is limed to the aglimes have coarse as well as fine and plow it under well in advance of optimum pH for the most sensitive particles which react with soil acids at seeding. Lime’s effectiveness begins crop in the rotation. Because lime different rates. The mesh rating when it is incorporated into the soil. If reacts very slowly with soil acids, it indicates the particle size of the lime: possible, don’t apply aglime where wind should be applied at least 1 year the smaller the mesh number, the or water erosion will remove it before it (preferably longer) before seeding coarser the aglime. Table 6-10 shows can be incorporated. alfalfa or other legumes. In many cases, that finer (60–100 mesh) aglime Soils can be limed in the summer, the best time to apply lime is when the particles result in a higher soil pH than even prior to harvest of another cutting crop rotation is coming out of alfalfa. coarser sizes over similar time periods. or two of forage. At that time, the soil This provides more time for reaction Fine particles begin neutralizing acids is in excellent condition to bear the and may result in two or three immediately, while coarser particles weight of a lime spreader. Soils with remixings of the lime with the soil. The continue the process after fine particles high buffering capacities (high clay pH will then be raised to the desired have dissolved. Consequently, coarse and/or high organic matter content) level by the time the rotation is aglime must be applied further in should be limed more in advance of the returned to alfalfa. advance than fine aglime to achieve the sensitive crop than coarser-textured Aglime applied immediately before same pH change. soils. These soils require more seeding a legume may not benefit the Coarse aglime must be applied at redistribution of lime particles to new seeding. This may result in a poor somewhat higher rates but is usually neutralize the entire plow layer. stand and reduced forage yield and less expensive per ton than fine lime. In Convenience. Fall and summer quality, particularly if the soil is initially addition, it may not be necessary to may be the most convenient times for quite acid. Topdressing the stand after relime as often where some coarse lime applying aglime. In the spring, long it is established may serve as a stopgap is used. When comparing prices, be waits for aglime can occur, there may measure but is not as effective as sure to evaluate materials on the basis be weight limitations on the roads, or neutralizing the entire plow layer. of amounts of lime needed to achieve the soil may be too wet to spread the similar effectiveness. aglime before it is time to plant. These problems can be avoided by applying Table 6-10. Soil pH when treated with three particle aglime on cropland in the fall or on hay sizes of aglime (Arlington, WI)a. fields in summer. Lime is not lost by leaching, and it will have more time to Time Particle size (mesh) neutralize soil acids. (months) 8–20 40–60 60–100 Other factors to consider ——————— soil pH ——————— Unlike fertilizer, aglime may not 1 5.00 5.35 5.43 promote increased plant growth immediately after application. This 12 5.65 5.96 6.19 doesn’t mean aglime is not needed—it simply takes effect more slowly. Also 24 5.91 6.33 6.37 unlike fertilizer, once a soil is limed 36 6.30 6.54 6.65 adequately, it may remain that way for several years without additional aglime aOriginal soil pH = 4.6; Plano silt loam. applications. In fact, once a pH of 6.5 C-6 10/18/05 11:12 AM Page 63

Chapter 6. Soil acidity and liming 63

to 7.0 is achieved, it is often 5 to 10 redistributes the lime particles, bringing reduces the scab problem on potatoes. years before an application of lime is them into contact with more acid soil. Elemental sulfur is the most commonly required again. The reasons for this are Therefore, it is important to used material to lower the soil pH, but the low solubility of limestone, the slow incorporate any needed lime it must be oxidized by bacteria in order dissolution of larger lime particles thoroughly before switching to a to cause this change. The reaction applied in prior applications, and the reduced tillage system. which increases soil acidity is as follows:

use of barn lime. Dairy farmers often In some instances, application of + = 2S + 3O2 + 2H2O —— > 4H + 2SO4 add some lime to their soils as barn the recommended amount of lime will sulfur oxygen water hydrogen sulfateion ion lime mixed with the manure. This not completely neutralize an acid soil. contribution, along with the coarse, This problem is commonly caused by slowly dissolving limestone particles poor incorporation or by not allowing previously applied, tends to maintain enough time for the lime to react. the soil pH over several years. Another reason why a soil might still be Table 6-11 shows how much sulfur Neutralizing soil acidity only acid after applying lime is deep is required to lower the pH of a occurs in the solution surrounding each plowing. The standard lime medium-textured soil. limestone particle because aglime is too recommendations are calculated for a Since bacterial action is required, insoluble to dissolve completely. The 7-inch plow layer. Thus, when a soil is the pH change occurs slowly. Apply no rate of the neutralization reaction plowed deeper than 7 inches, more than 500 pounds of sulfur per depends on how fast hydrogen ions can proportionally more lime will be acre at any one time. Test the soil move toward the lime particle, how fast required. between each application to make sure calcium and bicarbonate ions can move the pH is not lowered more than Correcting soil alkalinity away from the lime particle, and the desired. Except in small-scale plantings number of lime particles in a given At soil pH levels above 7.5, free (home gardens) and special crops, it is volume of soil. In other words, the calcium carbonate is usually found in not economically feasible to lower the finer the particles and the more evenly Wisconsin soils. If free calcium pH of an alkaline soil. For field crops they’re distributed throughout the soil, carbonate is present, it probably will the cost of the treatment will usually the faster the lime will react. If lime is not be feasible to acidify the soil exceed the value of any yield increases. mixed thoroughly with the soil, the soil because very large amounts of sulfur Occasionally, however, the pH of pH will rise within a few weeks after would be required. the soil should be lowered for certain liming. After that the pH increases very Aluminum and iron sulfates can special crops. Blueberries and some slowly until another tillage operation also be used to acidify soils in lawns or ornamentals need high levels of iron gardens. Unlike elemental sulfur, their and manganese so they must be grown effect is immediate. It requires about on very acid soils. Also, soil acidity six times more of these materials to

Table 6-11. Approximate amount of finely ground elemental sulfur needed to increase soil acidity (lower pH).

Desired Soil organic matter content (%) change in pH 0.5–2.0 2.0–4.0 4.0–6.0 6.0–8.0 8.0–10.0 >10.0

—————————— amount of sulfur needed, lb/a ——————————

0.25 250 750 1200 1700 2300 2100

0.5 500 1500 2500 3500 4600 5500

1.0 1000 3000 5000 7000 9200 11000 C-6 10/18/05 11:12 AM Page 64

64 MANAGEMENT OF WISCONSIN SOILS

change the pH as compared to sulfur. Because too much aluminum and iron Questions can be toxic to plants, do not apply more than 50 pounds per 1,000 square 1. What influence does soil pH have spread product B, which is the feet. on chemical and biolgical better buy? reactions? Acid peat moss usually has a pH of 9. Assume that two different liming 4.5 or less and is a good material to mix 2. List several ways by which soils materials have a neutralizing index with lawn or garden soils to make them become acid. of 60–69 and 90–99 and that the more acid. It also adds organic matter. cost of these materials is $9.00/ton 3. What is the difference between It is convenient to use on small garden and $18.00/ton, respectively. active acidity and reserve acidity? areas and for potting soil. It may make Which material is the better buy? up one-fourth the volume of potting Which of these forms is measured soil, depending on the pH of the soil when the soil is analyzed for its pH 10. When a field is to be limed in April with which it is mixed and the pH in water? and seeded in May, lime with a neutralizing index of 90–99 or requirement of the plants to be grown, 4. Is lime requirement more closely 100–109 is recommended rather On gardens, apply 1 to 2 inches on the associated with the active acidity or than lime with an index of 60–69. surface and spade or rototill to mix it in. the reserve acidity? Explain. As noted previously, fertilizers Why? 5. List several benefits of liming. containing ammonium nitrogen are 11 . How many tons of lime would be acid-forming. Ammonium sulfate is the 6. Explain why calcium carbonate required to raise the pH of the most acidifying per pound of nitrogen (CaCO3) will neutralize soil following soils to 6.3? (Use the applied. Ammonium sulfate (21-0-0) is acidity but calcium sulfate formula given on page 61.) the best nitrogen fertilizer for (CaSO4) will not. maintaining an acid soil, as with Water Buffer Weight blueberries, cranberries, and 7. A soil test recommendation calls Soila pH pH loss (%) hydrangeas. for 4 ton/a of 60–69 aglime. How much 40–49 aglime would be Plano 6.0 6.6 4.0 required? 70–79 aglime? 90–99 aglime? Fayette 5.8 6.7 1.5 8. An aglime vendor had samples of Tama 5.8 6.0 3.5 two of products tested, with the aAssume that all soils are plowed at a depth following results: of 7 inches.

Screen Screen analysis size (mesh) A B 12 . Assume that a field has a pH of 5.2 and is being cropped in a corn- ———%——— oats-alfalfa-alfalfa-alfalfa rotation. less than 8 5.0 2.0 When would be the best time to lime this field? Why? 8–20 20.4 4.5 13 . When an acid soil is limed in April 20–60 57.3 25.6 and seeded in May, the new alfalfa seeding sometimes fails to survive greater than 60 17.3 67.9 due to soil acidity. Explain how this can happen. CaCO3 equivalence 98.0 93.0 14 . Under what conditions would you What is the neutralizing index of recommend that the pH of a soil each product? If it costs $12/ton to should be lowered from 7.3 to 4.5? spread product A and $15/ton to How would you accomplish this? C-7 10/18/05 11:12 AM Page 65

CHAPTER 7 65 Biological properties of soil

Fertile soils are biologically active. environmental conditions limit growth This means they support the growth of of these beneficial organisms, crop a wide variety of microscopic plants yields can suffer. Factors favoring and soil animals, as well as terrestrial biological activity include the following: “The series of biophysical plants. Most soil organisms are ■ Food supply—soil organic matter beneficial, but some can cause plant and plant residues supply food and and biochemical processes disease or physical damage to the soil energy for most soil organisms. that follow [weathering] (e.g., excessive burrowing by rodents). Terrestrial plants obtain energy from Soil organisms range in size from the sun but depend on the soil for ultimately reorganize the microscopic, single-celled plants to nutrients. large burrowing animals. Immense initially haphazard mineral ■ Favorable temperature—each numbers of organisms live in fertile organism has an optimum constituents into a distinct, soils. A gram of such soil, for example, temperature range, above or below can contain more than 500 million internally ordered, living which its activity diminishes. microorganisms. natural body. This final Another important characteristic ■ Aeration—most organisms in metamorphosis is brought of a biologically active soil is the cycling cropped soils require adequate of carbon and several plant nutrients, aeration to supply oxygen. about by the activity and the such as nitrogen, phosphorus and ■ Favorable moisture—all organisms accumulated organic products sulfur, through plants and soil-dwelling require water. If soil is too dry, animals. These chemical elements are growth slows, and some organisms of myriad microscopic and in constant flux: they cycle from may die. If soil is too wet, aeration is macroscopic plants and decaying organic residue, to actively reduced. growing plants and animals, and back ■ Favorable pH—Each organism has animals which coinhabit again to decomposing organic matter. an optimum pH range in which it The information presented in this the soil as an integrated functions best. Some prefer acid chapter is concerned with animals or soils, but most do best in neutral or community.” microscopic plants living within the slightly alkaline soils. soil. Other chapters deal with the Daniel J. Hillel, Out of the Earth, 1991 growth of crops and native plants. ■ Absence of toxic substances—soil For organisms to grow and must be free of toxic substances for multiply in the soil, they must have organisms to thrive. Some organisms favorable environmental conditions. An produce toxins to help them environment that favors growth in one compete with other organisms. group of organisms may limit growth in People also introduce potentially another group. Some crops rely on toxic substances such as pesticides, interactions with organisms for heavy metals, salts and gases. Some optimum production. When are added deliberately, others inadvertently. C-7 10/18/05 11:12 AM Page 66

66 MANAGEMENT OF WISCONSIN SOILS

by digesting cellulose, the material that Mammals Soil fauna makes up cell walls of plants. Mammals burrow into soil for shelter, mixing soil and promoting Fauna refers to animals, including Earthworms aeration. They influence a relatively insects, as opposed to flora or plant life. Earthworms are very important in small portion of the total root zone. The main groups include arthropods, mixing soil and incorporating dead or Some feed on plant roots or eat seeds, mollusks, earthworms, protozoa, decaying plant remains. They have a damaging crops. Mammals of nematodes, and mammals. voracious appetite, consuming as much importance in soil include badgers, as 80 times their body weight of food Arthropods chipmunks, gophers, ground squirrels, per day. Their burrowing activity These invertebrate organisms mice, moles, prairie dogs, rabbits, improves aeration, water infiltration, include insects, spiders, and shrews, and voles. crustaceans. Arthropods have a jointed and drainage. They are most numerous body and limbs and a hard (chitinous) in undisturbed areas such as no-till shell. Microscopic forms important in corn fields, pastures, and deciduous Soil flora forests where there is an abundant soils include springtails and mites— Four principal groups of supply of litter and burrows are not both of which feed on fungi. Some microscopic plants in soil are the algae, disrupted by tillage. Some 1 to 1.5 mites also feed on other soil animals. bacteria, actinomycetes, and fungi. Larger arthropods include wood million earthworms per acre were lice, centipedes, millipedes, beetles and found in two productive Danish forest Algae other insects, and spiders. Wood lice soils. Collectively, they weighed in at Algae are the most numerous and feed on decaying plant material and are 1500 to 1750 pounds per acre. In an widely distributed of green plants, active in soil too dry for earthworms. English apple orchard, an average of excluding flowering plants. These Centipedes are predators on other soil 15.5 earthworm burrows per square multicellular organisms are found in fauna. Millipedes feed on decaying yard were found. This was estimated to fresh water, sea water, on land, in hot litter, although some feed on roots of be equivalent to one 1.4-inch drainage springs, and on arctic snows. They are living plants. A wide range of insects pipe per square yard. the primary food of aquatic animals. inhabit soil. Most insects burrow, an Protozoa Most species are photosynthetic, producing food from carbon dioxide activity that often improves aeration Protozoa are microscopic one- (CO ) with energy from light. and water infiltration. Some are more celled animals abundant in soils. Most 2 Therefore, they are important only near important in the larval stages. protozoa feed on soil fauna such as the soil surface where light is adequate. Wireworms, for example, are the larval bacteria and other protozoa. Some They are of greater significance in form of certain beetles and feed on plant bacteria apparently have a symbiotic aquatic environments such as rice roots. Ants feed on green vegetation, relationship with predatory protozoa. paddies and swamps. A gram of fertile other fauna, and some species feed on Soil protozoa live in the film of water soil contains 1,000 to 500,000 algae. seeds. In tropical and subtropical soils, surrounding soil particles. Protozoa termites are prominent in consuming have different ways of surviving dry Bacteria dead plant remains. Some species are periods: most form cysts while others Bacteria are one-celled organisms notorious for building huge mounds go into a state of suspended animation. and occur in a wide variety of species. and destroying timber in buildings. They revive quickly when moisture Fertile soils may contain over Mollusks returns. 500 million bacteria per gram Important soil mollusks include Nematodes (400 pounds per acre). They are active in organic matter decomposition and slugs and snails. Slugs feed on dead or Nematodes or eelworms are mineral transformations. Bacterial damaged vegetation. Some feed on microscopic worms. Many species populations increase rapidly when food succulent fruits and vegetables growing parasitize plant roots. Not all (fresh organic residues) is available, on or near the soil surface. A few species nematodes are parasites: some free- then decline as the supply runs out. of snails help to decompose plant matter living species feed on bacteria, protozoa, and other nematodes. C-7 10/18/05 11:12 AM Page 67

Chapter 7. Biological properties of soil 67

Actinomycetes associated with nearly all plants. But, within or between the root cells of the Actinomycetes are one-celled, plants with fine roots or root hairs, host plant. This type is found on many filamentous organisms. Most species such as grasses, are not nearly as plant species, including grasses. thrive between pH 6.0 and 7.5. dependent on mycorrhiza as those with Actinomycetes give freshly plowed soil tap roots, such as many trees. Most of its characteristic earthy odor. A gram of these relationships are symbiotic—the Carbon cycle fertile soil may contain as many as host plant provides soluble All organisms—including people 15 million actinomycetes (500 pounds carbohydrates to the root fungus, and and animals—require food for energy per acre). Some species are pathogenic the latter aids the host in nutrient and carbon for building body tissue. to plants and animals. Potato scab, for uptake, especially phosphorus. For most, the same food serves both example, is caused by a species of Mycorrhiza can be thought of as an purposes. Green plants, however, use actinomycete but can be controlled by extension of the plant’s root system. different sources of food for these two keeping the soil pH below 5.3. Mycorrhizal plants are sometimes more purposes. They obtain carbon from Tuberculosis is an example of a human drought tolerant, and they also protect carbon dioxide (CO2) and energy from disease caused by an actinomycete. the plant from plant pathogens and sunlight. Most other organisms obtain nematodes. Fungi carbon by eating green plants or eating There are two general types of animals that have eaten these plants. Fungi (yeasts, molds, mushrooms) mycorrhiza. In one type, the small Some of the food is “burned” to are multicellular, filamentous roots of the host plant are completely provide energy. Only about 20% of the organisms capable of vigorous encased in a sheath of fungal tissue. carbon in food is converted to cellular development, especially in acid soil. Filaments of fungal tissue extend tissue; the rest is respired as carbon There can be as many as 1 million outward into the soil like root hairs. dioxide. fungi per gram of fertile soil, weighing Other filaments penetrate the outer A simplified carbon cycle is shown about 1000 pounds per acre. This cells of the plant roots. This type is in figure 7-1. The carbon in diverse group of organisms fills many common on forest trees in temperate atmospheric carbon dioxide is niches in the ecosystem. The hairlike regions. In the other type, there is no incorporated into plant tissue by projections or filaments of fungi help external sheath of fungal tissue. Fungal photosynthesis. Plants may be hold soil aggregates together. Fungi filaments are partly external and partly consumed by animals or returned to secrete organic compounds which aid in the extraction of nutrients from rocks and organic matter. Some fungi Figure 7-1. The carbon cycle in soil. produce antibiotics and other sun CO compounds useful as pharmaceuticals. (energy) 2 Penicillin, for example, was isolated (0.04% in atmosphere) from soil fungi at the University of Wisconsin in the 1940s. A lichen is a complex plant photosynthesis plant and animal consisting of a fungus and an algae respiration growing together symbiotically. The alga synthesizes carbohydrates from crop harvest carbon dioxide (CO ) by 2 erosion photosynthesis and, in return for the root respiration, decomposition of carbon, the fungus extracts nutrients soil organic matter from the growth medium, which may plant and animal be rock, bark, or soil. residues Mycorrhiza are fungi that infect C plant roots. Mycorrhizal fungi are (carbon in soil organic matter) C-7 10/18/05 11:12 AM Page 68

68 MANAGEMENT OF WISCONSIN SOILS

the soil as residue. If eaten, most of the high. When warm currents lower the carbon is returned to the atmosphere as solubility level of calcium and Symbiotic carbon dioxide via animal respiration magnesium carbonate, these materials relationships or to the soil as animal waste. A small precipitate to form limestone. Other The term symbiosis describes the percentage is retained in milk and reservoirs of carbon include coal relationship between two organisms animal tissue. That carbon returns to deposits, petroleum, organic soils, and living in close association, usually to the cycle when the animal products are forests. the mutual benefit of each. A well- eaten by another animal. If the animal known example is the association of dies, most of the carbon incorporated Rhizobium bacteria with roots of into its tissue returns to the atmosphere Oxygen leguminous plants. The bacteria infect as the carcass decomposes. requirements the roots, and the roots encapsulate the The smaller animals and All organisms must respire; that is, bacteria in growths called nodules. microorganisms that cause they must use some source of energy to Within these nodules, the Rhizobia con- decomposition also give off carbon support their growth and development. vert nitrogen gas from the atmosphere dioxide in respiration and retain some Aerobic organisms require free oxygen into organic nitrogen for the host plant. carbon in their cells. The respired (O ). A good example of aerobic In exchange, the host plant provides carbon dioxide returns to the 2 respiration is the breakdown of glucose, the bacteria with organic carbon and atmosphere where it can be recycled a simple sugar, into carbon dioxide and mineral nutrients. Researchers estimate into new plant growth. water, with the release of energy: that Rhizobia annually fix as much as Microorganisms constantly 300 pounds of nitrogen per acre. produce carbon dioxide. Since it’s

heavier than air, the concentration of C6H12O6 + 6O2 ——> 6CO2 + 6H2O + energy (673 kcal) carbon dioxide carbon dioxide below ground is about glucose oxygen water 10 times higher than it is above ground. Some of this carbon dioxide dissolves in soil moisture to form carbonic acid. If the concentration of Anaerobic organisms can respire carbonic acid and soluble calcium are only in the absence of oxygen (O2), but high enough, calcium carbonate much less energy is obtained as compared to aerobic respiration. (CaCO3) may precipitate, removing the carbon dioxide from the cycle. Alcohol, for example, is the result of an Unlike most chemical solubilities, anaerobic process. The chemical the solubility of carbon dioxide in reaction below shows the fermentation water decreases as the temperature of sugar to produce alcohol. This increases. (That is one reason for reaction produces only 21 kcal of keeping carbonated beverages cold.) energy, as compared to 673 kcal for the The ocean is a vast reservoir of aerobic reaction. dissolved carbon dioxide and inorganic ions such as calcium (Ca++) and C6H12O6 ——->2C2H5OH + 2CO2 + energy (21 kcal) magnesium (Mg++). In cold ocean glucose ethanol carbon dioxide water, carbon dioxide solubility is very C-7 10/18/05 11:12 AM Page 69

Chapter 7. Biological properties of soil 69

roots. Organic compounds identified in Role of Plant roots root exudates include sugars, amino microorganisms Roots extract plant nutrients and acids, organic acids, and enzymes. For in nutrient water from soil. At the same time, they example, wheat exudes 2.6 to 22.5 mg secrete carbon dioxide and organic of carbon per plant during the first transformations compounds that serve as food for 2 months of growth. Carbon is a Soil organisms break down organic microorganisms. When the roots die, component of one of the organic matter, releasing the nutrients for use they become food for soil flora and compounds previously noted. The root by growing plants. Macroorganisms, fauna. After a dead root has decayed, zone immediately behind the root tip such as earthworms, are important in the root channel becomes a conduit for appears to be the major source of the initial decomposition process, air, water, and new roots. Thus, plant exudates. digesting large particles and secreting roots help shape the biological Microorganisms in the rhizosphere products which microorganisms properties of soil. seem to have some influence on decompose further. Ultimately, Soil microbiologists have observed nutrient availability, but their effect is nutrients are returned to their that larger numbers and types of still under study. Most of the past inorganic state, the form taken up by bacteria, fungi, and other organisms are research has concentrated on plants. Conversion of organic forms of found around plant roots than in the pathogenic organisms in the nutrients to inorganic is termed surrounding soil. This zone of soil near rhizosphere. In Russia a seed inoculant mineralization. plant roots is known as the rhizosphere. (Azotobacter chroococcum) to improve In addition to mineralization of Table 7-2 shows the distribution of nutrient availability has been only organic matter, soil microorganisms are several microorganisms with distances marginally successful. While involved in many nutrient from the root surface. In this study, the microorganisms in the rhizosphere transformation reactions. Most rhizosphere extended to 18 mm appear to increase crop yields, the reactions involving nitrogen, for (0.7 inch) from the root. connection is not fully understood. example, are mediated by High populations of More study is needed. microorganisms. Transformations of microorganisms in the rhizosphere are phosphorus, iron, manganese, and due to a greater supply of readily sulfur are also influenced by available organic material. This microorganisms. These reactions are material ranges from decaying roots to discussed in chapter 9. organic exudates (leakage) from healthy

Table 7-2. Microorganisms in the rhizosphere of 18-day-old blue lupine seedlings.

Distance from root Bacteria Streptomycetes Fungi

mm ————— 1000s per gram of dry soil —————

0 159,000 46,700 355

0–3 49,000 15,500 176

3–6 38,000 11,400 170

9–12 37,400 11,800 130

15–18 34,170 10,100 117

From Papovigas, G.C. and C.B. Davey. 1961. In E.W. Carson (ed.), 1971. The Plant Root and Its Environment, p. 157. Charlottesville. Univ. Press of Virginia. Reprinted by permission of the University Press of Virginia. C-7 10/18/05 11:12 AM Page 70

70 MANAGEMENT OF WISCONSIN SOILS

Questions 1. What benefits result from the decomposition of crop residue and animal wastes? 2. List six factors favoring biological activity in soil. 3. Name ten species of fauna that you have observed in soil. 4. Name at least three useful purposes served by earthworms. 5. In leguminous crops such as alfalfa, the crop benefits from its association with Rhizobium bacteria by receiving organic nitrogen fixed from atmospheric nitrogen by the bacteria. How do the bacteria benefit from this mutual association? 6. Why are alfalfa, soybean, and other leguminous plant seeds usually inoculated? What is in the inoculant that is beneficial to these crops, and how does it work? 7. A culture of photosynthetic blue- green algae is sold for application to soil. The seller claims that adding these algae will reduce the need for fertilizer. Would you buy this product? Why? 8. What are mycorrhiza? How do they benefit plants? 9. Define mineralization. Why is it necessary? 10.Organic soils (mucks and peats) subside when they are drained and farmed. Mineral soils do not subside. Explain why this difference occurs. C-8 10/18/05 11:13 AM Page 71

CHAPTER 8 71 Soil chemistry and plant nutrition

Essential plant lime, commercial fertilizers, or livestock nutrients manure and are not often deficient in soil. They are called secondary nutrients. Green plants have the unique The remaining elements—boron, ability to make everything they need to chlorine, copper, iron, manganese, “Each seed joined the earth, sustain growth from water, light, air, molybdenum, nickel, and zinc—are and an adequate supply of 17 essential entered into some mysterious needed by plants in very small elements. Lack of any one of these partnership with soil, water, quantities, hence they are called elements will hinder growth. Plants get micronutrients or trace elements. carbon, hydrogen, and oxygen from air air and sun and began to The terms primary, secondary, and and water. The remaining 14 elements grow and become part of the micro or trace have nothing to do with come from the soil (although they also the importance of a nutrient in crop living land.” receive small amounts of nitrogen and production. The lack of any one will sulfur from the atmosphere). Table 8-1 reduce crop yield. This concept is Ben Logan, The Land Remembers, 1975 lists all of the essential elements, the stated in the Law of the Minimum, forms taken up by plants, their primary which says that the growth of a plant source, their approximate concentration will be limited by the nutrient present in plants, and amounts in soil. in the least amount relative to its A plant nutrient is considered requirement. essential when a deficiency of the Carbon, hydrogen, and oxygen element makes it impossible for the together make up approximately 94% plant to complete its life cycle, when of the dry weight of plants, yet they are the deficiency cannot be corrected by rarely deficient. Sometimes a lack of substituting another element, and oxygen in poorly drained soils limits when the element is needed by a wide yields, but this is remedied by drainage, variety of species from many different not by adding oxygen. Rapidly growing plant families. greenhouse crops sometimes respond to Of the 14 essential elements an atmosphere enriched with carbon available from the soil, six—nitrogen, dioxide, but adding carbon dioxide to a phosphorus, potassium, calcium, field has never proven to be magnesium, sulfur—are required in economically beneficial. Most of soil relatively large amounts. Nitrogen, fertility, therefore, deals with the phosphorus, and potassium are the 14 remaining elements which make up most commonly deficient nutrients and approximately 6% of the dry weight of are sometimes referred to as the primary plants. nutrients. Calcium, magnesium, and sulfur are often added incidentally in C-8 10/18/05 11:13 AM Page 72

72 MANAGEMENT OF WISCONSIN SOILS

Table 8-1. The essential elements

— Nutrient content of a fertile silt loam — Element Form taken Concentration Amount in and symbol up by plantsa Major source in plants Total Available soil solution

——————— ppm ———————

Structural nutrients Carbon (C) Carbon dioxide Atmosphere 45% — — — (CO2)

Oxygen (O) Air (O2) Atmosphere, 43% — — — Water (H2O) water

Hydrogen (H) Water (H2O) Water 6% — — —

Primary nutrients – Nitrogen (N) Nitrate (NO3 ) Organic matter, 1–6% 2000 5–100 1–50 + Ammonium (NH4 ) atmosphere Phosphorus (P) Phosphate Soil minerals, 0.05–1.0% 1000 20–50 0.01–0.10 – = (H2PO4 , HPO4 ) organic matter Potassium (K) Potassium (K+) Soil minerals 0.3–6.0% 20000 100–150 5–15

Secondary nutrients Calcium (Ca) Calcium (Ca++) Soil minerals 0.1–3.0% 5000 1000–3000 10–100

Magnesium Magnesium Soil minerals 0.05–1.0% 4000 100–1000 5–50 (Mg) (Mg++)

= Sulfur (S) Sulfate (SO4 ) Organic matter, 0.05–1.5% 1000 10–20 1–10 precipitation

Micronutrients Boron (B) Borate Organic matter 2–75 ppm 50 2–10 trace – (H2BO3 ) Manganese Manganese Soil minerals 5–500 ppm 1000 10–20 trace (Mn) (Mn++)

Zinc (Zn) Zinc (Zn++) Soil minerals, 5–100 ppm 50 3–25 trace organic matter

Copper (Cu) Copper (Cu++) Soil minerals, 2–50 ppm 50 No reliable test trace organic matter

Iron (Fe) Iron Soil minerals, 10–1000 ppm 25000 No reliable test trace (Fe++, Fe+++) organic matter

Molybdenum Molybdate Soil minerals 0.01–10.0 ppm 1 No reliable test trace = (Mo) (MoO4 ) Chlorine Chloride Precipitation 0.05–3.0% 100 No reliable test trace (Cl) (Cl–)

Nickel (Ni) Nickel (Ni++) Soil minerals 0.1–10.0 ppm <50 No reliable test trace

a Other forms of many of these nutrients are present in the soil. This list includes only forms that can be used by plants. C-8 10/18/05 11:13 AM Page 73

Chapter 8. Soil chemistry and plant nutrition 73

charged ion called an anion. Non-essential Properties of Ions with the same charge repel elements chemical one another; ions with opposite charges attract one another to form a chemical An essential plant nutrient is one elements, atoms, bond. This is very similar to the way that is required for life, whereas a non- ions, and salts like poles of magnets repel each other, essential plant nutrient can increase Chemical elements are substances while opposite poles of magnets attract crop yield, but its absence will not that ordinarily cannot be decomposed each other. This relationship is shown cause the plant to die. Enhancing, or or changed into simpler substances. in figure 8-1. The compounds formed beneficial, non-essential elements can Nitrogen, phosphorus, and potassium by the chemical bonds between positive compensate for toxic effects of other are all chemical elements. An atom is and negative ions are termed salts. If elements or may replace mineral the smallest particle of an element these salts have a definite crystalline nutrients in some other function. which has the physical and chemical structure, they are called minerals. Examples of non-essential elements characteristics of that element. Atoms There is always an attraction include aluminum, cadmium, cobalt, are electrically neutral. However, many between positively and negatively lead, mercury, selenium, silicon, and atoms gain or lose electrons (negatively charged ions. However, the intensity of sodium. charged particles) and become the attraction depends on the ions. For Beneficial elements have not been electrically charged ions. If an atom or some salts this attraction is overcome deemed essential for all plants but may group of atoms loses one or more by interaction with water molecules. As be essential for some. The distinction electrons, it becomes a positively a result, these salts dissolve easily and between beneficial and essential is often charged ion called a cation. If an atom readily go into the soil solution. These difficult in the case of some trace or group of atoms gains one or more salts are described as being soluble. elements. Cobalt for instance is electrons, it becomes a negatively Potassium chloride (KCl) and essential for nitrogen fixation in legumes. Silicon, deposited in cell Figure 8-1. Attractive and repulsive forces between chemical walls, has been found to improve heat ions and soil particles are similar to the forces which repel or and drought tolerance and increase attract the opposite or like poles of bar magnets. resistance to insects and fungal

infections. Silicon, acting as a beneficial Like poles of magnets repel each other. element, can help compensate for toxic ➡ ➡ levels of manganese, iron, phosphorus, + – ➡ ➡ – + ➡ ➡ and aluminum as well as zinc deficiency. A more holistic approach to Ions and soil particles with like plant nutrition would not be limited to charges repel each other. ➡ ➡ nutrients essential to survival but soil — ➡ ➡ — would include mineral elements at ➡ ➡ particle levels beneficial for optimum growth. The list of essential elements may well increase in the future to include Opposite poles of magnets attract nutrients that are currently considered each other. ➡ ➡ non-essential. + – ➡ ➡ + – Some non-essential elements can ➡ ➡ become toxic to plants, animals, and Ions and soil particles with humans at high concentrations. Further opposite charges attract each other. discussion on the toxicity potential of ➡ ➡ ➡ ➡ soil non-essential elements can be found in + ➡ ➡ — particle chapter 11. C-8 10/18/05 11:13 AM Page 74

74 MANAGEMENT OF WISCONSIN SOILS

ammonium nitrate (NH4NO3) are Exchange sites on clay examples of soluble salts. In other cases, Sources of plant and organic matter the intensity of the attractive forces nutrients in the The clay and organic matter between ions is too strong to be particles contained in soil exhibit a overcome by the action of water. As a soil negative electrical charge which is a result, these salts dissolve in the soil Soil solution result of the way the component ions solution only slightly and are described Only small amounts of essential making up these particles are linked as being sparingly soluble or relatively plant nutrients are found in soil together. Since opposite charges attract, insoluble. Examples of relatively solution at any one time. Even on the the negatively charged clay and organic insoluble salts include calcium most fertile soils, plants would quickly matter particles attract and hold carbonate (CaCO3) and magnesium die if they had to depend on only the positively charged plant nutrients, such + carbonate (MgCO3), which make up quantity of nutrients in the soil as ammonium (NH4 ), potassium + ++ dolomitic limestone. Most oxides, such solution. Under actual conditions (K ), and calcium (Ca ). Positively as ferric oxide (Fe2O3) and the silicate plants do remove nutrients from the charged plant nutrients attracted to the minerals which make up the skeleton of solution. As these nutrients are negative charges on the soil particles are the soil, are very insoluble. removed from solution, soil reserves called exchangeable. See table 8-1 for a Most plant nutrients in release more nutrients. Hence, the listing of the electrical charges of plant commercial fertilizer are in the form of concentrations of plant nutrients in soil nutrients. moderately to very soluble salts. These solution tend to remain constant. Exchangeable nutrients are held salts dissolve rapidly in soil water to Since some nutrients exist in soil in against leaching but can easily be taken form ions which frequently react with a water soluble form, they are found up by plant roots. In this process an ion other ions or mineral surfaces in soil to primarily in soil solution. These include on a soil particle is exchanged for an form less soluble compounds. – = ion in the soil solution. Figure 8-2 nitrate (NO3 ), sulfate (SO4 ), borate Therefore, the solubility of a fertilizer – – illustrates the process. In this example, (H2BO3 ), and chloride (Cl ). All of before application often bears little these nutrients are negatively charged a potassium ion moves from the soil relationship to the solubility of the new and could be leached below the plant particle to the plant root. The root compound formed after the fertilizer root zone, especially on sandy soils. simultaneously excretes carbon dioxide reacts with the soil. If a nutrient remains very soluble Figure 8-2. Uptake of Plant root after reacting with the soil, as is the case exchangeable nutrients by plants. – with nitrate (NO3 ) salts, it is dissolved completely in the soil water and plants are able to take it up easily. However, it can also be leached more easily than less soluble salts. On the other hand, if the nutrient forms a very stable or insoluble compound, as is the case with most – phosphates (H2PO4 ), only a very small amount of the nutrient remains in soil ++ + solution. The amount of phosphate in Zn Ca++ H solution or in an available form depends Ca++ on the amount of stable phosphates Negatively charged CO2 present. As plants extract the nutrient soil particle + H O from the soil solution, more dissolves K 2 ++ from the stable form. Consequently, the + ++ Ca H CO H Mg 2 3 stable or “fixed” form of phosphorus H+ acts as a nutrient reservoir. – HCO3 C-8 10/18/05 11:13 AM Page 75

Chapter 8. Soil chemistry and plant nutrition 75

■ (CO2) into the soil solution as part of Complexed or chelated Moderate, but not excessive amounts respiration. The carbon dioxide reacts nutrients of soil moisture are present. with water (H2O) to form carbonic Certain types of positively charged ■ The soil pH is above 6.0. acid (H CO ), an unstable compound ions are held very tightly by the organic 2 3 ■ The soil is well-aerated. (Decompo- which splits into a hydrogen ion (H+) matter—much more tightly than sition is much slower in waterlogged and a bicarbonate ion (HCO –). The exchangeable ions are held. They are 3 soils because of a lack of oxygen.) hydrogen ion moves to the negatively said to be complexed or chelated. In Wisconsin, organic matter may charged surface of the soil particle to Copper (Cu++) and zinc (Zn++) are two decompose slowly in the spring because replace the potassium ion. Thus, one nutrients that are usually held as many of our soils remain cool and wet. positively charged ion is exchanged for chelates. As noted in chapter 1, the Therefore, the reserves of nitrogen and another positively charged ion. If a name chelate comes from the Greek phosphorus often are not released fast calcium ion (Ca++) had been exchanged word chele meaning claw. This term is enough to take care of the early growth instead of potassium, two hydrogen quite descriptive as the positively of a spring-seeded crop. For this reason ions would be required because the charged ions are literally held in the starter fertilizer is nearly always calcium ion fills two negative charges center of a negatively charged claw. recommended for corn and other row on the soil particle. Decomposition of organic crops even on fertile soils that could Exchangeable nutrients are a very matter otherwise supply sufficient plant important reservoir of plant nutrients nutrients. in soil. Nearly all of the ammonium, In addition to holding available plant nutrients in an exchangeable potassium, calcium, and magnesium Low-solubility compounds form, organic matter supplies used by plants comes from the Some plant nutrients react with previously unavailable nutrients when exchangeable form. Exchangeable ions in the soil to form extremely stable it is decomposed. Crop residues, nutrients are readily available to plants compounds. These compounds have manure, and other organic materials and, at the same time, are essentially very low solubilities in water. Plant contain considerable amounts of non-leachable. Soils cannot hold an nutrients which form this type of nitrogen, phosphorus, and sulfur and unlimited quantity of positively compound are phosphorus (H PO –), are a good source of most 2 4 charged ions. The amount of cations a molybdate (MoO =), iron (Fe+++) and, micronutrients, particularly boron 4 soil can hold can be measured and is in calcareous soils, manganese (Mn++). (table 8-1). Organic matter is an known as the cation exchange capacity Because of the low solubilities of these important reservoir of these nutrients, (CEC). Silty and clayey soils, for compounds, the concentrations of but organic forms of nutrients generally instance, will hold anywhere from 3 to these nutrients in soil solution are very cannot be used by plants. In order to 10 times more positively charged ions low. Even though it is quite insoluble, change or mineralize these nutrients than sandy soils. However, even the the surface of a stable compound does from an organic form (unavailable) to sands have sufficient “exchange act as a nutrient reservoir. When plants an inorganic form (available), the capacity” to hold all of the positively remove a nutrient like phosphate from organic matter must be decomposed by charged plant nutrients needed by soil solution, some of the phosphate on soil microorganisms. plants in an available but relatively the surface of the stable phosphate Soil microorganisms are non-leachable form. compound will dissolve. Thus, the microscopic living organisms which are concentration of phosphate in solution very sensitive to their environment. In tends to remain constant. Because of general, organic matter decomposition the low concentrations in the soil is hastened when: solution, leaching is rarely a problem ■ The soil temperature is 75° to 90°F. with these nutrients. (Microbial activity is very slow at temperatures below 50°F and decreases above 90°F.) C-8 10/18/05 11:13 AM Page 76

76 MANAGEMENT OF WISCONSIN SOILS

Soil rocks and minerals Large amounts of many plant Questions nutrients are found in soil rocks and 8 minerals. However, these nutrients are 1. List the 17 essential elements and . What is the significance of cation considered to be unavailable because the form each is taken in by plants. exchange capacity in soil? How can they are released much too slowly to Why are these elements said to be the cation exchange capacity of a support plant growth. Good evidence essential? soil be increased? for this is the fact that a soil low in 2. Soil fertility deals mainly with 9. The top 7 inches of soil in an acre available potassium (less than 100 ppm) 14 nutrients that make up only may contain as much as 4,000 lb may contain as much as 20,000 ppm of 5 to 10% of the dry weight of of nitrogen, 2,000 lb of total potassium (table 8-1). plants. The other three essential phosphorus, and 40,000 lb of nutrients are mostly ignored. potassium, yet the field requires Explain. addition of these nutrients to What constitutes obtain good yields. Why? a fertile soil 3. Define the following: a. atom 10.A sandy soil in central Wisconsin A fertile soil is one that has b. element and a silt loam in southern sufficient reserves to maintain a high Wisconsin both test high in c. anion enough concentration of nutrients in available phosphorus and soil solution to permit optimum plant d. cation potassium. If these soils are growth throughout the growing season. e. acid cropped and fertilizer is not An infertile soil cannot maintain a f. base applied, which soil will become sufficient concentration of plant g. salt depleted of its fertility first? Why? nutrients in the soil solution, reducing h. mineral plant growth and, consequently, crop 11.Farmers in Wisconsin usually get yields. For example, the nutrient 4. Which primary nutrient— response to starter fertilizer on reservoir in sandy soils is often quite nitrogen, phosphorus, or corn even when the soil tests high small because these soils contain very potassium—could be leached in phosphorus and potassium. little clay or organic matter as below the root zone if applied in Farmers in central Illinois seldom compared to silty soils. This is one the fall? get response to starter fertilizer on reason why sandy soils are often less high testing soils. What is the 5. Why do potassium or ammonium fertile than silty soils. reason for this difference? leach less easily than nitrate? Why do nitrates leach from soil whereas phosphates don’t, even though both are negatively charged ions? 6. Which essential element can be taken up by plant roots both as an anion and as a cation? 7. Describe the types of soils and the conditions under which potassium may leach into the subsoil. C-9 10/18/05 11:14 AM Page 77

CHAPTER 9 77 Soil and fertilizer sources of plant nutrients

The plant is a marvelous factory give off oxygen (O2), and water (figure 9-1). It combines carbon evaporating from leaf surfaces cools the dioxide (CO2) from the air with water plant on hot days. “...whoever could make two from the soil to make sugar in the To keep this factory operating at ears of corn or two blades of leaves, using solar energy to drive the capacity, the raw materials—soil system. With nutrients taken up from nutrients—must be supplied at rates grass grow upon a spot of the soil, sugar is then converted to equal to plant needs. This chapter ground where only one grew starch, protein, vitamins, oil, and describes each of the nutrients. before, would deserve better numerous other products. The leaves Figure 9-1. The plant factory. Source: Potash & Phosphate Institute. of mankind, and do more essential service to his country, than the whole race of politicians put together.”

Jonathan Swift, Gulliver’s Travels, 1726 C-9 10/18/05 11:14 AM Page 78

78 MANAGEMENT OF WISCONSIN SOILS

Chemical fixation. In the Function in plants Nitrogen manufacture of chemical nitrogen Nitrogen is a major constituent of The atmosphere contains about fertilizer, atmospheric nitrogen (N2) is protein. Plants contain 5 to 25% combined with hydrogen (H ) from protein and protein contains 16 to 78% nitrogen gas (N2). This is the 2 equivalent of more than 30,000 tons natural gas, under heat and pressure in 18% nitrogen. Nitrogen is also found per acre. However, most plants cannot the presence of a catalyst, to form in substantial amounts in chlorophyll, use nitrogen as it exists in the ammonia (NH3). Ammonia can be nucleic acids, enzymes, and many other atmosphere. It must first be converted sold for direct application, or it can be cellular compounds. through biological or chemical fixation. used to manufacture other forms of Nitrogen is mobile within the Biological fixation. Rhizobia nitrogen fertilizer such as ammonium plant. When deficiency occurs nitrogen and other bacteria that live in the roots nitrate (NH4NO3) or urea moves or translocates from the lower of legumes take nitrogen from the air (CO(NH2)2). leaves to the upper leaves. As a result, and fix it in a form that plants can use. the lower leaves first show the This mutually beneficial relationship characteristic yellowing. On corn, the between microorganisms and plants is yellowing starts at the leaf tip and called symbiosis. proceeds up the midrib of the leaf.

Figure 9-2. The nitrogen cycle. Atmospheric ➡ Industrial Removed from cycle N2 Volatilization - fixation➡

NO3 by harvesting NH3

➡ Nitrogen ➡ ➡ ➡ O2 fertilizer ➡ Urea

N2 1. Symbiotic fixation ➡ ➡ (legumes) N2O ➡ NO ➡ Manure Crop residue

Soil organic matter

Plant uptake 2. Ammonification

5. Immobilization 4. Denitrification Ammonium N + NH4

Nitrate N - NO3 3. Nitrification Leaching C-9 10/18/05 11:14 AM Page 79

Chapter 9. Soil and fertilizer sources of plant nutrients 79

Reactions in soils Leguminous plants, like all other the fall following a late-summer Nitrogen exists in many different plants, need nitrogen for growth. If harvest, alfalfa contains 130 to 230 forms. Several physical, chemical, and there is an abundance of plant-available pounds of nitrogen per acre. When biological processes affect its availability nitrogen already in the soil (from legumes decompose, the stored to plants. Collectively, these manure or residual fertilizer, for nitrogen is gradually mineralized or transformations make up the nitrogen example), a legume will use the soil- released in a plant-usable form and cycle, illustrated in figure 9-2. available nitrogen before expending becomes available to the next crop. Soil often contains 2,000 to 6,000 energy for the rhizobia-fixed nitrogen. Figure 9-3 shows the levels of nitrate- – pounds of organic nitrogen per acre in When soil nitrogen is low, however, the nitrogen (NO3 -N) in the soil profile the top 7 inches of soil (about 2 million legume uses rhizobia-fixed nitrogen for of several fields of first-year corn pounds), but almost all of this nitrogen its growth. No matter what its source, following alfalfa. The amount present is combined in stable organic matter nitrogen is incorporated throughout all depends on the density of the previous (humus) which decomposes very slowly parts of the plant; it is not concentrated alfalfa stand, soil texture, and height of and is largely unavailable to plants. only in the root nodules. The amount plants prior to killing the stand, either Research has shown that mineral soils of nitrogen contained in the above- by tillage, herbicide, or winter-kill. in Wisconsin will supply only about ground plant parts is about equal to Alfalfa residue often supplies all of the 25 to 75 pounds of available nitrogen that found in the roots. nitrogen needed by first-year corn. The per acre annually. Available nitrogen Legumes can store substantial suggested reduction in the application can be estimated based on the organic amounts of nitrogen. For example, in of fertilizer nitrogen following various matter content of the soil. About 5% of

the organic matter is nitrogen. Only – Figure 9-3. Soil nitrate-nitrogen (NO3 -N) levels where no nitrogen 1 to 3% of the organic nitrogen is fertilizer has been applied to corn following alfalfa. mineralized (made available) annually. For example, if a soil contains 2% April June organic matter with a nitrogen content 180 of 5%, and if the organic nitrogen 160 mineralizes at a rate of 2% per year, this soil would release annually 40 pounds 140 of available nitrogen per acre. (2% x 2,000,000 lb/a x 5% O.M. x 2% of N 120 mineralized = 0.02 x 2,000,000 x 0.05 x 0.02 = 40 lb/a nitrogen). 100 Symbiotic fixation of nitrogen occurs when legumes such as alfalfa, 80 clovers, soybeans, birdsfoot trefoil, beans, or peas are included in a 60

cropping system. (Reaction 1 in figure Nitrate-N in top foot of soil, lb/a 40 9-2.) Each legume requires association

with a specific Rhizobium bacteria to fix 20 atmospheric nitrogen. As long as the proper bacteria are present in the soil, 0 nitrogen-fixing nodules will form in the Arlington Marshfield Madison Fennimore Wausau roots of these plants as they grow. Wisconsin sites These bacteria are often added to the Source: Bundy et al., 1997. Using Legumes as a Nitrogen Source. soil as an inoculant, usually by coating University of Wisconsin-Extension publication A3517. the seed at planting time. C-9 10/18/05 11:14 AM Page 80

80 MANAGEMENT OF WISCONSIN SOILS

leguminous crops is given in table 9-1. 85°F, good aeration (well-drained soils), form within 1 to 2 weeks of Additional information on the and a pH of 5 to 8. application. With anhydrous ammonia, crediting the nitrogen supplied by Nitrification is the process by nitrification is much slower because the + legume crops can be found in which ammonium-nitrogen (NH4 -N) very high pH in the vicinity of the – Extension publication Using Legumes as is changed to nitrate-nitrogen (NO3 -N) ammonia band will markedly restrict a Nitrogen Source (A3517). by soil bacteria. (See reaction 3 in the activity of nitrifying bacteria. – Ammonification is the figure 9-2.) Nitrate ions (NO3 ) are Within 2 to 6 weeks the pH in the mineralization process by which certain readily available to plants, but they are ammonia band will return to its soil microorganisms change organic negatively charged and remain in soil original level, and nitrification will + nitrogen into ammonium ions (NH4 ). solution. Therefore, they may be proceed. (Reaction 2 in figure 9-2.) Ammonium leached below the root zone with water Denitrification is the process by nitrogen is available to plants but it is as it percolates through the soil. which anaerobic (absence of oxygen) not lost by leaching. The positively Nitrification occurs rapidly under soil bacteria change available nitrate- charged ammonium ions are held in conditions of good aeration, warm soil nitrogen into unavailable atmospheric exchangeable form by the negatively temperatures (60° to 85°F), and nitrogen (reaction 4 in figure 9-2). This charged particles of clay minerals and appropriate soil pH (6.5 to 7.0). When process occurs primarily in poorly soil organic matter. Environmental soil conditions are favorable, most of aerated, waterlogged soils. But, even in conditions enhancing ammonification the ammonium form of nitrogen well-drained soils, some denitrification include soil temperatures of 50° to commonly found in dry or liquid can occur inside dense soil clods that fertilizer will be changed to the nitrate drain very slowly. For denitrification to

Table 9-1. Nitrogen credits for previous legume crops.

Legume crop Nitrogen credit (lb/a) Exceptions

Forages First-year credit: Alfalfa 190 for a good standa Reduce credit by 50 lb/a N on sandy soils.b 160 for a fair standa Reduce credit by 40 lb/a N if plant regrowth 130 for a poor standa was less than 6–10 inches before tillage or plant death.

Birdsfoot trefoil, red clover Use 80% of alfalfa credit Same as alfalfa.

Second-year credit: Fair or good stand 50 No credit on sandy soilsb

Green manure crops Alfalfa 60–100 Use 40 lb/a N credit if field has less than Red clover 50–80 6 inches of growth before tillage. Reduce credit Sweet clover 80–120 by 50 lb/a N on sandy soils.b

Soybean 40 No credit on sandy soilsb

Leguminous vegetable crops Pea, lima, snap bean 20 No credit on sandy soilsb

a A good stand of alfalfa (>70% alfalfa) has more than 4 plants per square foot; a fair stand (30–70% alfalfa) has 1.5–4 plants per square foot; and a poor stand of alfalfa (<30% alfalfa) has fewer than 1.5 plants per square foot. b Sands and loamy sands. Source: L.G. Bundy. 1998. Understanding Plant Nutrients: Soil and Applied Nitrogen. University of Wisconsin-Extension publication A2519. C-9 10/18/05 11:14 AM Page 81

Chapter 9. Soil and fertilizer sources of plant nutrients 81

occur, readily decomposable organic decomposition, crop residues can be not a problem on silty or clayey soils matter must be present as a source of chopped or shredded. Crop residues during the growing season because energy. Because of this energy need about 20 pounds of nitrogen per nitrate seldom moves downward more requirement, little denitrification ton of dry matter to satisfy the than 2 feet. occurs deep in the subsoil or in requirements of the microorganisms Ammonium-nitrogen is held in an groundwater. decomposing the residue. For example, exchangeable form on soil particles and Denitrification takes place very 3 tons of corn stalks would require does not leach below the root zone. rapidly. If water stands on the soil for 60 pounds of nitrogen. Such a nitrogen Nitrate-nitrogen is not held by soil only 2 to 3 days during the growing application would be recommended if particles and can be leached below the season, most of the nitrate-nitrogen these low-nitrogen residues cause root zone. But, this does not necessarily will be lost by denitrification. temporary nitrogen deficiencies to mean that ammonium-nitrogen will be Applications of nitrogen should be occur, especially when the crop to be more effective than nitrate-nitrogen. delayed as long as possible on soils that grown needs additional nitrogen. Ammonium-nitrogen quickly changes often become waterlogged in the However, because of the expense and to nitrate-nitrogen under optimum soil spring. Also, use of a nitrification environmental concerns, nitrogen conditions. As a result, nitrogen loss inhibitor—a material that slows down should not be applied for the sole through leaching can occur even where the nitrification process—can be purpose of speeding up decomposition. nitrogen is initially applied as beneficial when preplant nitrogen is Soil test recommendations take residue ammonium. applied to soils that tend to be conditions into consideration. The On sandy soils where excessive temporarily waterlogged. nitrogen needed to decompose the leaching often occurs, ammonium- Immobilization is the conversion residue is built into the calculation of containing nitrogen fertilizers (e.g., of mineral forms of nitrogen to the nitrogen rate. urea, anhydrous ammonia, ammonium unavailable organic forms. (See reaction In addition to nitrogen losses due sulfate) sometimes do better than 5 in figure 9-2.) For example, to biological transformations such as nitrate-containing nitrogen fertilizers incorporating carbon-rich crop denitrification and immobilization, (e.g., ammonium nitrate). This residues, such as straw or corn stalks, nitrogen can be removed from the crop difference appears when substantial stimulates microbial activity. Available root zone by leaching and rainfall occurs shortly after application. nitrogen is then converted into volatilization. In this case the ammonium nitrogen microbial protein and will remain Leaching is the movement of would not yet be nitrified and would unavailable until the crop residue plant nutrients in the soil solution not be leached as easily as nitrate. decomposes. When the microbes die, below the root zone. Leaching of Organic sources of nitrogen are the nitrogen is again released in an nitrate-nitrogen can be very serious especially beneficial on sandy soils available form. Under ideal weather crop production and water quality because they serve as a reservoir of conditions, release of immobilized problems, especially on sandy soils. nitrogen that is slowly released during nitrogen will begin about 1 month after Since coarse-textured soils retain the growing season. incorporation of the organic matter. only about 1 inch of water per foot of Volatilization is the conversion The addition of nitrogen fertilizer soil, relatively small amounts of rain or of usable nitrogen to ammonia gas. may hasten residue decomposition, but irrigation water can readily move Direct loss of ammonia as a gas can most well-managed soils contain nitrate below the root zone. Well- occur when anhydrous ammonia is enough nitrogen to break down crop drained silty and clayey soils, however, injected into soils that are too wet or residues. The factor limiting commonly hold 2.5 to 3 inches of too dry so that the vapor escapes before decomposition of residues is usually the water per foot of soil, so very rapid the soil seals behind the applicator size of the residue pieces rather than the leaching on these soils occurs only knives. Volatilization can also take amount of nitrogen present. Small when rainfall is abnormally high or place when materials containing urea particles decompose much more nitrogen is over-applied. When rainfall (manure and other organic wastes; rapidly than large particles. To speed is normal or below normal, leaching is fertilizers such as urea, 28% nitrogen C-9 10/18/05 11:14 AM Page 82

82 MANAGEMENT OF WISCONSIN SOILS

solutions, and some mixed fertilizers) Nitrogen fertilizers. Many this gas in case eyes or mucous are applied to the soil surface and are different chemical and physical forms membranes are exposed to the vapors. not incorporated (table 9-2). of nitrogen fertilizer are available. If UAN (urea-ammonium nitrate) or Immediate incorporation of these properly applied, the various forms are pressureless nitrogen solutions are made materials eliminates volatilization equally effective, although one form by mixing roughly equal amounts of losses. Rainfall (as little as 0.2 inch) may have an advantage over another ammonium nitrate and urea in water to within 2 days after surface application under certain conditions. Table 9-3 lists form a fertilizer containing 28% or of urea-containing materials will greatly the general characteristics of the 32% nitrogen. Since the nitrogen in reduce or eliminate volatilization. Very important fertilizer sources of nitrogen. urea quickly converts to ammonium little ammonia loss will occur when The most widely used nitrogen when applied to the soil, these nitrogen ammonium nitrate, ammonium sulfate, fertilizer sources are discussed below. solutions provide three-quarters of the or ammonium phosphate are surface- Anhydrous ammonia has the highest nitrogen as ammonium and one- applied on acid or neutral soils. When concentration of nitrogen (82%). It is quarter as nitrate. the soil pH is above 8.0 some loss of stored under pressure as a liquid but Urea has the highest nitrogen ammonia can occur from these turns to a gas when the pressure is concentration of any dry nitrogen materials, so they should be incorporated released. The drop in pressure cools the fertilizer (45% N). It reacts with when applied on alkaline soils. surrounding air when anhydrous moisture to form ammonium ammonia is released. The puffs of carbonate, an unstable salt that Sources of nitrogen “steam” observed when injector knives decomposes into ammonia (gas), In addition to organic matter are raised is a result of moisture carbon dioxide, and water. contributions, nitrogen is also supplied condensing in the cooled air. Consequently, urea and solutions to soil and plants by commercial Anhydrous ammonia is very caustic containing urea must be incorporated fertilizers, manure and other organic and considered to be a hazardous by rain, tillage, or injection to byproducts, legumes, and precipitation. material. A container of water must minimize loss. Urea volatilizes more always be available when working with rapidly when surface residue prevents it from contacting the soil and in high temperature, high pH, and dry Table 9-2. Effect of ammonia volatilization from surface-applied weather. nitrogen fertilizers on the yields of corn and grass pasture.

Added N a b Crop Nitrogen source lost as NH3 Yield

—%— —bu/a—

Corn None — 83 Urea 16 122 UANc solution 12 125 Ammonium nitrate 2 132

—ton/a—

Grass pasture None — 0.74 Urea 19 1.09 Ammonium nitrate 1 1.30

a Nitrogen sources surface-applied at 50 and 100 lb/a of N for corn and 60 lb/a of N for grass pasture. Corn yields are averages of the two rates. b Ammonia loss determined by field measurement c UAN = a mixture of urea and ammonium nitrate Source: Oberle, S.L., and L.G. Bundy. Proc. 1984 Fert., Aglime & Pest Mgmt. Conf. 23:45–57. C-9 10/18/05 11:14 AM Page 83

Chapter 9. Soil and fertilizer sources of plant nutrients 83

Table 9-3. Nitrogen fertilizers.

Chemical Analysis Fertilizer formulation (N–P2O5–K2O) Physical form Method of application

Ammonium nitrate NH4NO3 33-0-0 dry prills Broadcast or sidedress. Can be left on the soil surface.

Ammonium sulfate (NH4)2SO4 21-0-0 dry granules Broadcast or sidedress. Can be left on the soil surface.a

Anhydrous ammonia NH3 82-0-0 high-pressure liquid Must be injected 6–8 inches deep on friableb moist soil. Excessive loss will occur from wet soils.

Aqua ammonia NH4OH 20-0-0 to 24-0-0 low-pressure liquid Must be injected 2–3 inches deep on friableb moist soils. Excessive loss will occur from wet soils.

Calcium nitrate Ca(NO3)2 15.5-0-0 dry granules Broadcast or apply in the row. Can be left on the soil surface.

Diammonium (NH4)2HPO4 18-46-0 dry granules Broadcast or apply in the row. phosphate Can be left on the soil surface.a

Low-pressure nitrogen NH4NO3 + 37-0-0 low-pressure liquid Must be injected 2–3 inches solutions deep on friableb moist soils. NH3 + H2O 41-0-0 Excessive loss will occur from wet soils.

Potassium nitrate KNO3 13-0-44 dry granules Broadcast or apply in the row. Can be left on the soil surface.

UAN or pressureless NH4NO3 + 28-0-0 pressureless liquid Spray on surface or sidedress. nitrogen solutions Incorporate surface applications to urea + H2O 32-0-0 prevent volatilization loss of NH3 from urea.

Urea CO(NH2)2 45-0-0 dry prills or Broadcast or sidedress. granules Incorporate surface applications to prevent volatilization loss of NH3 from urea.

a Incorporate on high pH soils. b Friable soils are those which are easily crumbled or pulverized. C-9 10/18/05 11:14 AM Page 84

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Ammonium nitrate contains 33% form and is not all available in the first significant contribution to the total nitrogen—half ammonium nitrogen, year following application. The amount nitrogen budget for the state. In fact, half nitrate-nitrogen. It attracts of nitrogen available to a crop depends the amount of nitrogen contributed moisture from the air and cakes up on the type of manure, the application from the atmosphere over the entire during periods of high humidity. It is rate, the method of application, and state (36 million acres) is roughly equal made into spherical pellets (prills) and the consecutive years of application. to that applied as fertilizer on 10 coated with a conditioning agent to Fertilizer nitrogen applications should million cropland acres. Lightning in an prevent caking. Never combine be reduced or eliminated following electrical storm can create enough ammonium nitrate and urea because manure applications. Table 9-4 lists energy to cause some oxygen (O2) and the mixture has a much greater affinity first-year nitrogen credits for solid and nitrogen (N2) to form various nitrogen for water than either material alone. liquid manure. Additional information oxides. These combine with water to Ammonium sulfate contains only on using manure as a nutrient resource form nitric acid (HNO3). Various 21% nitrogen. Consequently, shipping can be found in chapter 10. nitrogen oxides (primarily N2O and and handling cost per pound of Legumes. Nitrogen contributions NO) are emitted into the atmosphere nitrogen are high. It is a strongly from legume plants were previously by denitrification and by internal acidifying fertilizer and may be discussed in the “Reactions in Soils: combustion engines. A small portion of preferred where a low pH is needed. It Symbiotic Fixation” section of this these oxides reacts with oxygen to form is sometimes used as a source of sulfur chapter and are shown in table 9-1. nitrates, which return to the soil in (24% S). Also, it does not pick up Precipitation. In rural areas of precipitation. moisture from the air as readily as Wisconsin, precipitation accounts for ammonium nitrate or urea. about 10 pounds of available nitrogen Manure. Manure contains (ammonium + nitrate-nitrogen) per substantial amounts of nitrogen, but acre annually. This is a small addition much of the nitrogen is in the organic on a per-acre basis, but it is a

Table 9-4. Nitrogen content and first-year credits for solid and liquid manure.

Total nitrogen ———Nitrogen content of manure——— Type of available in Application —— Solid —— —— Liquid —— manure first year method Total Credit Total Credit

— % — —— lb/ton —— — lb/1,000 gal —

Beef 25 Surface 14 4 20 5 35 Incorporateda 14 5 20 7

Dairy 30 Surface 10 3 24 7 40 Incorporateda 10 4 24 10

Poultry 50 Surface 40 20 16 8 60 Incorporateda 40 24 16 10

Swine 50 Surface 14 7 50b 25c 65 Incorporateda 14 9 50b 33c

a Injected or incorporated within 72 hours of application. b Value for liquid indoor-pit swine manure. Use 34 and 25 for liquid outdoor-pit and liquid, farrow-nursery, indoor-pit swine manure, respectively. c Value for liquid indoor-pit swine manure. Use 17 (22 if incorporated) and 13 (16 if incorporated) for liquid outdoor-pit and liquid, farrow-nursery, indoor-pit swine manure, respectively. Adapted from: USDA-NRCS. 2005. Wisconsin Field Office Technical Guide. Sec. IV. Spec. 590. C-9 10/18/05 11:14 AM Page 85

Chapter 9. Soil and fertilizer sources of plant nutrients 85

Timing of nitrogen week after planting and most of the well-drained soils. However, spring- fertilizer applications recommended nitrogen is applied by applied nitrogen fertilizer is usually The timing of nitrogen fertilizer the tenth week after planting more effective than fall-applied applications can markedly affect their Fall applications are most nitrogen even with use of a nitrification efficiency and the potential for nitrogen effective on medium-textured, well- inhibitor. Using nitrification inhibitors losses. Supplying the needed nitrogen drained soils, where nitrogen loss with spring preplant nitrogen on just prior to the crop’s greatest demand through leaching or denitrification is medium-textured, well-drained soils or maximizes the efficiency of nitrogen usually low. They are not effective on with sidedress applications on any soil applications. For spring-planted crops, sandy soils, shallow soils over fractured type is not likely to improve yields. sidedress and spring preplant bedrock or fine-textured poorly drained Urease inhibitors such as applications provide greater nitrogen soils. If fall treatments are to be made NBPT (Agrotain) used with surface- efficiency than fall applications, which on medium-textured, well-drained applied urea-containing fertilizers can are usually 10 to 15% less effective in soils, they should be limited to reduce ammonia losses and improve increasing crop yields. application of ammonium forms of nitrogen efficiency. However, they do Sidedress applications of nitrogen only (anhydrous ammonia, not consistently increase yields. The nitrogen during the growing season are urea, ammonium sulfate), and they decision to use a urease inhibitor effective on all soils. Proper timing is should be delayed until soil should be based on the risk of nitrogen essential to provide available nitrogen temperatures are below 50°F to slow loss that could be controlled, the cost when the crop uses the nitrogen the conversion of ammonium to nitrate of using the inhibitor, and the cost and rapidly. For corn, this is usually 6 to by soil organisms. This conversion can convenience of other nitrogen sources 12 weeks after planting. To provide be delayed also by use of nitrification or placement methods that are not adequate nitrogen during this period of inhibitors (see below). Price and subject to ammonia loss. Alternatives rapid nitrogen use, sidedress convenience advantages associated with include injecting or incorporating the applications should be made no later fall-applied nitrogen must be weighed urea-containing fertilizers or using non- than 6 weeks after planting. Benefits against the possibility of nitrate- urea nitrogen sources. from using sidedress nitrogen instead of nitrogen losses and lower effectiveness. Nitrogen fertilizer preplant applications are greatest on Nitrification inhibitors such as timing summary sandy soils or on fine-textured, poorly nitrapyrin (N-Serve) or dicyandiamide To minimize leaching or drained soils, and in years when rainfall (DCD) used with ammonium forms of denitrification losses, follow these is above normal. Research on sandy nitrogen fertilizer can reduce nitrogen general recommendations. irrigated soils has shown consistently losses on soils where leaching or Sandy soils. Nitrogen should be higher corn yields with sidedress denitrification is likely. Nitrification applied as a sidedress treatment. For applications than with preplant inhibitors slow the conversion of irrigated crops, part of the nitrogen treatments. Further discussion of this ammonium to nitrate by soil organisms may be applied through the irrigation topic can be found in the “Methods of (Reaction 3 in figure 9-2). Because water. Fall or spring preplant Fertilizer Application” section of this leaching and denitrification occur treatments will result in excessive losses chapter. through the nitrate form of nitrogen, on these soils. If spring preplant Spring preplant applications maintaining fertilizer nitrogen in the applications must be made, apply are usually as effective as sidedress ammonium form should reduce ammonium forms of nitrogen treated treatments on medium-textured, well- nitrogen losses through these processes. with a nitrification inhibitor. For drained soils. The risk of leaching or Nitrification inhibitors are likely to irrigated crops, apply part of the denitrification in these soils is low. increase crop yields when used with nitrogen through the irrigation water. Multiple or split applications spring preplant nitrogen applications Well-drained silty or clayey of nitrogen through irrigation systems on sandy soils or fine-textured, poorly soils. Spring preplant or sidedress are also effective. For corn, these drained soils. Yield increases are also applications can contain any form of applications should be timed so that likely from inhibitor use with fall- nitrogen. If fall applications must be some nitrogen is applied by the sixth applied nitrogen on medium-textured, C-9 10/18/05 11:14 AM Page 86

86 MANAGEMENT OF WISCONSIN SOILS

made, use ammonium forms of necessary to build plant tissue and to calcium, and other elements, most of nitrogen with a nitrification inhibitor. absorb plant nutrients and water. which are not soluble in water. Both Poorly drained soils. Sidedress The leaves of phosphorus-deficient organic and inorganic forms of applications of nitrogen should be plants most often appear dark bluish phosphorus are important sources for made on these soils. Use of a green, frequently with tints of purple or plant growth, but their availabilities are nitrification inhibitor is recommended bronze. On corn, purpling occurs controlled by soil characteristics and for spring preplant treatments. around the margins of the lower leaves, environmental conditions. Additional information on and the plant is short and dark green. Phosphorus fixation. One of nitrogen management practices is Some corn hybrids exhibit a purple the unique characteristics of contained in chapter 11. tinge on the lower stalk of young phosphorus is its immobility in soil. plants, a condition that can be Practically all soluble phosphorus from confused with phosphorus deficiency. fertilizer or manure is converted in the Phosphorus Reddening of corn leaves and stalks in soil to water-insoluble phosphorus Soils generally contain 500 to the fall is not an indication of within a few hours after application 1,000 ppm of total (inorganic and phosphorus deficiency, but of a process (figure 9-4). Phosphorus occurs in the organic) phosphorus, but most of this that occurs naturally as corn matures. soil solution as the negatively charged – phosphorus is in a “fixed” form that is Phosphorus-deficient alfalfa is stunted phosphate ion H2PO4 in acid soils or = unavailable for plant use. Soluble and dark bluish green, but purpling HPO4 in alkaline soils. These ions phosphorus in fertilizer or other does not occur. react readily with iron, aluminum, and manganese compounds in acid soils nutrient sources is quickly converted to Reactions in soils less-available forms when added to the and with calcium compounds in The two main types of phosphorus soil. In spite of this, soil test summary neutral and alkaline soils. They become in soils are organic and inorganic reports show that available phosphorus strongly attached to the surfaces of (figure 9-4). The organic form is found has been increasing steadily over the these compounds or form insoluble in humus and other organic materials. years. Although some Wisconsin soils phosphate precipitates. These reactions The inorganic portion occurs in various may require phosphorus additions for remove immediately available phosphate combinations with iron, aluminum, optimum yields, the past use of phosphorus fertilizer and applications of manure have led to unnecessarily Figure 9-4. The phosphorus cycle. high phosphorus levels on the majority of fields. Wisconsin soil test results for rainfall field crops had an average soil test phosphorus level of 52 ppm extractable crop harvest phosphorus for over 650,000 samples fertilizer analyzed between 1995 and 1999. This plant residues, value is excessively high for most crops. manure, biosolids runoff Function in plants Phosphorus (P) is a major organic P inorganic P constituent of the nucleus of plant plant uptake cells. Because of this, plants need it in continuous supply for all cell division including flowering, fruiting, and seed stable, soil solution, stable, formation. Phosphorus is also an unavailable P available P unavailable P important component of the compounds that transfer energy within P leaching the plant. Such energy transfers are Source: S.J. Sturgul and L.G. Bundy. 2004. Understanding Soil Phosphorus. University of Wisconsin-Extension publication A3771. C-9 10/18/05 11:14 AM Page 87

Chapter 9. Soil and fertilizer sources of plant nutrients 87

ions from the soil solution. Unlike fertile soil is able to maintain the Sources of phosphorus nitrate ions, phosphate ions rarely phosphorus concentration in the soil In addition to organic matter and leach, even in sandy soils. Studies of solution at a level high enough to meet soil mineral contributions, phosphorus highly fertilized, intensively farmed the needs of crops during periods of is also supplied to soil and plants by land indicate that the annual loss of peak demand. commercial fertilizers, manure, and phosphorus in drainage water seldom Phosphorus in organic other organic byproducts. exceeds 0.1 pounds per acre. The plow matter. The relative amounts of Phosphorus fertilizers layer of the soil usually retains almost all organic and inorganic phosphorus vary Rock phosphate. Rock phosphate is (98 to 99%) of the applied phosphorus. considerably. In Wisconsin, organic the original source of nearly all This means that very little phosphorus phosphorus accounts for 30 to 50% of phosphorus fertilizer sold in the United moves into or through the subsoil. Acid the total phosphorus in most mineral States. Mined rock phosphate is too soils fix more phosphorus than neutral soils. Decomposition (mineralization) insoluble (less than 1% water soluble) soils; liming acid soils to a pH of 6.0 to of organic matter converts organic to be a useful source of phosphorus for 6.8 increases the availability of both soil forms of phosphorus to inorganic crops, except when very finely ground and fertilizer phosphorus. available forms. As with the and applied to soils with a pH below The concentration of phosphorus mineralization of organic nitrogen, 6.0. During the manufacture of in the soil solution is about 0.02 to 0.1 organic phosphorus is released more fertilizer, insoluble rock phosphate is ppm. If this were the only source of rapidly in warm, well-aerated soils. treated with an acid to convert it to phosphorus available to plants, the This explains why crops grown in cold, more-available superphosphate or supply would be exhausted in a few wet Wisconsin soils often show growth ammonium phosphate. This process hours when crops are growing rapidly. response to row-applied (starter) neutralizes much of the acid; But this does not happen because the phosphorus even though the soil may application of phosphate fertilizer phosphorus removed from solution by be well supplied with phosphorus or results in very little residual acidity plants is quickly replenished from broadcast phosphorus fertilizer has when it is applied to the soil. The many slowly available sources including been added. common phosphate fertilizers, listed in that “fixed” by iron, aluminum, and table 9-5, are seldom applied alone in calcium compounds (figure 9-4). A Wisconsin. Usually they are

Table 9-5. Sources of phosphorus fertilizer.

Fertilizer analysis Water Name of fertilizer Chemical formula N-P2O5-K2O solubility

——————— % ———————

Ammoniated superphosphate variable variable 60

Ammonium polyphosphate NH4H2PO4 + (NH4)3HP2O7 Liquid 10-34-0 100 Dry 15-62-0 100

Diammonium phosphate (NH4)2HPO4 18-46-0 >95

Monoammonium phosphate NH4H2PO4 11-48-0 92

Ordinary superphosphate Ca(H2PO4)2 + CaSO4 0-20-0 85

Rock phosphate 3Ca3(PO4)2CaF2 0-32-0 <1

Triple superphosphate Ca(H2PO4)2 0-46-0 87 C-9 10/18/05 11:14 AM Page 88

88 MANAGEMENT OF WISCONSIN SOILS

manufactured or blended with nitrogen, potassium, or both to form a Table 9-6. Effect of various sources of row-applied phosphorus on mixed fertilizer such as 6-24-24 or corn yield (Arlington, WI). 9-23-30. As shown in table 9-6, the various sources of phosphorus are Fertilizer Sources of phosphorus Corn yield equally effective in improving crop grade in commercial 6-24-24 (% of control) yields. —— Control—no phosphorus added — Orthophosphate versus polyphosphate. Sources of phosphorus 6-24-24 Ammoniated superphosphate +13.5 – = containing the H2PO4 or HPO4 ions are called orthophosphates. 6-24-24 Concentrated superphosphate +16.7 Polyphosphates contain a mixture of 6-24-24 Monoammonium phosphate +16.7 orthophosphate and some long-chain phosphate ions such as pyrophosphate, Source: Schulte, E.E. and K.A. Kelling. 1996. Soil and Applied Phosphorus. University of – Wisconsin-Extension publication A2520. (HP2O7)3 . Commercially produced polyphosphate contains approximately 50% orthophosphate and 50% long- chain phosphate compounds. is topdressed on forages, water “reserve” level of phosphate in soil. The Claims that polyphosphates are solubility makes little or no difference. phosphorus in rock phosphate becomes superior to orthophosphates exaggerate University of Wisconsin research available only when the soil is acid their ability to partially chelate or shown in table 9-6 illustrates that the (below pH 5.5), and therefore its use combine with certain micronutrients differences in water solubility among by Wisconsin dairy farms is not and hold them in an available form. ammoniated superphosphate (60% recommended. The pH should be Research has not demonstrated that soluble), concentrated superphosphate about 6.8 for high-quality alfalfa and at this difference improves yields or (85% soluble), and monoammonium least 6.0 to 6.2 for most other increases nutrient uptake in most soils. phosphate (92% soluble) did not agronomic crops. Research in the Polyphosphate ions react with soil influence yields. Increasing the amount 1950s clearly demonstrated that rock moisture to form orthophosphates of water-soluble phosphorus above phosphate is not an effective relatively rapidly (1 to 2 weeks). On 60% did not increase yields. All phosphorus source in most soils. almost all soils, orthophosphate and commonly used phosphorus fertilizers Manure polyphosphate fertilizers are equally presently sold in Wisconsin (except Manure contains substantial effective. rock phosphate) contain at least 85% amounts of phosphorus but, similar to The main advantage of water-soluble phosphorus. nitrogen, much of the phosphorus is in polyphosphate is in the production of Liquid versus dry phosphate. the organic form and is not all available higher analysis grades of both liquid Compared to conventional dry in the first year following application. and dry fertilizers. Also, in liquid fertilizers, liquid fertilizers are easier to The amount of manure-phosphorus fertilizers polyphosphates can bind handle, mix, and apply. Despite claims available to a crop depends on the type micronutrients such as zinc and to the contrary, research has shown that of manure, the application rate, and the manganese and hold them in solution; liquid phosphate does not improve consecutive years of application. whereas with orthophosphates, these fertilizer phosphorus availability or Fertilizer phosphorus applications trace elements would precipitate. recovery. Soil interactions control should be reduced or eliminated Water solubility. The amount of phosphorus uptake, not the physical following manure applications. Table water-soluble phosphorus in the form of the fertilizer applied. 9-7 lists first-year nitrogen credits for different sources of available Rock phosphate versus solid and liquid manure. Additional phosphorus varies considerably (table superphosphate. Rock phosphate is information on using manure as a 9-5). However, when phosphorus is sometimes recommended instead of nutrient resource can be found in broadcast and incorporated or when it superphosphate for building up the chapter 10. C-9 10/18/05 11:14 AM Page 89

Chapter 9. Soil and fertilizer sources of plant nutrients 89

Methods of phosphorus formed by the plant. It is involved in fertilizer application Potassium the opening and closing of stomata Plants need relatively large Soils commonly contain over (leaf pores). Potassium also balances the amounts of phosphorus early in the life 20,000 ppm of total potassium (K). negative charges of organic and cycle. Root development is limited in Nearly all of this potassium is a inorganic anions within the plant. It cool, wet soils, and very little structural component of several soil appears to be involved in starch phosphorus is released from soil minerals, such as mica and feldspar, formation, translocation of sugars, organic matter. Some studies have and is unavailable to plants. Plants can nitrogen assimilation, and several other found band-applied phosphorus to be use only the exchangeable potassium on metabolic processes. Potassium uptake nearly twice as efficient as broadcast the surface of soil particles and is also linked to increased resistance to phosphorus in cold soils. In well- potassium dissolved in the soil water. disease and lodging, increased drained, fertile soils that warm up early This often amounts to less than 100 carbohydrate production, and in the spring, however, row and ppm. improved winter hardiness of alfalfa. broadcast applications are often equally Large quantities of potassium are On corn, soybean, and other field effective. Since phosphorus moves very removed when whole plants are crops, potassium deficiency appears as a little from the point of application, row harvested, such as alfalfa, corn silage, yellowing or scorching of the margins fertilizer should be placed 1–2 inches to and other forages. Grain and seed of older leaves. In alfalfa, the deficiency the side and below the seed. Seed- harvests remove much less potassium. appears as whitish-gray spots along the placed or pop-up starter fertilizers can Most Wisconsin soils need relatively outer margin of the recently matured also be used, but the application rates large quantities of applied potassium and older leaflets. As the deficiency must be reduced to avoid damage to because of removal by crops and becomes more severe, the affected area the seed and young plants. Optimum because Wisconsin soils have little increases, and the leaves or leaflets may starter fertilizer rates depend on soil test native exchangeable potassium. become completely yellow and/or drop levels, the distance between fertilizer off. Because potassium is a very mobile and seed, soil texture, and the salt index Function in plants element within the plant, deficiency of the fertilizer applied. See “Methods Plants need large quantities of appears on the older leaves first. of Fertilizer Applications” in this potassium. Unlike nitrogen and chapter for more detailed information phosphorus, potassium does not on starter fertilizer. become part of organic compounds

Table 9-7. Phosphorus content and first-year credits for solid and liquid manure.

Total P2O5 ——— P2O5 content of manure ——— Type of available in —— Solid —— —— Liquid —— manure first year Total Credit Total Credit

— % — —— lb/ton —— — lb/1,000 gal —

Beef 60 9 5 9 5

Dairy 60 5 3 9 5

Poultry 60 50a 30b 16 6

Swine 60 10 6 42c 25d

a Value for chicken manure. Use 40 and 21 for turkey and duck, respectively. b Value for chicken manure. Use 24 and 13 for turkey and duck, respectively. c Value for liquid indoor-pit swine manure. Use 16 and 23 for liquid outdoor-pit and liquid, farrow-nursery, indoor-pit swine manure, respectively. d Value for liquid indoor-pit swine manure. Use 10 and 14 for liquid outdoor-pit and liquid, farrow-nursery, indoor-pit swine manure, respectively. Adapted from: USDA-NRCS. 2005. Wisconsin Field Office Technical Guide. Sec. IV. Spec. 590. C-9 10/18/05 11:14 AM Page 90

90 MANAGEMENT OF WISCONSIN SOILS

Reactions in soils Readily available potassium soils do not contain enough clay to The three forms of soil potassium is dissolved in soil water or held on the hold the potassium. are unavailable, slowly available or surface of clay particles, within Organic matter particles hold most fixed, and readily available or “expanded” clay layers, or other soil positively charged nutrients tightly. exchangeable potassium. colloids. Dissolved potassium levels in Potassium is an exception because the Unavailable soil potassium is soil water are usually 5 to 10 ppm. attraction between potassium ions and contained within the crystalline Plants absorb dissolved potassium organic matter particles is relatively structure of micas, feldspars, and clay readily, and as soon as the weak. Consequently, some potassium minerals. Plants cannot use the concentration of potassium in the soil leaches from organic soils (peats and potassium in these very insoluble solution drops, more is released into mucks). Loss of potassium by leaching forms. Over long periods, these the solution from the exchangeable is one reason sandy and organic soils minerals weather or break down, forms. Most soil tests for available often test relatively low in available releasing their potassium as the potassium measure the readily available potassium, especially when tested in the available potassium ion (K+). This forms but not the unavailable and spring. These soils require precise process is far too slow to supply the full slowly available forms. annual potassium applications, since it potassium needs of field crops. Since clay and organic matter is not possible to build up high However, trees and long-lived particles hold potassium ions in an potassium reserves. perennials obtain a significant portion exchangeable or available form, Figure 9-5 illustrates the forms and of their potassium requirement from potassium does not leach from silty or reactions of potassium in soil. Plants the weathering of minerals containing clayey soils. Some leaching may take take up potassium from the soil potassium. place in very sandy soils because sandy solution, but this is rapidly replenished Slowly available potassium is associated with clay minerals. As Figure 9-5. Forms and availability of soil potassium. mentioned in chapter 2, individual clay particles are composed of many layers of mineral matter, each separated by water. The layers within certain clay ➡ Crop harvest particles are “collapsed” and have

trapped or “fixed” the potassium ion. ➡

In this trapped or fixed position

Fertilizer Manure ➡ Residue potassium is considered to be slowly ➡ available. Plants cannot use much of K+ K+ the slowly available potassium during a Soil organic matter Soil water Ve single growing season. However, the ry slow supply of fixed potassium largely Rapid determines the soil’s ability to supply ➡ potassium over extended periods of time. For instance, the sandy and silty Readily available + ++ ++ + + exchangeable K K Ca Mg NH4 K soils of central and north-central within expanded clay Wisconsin inherently have lower soil tests for available potassium because these soils have a very low supply of Slow

fixed potassium. In contrast, the red ➡ Micas ➡ Feldspars clay soils of eastern Wisconsin are Clay minerals examples of soils that contain Slowly available fixed K within K+ Ca++ Mg++ NH + K+ Slow significant amounts of slowly available collapsed clay 4 potassium. C-9 10/18/05 11:14 AM Page 91

Chapter 9. Soil and fertilizer sources of plant nutrients 91

from the exchangeable potassium sources of potassium fertilizer are used (Cl2), which is used for water reserves on organic and mineral for crops needing sulfur or magnesium purification, is manufactured from colloids. Potassium added as fertilizer, applications as well. Also, some crops chloride salts and is extremely reactive manure, or crop residue is readily such as smoking tobacco require the and unstable. The non-reactive soluble and goes into solution. It then sulfate form of potassium to maintain chloride is the form present in soils and becomes attracted to the negative crop quality. The tobacco does not the form found in fertilizer. In fact, the cation exchange sites. Some of the burn properly when chloride has been potassium chloride in fertilizer (KCl) is exchangeable potassium may become added to the soil. Potassium nitrate is simply a salt, similar to table salt “fixed” by entrapment in certain clay often used in greenhouses to reduce the (NaCl), and will not affect soil minerals. Fixed potassium is released incidence of salt injury, but it is organisms when applied at slowly when solution potassium drops generally too expensive to use in the recommended rates. to low levels. Most soil potassium (95 field. When high rates of potassium are Red versus white potash. Muriate of to 98%) is present in insoluble minerals needed or when soil salinity is a potash is mined as a mixture of that release potassium very slowly upon problem, potassium fertilizer potassium chloride and small quantities chemical weathering. applications should be split or materials of sodium chloride, clay, and several with a lower salt index, such as impurities, including iron. The iron Sources of potassium potassium sulfate or potassium impurities give muriate of potash its In addition to organic matter and magnesium sulphate, should be used. reddish color. Removing the impurities soil mineral contributions, potassium is Chloride versus sulfate. The gives a white product containing 62% also supplied to soil and plants by fertilizer source of potassium is potash, slightly higher than the 60% commercial fertilizers, manure, and sometimes debated, especially for row potash in red potash. White potash has other organic byproducts. fertilizers. Some advisors maintain that no agronomic advantage over red Potassium fertilizers the chloride in potassium chloride potash and is more expensive. Since The most common source of reduces the uptake of phosphorus, white potash contains fewer impurities, potassium for use on field crops is while the sulfate in potassium sulfate it does have an advantage when used in potassium chloride, or muriate of does not. However, research does not a mixed liquid fertilizer because it does potash (0-0-60). Most of the U.S. show that the sulfate form of potassium not precipitate as easily as red potash. supply of potassium chloride is mined is any better than the chloride form. Manure from vast underground deposits in The names chlorine and chloride Manure contains substantial Saskatchewan, although some is also are frequently confused. The element amounts of potassium, but, similar to mined in the western U.S. It is the least chlorine exists in nature as chloride nitrogen and phosphorus, some of the expensive source of potassium and is as salts of calcium, magnesium, potassium is in the organic form and is effective as other materials (table 9-8) potassium, and sodium. Chlorine gas not all available in the first year for most cropping situations. Other

Table 9-8. Potassium fertilizers.

Chemical Fertilizer analysis (%) Name of fertilizer formula N-P2O5-K2O Salt index Potassium chloride KCl 0-0-60 to 116 (muriate of potash) 0-0-62

Potassium-magnesium K2SO4•2MgSO4 0-0-22 43 sulfate

Potassium nitrate KNO3 13-0-44 74

Potassium sulfate K2SO4 0-0-50 46 C-9 10/18/05 11:14 AM Page 92

92 MANAGEMENT OF WISCONSIN SOILS

following application. The amount of Calcium the normal emergence and unfolding of manure potassium available to a crop Calcium (Ca) is relatively new leaves, a condition known as depends on the type of manure, the abundant in soils and rarely limits crop buggy whipping. However, other application rate, and the consecutive production. It makes up about 3.6% of stresses such as herbicide injury more years of application. Fertilizer the earth’s crust. It is present in soil commonly cause buggy whipping. potassium applications should be minerals such as amphibole, apatite, Reaction in soils. Calcium is reduced or eliminated following calcite, dolomite, feldspar, gypsum, and the predominant positively charged ion manure applications. Table 9-9 lists pyroxene. Calcium is a component of (Ca++) held on soil clay and organic first-year potassium credits for solid cell walls and is also important for cell matter particles because it is held more and liquid manure. Additional division and elongation, permeability tightly than magnesium (Mg++), information on using manure as a of cell membranes, and nitrogen potassium (K+), and most other nutrient resource can be found in metabolism. It is different from most exchangeable cations. Parent materials chapter 10. plant nutrients in that it is only moved from which soils are formed also within the plant by the water moving usually contain more calcium than from the roots through the leaves. magnesium or potassium. Therefore, Secondary Calcium deficiency is rare for soils normally have large amounts of nutrients Wisconsin field crops. The few known exchangeable calcium (300 to 5000 Calcium, magnesium, and sulfur instances were usually associated with ppm). Leaching of calcium through are known as secondary nutrients, but acid soils (pH 5.0 or less) low in soils does not normally occur to any this does not mean that they play a organic matter. When calcium is appreciable extent because of its secondary role in plant nutrition. They deficient, a plant’s terminal buds and relatively strong attraction to the simply do not limit plant growth as roots fail to develop. Deficiency surface of clay particles. Calcium/magnesium ratios. frequently as nitrogen, phosphorus, or symptoms show up first at the growing potassium, the primary nutrients. points because calcium is immobile in Claims regarding the “balance” of plants. In calcium-deficient corn, the calcium and magnesium and the need new leaf tips stick together and prevent to adjust the ratio of calcium to

Table 9-9. Potassium content and first-year credits for solid and liquid manure.

Total K2O ——— K2O content of manure ——— Type of available in —— Solid —— —— Liquid —— manure first year Total Credit Total Credit

— % — —— lb/ton —— — lb/1,000 gal —

Beef 80 11 9 20 16

Dairy 80 9 7 20 16

Poultry 80 30 24 12 10

Swine 80 9 7 30a 24b

a Value for liquid indoor-pit swine manure. Use 20 and 22 for liquid outdoor-pit and liquid, farrow-nursery, indoor-pit swine manure, respectively. b Value for liquid indoor-pit swine manure. Use 16 and 18 for liquid outdoor-pit and liquid, farrow-nursery, indoor-pit swine manure, respectively. Adapted from: USDA-NRCS. 2005. Wisconsin Field Office Technical Guide. Sec. IV. Spec. 590. C-9 10/18/05 11:14 AM Page 93

Chapter 9. Soil and fertilizer sources of plant nutrients 93

magnesium in Wisconsin soils are Table 9-10. Sources of calcium. unsubstantiated. Those who favor this idea suggest that Wisconsin soils Approximate chemical Percent Material formulation calcium contain low or deficient levels of calcium and/or toxic levels of Calcitic lime CaCO3 40 magnesium, and that calcitic limestone Dolomitic lime CaCO + MgCO 22 (CaCO3) or gypsum (CaSO4) is 3 3 needed to correct this condition. Gypsum CaSO •2H O22 Research conducted in Wisconsin does 4 2 not support these claims. Soils with a Ordinary superphosphate, Ca(H2PO4)2 + CaSO4 20 pH above 6.0 usually contain adequate 0-20-0 amounts of exchangeable calcium for agronomic crops, and magnesium levels Paper mill lime sludge ————— 38 in Wisconsin are not toxic. Slaked lime Ca(OH)2 54 Calcium/magnesium ratios typically range from 1:1 to 8:1, which research Triple superphosphate, 0-46-0 Ca(H2PO4)2 14 has proven to support normal plant growth. Dolomitic lime (CaCO3 + MgCO3) has a calcium/magnesium ratio (about 2:1) that is within the amount of calcium in several liming of the plant leaves. Because magnesium range for normal crop growth. and fertilizing materials. Gypsum moves readily from lower to upper Dolomitic limestone is considerably contains 20 to 22% calcium. It is not parts of the plant, the deficiency less expensive than calcitic limestone recommended as a source of calcium appears first on the lower leaves. As the and gypsum. Research does not support except for soils with a low cation- deficiency becomes more severe, the using more expensive products to add exchange capacity supporting crops leaves may turn reddish purple. calcium or change the that require an acidic soil. Deficiency symptoms are not calcium/magnesium ratio. Consult definitive, and it is sometimes difficult Magnesium Extension publication Soil Calcium to to distinguish between magnesium Magnesium (Mg) is abundant in Magnesium Ratios—Should You Be deficiency or toxicity of manganese, Wisconsin soils. It makes up about Concerned? (A2986) for more although the latter cases are usually 2.7% of the earth’s crust. Many information. confined to newer plant growth. common soil minerals contain Sources of calcium. Limestone Animals grazed on grass pastures magnesium, including amphibole, applied to correct soil acidity is the low in magnesium sometimes develop biotite, chlorite, dolomite, predominant source of applied calcium. hypomagnesemia, or grass tetany. This montmorillonite, olivine, pyroxene, The limestone quarried in Wisconsin problem occurs primarily where calcitic serpentine, and vermiculite. Soils contains 300 to 400 pounds of calcium limestone (CaCO ) is used as a liming developed from coarse-grained rocks 3 per ton. The amount of calcium material. Grass tetany is rare in low in these minerals tend to be low in normally added in limestone Wisconsin because dolomitic limestone magnesium. Most fine-textures soils applications, combined with the (CaCO + MgCO ) has been used on and soils developed from rocks high in 3 3 relatively large amounts of most of our soils and because forage magnesium minerals contain adequate exchangeable calcium in Wisconsin legumes, which contain higher levels of amounts. Magnesium is a component soils, far exceeds the 25 to 100 pounds magnesium than do grasses, make up a of chlorophyll in plants and is also an per acre annually removed by crops. substantial part of livestock rations. activator of several enzyme systems Dolomitic lime is recommended for Reaction in soils. Magnesium within the plant. correcting soil acidity in Wisconsin, ions are held on the surface of clay and A deficiency of magnesium results although some calcium is supplied organic matter particles. While this in an interveinal yellowing (chlorosis) from other sources. Table 9-10 lists the exchangeable form of magnesium is C-9 10/18/05 11:14 AM Page 94

94 MANAGEMENT OF WISCONSIN SOILS

available to plants, it will not leach Sources of magnesium. The Function in plants. Sulfur is a easily from the soil. most economical way of correcting component of the amino acids cysteine, Acid soils, especially sands, often magnesium deficiency in an acid soil is cystine, and methionine. These amino contain relatively low levels of to apply dolomitic limestone. If soil pH acids are among the building blocks of magnesium. Neutral soils or those with is already high, however, or if the crop protein, and shortage of sulfur retards a high pH usually contain more than requires an acid soil (such as potato and synthesis of proteins. 500 parts per million (ppm) of some fruits), then other carriers of Sulfur, as a constituent of nitrate exchangeable magnesium. Use of magnesium such as Epsom salts reductase, is involved in the conversion dolomitic lime has prevented (MgSO4•7H2O) or potassium- of nitrate into organic nitrogen. Sulfur magnesium deficiency in most of magnesium sulfate (K2SO4•2MgSO4) deficiency consequently interferes with Wisconsin. However, a few of the soils must be used. If excessive potassium nitrogen metabolism, which explains that may be deficient are listed below: fertilization has induced magnesium why nitrate accumulates when sulfur is ■ soils limed with materials low in deficiency, Epsom salts are the best deficient and why sulfur deficiency magnesium, such as paper mill source. Correction of magnesium resembles nitrogen deficiency in many waste, marl, or calcitic limestone; deficiency with Epsom salts or crops. However, the symptoms usually potassium-magnesium sulfate requires are not as dramatic and are not ■ acid sandy soils (usually in central 50 to 100 pounds of magnesium per localized on the older leaves. Lack of and north-central Wisconsin); acre when broadcast or 10 to 20 sulfur appears as a light green coloring ■ organic soils containing free calcium pounds per acre when applied in a of the whole plant. Legumes, especially carbonate or marl. band alongside the row. Table 9-11 alfalfa, have a high sulfur requirement, In sandy soils, application of high provides the magnesium content of so deficiencies usually appear on these rates of potassium or ammonium common magnesium sources. crops first. Corn, small grains, and fertilizer often heightens magnesium other grasses show sulfur deficiencies Sulfur deficiency. High concentrations of less frequently. Sulfur deficiency in Sulfur (S) is present in plants at these cations in the soil solution corn sometimes mimics other concentrations similar to those of interfere with magnesium uptake by deficiencies such as manganese or phosphorus, calcium, and magnesium. plants. This interference, called magnesium in that it causes interveinal Legume forages and cole crops antagonism, usually does not occur chlorosis: the upper leaves tend to be (broccoli, cabbage, etc.) have relatively when the soil contains more striped, with the veins remaining a high sulfur requirements. Like exchangeable magnesium than darker green than the area between the exchangeable potassium. nitrogen, sulfur is taken up as an anion = veins. (SO4 ).

Table 9-11. Sources of magnesium.

Chemical Percent Material formula magnesium

Dolomitic lime CaCO3 + MgCO3 8–20

Epsom salts MgSO4•7H2O10

Kieserite MgSO4•H2O18

Potassium magnesium sulfate K2SO4•2MgSO4 11 C-9 10/18/05 11:14 AM Page 95

Chapter 9. Soil and fertilizer sources of plant nutrients 95

Reactions in soils. Sulfur into unavailable sulfide sulfur in as nitrate-nitrogen, and some acid, transformations are very similar in waterlogged soils. Fortunately, this clayey subsoils contain sizeable reserves some respects to those of nitrogen. immobilized or reduced sulfur is of available sulfate. Most sulfur in the soil is unavailable as usually only temporarily unavailable. Sources of sulfur. Soils a part of the soil organic matter. As As the soil warms or as aeration commonly contain 200 to 600 pounds shown in figure 9-6, organic sulfur and improves, this unavailable sulfide sulfur of total sulfur per acre. Nearly all is in reduced sulfide sulfur (S=) combine combines with oxygen to again form the unavailable, organic form. As with oxygen to form available sulfate- available sulfate-sulfur. But under organic matter decomposes, a small = sulfur (SO4 ) in warm, well-aerated prolonged waterlogged conditions, as portion of this sulfur is converted into soils. This process is very similar to the in a marsh, sulfur can be lost as available (inorganic) sulfate-sulfur. conversion of organic nitrogen into hydrogen sulfide gas (H2S). Approximately 2.8 pounds of sulfur per + available ammonium (NH4 ) and Harvesting and leaching remove acre are released annually from each – nitrate-nitrogen (NO3 ). sulfur from soil. Sulfate-sulfur is not 1% organic matter in Wisconsin soils. Available sulfate-sulfur is tied up readily held by soil particles, except for Another source of sulfur is atmospheric by bacteria during the decomposition acid clays, so in most soils it can be deposition, which results from the of crop residues rich in carbon. leached below the root zone. However, burning of coal and, to a lesser extent, Available sulfur can also be changed sulfate-sulfur does not leach as readily oil and gas. This atmospheric sulfur is

Figure 9-6. The sulfur cycle. O2 + H2O

Atmospheric hydrogen and sulfate Sulfur dioxide Removed from cycle + = ions (H + SO4 ) Acid rain

(SO2) by harvesting

Leaf ➡

absorption ➡ O ➡ 2 Sulfate-sulfur Burning of fossil =

SO4 fertilizer

fuels and organic ➡ ➡ Elemental H S residue 2 Manure sulfur (S) Crop residue fertilizer

Soil organic matter

Plant uptake Bacterial assimilation Bacterial oxidation (immobilization) Volatilization

Sulfide-sulfur S=

Sulfate-sulfur = SO4 Bacterial reduction

Leaching C-9 10/18/05 11:14 AM Page 96

96 MANAGEMENT OF WISCONSIN SOILS

washed from the air and deposited on incorporated to some extent by falling to crops in the year of application. An the land in rainwater and snow. Each into cracks when the soil dries or by the additional source of sulfur is the year, precipitation typically deposits activity of earthworms and burrowing subsoil. Clayey, acidic subsoils may 5 to 15 pounds of sulfate-sulfur per insects. If the soil is known to be contain substantial amounts of plant- acre in Wisconsin. Western and deficient in sulfur, include some available sulfate-sulfur. Annual sulfur- northern Wisconsin receive about sulfate-sulfur in topdress applications supplying capacities of subsoils are 5 pounds of sulfate-sulfur per acre for immediate sulfur availability. considered low at 10 pounds per acre, annually; the remainder of the state Sandy soils may require annual medium at 20 pounds per acre, or high gets about twice as much. applications of sulfate forms of sulfur at 40 pounds per acre. All sulfate forms of sulfur fertilizer because the sulfate leaches through Row crops and small grains require are equally effective when surface- these soils relatively rapidly. Irrigation about 10 pounds of sulfur per acre in applied or incorporated (table 9-12). water, however, may contain sufficient sulfur-deficient areas. Alfalfa requires Elemental sulfur, however, is insoluble sulfate-sulfur for the crop. In these 25 to 50 pounds per acre if applied and must be transformed into sulfate- cases, response to fertilizer sulfur is during the seeding year or 15 to 25 sulfur by soil bacteria before plants can likely only in years with above-average pounds per acre when topdressed on use it. The rate of this transformation rainfall, when little irrigation water is established alfalfa. These treatments depends on particle size and degree of applied. generally will supply enough sulfur to mixing with the soil. To be effective, Manure is another source of sulfur. last 2 to 3 years. Sulfur may be applied elemental sulfur should be worked into The sulfur contribution from manure as row fertilizer, but thiosulfate should the soil well in advance of the time the varies with animal species and rate of not be seed-placed. crop needs it. Without mechanical application (table 9-13). About 60% of incorporation, elemental sulfur is total manure sulfur becomes available

Table 9-12. Sulfur fertilizers.

Chemical Fertilizer analysis Sulfur Material formula N–P2O5–K2O content — % — — % — Very soluble

Ammonium sulfate (NH4)2SO4 21-0-0 24

Potassium sulfate K2SO4 0-0-50 18

Potassium-magnesium sulfate K2SO4•2MgSO4 0-0-22 23 a Ammonium thiosulfate (NH4)2S2O3 + H2O 12-0-0 26

Magnesium sulfate (Epsom salts) MgSO4•7H2O 0-0-0 14

Ordinary superphosphate Ca(H2PO4)2 + CaSO4 0-20-0 14

Slightly soluble

Calcium sulfate (gypsum) CaSO4•2H2O 0-0-0 17

Insoluble Elemental sulfur S 0-0-0 88–98

aAmmonium thiosulfate is a 60% aqueous solution. C-9 10/18/05 11:14 AM Page 97

Chapter 9. Soil and fertilizer sources of plant nutrients 97

Only 0.5 to 2.5% of boron in the soil matter are deficient in boron more Micronutrients is available to plants. Soils may contain often than other soils. Plants need only very small 0.5 to 2.0 parts per million (ppm) of When the surface soil dries out, amounts of micronutrients (trace available boron, but more than 5.0 plants are unable to feed in the zone elements) for optimum growth. While ppm of available boron can be toxic to where most of the available boron is a deficiency of any essential element many agronomic crops. Lack of boron present. This can lead to boron greatly reduces plant growth, the often limits production of forage deficiency. When rain or irrigation overuse of some micronutrients can be legumes (alfalfa, clover, trefoil) and of moistens the soil, the plants can again detrimental. The danger of building up some vegetable crops in the state. feed from the surface soil and the toxic levels is greater on coarse-textured Plants take up less than 0.5 pounds of boron deficiency often disappears. soils such as sands and sandy loams boron per acre, yet lack of this nutrient Like nitrates, boron is not readily than on finer-textured soils. can reduce yields severely. When held by the soil particles and moves Micronutrients should be applied deficient, the plants’ growing points down through coarse-textured soils, only in the following situations: stop developing and will eventually die often leaching below the root zone of if the deficiency persists. many plants. Because less leaching ■ when the soil test is low, Crops vary in their need for boron. occurs on fine-textured silts and clays, ■ when definite micronutrient Crops with a high requirement include these soils are not boron deficient as deficiency symptoms appear on the alfalfa, beet, canola, cauliflower, celery, often as sands. plant, sunflower, tomato, birdsfoot trefoil, On alfalfa, the easiest way to apply ■ when plant analyses indicate low and forage brassicas. Those with a boron is in combination with levels in the plant, and medium requirement are apple, topdressed fertilizers. If a soil tests low asparagus, broccoli, brussels sprouts, in available boron or if a deficiency ■ on specific crops that have a very cabbage, carrot, lettuce, melons, radish, appears, apply 0.5 to 1.0 pounds of high micronutrient requirement. red clover, spinach, tobacco, and vetch. boron per acre each year or 2 pounds Boron The storehouse for most of the per acre once in the rotation as a Boron (B) is needed by plants for boron in soils is the soil organic matter. topdressing for forage legumes. For cell division, cell wall synthesis, and As a result, most of the available boron forage legumes grown on sandy soils, pollen germination. Boron deficiencies is in the plow layer, where organic an annual application of 0.5 to 1.0 in Wisconsin are more widespread than matter is highest. Soils low in organic pounds of boron per acre minimizes deficiencies of any other micronutrient. the leaching effect. Never use a borated

Table 9-13. Sulfur content and first-year credits for solid and liquid manure.

Total sulfur ————Sulfur content of manure———— Type of available in —— Solid —— —— Liquid —— manure first year Total Credit Total Credit

— % — —— lb/ton —— — lb/1,000 gal —

Beef 60 1.5 0.9 2.3 1.4

Dairy 60 1.3 0.8 2.3 1.4

Poultry 60 4.0 2.4 5.0 3.0

Swine 60 2.5 1.5 4.2 2.5

Source: University of Wisconsin Soil & Forage Analysis Laboratory, Marshfield, WI. C-9 10/18/05 11:14 AM Page 98

98 MANAGEMENT OF WISCONSIN SOILS

fertilizer in the row for corn or identified on extremely acid soils (pH leaf and usually stays in the lower half soybean, or in the drill for oats. The less than 5.0). of the leaf. boron concentrated in a band is toxic One of the main reasons for liming In broadleaf plants, zinc deficiency to germination of these crops and may acid soils, especially for legumes, is to results in a shortening of internodes cause severe injury. prevent manganese toxicity. The (rosetting) and a decrease in leaf size amount of manganese in solution (little leaf). Snapbean develops a Manganese decreases 100-fold for each unit rise in yellowing between the leaf veins Manganese (Mn) functions as an soil pH (as from 5.0 to 6.0). Where (interveinal chlorosis). However, it is enzyme activator for steps in manganese deficiency exists as a result very difficult to distinguish between photosynthesis. It is an element found of high pH, it is easier to correct the zinc and manganese deficiencies in this in plant tissue at concentrations deficiency by adding a manganese crop. ranging from 10 to 500 ppm or more. fertilizer than by attempting to acidify Crops generally take up less than In most plants, it is deficient at less the soil. 0.5 pounds of zinc per acre, yet when than 10 ppm and toxic when the Broadcast applications of zinc is deficient, crop yields are reduced concentration exceeds about 300 ppm. manganese fertilizer or attempts to markedly. Plants vary considerably in Deficiency symptoms are most build soil test manganese levels are not their requirements for zinc. Crops with common in oats, snapbeans, and recommended, particularly on high high zinc requirements include corn, soybeans grown in high pH (6.5 or pH, high organic matter soils because onion, and spinach. Those with greater) mineral soils and neutral to of their capacity to rapidly fix medium requirements are barley, beans, alkaline organic soils. Symptoms appear manganese. Band application reduces beets, canola, cucumber, lettuce, as interveinal chlorosis of the younger chemical fixation by reducing contact lupine, potato, radish, sorghum-sudan, leaves because manganese is an with soil particles. Mixing manganese soybean, tobacco, and tomato. Other immobile element. In oats, the with ammonium nitrogen in a fertilizer crops have low zinc requirements and symptoms show up as specks of dead band further improves its availability as seldom exhibit zinc deficiency. In tissue, giving the deficiency the name a result of the acidity produced as Wisconsin, zinc deficiencies have been “gray speck disease.” ammonium converts to nitrate. observed on corn, snapbean, and a few Crops with high manganese Although chelated manganese is other vegetable crops. requirements include beans (lima, effective as a foliar application, its use Scalped or severely eroded soils are snap), lettuce, oat, onion, radish, as a soil application can actually more apt to be zinc deficient than well- raspberry, soybean, spinach, sorghum- aggravate the deficiency. Apparently, managed soils. Also, sands, sandy sudan, and wheat. Those with medium the manganese chelate converts to the loams, and organic soils are more likely manganese needs are barley, beet, more stable iron chelate causing the to be zinc deficient than silty or clayey broccoli, brussel sprout, cabbage, plant to take in more iron, which soils. This is due to the fact that sandy carrot, cauliflower, celery, corn, suppresses the uptake of manganese. and organic soils originally contain low cucumber, pea, potato, tobacco, and total zinc levels. Severe soil compaction tomato. Zinc can also reduce zinc availability. Manganese availability increases as Zinc (Zn) is required for the Soil acidity (pH) influences the soil pH decreases. Manganese toxicity synthesis of a growth hormone availability of zinc more than any other is common in acid soils below pH 5.5, (indoleacetic acid) by plants. Also, it factor, with lower zinc solubility as the especially when these soils are low in functions as an enzyme activator in pH increases. Therefore, zinc organic matter and temporarily carbohydrate metabolism and protein deficiency usually is limited to soils waterlogged. Acid, sandy soils are likely formation. Deficiency symptoms with a pH above 6.5. Overliming of to contain high manganese levels. usually appear first on relatively young soils, especially sands, may induce zinc Crops susceptible to manganese leaves early in the growing season. On deficiency. toxicity include asparagus, forage corn, a broad band of bleached tissue legumes, mint, and pea. Manganese appears on either side of the midrib. toxicity of potato has also been The deficiency begins at the base of the C-9 10/18/05 11:14 AM Page 99

Chapter 9. Soil and fertilizer sources of plant nutrients 99

Copper exception is soil application of the Chlorine Copper (Cu) serves as an activator stable chelate, FeDDHA, that has had The earth’s crust contains about of several enzyme systems in plants. It some success in correcting iron 500 parts per million of chlorine (Cl), is present in soils at concentrations of deficiency. with average soil concentration 2 to 100 ppm with an average value of estimated at 100 ppm. Chlorine is a Molybdenum about 30 ppm. Beets, lettuce, onion, “universal contaminant.” It is present as Plants need extremely small spinach, sunflower, and tomato have chloride in ocean water and gets into amounts of molybdenum (Mo). relatively high copper requirements. the atmosphere as ocean spray. Plants Normal tissue concentrations are 0.03 Copper deficiency is rare in Wisconsin. require chlorine for certain photo- to 1 ppm. Molybdenum is required for Occurrences have been confined to acid chemical reactions in photosynthesis. symbiotic nitrogen fixation and for organic soils. Organic matter binds Chlorine uptake affects the degree of converting nitrate ions into organic copper more tightly than any other hydration of plant cells and balances nitrogen in the plant. Hence, the first micronutrient. Copper toxicity in some the charge of positive ions in cation symptom of molybdenum deficiency is sandy soils has resulted from repeated transport. Chlorine deficiency has been nitrogen deficiency. If the deficiency is use of copper-containing fungicides induced in the laboratory, but it has severe, the leaf edges of some vegetable over many years. never been observed under field crops may become brown and curl conditions in Wisconsin. Response to Iron upward (cupping). Cupped leaves may chlorine, expressed as reduced Iron (Fe) is required for synthesis look rolled and show interveinal incidence of disease and higher yield in of chlorophyll by plants, but it is not chlorosis. Molybdenum deficiency in small grains, has been observed in a few part of the chlorophyll molecule. Iron cauliflower leads to a classic condition studies in Oregon and the Dakotas. is very immobile in plants, so known as whiptail, in which leaves The soils in these states have high levels deficiency symptoms appear on new sometimes appear crinkled or withered. of potassium so potassium chloride growth. The veins of young leaves Broccoli, cauliflower, lettuce, onion, fertilizer (0-0-60) is seldom applied. remain green, but the area between the spinach, and table beets are responsive However, because Wisconsin soils tend veins becomes yellow (chlorotic). Each to this element; corn, small grains, and to be inherently low in potassium, new leaf emerges paler than the one potato are not. application of potassium chloride before. Eventually, new leaves, Soil acidity has a marked influence fertilizer and manure has precluded including the veins, are creamy white, on the availability of molybdenum. As chlorine deficiency. devoid of chlorophyll. soil pH decreases, the availability of Iron deficiency has rarely been molybdenum decreases. Liming alone Nickel observed on field or vegetable crops in is usually enough to correct a Nickel has recently been identified Wisconsin, except that iron chlorosis deficiency. Legume crops grown on as an essential plant nutrient. It is has occasionally been observed on very acid soils should be seed-treated needed by plants to form the enzyme soybeans grown on alkaline soils (pH with molybdenum. Soil applications of urease which breaks down urea- above 7.0). However, turfgrass, pin oak molybdenum are not recommended nitrogen for plant use. Nickel is also trees, and some ornamentals such as because only 1 ounce per acre is involved in plant uptake of iron from yews occasionally develop iron required, and this amount would be soil. Deficiencies of nickel are not deficiency when grown on alkaline difficult to spread evenly even if mixed known to exist in Wisconsin. soils. The deficiency can be corrected with another fertilizer. Seed treatment Generally, there is greater concern by spraying the foliage several times or foliar sprays are the recommended about nickel toxicity, particularly on with ferrous sulfate or an iron chelate. application techniques. Follow soils where sewage sludge has been Soil applications are not very effective molybdenum recommendations closely applied. (See chapter 11 for further because of the rapid transformation of because excess molybdenum in feed or information.) iron contained in fertilizer to forage can cause animal health unavailable forms in the soil. An problems (molybdenosis). C-9 10/18/05 11:14 AM Page 100

100 MANAGEMENT OF WISCONSIN SOILS

except for cations which are held on the Copper, boron and zinc form Summary of the soil cation exchange sites. stable organic complexes. Iron and fate of applied Nutrients with similar chemical manganese do so to a lesser extent. properties undergo similar chemical Calcium, magnesium, potassium nutrients reactions when applied to the soil. The and ammonium-nitrogen are the The chemical form of the plant fate of applied nutrients is summarized predominant exchangeable cations. nutrients in fertilizers and the reactions in table 9-14. Nitrate, sulfate, borate Much lesser amounts of copper, iron, which take place after they are added to and chloride ions tend to remain in manganese, and zinc are also found in soil have been discussed. All nutrients solution. Phosphorus, iron, manganese, the soil as exchangeable cations. applied as fertilizer must first dissolve and molybdenum form insoluble Exchangeable ammonium is relatively in soil moisture. Some remain in compounds. Elemental sulfur is high immediately after application but solution until they are absorbed by insoluble, but it is slowly oxidized to is quickly converted to nitrate under plant roots or leach with percolating soluble sulfate by sulfur-oxidizing favorable temperature, moisture, and water. Most nutrients, however, move bacteria in soil. pH conditions. out of soil solution and form insoluble compounds and organic complexes,

Table 9-14. Fate of applied nutrients under normal soil conditions.

Nutrient Chemical form(s) of Where found Leaching added the added nutrient in the soil susceptibility

– Nitrogen NO3 = Sulfur SO4 soil solution high – Boron H3BO3, H2BO3 Chlorine Cl–

– = Phosphorus H2PO4 , HPO4 insoluble very Sulfur Sa compounds low Manganese Mn++ Iron Fe++, Fe+++ = Molybdenum MoO4 – Boron H2BO3 organic very Copper Cu++ complexes low Zinc Zn++

+b Nitrogen NH4 soil low to Potassium K+ exchange moderate Calcium Ca++ sites Magnesium Mg++

a = Elemental sulfur (S) is slowly converted to sulfate (SO4 ). b + + Ammonia (NH3) is immediately changed to ammonium (NH4 ) when injected into the soil. Ammonium (NH4 ) – is rapidly converted to nitrate (NO3 ) by soil bacteria during the growing season. C-9 10/18/05 11:14 AM Page 101

Chapter 9. Soil and fertilizer sources of plant nutrients 101

At the present time, fertilizer with another element—a carrier—to Fertilizer analysis phosphorus and potassium are still form a fertilizer salt. In nature they are The analysis of fertilizer is given in guaranteed on the oxide basis, and combined with other elements— terms of the percent total nitrogen, likely will remain so, because the carriers—to form salts. Fertilizer salts fertilizer industry has no interest in are stable and can be handled easily. For available phosphate (P2O5), and water- changing to the elemental basis. A few example, the most concentrated soluble potash (K2O), as determined in a laboratory. Fertilizer grade is the common fertilizers expressed both ways commercial source of potassium is guaranteed minimum analysis in are given below: potassium chloride. It is a 50:50 percent of the major plant nutrient mixture of potassium (K) and chloride Approximate (Cl) so it contains no filler; it consists elements in the fertilizer. If an analysis Oxide basis elemental basis of 6-24-24 is given for a fertilizer entirely of potassium and the chloride material, it contains 6% total nitrogen, —— % —— —— % —— carrier. 24% available phosphate, and 24% water soluble potash. An application of 10-20-20 10-9-17 Forms of 200 pounds per acre of 6-24-24 would 6-24-24 6-10-20 mean that 12 pounds of nitrogen commercial (200 lb x 6% N), 48 pounds of 9-23-30 9-10-25 fertilizer phosphate (200 lb x 24% P O ) and 2 5 Fertilizers are sold in different 48 pounds of potash (200 lb x 24% 0-15-30 0-7-25 forms: as dry granules; as a pressureless K O) were applied. 2 liquid; and, in the case of nitrogen, as a Expression of the phosphorus and When a fertilizer such as 6-24-24 high-pressure liquid. No difference in potassium in the oxide form, even (6-10-20 on the elemental basis) is crop response has been noted between though there is no phosphate nor used, farmers sometimes question why the different forms of fertilizer when potash in fertilizer, is a carryover from they have to buy 46% filler with their equivalent amounts of plant nutrients the early days of agricultural chemistry. 54% (6% + 24% + 24% = 54%) are applied. Two pounds of liquid It would be simpler and less confusing fertilizer. There is little, if any, filler in 8-8-8 is just as effective as 1 pound of to express the content of phosphorus the fertilizer sold today; in this example dry 16-16-16. The choice of which and potassium on the elemental basis the remaining 46% is carrier. The form of fertilizer to apply should be (P and K), but the oxide analysis (P O 2 5 elemental forms of phosphorus and made on the basis of cost per pound of and K O) has become so entrenched 2 potassium are very unstable. In their plant nutrient, convenience, and that it would be difficult to change. pure form, these materials are so availability of materials. Table 9-15 summarizes phosphorus and reactive that they immediately burst Occasionally, extravagant claims potassium terminology. into flames if exposed to air. To apply are made for certain liquid or dry To convert from one means of plant nutrients like phosphorus and fertilizers made from “special” sources expression to another, use the following potassium they have to be combined of plant nutrients. These claims are not conversion factors:

Phosphorus (P) = phosphate (P2O5) x 0.44 Phosphate (P O ) = phosphorus (P) x 2.29 2 5 Table 9-15. Phosphorus and potassium terminology. Potassium (K) = potash (K2O) x 0.83

Potash (K2O) = potassium (K) x 1.20 Element name Oxide name Plant uptake and symbol and symbol form

– Phosphorus (P) Phosphate (P2O5)H2PO4 + Potassium (K) Potash (K2O) K C-9 10/18/05 11:14 AM Page 102

102 MANAGEMENT OF WISCONSIN SOILS

substantiated by research results. 10-20-20. A method of comparing the Manufactured and blended Furthermore, since plants take up the costs of fertilizers with different grades fertilizers differ in the composition ionic form of the nutrient, differences is discussed in chapter 13. of individual fertilizer granules. A between the various carriers or sources Premium grades of fertilizer are manufactured, or homogeneous, of plant nutrient would not be available for some crops. These contain fertilizer is chemically combined so that expected. slightly higher levels of micronutrients each granule theoretically has the same than that removed by the crop and, composition. A blended fertilizer is a Fertilizer grades therefore, may be regarded as a mixture of particles of different Fertilizer materials are sold maintenance application. This, materials to give the desired according to different percentages of however, is not always a profitable composition. Which is better? Field plant nutrients, commonly called practice because there may be sufficient studies have shown that blended fertilizer grades. A fertilizer ratio is the levels of some micronutrients in the soil fertilizers made up of particles of the relative proportion of the percentages to last for hundreds of years. same size and density are just as of nitrogen, phosphate, and potash in Another important point is that if effective as manufactured fertilizers. the mixture. A 6-24-24 fertilizer, for a severe deficiency of a micronutrient However, manufactured fertilizers have example, has a ratio of 1:4:4. When exists, most “premium” grades will not some advantage when including comparing the cost of different contain enough of the deficient ingredients such as micronutrients or fertilizers, valid comparisons can be nutrient to correct the problem. pesticides because the additives can be made only between fertilizer grades Whenever soils are deficient in boron, more evenly combined with the having the same ratio of N:P O :K O. 2 5 2 copper, manganese, or zinc, use a fertilizer particles. A 5-20-20 and a 6-24-24 have the same special mix fertilizer that contains the Liquid versus dry fertilizer is ratio (1:4:4). The 5-20-20 should cost required amount of the deficient a choice that should be based on 5⁄6 as much as the 6-24-24. Similarly, micronutrient. convenience in handling, cost of 5-10-10 should cost half as much as nutrients, and availability of equipment

Table 9-16. Comparison of liquid and dry starter fertilizers for corn.

Rate of —— Nutrients applied —— Corn a Material Form application N P2O5 K2O yield

——————————— lb/a —————————— bu/a

Control — 0 0 0 0 125

Seed-placed 9-18-9 liquid 36 3.2 6.5 3.2 133

7-14-7 liquid 46 3.2 6.5 3.2 128

Side (row) placed 6-24-24 liquid 100 6 24 24 139

6-24-24 dry 100 6 24 24 137

6-24-24 liquid 200 12 48 48 141

6-24-24 dry 200 12 48 48 138

a Three-year average except for control (two-year average). Source: Wolkowski, R.P., and K.A. Kelling. 1985. J. Fert. Issues 2:1–4. C-9 10/18/05 11:14 AM Page 103

Chapter 9. Soil and fertilizer sources of plant nutrients 103

for handling, storage, and application. pounds K2O per acre is recommended The fact that nutrients in liquid Methods of as a starter at planting. In most fertilizer are already dissolved does not fertilizer cornfields, all the recommended P2O5 make them more available to plants. and K2O can be applied as starter Availability is controlled by the application fertilizers. On soils with test levels in reactions these nutrients undergo with There are many methods of the excessively high range, starter soil particles when added to the soil, fertilizer application. The principal fertilizer applications in excess of 10 methods are discussed below. the same as with dry materials. When pounds N, 20 pounds P2O5, and 20 applied at the same rate, there is no Starter or row application pounds K2O per acre should be avoided. difference in performance between Starter or row application of Corn yield responses to starter liquid and dry fertilizer (table 9-16). fertilizer is often needed to get a row fertilizer additions do occur on soils However, as would be expected, lower crop off to a fast start in the spring. that are excessively high in phosphorus rates of seed-placed fertilizer are not as This treatment is particularly valuable and potassium. The probability of a effective as much higher rates of side- during a cool, wet spring when yield response can be estimated using placed fertilizer. nitrogen and phosphorus are not site-specific information about Liquid fertilizer is often more released fast enough from organic individual fields. Crop yield increases costly than dry fertilizer because (1) matter to satisfy the early needs of the with starter additions are much more there is a cost involved in adding water crop. Starter fertilizers promote likely if soil test potassium levels are less to make a liquid and in transporting vigorous seedling growth by providing a than 140 ppm and/or the corn is the liquid, and (2) more expensive, high concentration of readily available planted too late to achieve its full yield purified materials must be used to nutrients near the germinating seed. potential. Responses are more likely prevent impurities and precipitates A minimal amount of starter with late planting dates and long- from plugging applicator hoses, valves, fertilizer is recommended for corn season relative maturity hybrids. The and nozzles. However, the extra cost of planted in Wisconsin soils that are slow probability of response to starter liquid fertilizer may be offset by the to warm in the spring. For corn grown fertilizer on excessively high testing convenience, ease of handling, on medium and fine-textured soils, a soils at a range of hybrid relative improved mixing of additives, or other minimum application of 10 pounds maturity and planting dates is shown in factors. table 9-17. nitrogen, 20 pounds P2O5, and 20

Table 9-17. Probability of obtaining a positive economic return from starter fertilizer for corn grown on soils with excessively high phosphorus and potassium levels.a

Corn relative ———————————————Planting date——————————————— maturity ratings 4/25 5/1 5/5 5/10 5/15 5/20 5/25 5/30

—————————————————— % probability —————————————————

90 10 15 20 25 30 35 40 45

95 15 20 25 30 35 40 45 50

100 20 25 30 35 40 45 50 55

105 25 30 35 40 45 50 55 60

110 30 35 40 45 50 55 60 65

a This table does not alter current recommendations for early planting and selection of corn hybrids with appropriate relative maturities for the production zone. Source: Bundy, L.G. and T.W. Andraski. 1999. Site-specific factors affecting corn response to starter fertilizer. J. Prod. Argic. 12:664-670. C-9 10/18/05 11:15 AM Page 104

104 MANAGEMENT OF WISCONSIN SOILS

Salt injury to germinating seeds As noted previously, the phosphate than 80 pounds per acre of broadcast can occur when nitrogen or potassium ion is rapidly fixed when it comes in phosphate on a phosphorus-deficient fertilizers are placed too close to the contact with the soil. Concentrating soil. seed or at too high a rate. The seed or the phosphorus in a band delays By itself, row nitrogen has no seedling dehydrates because water fixation as compared to a broadcast advantage over broadcast nitrogen. moves out of tissue membranes to application. For this reason row-applied Experiments using ammonium nitrate dilute the salt. This is the same process phosphorus tends to be more effective alone in the row or in combination that causes your skin to wrinkle when than broadcast phosphorus. Table 9-18 with broadcast nitrogen show that the you swim for a long time in the ocean. shows that 40 pounds per acre of row- row nitrogen was merely additive to the There should always be some soil applied phosphate was more effective broadcast nitrogen. Nevertheless, between fertilizer and seed. Exceptions are that very small amounts of fertilizer Figure 9-7. Starter fertilizer in a 2x2 placement. can be applied directly with the seed. Salt injury can also result from excessive rates of other soluble fertilizers, as well as organic amendments. Starter fertilizers are typically applied in a band about 2 inches below and 2 inches to the side of the seed (figure 9-7).

Source: S.J. Sturgul and L.G. Bundy. 2004. Understanding Soil Phosphorus. University of Wisconsin-Extension publication A3771.

Table 9-18. Effect of row-applied and broadcast phosphate when applied to a phosphorus-deficient soila (Arlington, WI).

Annual phosphate (P2O5) application Broadcast Row Corn yieldb

——————— lb/ac ———————— % of control

00 —

0 40 + 10.1

80 0 + 4.0

80 40 + 11.1

a The initial soil test for available phosphorus was 12 ppm. b Four-year average. c Each treatment was applied each year for 4 years. Source: Powell, R.D. 1974. Proc. 1974 Fert., Aglime & Pest Mgmt. Conf. 13:23-31. C-9 10/18/05 11:15 AM Page 105

Chapter 9. Soil and fertilizer sources of plant nutrients 105

nitrogen should be included in row (100 lb/a of 8-48-12) at all soil test In summary, crop response to row fertilizer because it improves the potassium levels, but the response fertilizer is greatest under the following availability of phosphorus, possibly by decreased as soil test potassium circumstances: keeping phosphorus more soluble. increased (table 9-19). Response was ■ soil phosphorus or potassium is low Some potassium should always be greatest in the ridge-plant system at low ■ cold, wet conditions that retard early included in the row fertilizer, regardless soil potassium. plant growth of the soil test level. This is particularly A side-placement applicator is now important in no-till and ridge-till used for application of most row ■ reduced tillage systems where the soil tends to be more fertilizer. The fertilizer is placed far ■ compacted soils compacted than moldboard- or chisel- enough from the seed to prevent salt ■ for corn, longer season hybrids that plowed fields. Corn grown on a Plano damage, but the plant roots grow into are planted late. silt loam responded to row fertilizer the fertilizer band within a few days. Row fertilization can also be accomplished by using a seed-placed or Table 9-19. Effect of tillage and row fertilizer on corn yield (Arlington, WI). “pop-up” application. With this treatment, a small amount of fertilizer Tillage system Soil test K, ppm is placed directly with the seed. The and rate of 8-48-12 Very low High Excessive main advantage of this treatment over

——————— yield, bu/a —————— the conventional row treatment is that the starter response is obtained with Ridge till much less fertilizer to handle at 100 lb/a 127 163 165 planting time. Also, this system does 0 lb/a 82 151 162 not use an additional fertilizer disk Response 45 12 3 opener, an advantage in reduced tillage Chisel plow systems. Conventional row fertilizer is 100 lb/a 156 167 171 unnecessary as long as the seed-placed 0 lb/a 143 160 163 treatment is augmented with broadcast Response 13 7 8 fertilization of any needed phosphorus and potassium. Application rates for Moldboard plow 100 lb/a 163 176 169 seed-placed fertilizers must be reduced 0 lb/a 143 171 162 to avoid damage to the seed and young Response 20 5 7 plants (table 9-20). Seed-placed fertilizer treatments Source: Schulte, E.E. 1980. Proc. 1980 Fert., Aglime & Pest Mgmt. Conf. 19:113–121. are not without drawbacks. Seed-placed fertilizer should not be used on soybeans, snapbeans, and other large- Table 9-20. Maximum recommended starter fertilizer rates seeded legumes because these crops are for corn. extremely sensitive to salt injury. Also, they may delay emergence of corn a ———— Soil type ———— day or two, and high application rates Placement method Sands Silts and clays can reduce germination. This is ——— lb/acre fertilizer ——— especially true on sandy soils. To minimize problems, limit the rate of With seed (pop-up) 50a 50a

Side (2" x 2") placement 300 500

a Limit combined nitrogen and potash (K2O) to 10 lb/acre. C-9 10/18/05 11:15 AM Page 106

106 MANAGEMENT OF WISCONSIN SOILS

N+ K2O to 10 pounds per acre. This parts of the field and too high for Also, sidedressed nitrogen remains means that a mixed fertilizer such as others. Variable rate spreading exposed on the soil surface where it is 6-24-24 would have to be limited to technology permits the adjustment of more vulnerable to loss by volatilization 33.3 pounds per acre (33.3 lb/a x .06 = the rate of a given nutrient “on-the-go.” when herbicides rather than cultivation 2 lb of N; 33.3 lb/a x .24 = 8 lb of This technology requires an accurate are used to control weeds. K2O). Never use urea in seed-placed fertility map based on intensive Split-sidedressed nitrogen applied fertilizer. A band of concentrated urea sampling. The fertility map with to corn on Plainfield sandy loam produces gaseous ammonia that known geographic coordinates is increased yield by 5 to 21% compared inhibits germination and damages computerized and used to adjust to preplant nitrogen, depending on the seedlings. fertilizer rates in a variable rate spreader rate applied (table 9-21). Equally fitted with global positioning important from an environmental Broadcast and topdress equipment. standpoint, recovery of applied applications Yield variability across a field is nitrogen increased from 37 to 47% Broadcast fertilizer is spread more often a result of variability in soil with preplant nitrogen to 57 to 84% uniformly over the surface of the field properties such as texture, compaction, with split-sidedressed nitrogen. and incorporated before planting by or water-holding capacity than soil To coincide with plant uptake, tillage or cultivation. Topdressed fertility. Technology is now available to sidedress applications to corn should be fertilizer is applied uniformly over the measure yields electronically while made no later than 6 weeks after surface after emergence of the crop, harvesting. A map prepared from this planting. Do not sidedress with usually a small grain or legume forage. data can be used for field inspection of anhydrous ammonia when the soil is In dry seasons, phosphorus and low-producing areas and soil sampling too wet. Wet soil does not seal well potassium applied before plowing may based on yield level. If yield variability behind the injector knives. Some give better yield results than is due to soil physical characteristics or nitrogen will be lost, and the crop may applications after plowing. This is low fertility, fertilizer rates can be be injured by the escaping ammonia gas. because plowing incorporates the adjusted accordingly for such areas. nutrients more deeply than disking, Injection Such precision farming has the making them more available during dry Fertilizer can be injected using potential for reducing fertilizer costs weather. knives. This technique deposits the and environmental problems arising Fertilizer can be broadcast as a fertilizer in rows or bands, so the knives from over-fertilization. topdressing on established alfalfa and should be spaced close enough to allow grass pastures. Even though this Sidedress applications for uniform distribution. Another topdressed fertilizer remains near the Sidedress applications place injection technique is the spoke wheel surface of the soil, these crops make fertilizer, typically nitrogen, next to or injector. Liquid fertilizer is forced very good use of it. between the rows during the growing under high pressure through spokes of Broadcast and topdress season. These treatments are effective a wheel that penetrate the soil to the applications can be made with farm on all soils, but offer the greatest desired depth. Fertilizer is injected spreaders or commercial trucks or advantage on sandy soils and poorly when the spoke enters the soil. trailers. Bulk-spread materials can be drained soils. Sidedress applications Foliar application either manufactured fertilizer, such as place nitrogen in the soil just before the Plants can absorb small amounts of 6-24-24, or blended fertilizer made by plant needs it most, reducing the nutrients through their leaves. The mixing materials such as 18-46-0 and amount of time nitrogen is exposed to usefulness of foliar applications 0-0-60. loss by leaching or denitrification. depends on the total quantity of a Most fields are not uniform with Potential loss of nitrogen from urea nutrient needed by the crop. For respect to fertility. A fertilizer that cannot be incorporated in no-till instance, zinc and manganese can be recommendation based on average soil or other conservation tillage programs applied successfully as foliar sprays test levels for a field may be too low for limits the choices of nitrogen fertilizer. C-9 10/18/05 11:15 AM Page 107

Chapter 9. Soil and fertilizer sources of plant nutrients 107

because corn requires less than 0.3 Fertigation ■ It eliminates one or more field pounds per acre of these nutrients. On Fertigation is the application of operations. the other hand, plants require so much fertilizer in irrigation water. Nitrogen is ■ It provides an opportunity to correct nitrogen, phosphorus, and potassium the principal nutrient applied by nutrient deficiencies that show up or that foliar applications would be fertigation, although potassium, sulfur, are diagnosed when the crop is too impractical. Fifteen to 20 separate foliar and micronutrients can also be applied tall for conventional application applications would need to be made to this way. Phosphorus is seldom applied equipment. provide enough of these nutrients on a by fertigation because it forms Apply soluble nutrients near the deficient soil and to avoid leaf burn. precipitates of calcium, magnesium, or middle of the irrigation period. This Furthermore, foliar applications of the iron phosphates that could plug up prevents them from being leached primary nutrients do not significantly nozzles. Nitrogen is applied mainly as below the root zone and gives sufficient increase yields when the recommended 28% nitrogen solution. Do not use water to carry them into the soil. amount of fertilizer is applied to the anhydrous ammonia because it can Check valves must be used to ensure soil. cause precipitation of iron and calcium that fertilizer does not back-siphon into and because ammonia will be lost to Dribble application the well and groundwater. the atmosphere. Nitrogen solution is sometimes There are several advantages to dribbled onto the soil surface with drop fertigation: nozzles from a sprayer. The object is to minimize the amount of surface to ■ It allows the grower to apply which the urea is exposed. When a row nutrients, especially nitrogen, close crop is cultivated, nitrogen can be to the time of rapid plant uptake, dribbled onto the soil surface and then lessening the chances of loss by incorporated with the cultivator. leaching.

Table 9-21. Effect of rate and time of nitrogen application on corn yield and recovery of applied nitrogen on an irrigated, sandy soil (Hancock, WI, 2003–04).

———— Yield ———— — Nitrogen recovery — N rate Preplant Split-sidedress Preplant Split-sidedress

lb/acre ——— bu/acre ——— ———— % ————

09696— —

50 122 142 47 84

100 145 175 45 79

150 164 194 42 73

200 180 202 40 66

250 193 202 37 57

Average 161 183 42 72

a Split-sidedress treatments applied 4 and 7 weeks after planting. Source: Bundy. L.G., and T.W. Andraski. 2004. Unpublished data. C-9 10/18/05 11:15 AM Page 108

108 MANAGEMENT OF WISCONSIN SOILS

Questions 1. A farmer in southern Wisconsin 7. The phosphate in one 5-20-20 17. Is elemental sulfur or potassium grows continuous corn on a low- fertilizer is 100% water soluble, sulfate more effective when lying field that is somewhat poorly while the phosphate in another topdressed on established alfalfa? drained. The corn often shows 5-20-20 fertilizer is only 60% Give reasons. signs of nitrogen deficiency despite water soluble. In comparing these 18. Discuss the soil conditions the fact that 400 pounds per acre two fertilizers on corn, no favoring deficiency and the crops of ammonium nitrate (33-0-0) is difference in response is noted. most likely to show the deficiency broadcast on this deep silt loam Why? for each of the following soil each fall. What is the most 8. Under what soil and cropping micronutrients: likely reason for the appearance of conditions would rock phosphate a. Boron the nitrogen deficiency? be a satisfactory source of b. Manganese 2. Crops on irrigated sandy soils show phosphorus? c. Zinc very little difference between non- d. Copper 9. Why doesn’t phosphate (H PO –), leachable ammonium sources of 2 4 e. Iron a negatively charged ion, leach out nitrogen and leachable nitrate f. Molybdenum of the soil? sources. Why? 19. Some micronutrients can be 10.Explain why a band application of 3. How can nitrogen losses from fall- applied successfully as a foliar phosphate is often more effective applications be minimized? spray, but foliar application of than an equivalent amount of nitrogen, phosphate, and potash is 4. A farmer harvests one-half of a broadcast phosphate. not recommended. Explain. well-fertilized corn field for silage 11.What is the most commonly used corn and the other half for ear 20.Could 40 pounds per acre of source of potassium? Why? corn. The following year the field 10-10-10 be applied safely as a is planted to oats. Which half of 12.Potassium does not leach generally. seed-placed or pop-up treatment the oats field will be more apt to However, some leaching will take on corn? On soybeans? Give lodge? Why? place on very sandy soils and reasons. organic soils. Explain why. 5. If nitrogen fertilizer is surface 21. Outline a nitrogen fertilization applied and not incorporated, 13.Most Wisconsin soils contain program for corn grown on ammonium sulfate or ammonium lower levels of available potassium irrigated sands in central nitrate is recommended instead of than soils in neighboring states, Wisconsin that will minimize urea. Why? even though our use of potash per leaching losses. cropland acre is as high or higher 6. Identify the source of nitrogen than most of these states. Explain which is why. a. difficult to apply to wet, stony, high-residue soils. 14.Explain why calcium deficiency is b.also a carrier of sulfur. not a problem on soils with a pH c. apt to cause plant damage when of 6.0 or above. improperly sidedressed. 15.What soil conditions can cause d.used more rapidly by plants, magnesium deficiencies? especially when applied to cool soils. 16.What soil and cropping conditions would have the most response to sulfur fertilizer? C-10 10/18/05 11:15 AM Page 109

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Soil amendments

A soil amendment is any material soil microorganisms process it for food applied to the soil to improve crop and energy. When applied at yield or quality. Technically, recommended rates, manure provides commercial fertilizers are amendments, the following benefits: “And by plentiful dunging, but the term is generally used to ■ It adds essential plant nutrients. describe materials other than fertilizers. which is owing to flocks and ■ It acts as a mulch. herds of cattle, the earth ■ It adds organic matter to soil. produces her fruit in great Organic ■ It improves soil structure. amendments ■ It improves tilth. abundance.” The principal organic soil ■ It increases cation exchange capacity. amendments used in Wisconsin are Columella, L.J.M. Circa 40 A.D. ■ manure, municipal biosolids (sewage It improves infiltration of water. sludge), and whey. Crop residue is not ■ It reduces runoff. considered an amendment unless it is Composition. Manure is a good harvested and transported to another source of nitrogen, phosphorus, field. Other organic amendments potassium, and other nutrients but it include compost, sawdust, wood chips, varies greatly in composition. Table 10-1 fibrous paper mill sludge, leaves, grass provides an estimate of the total clippings, and peat moss. nutrient content of manure. Numerous factors affect the nutrient content of Manure manure, including: animal species and Manure is a byproduct of age, bedding type and amount, feed Wisconsin’s vibrant animal agriculture composition and digestibility, and industry. The manure produced by the manure handling and storage state’s dairy cows alone is estimated to procedures. The composition of liquid be 33.6 million tons annually. Manure manure depends on how much water is generated in such quantities is a used to dilute the fresh manure so that significant source of nutrients for crops it can be handled as a liquid. and soils. It is also a resource that must In addition to nitrogen, phosphate, be managed appropriately to fully and potash, manure contains all of the utilize its nutrients in a manner that other essential nutrients. Subsequently, minimizes environmental risk. soils to which manure is applied Unfortunately, because of its low value regularly are rarely deficient in sulfur or per unit volume and handling micronutrients. problems, manure is too often treated There are other benefits of as a waste. applying manure to soil. On the soil When manure is applied to surface, manure acts as a mulch and cropland, its nutrients are recycled as reduces erosion. Incorporating it into C-10 10/18/05 11:15 AM Page 110

110 MANAGEMENT OF WISCONSIN SOILS

the soil improves water infiltration and commercial fertilizer to apply) are only collecting and handling a representative soil structure, which in turn reduces 3 pounds of nitrogen, 3 pounds of manure sample and copies of the erosion and provides a better phosphate and 7 pounds of potash for information sheet that needs to environment for root development. each ton. Incorporating the dairy accompany a manure sample can be Only a portion of the total manure reduces volatilization losses of found online at the University of nutrients in manure is available to nitrogen so the manure-nitrogen credit Wisconsin Soil and Forage Analysis plants after application to soils. Some can be increased an additional 1 pound Lab’s web site (uwlab.dyndns.org/ nutrients are “tied up” in the organic of nitrogen per ton of manure. The marshfield). The nutrient content of matter of the manure and are released available nutrient content of manure manure can vary significantly from the over a number of years. To accurately increases when manure is applied to the values in table10-2. In addition to assess manure nutrient credits, it’s same field for 2 or more consecutive livestock species, animal bedding, essential to account for the available years. See the references cited in table livestock feed, manure dilution, nutrient content of manure (table 10-2). 10-2 for additional information. storage, and mixing are all variables For example, even though a ton of Laboratory analysis provides that influence nutrient content. The dairy manure may contain 10 pounds the best estimate of the nutrient nutrient content averages in table 10-2 of nitrogen, 5 pounds of phosphate, content of manure—provided a should only be used when lab analysis and 9 pounds of potash, the available representative sample(s) is submitted to has not been done. An example of nutrient credits (reductions in the lab. Detailed instructions on manure analysis reports from the

Table 10-1. Estimated total nutrient content of solid and liquid livestock manure.

Nitrogen Phosphate Potash Species Dry matter (N) (P2O5)(K2O)

Solid manure — % — ———————— lb/ ton ————————

Dairy 24 10 5 9

Beef 35 14 9 11

Swine 20 14 10 9

Chicken 60 40 50 30

Turkey 60 40 40 30

Liquid manure —————— lb/1,000 gal —————

Dairy 6 24 9 20

Beef 5 20 9 20

Swine—indoor pit 7 50 42 30

Swine—outdoor pit 4 34 16 20

Swine—farrow-nursery indoor pit 3 25 23 22

Poultry 3 16 10 12

Adapted from: USDA-NRCS. 2005. Wisconsin Field Office Technical Guide. Sec. IV. Spec. 590. Wis. Conservation Planning Technical Note WI-1. C-10 10/18/05 11:15 AM Page 111

Chapter 10. Soil amendments 111

Table 10-2. Average first-year available nutrient content of solid and liquid livestock manure.a

Nitrogen Phosphate Potash Species Dry matter (N) (P2O5)(K2O)

Solid manure — % — ———————— lb/ ton ————————

Dairy 3 4 3 7

Beef 4 5 5 9

Swine 7 9 6 7

Chicken 20 24 30 24

Turkey 20 24 24 24

Liquid manure —————— lb/1,000 gal ——————

Dairy 7 10 5 16

Beef 5 7 5 16

Swine—indoor pit 25 33 25 24

Swine—outdoor pit 17 22 10 16

Swine—farrow-nursery indoor pit 13 16 14 18

Poultry 8 10 6 10

a Averages are based on information collected from Wisconsin soil testing laboratories. Values are subject to revision. Consult www.datcp.state.wi.us/arm/agriculture/land-water/conservation/nutrient-mngmt/planning.jsp for the latest information. Adapted from: USDA-NRCS. 2005. Wisconsin Field Office Technical Guide. Sec. IV. Spec. 590. Wis. Conservation Planning Technical Note WI-1.

Table 10-3. Estimated nutrient availability from livestock manure. University of Wisconsin soil testing lab can also be found on the previously —— Nitrogen (N) —— Phosphate Potash Species surface incorporated (P O )(KO) mentioned web site. 2 5 2 When reading manure nutrient ———————————— % a ———————————— analysis results, be certain to use the available nutrient content—not total Dairy 30 40 60 80 nutrient content—when calculating Beef 25 35 60 80 manure nutrient credits. Some labs may report only the total nutrient Swine 50 65 60 80 content values. Table 10-3 lists the estimated first-year nutrient availability Poultry 50 60 60 80 from various manures. a Values are the percentage of available nutrients relative to the total nutrient content of Nutrient crediting. Nutrient manure. If manure has been applied to the same field at similar rates for 2 consecutive years, credits are the reductions in fertilizer increase the nutrient values in the table by 10 percentage points. If manure has been applied application that can be made when to the same field at similar rates for 3 consecutive years, increase the nutrient values in the manure (or other non-commercial table by 15 percentage points. Adapted from: USDA-NRCS. 2005. Wisconsin Field Office Technical Guide. Sec. IV. Spec. 590. Wis. Conservation Planning Technical Note WI-1. C-10 10/18/05 11:15 AM Page 112

112 MANAGEMENT OF WISCONSIN SOILS

fertilizer sources of plant nutrients) is increases phosphorus losses. Winter ■ If manure is applied to frozen soils applied to soil. In order to use manure applications of unincorporated manure on slopes of 9% or less and protect as a nutrient resource, both the are particularly susceptible to these areas from upslope runoff. available nutrient content and the phosphorus losses. ■ Do not apply manure to frozen soils manure application rate must be Manure management on slopes between 9 and 12% unless known. For example, if dairy manure guidelines. Additional guidelines and contour strips, terraces or other containing 3 pounds of plant-available recommendations for manure conservation measures are in place. nitrogen per ton is applied at 20 tons management include the following: ■ Do not apply manure to frozen or per acre, a nitrogen credit of 60 pounds ■ Do not exceed tolerable soil loss (T) snow-covered soils on slopes greater per acre can be subtracted from the soil on fields receiving manure. than 12%. test recommendation for nitrogen. ■ Estimating application rates. Limit manure application to the ■ Do not apply manure where there is annual crop removal rate for Manure must be applied uniformly less than 20 inches of soil over phosphorus unless it is incorporated. across fields and the application rate bedrock unless it can be applied in If incorporated, higher rates can be must be known if manure is to be used the fall when soil temperatures are applied to meet the nitrogen needs as a fertilizer resource. Manure below 50°F and limited to 120 of the crop to be grown. application rates cannot be estimated pounds of available nitrogen per visually! To get a reasonably accurate ■ Realize that when applying manure acre. estimate of application rates, the to meet the nitrogen needs of a ■ On sandy soils where crops are not manure spreader must be calibrated. subsequent crop, an over-application growing, delay fall application until For solid manure, this is done by of phosphorus and potassium is soil temperatures are below 50°F. If a determining the weight of the spreader likely to result. perennial or cover crop is growing, and the area covered. The insert Know ■ Monitor soil test phosphorus levels fall application can be made at any How Much You Haul! provides details on fields receiving manure. If levels time. on how to do this. reach 100 ppm or more, reduce Other considerations. For Incorporation. Incorporating or manure application rates and plant a greatest efficiency of manure nutrient injecting manure by tillage soon after crop that removes substantial utilization, have the manure analyzed application—generally, within 3 days— amounts of phosphorus, such as and the soil tested. Apply more manure can conserve nitrogen by limiting alfalfa or silage corn. to fields testing low in phosphorus and ammonia losses. It can also control ■ Do not apply manure to frozen soils potassium and less manure to fields odors. However, tillage to incorporate within 1,000 feet of lakes and 300 with a high soil test. manure, especially in spring, can feet of rivers and streams. As long as the manure is handled increase sediment and phosphorus properly, daily spreading or seasonal ■ Never apply manure in grass losses by increasing soil erosion. spreading from a manure storage waterways, terrace channels, near Unincorporated, spring-applied system is equally effective at improving open surface drains, or other areas manure can lower runoff volume and crop yield. where water flow may concentrate. erosion by increasing residue cover and A number of university water infiltration into the soil. ■ If manure is to be applied to publications, available from county Incorporated manure can also unfrozen soils within 1,000 feet of Extension offices or the web sites cited lower phosphorus losses in runoff in lakes and 300 feet of rivers and in this chapter, discuss manure some cases. Incorporating manure in streams, use one or more of the management in greater detail. Be aware the fall often lowers runoff volume and following precautions: (1) install or that various federal, state, and local total phosphorus losses. Unincorporated maintain buffers along the water regulations may impact manure manure applied in the fall to relatively body, (2) maintain at least 30% crop management strategies. The USDA- smooth (sealed) soil surfaces such as residue cover, (3) incorporate Natural Resources Conservation those found following no-till corn or manure within 72 hours leaving Service’s nutrient management standard soybean or established alfalfa often adequate crop residue cover. (Wisconsin Field Office Technical Know How Much You Haul ! To use manure as a quality, dependable fertilizer, you must accurately figure your spreading rate and calculate your manure nutrient credits. This whole process can take less than a hour! All you need to get started is this sheet, a calculator and portable axle scales. Contact your land conservation department, county extension agent or the Nutrient and Pest Management Program (877) 426-0176 for assistance with scales.

STEP 1. DETERMINE LOAD WEIGHT TOOLS NEEDED: CALCULATOR, PORTABLE AXLE SCALES Using a typical load size, the tractor with spreader is weighed empty and full, axle by axle.

What is typical? If you normally haul one load every day at about the same time, weigh a load with 24 hours worth of manure. Or if you normally wait until the spreader is filled to capacity, weigh the spreader filled.

STEP 2. DETERMINE SPREADING RATE TOOLS NEEDED: CALCULATOR AND FIELD RECORDS OR MEASURING WHEEL* You can now calculate your tons per acre spreading rate using field records on how many loads you put on a particular field of known acreage (see equations on other side). This rate can be considered the “standard” for the farm. Make sure you use typical ground speed, PTO speed and spreader settings. To develop variable rates (such as high, medium and low) experiment with different speeds and spreader settings. These rates could be useful when dealing with fields that have special fertilizer, tillage or environmental considerations. *You can get an estimate of a per acre rate right away by using a measuring wheel on the area just spread. Use caution with this method since it does not take into account overlap or load tapering.

STEP 3. DETERMINE MANURE NUTRIENT CREDITS TOOLS NEEDED: CALCULATOR Using University of WI guidelines (table on other side) you can estimate the available nutrient content per ton of the manure you are spreading. You can also have your manure analyzed for its specific nutrient content. From either of those numbers, you can figure your manure nutrient credits per acre. (If you develop variable rates, use additional sheets to determine their manure nutrient credits.) Now you have the information you need to accurately use manure as a fertilizer!

It’s a good idea to repeat this process for any different types of spreaders or manure you routinely apply on your farm. For more copies of this publication or information on developing a nutrient management plan for your farm, contact your land conservation department, county extension agent or the NPM program. Spreader Information Manufacturer / Manure Type / Ground Speed / PTO Speed / Spreader Settings

STEP 1. DETERMINE LOAD WEIGHT

FULL Left wheel Right wheel Rear tractor axle Front spreader axle

Rear spreader axle Full total lb + = EMPTY Rear tractor axle Front spreader axle

Rear spreader axle Empty total lb + =

Full total - Empty total ÷ 2000 = Tons Manure/Load STEP 2. DETERMINE SPREADING RATE Method 1: Using field records, enter the number loads applied on a known acreage. # of loads # of acres loads /acre Tons Manure/Load Tons / Acre ÷ = x =

Method 2: Estimation only. Using a measuring wheel, measure the area just spread with a single load. Tons Manure/Load ft wide ft length Tons / Acre Estimate [ x=43,560 ft2/Acre] ÷ [ x ]

Nutrients available for crop use in the STEP 3. DETERMINE MANURE NUTRIENT CREDITS first year after spreading solid manure.

Enter the available nutrient content of manure Inc.* Not Inc. Animal NNPO K O lb/Ton Tons / Acre lb/Acre 2 5 2 lb/ton N x= Dairy 4337

Beef 5459 x= P2O5 Swine 9767

x= Chicken 24 20 30 24 K20 * Incorporated into the soil within 72 hours after spreading. Multiply the nutrient content by the spreading rate to get Source: Department of Soil Science, College of Agricultural and Life Sciences, University of Wisconsin-Madison, University of Wiscon- the pounds per acre of each nutrient. sin-Extension.

For more copies of this publication, please contact the Nutrient and Pest Management Program’s Regional offices: Southwest (800) 745-9712, Southcentral (800) 994-5853, Southeast(800) 994-5852, Northwest (800) 228-8672, Northeast (920) 391-4652 or our UW-Madison office at (608) 265-2660. Visit our website (ipcm.wisc.edu). C-10 10/18/05 11:15 AM Page 113

Chapter 10. Soil amendments 113

Guide – Standard 590) contains have exceptional quality and are safe valid concern regarding the heavy metal numerous manure application enough to be used in horticultural content of biosolids. Heavy metals are restrictions. A current version of the applications. A well-known example is elements such as lead, mercury, and nutrient management standard can be Milorganite produced by the cadmium that can be toxic to animals if found on the Wisconsin Department of Milwaukee Metropolitan Sewerage ingested in certain concentrations. The Agriculture, Trade and Consumer District. Most other materials are risk of contacting heavy metals in Protection site at www.datcp.state.wi.us/ classified as Class B materials and are biosolids is managed by applying them arm/agriculture/land-water/conservation/ generally applied in bulk to agricultural to soils that have a pH of 5.5 or higher. nutrient-mngmt/planning.jsp. land following the strict criteria At such pH levels, the heavy metals described in the following paragraphs. become tied up in the soil, significantly Biosolids Composition. The nutrients and reducing their availability to plants. Biosolids (sewage sludge) are a other components of a biosolid reflect They are further restricted through the product of the biological treatment of the origin of the wastewater. There is a establishment of maximum, or ceiling, wastewaters. These materials are risk of pathogens in municipal concentrations in soils. Risk of created from a variety of industries, biosolids, which is addressed through accumulating toxic levels of heavy including the processing of sewage by treatment using biological digestion, metals is considered to be low when the municipalities, food processing, and heat, or lime. It is further addressed concentration of metals in biosolid falls paper making. They are the result of through restrictions that prevent below these levels. A list of these the current best technology for spreading within critical distances from elements, the ceiling concentrations, purifying industrial and municipal wells, schools, dwellings, etc. and and the concentrations for three wastewater, with the goal of returning through the type of crop that can be Wisconsin communities is shown in the greatest percentage of the water as grown on the amended soil. There is a table 10-4. clean effluent to surface or ground water. Biosolids contain the undecomposable solids from the Table 10-4. Biosolid heavy metal ceiling concentrations and the wastewater and the cells of bacteria that heavy metal content of three Wisconsin biosolid materials. processed the waste material. There are three options for the management of Ceiling — Average concentrations, 2002 — biosolids: (1) land application to utilize Element concentration Appleton Waupaca Weyauwega nutrients and organic matter, ———————————— ppm ———————————— (2) landfilling, and (3) incineration. Landfilling and incineration are often Arsenic 75 3.7 4.6 3.1 more expensive options and have significant environmental drawbacks. Cadmium 85 0.6 1.4 0.8 The creation and use of municipal Copper 4,300 167 208 128 biosolids are regulated by the Wisconsin Department of Natural Lead 840 12.9 15.5 28.6 Resources. State code contains standards supplied by the U.S. Mercury 57 0.3 1.2 0.5 Environmental Protection Agency that Molybdenum 75 11.9 12.5 30.5 were created following a national review process. The standards specify Nickel 420 10.7 7.6 6.5 criteria for pathogens, heavy metals, and vector (flies, rodents, etc.) Selenium 100 0.1 2.6 1.0 attraction. Wisconsin recognizes two Zinc 7,500 224 281 274 types of municipal biosolids based on these three factors. Class A biosolids Source: P. Grienier. 2002. City of Appleton. C-10 10/18/05 11:15 AM Page 114

114 MANAGEMENT OF WISCONSIN SOILS

Application of biosolids. plus 100% of the mineral nitrogen. nitrogen needs will result in the over- Fields for the land spreading of Before selecting a biosolid application application of phosphorus. This biosolids must be individually approved rate, credits for legumes and manure, relationship is even more significant in based on specific site criteria. or previous biosolid applications must the case of biosolids because treatment University of Wisconsin soil test first be subtracted from the processes sequester phosphorus in the recommendations are used to determine recommended nitrogen rate. Several solids so that the effluent phosphorus the rate of biosolid application. Crop municipalities have opted to use lime concentration is low. Table 10-5 shows selection is determined by the potential stabilization in their biosolid the soil test phosphorus values P at contact with the soil. For example, management process. Lime-stabilized Elkhorn following the long-term crops grown in the soil (e.g., carrot, biosolids are an excellent liming application of biosolids. potato) cannot be harvested from a material and should be used as a Whey treated soil within 38 months of substitute for aglime rather than a Whey is a byproduct of cheese application. For crops that may touch nitrogen fertilizer. making. It is the liquid remainder of the soil (e.g., green beans, peas), the Biosolids are an excellent source of milk after the solids (curds) are period is 14 months. The period for nitrogen and when applied properly removed. About one-third of the whey common field crops like corn and replace the need for nitrogen fertilizer. produced by cheese plants in the soybean is 1 month. Most biosolid Figure 10-1 shows a comparison United States is applied to the land. application rates are based on the between fertilizer and biosolids applied The remainder is fed directly to nitrogen need of the crop. Current for 11 consecutive years at Elkhorn, animals or is processed into foods, rules provide a biosolid nitrogen credit Wisconsin. Similar to manure, pharmaceuticals, or industrial products. of 25% of the organic nitrogen content application of biosolids to meet crop

Figure 10-1. Corn response to 11 years of biosolid and nitrogen fertilizer application (Elkhorn, WI, 1984–94).

180

160

140

120

100 Control Biosolid 80 N fertilizer

Yield (bu/a)

60

40

20

0 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 Source: Peterson, A.E. 2002. Dept. of Soil Sci. Univ. Wis.-Madison. C-10 10/18/05 11:15 AM Page 115

Chapter 10. Soil amendments 115

Composition. Whey is an water added with the whey depletes soil fields where organic amendments are excellent source of plant nutrients. oxygen temporarily, inducing unavailable, the best way to maintain Based on the analysis in table 10-6 half manganese toxicity in alfalfa. And soil organic matter is to fertilize an acre-inch would provide adequate third, the high sodium chloride content adequately with commercial fertilizer nitrogen for corn. Whey contains 5 to of some wheys can cause salt damage. and then return to the soil the large 6% solids, most of which is lactose, yield of residue that will be left after the Miscellaneous organic with the remainder being protein and crop is harvested. amendments nutrients. Any material that adds organic A number of other organic Handling of whey. Whey is matter to the soil economically should amendments are available in some typically spread through irrigation be encouraged. Carbonaceous material localities. These include peat moss, systems or by truck spreading; that is, low in nitrogen, such as sawdust and wood chips, sawdust, fibrous paper mill by opening a valve at the rear of a tank wood shavings, will induce nitrogen waste, leaves, and lawn clippings. Aside truck and directing the whey onto a deficiency if applied at high rates from sawdust and wood shavings used spreader baffle. without including a supplementary for bedding, most of these materials are The soluble carbohydrates in whey source of nitrogen. Leaves are not widely available and have no are a readily available source of energy borderline. If incorporated in the fall, advantage over manure. They are better for soil microorganisms. Whey they should break down by spring. suited to lawns, gardens, and small stimulates the growth of these There is no advantage to composting specialty farms. Near urban areas, the organisms and they multiply rapidly. the leaves before incorporation. The availability of leaves, leaf compost, and This improves the soil structure and the same processes take place in the soil as yard waste is likely to increase. rate of water infiltration. Municipalities must restrict leaves, yard Whey should not be applied to waste, and lawn clippings from their alfalfa for several reasons. First, alfalfa Table 10-6. Nutrient analysis for landfills and many have set up yard whole whey.a does not need the added nitrogen. waste composting sites. When Second, the rapid stimulation of available, these materials can be applied Amount per microbial activity coupled with the Nutrient acre-inchb advantageously to agricultural land. For

— lb —

Table 10-5. Soil test phosphorus content following Nitrogen (N) 330 16 consecutive years of biosolid application (Elkhorn, WI a 1979–94). Phosphate (P2O5) 250

————— Sampling depth (in) ————— Potash (K2O) 480 Treatment 0–6 6–12 12–18 18–24 24–30 30–36 Calcium 80 ——————————— ppm ——————————— Magnesium 15 Control 75 20 18 25 27 26 Chlorine 265 3 ton/a 210 160 23 27 38 32 Sodium 115 6 ton/a 270 230 38 22 38 27 a Not representative of whey permeate or a Soil samples collected in 2002. deproteinized whey. b Source: Peterson, A.E. 2002. Dept. of Soil Sci. Univ. Wis.-Madison. One acre-inch is 27,300 gals/acre. Solid content is 14,890 lb/acre-inch. Source: Kelling,K.A., and A.E. Peterson. 1981. Using Whey on Agricultural Land—A Disposal Alternative. University of Wisconsin-Extension publication A3098. C-10 10/18/05 11:15 AM Page 116

116 MANAGEMENT OF WISCONSIN SOILS

Table 10-7. Carbon to nitrogen in a compost heap. The ratio of carbon Gypsum ratios (C:N) of selected organic to nitrogen (C:N) in several materials is In some Great Plains and Western amendments. shown in table 10-7. If the carbon to states, high levels of sodium in soils Carbon to nitrogen ratio is greater than 30, cause the clay to disperse rather than Amendment nitrogen ratio microorganisms will use available soil form aggregates. Water does not move nitrogen for their needs. If the carbon through these soils easily, and they are Alfalfa hay 12:1 to nitrogen ratio is less than 20, difficult to work. Because of the microorganisms will mineralize the sodium, the pH is over 8.3. These soils Rotted manure 15:1 organic nitrogen and increase the can be reclaimed by replacing the + Grass clippings 19:1 supply of available nitrogen (NH4 -N sodium with calcium, and gypsum – + NO3 -N) in the soil. If the carbon to (CaSO4•2H2O) is often used for that Tree leaves 60:1 nitrogen ratio is between 20 and 30 the purpose. Wisconsin has very few, if any, level of available nitrogen remains naturally occurring high-sodium soils Cornstalks 60:1 unchanged. although the use of road salt can cause Straw 80:1 sodium problems in ditches along some sections of major highways and streets. Sawdust 500:1 Inorganic Gypsum applied to soils unaffected by Wood shavings 500:1 amendments sodium provides no benefit to soil Ground limestone, paper mill lime structure. If the soil is low in sulfur or Source: Schulte, E.E., and K.A. Kelling. sludge, and gypsum are the inorganic calcium, gypsum is a good source. 1989. Organic Soil Conditioners. amendments most commonly applied Otherwise, it has no value as an University of Wisconsin-Extension additive. publication A2305. to soil. The benefits of liming materials were discussed in chapter 6, “Soil Scraps of gypsum wallboard, a Acidity and Liming.” material commonly used to cover interior walls, are usually landfilled

Table 10-8. Yield response of alfalfa to the application of crushed wallboard at four Wisconsin locations.

Treatment Arlington Ashland Lancaster Spooner

—————————————— tons/a ——————————————

Control 4.0 2.6 4.2 3.4

Sulfura—50 lb/a 4.0 2.7 4.0 3.6

Crushed wallboard 1 ton/a 4.1 2.7 4.2 3.7 4 tons/a 3.9 2.8 4.1 3.8 16 tons/a 4.1 2.8 4.1 3.9

a Applied as gypsum fertilizer. Source: Wolkowski, R.P. 2003. Using Recycled Wallboard for Crop Production. University of Wisconsin-Extension publication A3782. C-10 10/18/05 11:15 AM Page 117

Chapter 10. Soil amendments 117

along with other construction debris. It nonconventional manner, (3) wetting are unprocessed except for grinding, is estimated that approximately agents and surfactants, (4) biological such as granite, glauconite, clay, and 1 pound of wallboard waste is created inoculants and activators, (5) plant natural deposits consisting mostly of for every square foot of construction stimulants and growth regulators, and gypsum or sand, are sometimes sold as area; resulting in about 1 ton of scrap (6) nonconventional soil management soil conditioners. Humates or humic per home. Rather than being disposed, programs. acids discarded during the mining of wallboard can be pulverized and Non-traditional soil amendments coal are pulverized and also sold as soil applied to soil to supply calcium and/or should be used with caution and not as a conditioners. Salts from evaporated sea sulfur. substitute for tried and proven practices. water or sulfates in combination with A study that evaluated the response A few products show beneficial results, organic extracts or materials such as of alfalfa to the application of but the yield increases have been small. kelp or whey may be similarly wallboard was conducted over a 3-year There is a significant amount of infor- marketed as conditioners. period at four Wisconsin locations. mation available about many of these Advertising materials suggest that The study compared the agronomic products. All of the land-grant universi- the products will loosen compacted rate of sulfur applied with gypsum ties in the North-Central region share in soil, improve water infiltration, make fertilizer to rates of crushed wallboard developing a database on nonconven- tillage easier, eliminate wet spots, ranging between 1 and 16 tons per tional products. Information from this improve the moisture-holding capacity, acre. Yield data from the second hay database is published as a compendium stimulate soil microorganisms, reduce year are shown in table 10-8. These of research reports entitled Nonconven- drought damage, or create a better root data show a small but significant tional Soil Additives: Products, Companies, environment. Four commercially positive response to the wallboard Ingredients, and Claims. This publication available soil conditioners tested in application at Ashland and Spooner. is frequently updated and can be found Illinois, South Dakota, and Wisconsin Both of these locations are in on the University of Wisconsin Soil as additives for corn showed no benefit. northwestern Wisconsin, a region Science Extension web site at Mineral nutrient sources where the contribution of sulfur in www.soils.wisc.edu/extension/ Some amendments in this category rainfall is low. publications/NCR.htm. Before trying have a guaranteed nutrient content on Large applications of available any of these products, seek out available the label and are promoted as being calcium will displace other positively information and then use it only on a needed in very small quantities. Other charged ions from soil-clay surfaces, small scale initially. Understand the products contain small quantities of subjecting them to loss from the soil by conditions and crop for which the secondary or micronutrients. Some leaching. To prevent this, University of product is recommended, have clear contain small quantities of non- Wisconsin research results suggest that instructions concerning application, and essential elements. Many of the crushed wallboard applications be know what the product is expected to materials are extracted, composted, or limited to 2 tons per acre on sandy soils accomplish. Compare the performance fermented from various organic sources and 5 tons per acre on medium- of these products against customary such as fish, seaweed, whey, or manure. textured soils. practices. Increased yields, reduced fertilizer need, Soil conditioners balanced nutrition, a natural form of Non-traditional Soil conditioners are materials that plant food, low salt content, and claim to improve the physical condition increased nutrient availability are some soil amendments of the soil. In general, this implies of the claims offered. Increasing fertilizer prices and the improved soil structure through better However, not all products fulfill search for ways to produce crops more aggregation. Materials promoted as soil the manufacturer’s claims. For example, efficiently have spurred the introduction conditioners include unprocessed rock one product purportedly would reduce of many non-traditional soil amend- phosphate or ground limestone that the amount of fertilizer needed in the ments. These amendments are classified may be combined with composted regular fertilizer program. A Wisconsin into six categories: (1) soil conditioners, organic materials. Mineral deposits that study testing that claim found no yield (2) mineral nutrient sources used in a C-10 10/18/05 11:15 AM Page 118

118 MANAGEMENT OF WISCONSIN SOILS

increase. In this study, the fertilizer was thatch cover). These materials have no Biological inoculants and placed with the seed at rates of 1 and effect on wettable soils. The claims activators 2 quarts per acre and applied as a foliar made for wetting agents and surfactants Inoculation of leguminous crop application at 1 quart per acre at the include loosening of tight soils, seed with Rhizobium bacteria to ensure 8-leaf stage, as recommended by the increased water infiltration, increased good nodulation and nitrogen fixation manufacturer. As seen in table 10-9, moisture-holding capacity, improved is a well-accepted practice. Soil the low rate of additional fertilizer tile drainage, and elimination of wet inoculation with free-living nitrogen applied to the seed or on the plant spots. Some also claim increased fixers has not been very successful. leaves gave no increase in yield over nutrient availability, increased protein Other inoculants containing organisms fertilizer alone. content of crops and increased yield. claimed to enhance organic matter None of five wetting agents tested in a decomposition have given negative Wetting agents and Kansas State study had any influence results in trials conducted in Illinois, surfactants on crop yield or infiltration of water. Minnesota, and Wisconsin. Some Wetting agents and surfactants Application of a wetting agent at the inoculants are claimed to produce have been used with herbicides and recommended rate of 2 quarts per acre growth-stimulating substances by insecticides for many years. Some to Plano silt loam, with or without organisms on the seed, in the soil, or research has shown that nonionic nitrogen, had no effect on corn yield near plant roots. Claims for these wetting agents can increase water (table 10-10). inoculants have not been substantiated infiltration on water-repelling soils by research. A mixture of several (such as peats or turf with a heavy

Table 10-9. Influence of seed-placed and foliar applications of a12-6-6 liquid fertilizer on corn yielda (Arlington, WI). Table 10-10. Influence of a wetting Seed-placed Foliar Corn yield agent on corn yielda (Arlington, WI). ———— qt/ab ———— bu/a Nitrogen Wetting Corn 0 0 139 applied agent yield

1 1 140 lb/a qt/a bu/a

2 1 136 0062

a All plots received 100 lb/a of 9-23-30 fertilizer as a 0259 row treatment plus 150 lb/a of supplemental nitrogen. 93 0 132 b One quart of 12-6-6 weighed about 2.5 lb and contained 0.3 lb nitrogen, 0.15 lb phosphate 93 2 131 (P2O5) and 0.15 lb potash (K2O). Source: Kelling, et al. 1980, 81. Unpublished research 168 0 144 report. Dept. of Soil Sci., UW-Madison. 168 2 144

a Three-year average. Source: Wolkowski, et al. 1985. Agron. J. 77: 695–698. Reproduced with permission of the American Society of Agronomy, Inc., Madison, WI. C-10 10/18/05 11:15 AM Page 119

Chapter 10. Soil amendments 119

microorganisms applied as a seed on horticultural crops to control An activator consisting of a culture coating and as a soil inoculum did not rooting, fruit set, ripening, shape, and of Lactobacillus bacteria on a whey base affect the yield of corn at either of two fruit drop. A number of naturally with an extract of Norwegian kelp was sites in 3 years (table 10-11). occurring products have been marketed tested on alfalfa in Illinois and on for field crops with claims for growth potatoes in Wisconsin (table 10-12). Plant stimulants and regulation. Some are produced by Small but statistically significant yield growth regulators fermentation of agricultural waste increases were obtained in both cases Plant growth regulators are products. They are promoted for use by when examined over 3 years but not compounds other than nutrients that soil, seed, or foliar application. The when only 1 year was considered. Use affect plant processes in some beneficial claimed benefits often include nutrient of this product on corn and soybeans in way to increase yield, improve quality, release, better rooting, drought Wisconsin gave no beneficial effect. or facilitate harvesting. Growth resistance, improved quality, and higher regulators have been used successfully yields.

Table 10-11. Influence of a soil inoculanta on corn yield.

Nitrogen Soil appliedb inoculum Seed coat Corn yield

lb/a lb/a g/25 lb seed bu/a Table 10-12. Influence of a 00079growth stimulant on alfalfa and potato yields.a 0 6 10 84 Activator Crop 75 0 0 131 added (oz/a) yield

75 6 10 132 Alfalfa ton/a

150 0 0 139 0 6.00

150 6 10 137 4 6.15

a The soil inoculant was labeled as containing Actinomyces thermophilus, Azotobacter 8 6.26 chroococum, Mixobacter spp., Streptomyces fulvourides, and Bacillus subillus in a whey base. The seed coating was purported to contain growth regulators and 16 6.27 micronutrients. Results are the average of 3 years at two locations. b All plots received 200 lb/a of 9-23-30 as a starter. 32 6.64 Source: Wolkowski, R.P., and K.A. Kelling. 1984. Agron. J. 76: 189–192. Reproduced Potato cwt/a with permission of the American Society of Agronomy, Inc., Madison, WI. 0 107

4b 113

a Standard fertilizer recommendations were applied to all treatments. b Three applications. Source: Kelling et al. 1983. Solutions, May/June: 18–26. C-10 10/18/05 11:15 AM Page 120

120 MANAGEMENT OF WISCONSIN SOILS

Questions 1. A farmer spreads dairy manure at a rate of 25 tons per acre on an 80-acre field. a. How many pounds per acre of total nitrogen, phosphate, and potash will the field receive? b. How many pounds of these nutrients will be available to crops in the growing season following manure application? (Assume that the manure is incorporated the same day that it is applied.) 2. What benefit do manure, sewage sludge, and whey offer besides supplying nutrients? 3. How do sewage sludge and whey compare with manure as plant nutrient sources? 4. It is recommended that land to which sewage sludge will be applied should be limed to a pH of 6.5 or higher. Why? 5. Explain how applying sawdust to soil could induce nitrogen deficiency in crops. 6. Of what value is gypsum as a soil amendment? Under what conditions would you recommend that it be used? 7. Under what conditions are wetting agents useful in crop production? C-11 10/18/05 11:16 AM Page 121

CHAPTER 11 121 Environmental concerns and preventive soil management practices

Nutrients, pesticides, and other Nitrates in substances need to be managed groundwater properly to meet crop requirements Groundwater supplies without harming human or animal approximately 70% of the drinking “The earth has always health or the quality of our water water in Wisconsin. Nitrate is the most resources. Nutrients of concern with nurtured us, despite our common contaminant of groundwater. respect to water quality are nitrogen Federal and state drinking water scornful abuse, and we can and phosphorus. Generally, nitrate- standards specify that water used for nitrogen is a groundwater concern and no longer continue to behave human consumption should not phosphorus is a surface water issue; contain more than 10 ppm of nitrate- as its ungrateful offspring. It however, nitrogen can also be factor in nitrogen (NO –-N). This value is some surface water quality problems. 3 is time for us to nurture the equivalent to 44 ppm nitrate (NO –). Excess nitrates in drinking water can 3 Laboratories report water nitrate earth in return.” cause human and animal health content as either nitrate-nitrogen or problems, while excess phosphorus in nitrate. Many private wells in D.J. Hillel. Out of the Earth, 1991 lakes and streams can lead to algal Wisconsin exceed this level. blooms and excessive growth of aquatic The health concern with nitrate plants. Pesticides used to control weeds, contamination of drinking water is insects, and diseases can cause health largely focused on infants under 6 problems if they get into drinking months of age. Infants, as well as young water or food. (Discussion of pesticide livestock, are susceptible to a condition management is beyond the scope of called methemoglobinemia, or “blue this soil management publication.) baby syndrome” if they consume water Lastly, heavy metals, occurring or formula that contains elevated levels naturally or added incidentally, are also of nitrate-nitrogen. Bacteria in a baby’s of some concern because at high mouth and stomach convert ingested concentrations they interfere with nitrate to nitrite (NO –). The nitrite various plant and animal metabolic 2 reacts with iron in the blood’s processes. hemoglobin, reducing the capacity of blood to carry oxygen. The result, in rare circumstances, can be fatal to infants. Although water containing more than 10 ppm of nitrate-nitrogen is not recommended for human C-11 10/18/05 11:16 AM Page 122

122 MANAGEMENT OF WISCONSIN SOILS

consumption, adults and livestock may The map, Groundwater Rate of application be able to tolerate considerably higher Contamination Susceptibility in Nitrogen applied but not recovered levels. However, pregnant women and Wisconsin, shows where groundwater is by crops can contribute nitrate to nursing mothers should also avoid most easily contaminated with nitrates groundwater through leaching. drinking water high in nitrate. Chronic and pesticides. This map considers only Recovery of applied fertilizer nitrogen health effects due to long-term the likelihood of water moving from decreases as the amount added ingestion of water containing high the soil surface to the water table. It increases. The results of a research trial levels of nitrate are being investigated. does not consider the type of on corn, presented in table 11-1, Sources of nitrate include nitrogen contaminant or the amount in the soil. demonstrate this principle. The crop released from organic matter through The main factors involved in recovered less nitrogen with each microbial decomposition, nitrogen determining susceptibility of successive increment of fertilizer. The fixed from air by nitrogen-fixing groundwater to contamination are the optimum economic yield was obtained organisms, and nitrogen added in type of bedrock, depth to bedrock, with 160 pounds of nitrogen per acre. manure, fertilizer, sludge, rain, or other depth to the water table, soil texture, This would usually be the best rate to inputs. Nitrate is a soluble, negatively and other characteristics of surface apply. However, if nitrate charged ion. It is not held on cation deposits occurring between the topsoil contamination of groundwater is a exchange sites in the soil, nor is it and bedrock. The text accompanying major problem in the area, using lower adsorbed onto colloid surfaces. Hence, the map explains the importance of rates of nitrogen could help reduce it moves with percolating water. most of these factors. nitrate losses because more of the Nitrate movement is greatest when the Farmers have no control over the applied nitrogen is recovered by the inputs exceed plant requirements and amount of nitrate contributed by crop at lower nitrogen rates. in soils where percolation to rainfall or soil organic matter. They Only a portion of the nitrogen not groundwater is high. can, however, manage the inputs from recovered by the crop may find its way fertilizer, legumes, and manure to to the groundwater. Some will be prevent groundwater contamination. immobilized by soil microorganisms and become part of the pool of organic nitrogen, some may undergo Table 11-1. Recovery of applied nitrogen by corn in relation to denitrification and be returned to the the amount applied. atmosphere, and some will simply remain in the root zone and be Rate of Nitrogen recovery in grain available to plants the next season. nitrogen Corn yield Incremental Total Nevertheless, the potential exists for some of the unused nitrogen to enter — lb/a — — bu/a — ———— % ———— the groundwater. 093—— In the past, some farmers added extra nitrogen as “insurance” to make 40 115 45 45 sure plants had enough nitrogen to take advantage of favorable weather 80 131 45 40 conditions. Decades of Wisconsin 120 138 20 37 research has shown that the optimum economic rate of nitrogen for corn is 160 144 17 32 independent of weather variables that 200 145 0 25 influence yields. In other words, it takes about the same amount of Source: Bundy et al., 1992. Nutrient Management—Practices for Wisconsin Corn Production and Water Quality Protection. University of Wisconsin-Extension publication A3557. C-11 10/18/05 11:16 AM Page 123

Chapter 11. Environmental concerns and preventive soil management practices 123

Figure 11-1. Corn yield response to nitrogen application over several years on a Plano silt loam soil.

Corn grain yield (bu/a) optimum N rate

Nitrogen rate (lb/a) Source: Adapted from Bundy et al., 1992. Nutrient Management— Practices for Wisconsin Corn Production and Water Quality Protection. University of Wisconsin-Extension publication A3557.

nitrogen to reach the economic Methods to improve and estimates the amount present in optimum in a poor year as it does in a nitrogen rate the third foot. Most soils contain about good year (figure 11-1). The reason for recommendations 50 pounds per acre of nitrate-nitrogen this is that recovery of available Nitrogen recommendations for in the top 3 feet of soil in the spring, nitrogen is higher under favorable corn can be fine-tuned by testing the even when no nitrogen was applied the growing conditions so that a higher soil for the amount of nitrate in the soil previous year. This “background” level yield is possible. Plant roots proliferate profile. Two tests are available, a represents nitrogen present at a level more under good growing conditions, preplant soil profile nitrate test and a too low for plants to extract. The total enabling the plant to extract more soil pre-sidedress soil nitrate test. Soil nitrate in the top 3 feet of soil minus nitrogen than it could under poorer testing for nitrogen allows corn 50 pounds per acre for background conditions. nitrogen recommendations to be nitrogen is subtracted from the nitrogen The best way to determine the adjusted for the numerous year- and recommendation. Suppose a preplant optimum economic rate of nitrogen to site-specific conditions that can soil profile nitrate test shows nitrogen is apply is to have the soil tested in a influence nitrogen availability. already present at 140 pounds per acre laboratory using procedures developed The preplant soil profile and the nitrogen recommendation calls by the University of Wisconsin. nitrate test, taken in the spring prior for 160 pounds per acre. The Current recommendations for corn are to corn planting, measures the carryover recommendation adjusted for soil based on soil organic matter, soil nitrate-nitrogen in the top 2 feet of soil profile nitrate would be calculated texture, growing degree days, and yield using the following equation: potential of the soil. Recommendations for other crops are based on soil organic – Soil test N – Soil profile NO3 -N credit = Adjusted N matter and yield goal. recommendation (profile N – background N) recommendation

160 lb/a – 90 lb/a = 70 lb/a (140 lb/a – 50 lb/a) C-11 10/18/05 11:16 AM Page 124

124 MANAGEMENT OF WISCONSIN SOILS

In years with below-normal The residual nitrate level in the soil spring manure applications or previous precipitation in the fall, winter, and profile depends on three main factors: legume crops. spring, substantial amounts of residual soil type, prior precipitation, and The pre-sidedress nitrate nitrate-nitrogen can carry-over from previous nitrogen application rates. test is the other soil test for nitrogen one growing season to the next. Carry-over of nitrate-nitrogen is always available to corn growers. Samples for Measuring and accounting for residual expected to be low on sandy soils. In this test are collected from the top foot nitrogen can reduce nitrogen other soils, carry-over of nitrogen can of soil when corn is 6 to 12 inches tall. recommendations for corn significantly. be expected if precipitation during the With its later sampling period, the pre- For example, in April of 1989, 1990, previous growing season and over- sidedress nitrate test can measure the and 1991 the average nitrate-nitrogen winter period is low (table 11-2). amount of nitrogen released from in the top 3 feet of soil was 202, 193 Figure 11-2 illustrates a study on a previous legumes and manure and 124 pounds per acre, respectively, Dubuque silt loam that showed higher applications. This test can be a valuable for samples received by the UW-Soil nitrogen applications resulted in higher tool for confirming the amount of and Plant Analysis Lab. Precipitation residual nitrate levels following the dry nitrogen credited from manure or during the 1988 and 1989 growing years of 1988 and 1989. Carry-over previous legume crops. If the soil seasons was very limited as reflected in nitrogen was lowest in 1992, a year contains 21 ppm or more, no the higher levels of residual soil nitrate with the highest over-winter additional nitrogen is needed. If there for 1989 and 1990. Adjusting nitrogen precipitation. is less than 21 ppm nitrate-nitrogen, a rates for residual nitrate not only lowers Because soil sampling for the sidedress application is warranted at the a grower’s fertilizer bill, it also reduces preplant soil profile nitrate test occurs rates shown in table 11-3. the amount of nitrate available for early in the spring, it will not measure leaching to groundwater. any nitrogen released from fall or

Figure 11-2. Nitrate-nitrogen to a depth of three feet as influenced by the rate of nitrogen applied the preceding year on a Dubuque silt loam. The numbers above the bars for each year are the amounts of overwinter precipitation (October–April) in inches.

Annual nitrogen applied, lb/a 050 100 200 500

8.8" precip.

400

13.1" precip. 16.9" precip. 300

200

11.2" precip. Nitrate-nitrogen, lb/a Nitrate-nitrogen, 19.7" precip. 100

0 1988 1989 1990 1991 1992 Source: Bundy et al., 1993. Proc. 1993 Fert., Aglime & Pest Mgmt. Conf. 32:213–222. C-11 10/18/05 11:16 AM Page 125

Chapter 11. Environmental concerns and preventive soil management practices 125

offices have information on how to Table 11-2. Potential for nitrogen carryover based on collect manure samples and where to soil type and overwinter precipitation. have them analyzed. Timing of nitrogen —— Overwinter precipitation —— Soil Below Above applications type normal Normal normal The more time that elapses between nitrogen application and Potential for nitrogen carryover uptake by the crop, the more Sandy soils low low low opportunity there is for leaching of nitrate to groundwater or loss by Loams high medium low denitrification. Loss by leaching is of greater concern on sandy soils than on Silt loams, silty clay loams high high low silt loams or silty clay loams. The problem is greatest on irrigated sands. Corn uses nitrogen slowly for the first month after planting. Rapid uptake Nitrogen credits Manure can supply high levels of begins about 6 weeks after planting and When a soil test recommendation nitrogen, as well as other nutrients. The continues until tasseling. Uptake calls for a given amount of nutrients, nitrogen credits for various kinds of continues until maturity but at a slower the recommendation is often manure are presented in table 10-2. pace. interpreted as meaning commercial These values are based on averages of To minimize the risk of nitrate fertilizer. However, nutrients added in many manure analyses. Analyzing the leaching, do not apply nitrogen in the manure or other organic byproducts manure for nutrient content will yield fall, especially on coarse-textured soils. and nitrogen from previous leguminous more precise credits. County Extension Fall to spring precipitation, soil texture, crops are a source of fertilizer nutrients that should be accounted for and “credited” against the base nutrient Table 11-3. Corn nitrogen recommendations based on the recommendations given from the soil pre-sidedress soil nitrate test (PSNT). test report. Legume crops, when grown in ———Soil yield potentiala——— rotation, supply substantial amounts of PSNT result Very high/high Medium/low nitrogen to crops that follow. A good —N (ppm)— ——N application rate (lb/a)—— stand of alfalfa will provide all the nitrogen needed by a following crop of 21 0 0 corn. If information on previous legume crops is provided when 20–18 60 40 submitting soil samples to the 17–15 100 40 laboratory, Wisconsin soil test recommendations will automatically 14–13 125 80 credit the nitrogen contribution and subtract it from the amount 12–11 150 80 recommended. Sometimes cropping < 10 160b 120b plans change and it becomes necessary for farmers or their advisors to make a To determine a soil’s yield potential, consult University of Wisconsin-Extension these adjustments. Table 9-1 tells how publication Soil Test Recommendations for Field, Vegetable and Fruit Crops much nitrogen to subtract from the (A2809). b No adjustment made to corn recommendations. amount recommended. C-11 10/18/05 11:16 AM Page 126

126 MANAGEMENT OF WISCONSIN SOILS

and soil moisture all influence the Multiple (or split) applications of ground is frozen. During this period, potential for loss of fall-applied nitrogen during the growing season are soluble ammonium and nitrate- nitrogen. If fall applications must be another option for reducing losses on nitrogen may be lost in substantial made, limit them to ammonium forms sandy soils. Additional information on quantities in runoff water. Winter or of nitrogen (anhydrous ammonia, urea, the timing of nitrogen applications and spring runoff can also carry organic ammonium sulfate) on medium- how it affects crop yield and the nitrogen from manure solids. The best textured, well-drained soils. Fall potential for loss of nitrate is discussed way to prevent winter nitrogen loss is applications should be delayed until in chapter 9. by avoiding winter application of soil temperatures are below 50°F. If Nitrification inhibitors slow manure on frozen sloping land. applications of nitrogen must be made the bacterial conversion of ammonium The use of manure storage facilities + – with soil temperatures greater than (NH4 ) to nitrate (NO3 ). They can be is recommended for periods when land 50°F, include a nitrification inhibitor used with ammonium or ammonium- application is inadvisable. These with the fertilizer to further reduce the forming fertilizers. The effectiveness of facilities should be constructed and risk of leaching. the inhibitor depends on when it is located to minimize runoff losses and Spring preplant applications of applied and on soil conditions. The direct seepage to groundwater. nitrogen are environmentally sound on probability of increasing corn yields in Chapter 10 gives more detailed well-drained, medium-textured soils. Wisconsin by using nitrification recommendations for handling manure. When making spring preplant inhibitors is summarized in table 11-4. Irrigation scheduling applications on sandy or poorly- Manure management Over-irrigation and excess rainfall drained soils, use ammonium forms of Manure applications can become can cause substantial leaching of nitrate nitrogen treated with a nitrification an environmental concern if manure to groundwater. Furthermore, over- inhibitor. Sidedress applications are nutrients are not credited against irrigation is uneconomical. See more effective on sandy soils than fertilizer recommendations or if chapter 4 for a discussion of irrigation preplant applications with nitrification applications result in manure runoff to scheduling as a means of reducing inhibitors. On corn, make sidedress lakes or streams. The latter is especially leaching. applications 4 to 6 weeks after planting. a concern during the winter when the

Table 11-4. Relative probability of increasing corn yield by using nitrification inhibitors.

—————— Time of nitrogen application —————— Spring Spring Soil Fall preplant sidedress

Sands and loamy sands not recommended good poor

Sandy loams and loams fair good poor

Silt loams and clay loams

well-drained fair poor poor

somewhat poorly drained good fair poor

poorly drained good good poor C-11 10/18/05 11:16 AM Page 127

Chapter 11. Environmental concerns and preventive soil management practices 127

Urease inhibitors ■ Manage fall manure applications supply in the water, killing fish and Urease inhibitors are chemical carefully on excessively well-drained other aquatic organisms. In addition, compounds that can be added to urea soils (i.e., sands). nuisance growth of aquatic vegetation or urea-containing fertilizers to slow ■ Store manure in properly located reduces the recreational and aesthetic the action of the soil enzyme “urease” and constructed facilities during value of lakes. For those communities in converting urea to ammonium periods when land application is not drawing their drinking water from compounds in soil. The advantage of advisable. surface water, certain algae can cause slowing urease activity is to reduce taste and odor problems, and may pose ■ Manage barnyards and feedlots to ammonia volatilization losses from health hazards. minimize leaching and runoff losses. surface-applied urea-containing The growth of algae and other fertilizers. The challenge in deciding if ■ Schedule irrigation to minimize aquatic plants can be limited by and when to use a commercially leaching. restricting the supply of any of the available urease inhibitor is the ■ Manage fertigation systems carefully. essential elements. Because phosphorus identification of those situations where is the element most often limiting ■ Diversify crop rotations to include its use will conserve fertilizer nitrogen growth in fresh water environments, crops that can use residual nitrogen. and result in a yield benefit. Typically, and possibly the most easy to control, it urease inhibitors have their greatest ■ When possible, plant a fall cover is seen as the “villain” in potential for benefit in cropping crop. eutrophication. situations that are high risk for losing Rate of application significant amounts of nitrogen Applying more phosphorus than through ammonia volatilization and no Phosphorus in crops need is unwise economically as other practical management alternatives surface water well as environmentally. Soil testing are available. Phosphorus is usually not a should be used to determine the problem in groundwater because: Best management amount of phosphorus to apply. Soil (1) elevated concentrations in drinking practices for nitrogen test laboratories base phosphorus water do not pose a health threat, and The following management recommendations on realistic yield (2) the concentration of phosphorus in practices will help to minimize nitrogen goals to ensure optimum yields. the water that percolates through soil losses and protect water quality. solution is low, even on heavily Phosphorus credits ■ Apply nitrogen at recommended fertilized soils. However, phosphorus is Phosphorus applied as manure rates. a problem in runoff because it should be credited against fertilizer ■ Use soil nitrate tests when encourages the growth of algae and recommendations. Table 10-2 identifies appropriate. nuisance weeds in surface waters, how much phosphorus credit to take for various kinds of manure. Land ■ Credit nitrogen contributions from especially in lakes or reservoirs where legumes, manure, and other organic water movement is very slow. application of manure to cropland byproducts. Nutrient enrichment of surface recycles nutrients, but can also lead to water (eutrophication) occurs in the build-up of phosphorus in soils, ■ Do not apply nitrogen fertilizer in nature, and it is a natural process of the which in turn, increases the potential the fall. aging of lakes that takes place regardless for losses via runoff and soil erosion. ■ Use nitrification inhibitors when soil of farming practices. However, nutrient Manure is often applied to cropland at conditions and nitrogen application runoff accelerates the process. Excess rates to meet the nitrogen need of the timing may promote leaching. nutrients in surface water cause algae crop. The available nitrogen and ■ Incorporate or inject manure. blooms and abnormally high phosphorus contents of dairy and other production of algae and aquatic plants. animal manures are about equal (table As the aquatic plant material 10-2). However, the nitrogen need of decomposes, it depletes the oxygen corn, for example, is generally two to C-11 10/18/05 11:16 AM Page 128

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three times greater than the phosphorus crop requires. To minimize potential As stated in the manure need (table 11-5). The consequence of environmental problems, sludge or management for nitrogen section of applying manure at rates to meet the whey should not be applied to sloping this chapter, the use of manure storage nitrogen need of corn is that land where erosion is not controlled. facilities is recommended for periods phosphorus applications will exceed One option for drawing down when land application is unsuitable. crop removal (figure 11-3). The result high soil test phosphorus levels is to These facilities should be constructed is the build-up of phosphorus in plant crops that remove large quantities and located to minimize runoff and cropland soils. Long-term manure of phosphorus. Such crops include seepage losses. applications have elevated the soil legume forages and corn silage. Until recently, the recommendation phosphorus level of many soils above for land-applied manure was to Manure management the range necessary for optimum crop incorporate it within 3 days of As with nitrogen, a general growth. This trend is especially application whenever possible. Similar management practice for phosphorus is prevalent in areas of concentrated to fertilizer-phosphorus, manure- to avoid manure applications to sloping livestock operations. Once soil test phosphorus will bind with soil particles frozen lands. Losses of phosphorus in phosphorus exceeds optimum levels, when they are in close contact. runoff vary greatly from year to year future manure applications should be Incorporating manure reduces the and depend on conditions such as the limited to rates that only replace the amount of dissolved (or soluble) amount and timing of winter and phosphorus removed by the crop. phosphorus in runoff because spring precipitation, depth of snow Credits for phosphate in sewage phosphorus can bind to soil particles. cover, and spring freeze-thaw patterns. sludge, whey, and other waste materials However, incorporating manure have not been established. These materials are typically applied on the basis of their available nitrogen content and the nitrogen needs of the crop to Figure 11-3. Nitrogen-based manure application strategy for corn. be grown. Subsequently, more phosphorus will be applied than the

Table 11-5. Recommended nutrient application rates for corn grain at optimum soil test levels.

Corn — Application rates — target yield N P2O5 K2O

bu/a ————— annual lb/a————— Source: Sturgul, S.J. and L.G. Bundy, 2004. Understanding Soil 200 160 75 55 Phosphorus. University of Wisconsin-Extension publication A3771.

160 160 60 45

120 160 45 35

Source: Kelling et al., 1998. Soil Test Recommendations for Field, Vegetable, and Fruit Crops. University of Wisconsin- Extension publication A2809. C-11 10/18/05 11:16 AM Page 129

Chapter 11. Environmental concerns and preventive soil management practices 129

involves tillage, which can increase soil reaches surface waters. Numerous Source areas vary in location and erosion. Loss of sediment by soil management practices for runoff and magnitude of phosphorus contribution erosion increases total phosphorus loss soil erosion control have been due to weather conditions such as the (total phosphorus is the sum of researched, developed, and intensity and length of rainfall, as well sediment- and dissolved-phosphorus). implemented. Runoff and erosion as land characteristics such as soil Manure broadcast on the surface control practices range from changes in moisture, soil erodability, soil water (without incorporation) acts as mulch, agricultural land management (cover storage capacity, topography, etc. Not lowering soil erosion. Unincorporated crops, diverse rotations, conservation all areas that would be obvious manure applications tend to reduce tillage, contour farming, and contour phosphorus sources have a pathway to total phosphorus losses by lowering soil strip cropping) to the installation of surface water. On the other hand, not erosion but increase dissolved structural devices (buffer strips, all areas with high potential for phosphorus losses. Incorporating diversions, grade stabilization transport have a significant source of manure with tillage may lower structures, grassed waterways, and phosphorus. The many factors dissolved phosphorus losses but tends terraces). The most commonly used, influencing phosphorus movement to increase total phosphorus losses. widely adopted, and easily from the landscape make it challenging Recent Wisconsin findings suggest that accomplished conservation practice is to identify areas prone to losing the traditional management maintaining surface residue through phosphorus. Various landscape recommendation for incorporating various types of conservation tillage. assessment tools have been developed manure may not minimize cropland See chapter 5 for a discussion of soil over the years to identify sites requiring phosphorus losses if total phosphorus conservation practices. improved management to minimize reductions are the objective. This is environmental risk. Identification of particularly true for spring manure The phosphorus index is one landscape areas prone to applications. With regulatory agencies tool that calculates the risk of phosphorus loss currently using total phosphorus as the phosphorus loss from individual fields parameter on which to base regulations, Phosphorus that reaches a lake or and provides management a general recommendation to surface stream often originates from small areas recommendations to reduce those apply manure without incorporation to within a watershed. One study found losses. The phosphorus index evaluates fields with soil conservation practices in that less than 10% of the area within both source and transport factors in its place is appropriate. As a general the investigated agricultural watersheds determination of phosphorus loss practice, using conservation tillage, was responsible for 90% of the potential (figure 11-4). With the whether no-till or reduced tillage, will phosphorus contained in runoff. help keep soil particles on the field by increasing surface residue, which will in Figure 11-4. Critical phosphorus source and transport turn lower the loss of phosphorus in area identification. runoff to lakes and streams. Chapter 10 gives more detailed recommendations for managing manure. Erosion control Most of the phosphorus found in surface water is associated with the organic matter and soil particles that erode from the land. The key to minimizing nutrient contributions to surface waters is to reduce the amount Source: Sturgul, S.J. and L.G. Bundy, 2004. Understanding Soil Phosphorus. of runoff and eroded sediment that University of Wisconsin-Extension publication A3771. C-11 10/18/05 11:16 AM Page 130

130 MANAGEMENT OF WISCONSIN SOILS

identification of critical areas where ■ Use the phosphorus index to identify Assessment of on-farm both source and transport factors fields prone to excessive phosphorus nutrient resources coincide, appropriate management loss. The amount of crop nutrients practices can be applied to reduce More extensive information on the supplied to fields from on-farm phosphorus losses. A phosphorus index management of phosphorus can be nutrient resources such as manure, has been developed for Wisconsin and found in University of Wisconsin- legumes, and organic wastes needs to can be found at wpindex.soils.wisc.edu. Extension publication Understanding be determined and deducted from the Soil Phosphorus: An Overview of soil test report’s base fertilizer Best management Phosphorus, Water Quality, and recommendations. Manure applications practices for phosphorus Agricultural Management Practices to fields supply crops with nitrogen, A summary of the best (A3771). phosphorus, and potassium—as well as management practices to minimize sulfur and organic matter. Legume phosphorus losses are as follows: crops such as alfalfa, clover, and ■ Use soil-erosion control practices to Nutrient soybean supply nitrogen to the crops minimize soil loss and runoff. management that follow them. ■ Apply phosphorus at recommended planning Nutrient crediting rates for the crop to be grown. Formal plans detailing a farm’s Once the on-farm nutrient ■ Base phosphorus application rates on nutrient application strategy have been resources are determined, commercial realistic yield goals. developed for many farms in fertilizer applications need to be ■ Credit phosphorus contributions Wisconsin. A nutrient management adjusted to reflect these nutrient from manure and other organic plan is required for participation in credits. This action not only reduces byproducts. various federal and state farm programs commercial fertilizer bills, but it also involving cost-sharing. A farm nutrient protects water quality by eliminating ■ Incorporate broadcast applications of management plan can also be a nutrient applications in excess of crop phosphorus fertilizer. requirement of county ordinances need. Excessive nutrient additions to ■ Incorporate or inject manure in a dealing with the construction of cropland can result in contamination of manner that does not increase soil manure storage facilities or livestock groundwater as well as lakes and erosion. expansion. streams. ■ Avoid applying manure to sloping Ideally, a farm nutrient Management skills come into play frozen or saturated soils. management plan is a strategy for when determining nutrient credits. For ■ Store manure in properly located obtaining the maximum return from example, to properly credit the and constructed facilities during on- and off-farm fertilizer resources in a nutrients supplied from manure, a periods when land application is not manner that protects the quality of grower must know both the manure advisable. nearby water resources. Each of the application rate and the crop-available basic components to all farm nutrient nutrient content of the manure. To ■ Target fields with low soil test management plans are described below. credit the nitrogen available to crops phosphorus levels for manure following alfalfa, the condition of the Soil testing applications. alfalfa stand as well as last cutting date Complete and accurate soil tests ■ Control runoff from barnyards and and soil texture need to be known. feedlots. are the starting point of any farm nutrient management plan. All ■ Do not surface-apply manure on cropland fields must be tested or have sloping, no-till cropland. been tested recently, generally within ■ Install buffer strips adjacent to the last 4 years. From the soil test surface waters receiving runoff from results, base fertilizer recommendations cropped fields. for each field are given. C-11 10/18/05 11:16 AM Page 131

Chapter 11. Environmental concerns and preventive soil management practices 131

Consistency with the Manure spreading plan management standard periodically farm’s conservation plan The majority of any nutrient changes with revisions, but basically A nutrient management plan needs management plan for livestock farms requires producers to follow University to be consistent with a farm’s soil will deal with the manure spreading of Wisconsin recommendations for conservation plan. The conservation plan. The amount of manure a farm nutrient inputs to cropland. The plan is an important component of any produces has to be applied to fields in a standard also contains additional nutrient management plan for it manner that makes sense both restrictions on the timing and location contains needed information on environmentally and agronomically. of nutrient applications to agricultural planned crop rotations, field slopes Planned manure applications should be fields. A current version of the nutrient (which is important when planning made at rates that do not exceed crop management standard can be found at manure applications), and conservation nutrient need as identified in the soil www.datcp.state.wi.us/arm/agriculture/ measures needed to maintain soil test report. The nutrient management land-water/conservation/nutrient- erosion rates at “T” or tolerable rates. plan should also prioritize those fields mngmt/planning.jsp. In the event that a soil conservation that would benefit the most from the plan does not exist, or the existing plan manure-supplied nutrients while does not meet “T”, the information posing minimal threats to water quality. Non-essential contained in a conservation plan will Also, the nutrient management plan elements have to be obtained before the nutrient will identify those fields with manure Plants take up some elements from management plan can be developed. spreading restrictions. Examples of the soil solution simply because they such restrictions would be fields Manure inventory are present even though they are not adjacent to lakes and streams, sloping Probably the most challenging needed by the plant. Some of these are fields where the threat of spring runoff aspect of developing and implementing essential to animals, such as cobalt, prohibits manure applications in the a farm nutrient management plan is the iodine, and selenium. At high winter, and fields in the vicinity of advance planning of manure concentrations these non-essential wells, sinkholes, or fractured bedrock. applications to cropland fields. elements may pose a potential health The seasonal timing of manure This involves estimating the threat if they get into the food chain. applications to cropland will also be amount of manure produced on the Selenium, for example, is found at toxic identified in a nutrient management farm and then planning specific concentrations for grazing animals in plan. The timing of planned manure manure application rates for individual some plant species that accumulate this applications will depend upon each cropland fields. Sounds challenging— element in the Great Plains, but it is farm’s manure handling system. and it is, but there are some tricks to sometimes deficient in forage grown in Manure application periods for a the trade. One of them is calibrating Wisconsin soils. Low selenium in the farmer with manure storage will be your manure spreader. This can be diet of animals causes “white muscle” significantly different from that of a done using scales—either platform disease. farmer who has to haul manure on a scales or portable axle scales available All elements occur naturally in daily basis. from the county Extension or Land soils and in the earth’s crust. They Conservation office. Once calibrated, The 590 nutrient become of concern only when the level the number of tons (or gallons) of management standard is high enough to threaten human and manure the spreader typically holds is The 590 standard is a United animal health. Table 11-6 identifies the known. With this information, specific States Department of Agriculture— potential toxicity level of several manure application rates for fields can Natural Resources Conservation elements and table 11-7 lists their be planned. Service document that defines the sources. minimum requirements and One source of heavy metals is components of an acceptable nutrient municipal biosolids (sewage sludge). management plan. The 590 nutrient Table 10-4 lists the concentrations of C-11 10/18/05 11:16 AM Page 132

132 MANAGEMENT OF WISCONSIN SOILS

Table 11-6. Potential toxicity of several elements taken up by plants.

——— Essentiality ——— ——— Toxicity ——— Element Symbol Plants Animals Plants Animals

Arsenic As No No Moderate High

Cadmium Cd No No Moderate Higha

Cobalt Co No Yes Low Moderate

Chromium Cr No No Low Low

Copper Cu Yes Yes Moderate Moderate

Iron Fe Yes Yes Low Low

Lead Pb No No Low Higha

Manganese Mn Yes Yes Moderate Moderate

Mercury Hg No No Low Higha

Molybdenum Mo Yes Yes Moderate High

Nickel Ni No Yes High Moderate

Selenium Se No Yes Moderate High

Zinc Zn Yes Yes Moderate Low

a Cumulative effects. Source: Keeney, D.R., et al. 1975. Guidelines for the Application of Wastewater Sludge to Agricultural Land in Wisconsin. DNR Tech. Bull 88. Madison, WI.

each of the heavy metals found in Research shows that heavy metals (table 11-8). In fact, none of the six sewage sludge. Interestingly, those do not accumulate uniformly within a metals tested accumulated in the grain. concentrations are much lower than plant—seeds and fruits usually contain Heavy metal loading from biosolid those collected two decades earlier. much lower levels of heavy metals than application is regulated by monitoring Recycling of metals and tighter U.S. do the vegetative plant parts. In a the elemental content of waste Environmental Protection Agency 6-year study, the concentrations of materials and maintaining levels below (EPA) and Wisconsin Department of heavy metals in corn were measured EPA-specified ceiling concentrations. A Natural Resources (DNR) restrictions when Milwaukee sewage sludge was risk assessment that evaluated 14 are probably responsible for this applied annually at a rate of 6 ton/a potential pathways of exposure to decrease. Also, many municipalities (dry weight basis). Researchers found humans established these work with industry to pre-treat elevated concentrations of cadmium, concentrations such that 100 years of wastewaters to lower the input of heavy copper, and zinc in corn earleaf and consecutive applications would not metals. stover tissue but not in the grain present an unnecessary risk. C-11 10/18/05 11:16 AM Page 133

Chapter 11. Environmental concerns and preventive soil management practices 133

Table 11-7. Sources of metals in the environment.

————— Source ————— Element General Specific

Arsenic Agricultural Arsenical pesticides used in the past.

Cadmium Agricultural Impure phosphate fertilizers. Industrial Electroplating, pigments, chemicals, alloys, automobile radiators and batteries.

Chromium Industrial Refractory bricks, plating of metals, dying and tanning, corrosion inhibitors.

Copper Electrical Wire, apparatus. Plumbing Copper tubing, sewage pipes. Industrial Boilers, steampipes, automobile radiators, brass. Agricultural Fungicides, fertilizers.

Lead Plumbing Caulking compounds, solders. Industrial Pigments, production of storage batteries, gasoline additives, anti-corrosive agents in exterior paints, ammunition.

Mercury Electrical Apparatus. Industrial Electrolytic production of chlorine and caustic soda, measuring and control instruments, pharmaceuticals, catalysts, lamps (neon, fluorescent and mercury- arc), switches, batteries, rectifiers, oscillators, paper and pulp industries. Household Paints, floor waxes, furniture polishes, fabric softeners, antiseptics. Agricultural Fungicides.

Nickel Industrial Electroplating, stainless and heat-resisting steels, nickel alloys, pigments in paints and lacquers.

Selenium Industrial Photocopiers, rectifiers in electrical equipment.

Zinc Agricultural Pesticides, superphosphates. Household Pipes, utensils, glues, cosmetic and pharmaceutical powders and ointments, fabrics, porcelain products, oil colors, antiseptics. Industrial Corrosion-preventive coating, alloys of brass and bronze, building, transportation and appliance industries. Plumbing Galvanized sewage pipes.

Source: Keeney, D.R. et al. 1975. Guidelines for the Application of Wastewater Sludge to Agricultural Land in Wisconsin. DNR Tech. Bull 88. Madison, WI. C-11 10/18/05 11:16 AM Page 134

134 MANAGEMENT OF WISCONSIN SOILS

Table 11-8. Effect of sewage sludge and fertilizer on the concentration of heavy metals in corn.

Amendment Cd Cr Cu Ni Pb Zn

——————————— ppm ————————————

Ear leaf Control 0.29 1.16 6.8 1.22 1.61 19 Sludgea 0.35 1.08 10.2 1.15 1.35 80 Fertilizerb 0.20 0.96 7.8 1.06 1.12 24

Stover Control 0.21 0.21 1.6 0.63 <1.0 18 Sludgea 0.22 0.20 1.52 0.74 <1.0 22 Fertilizerb 0.14 0.23 1.38 0.42 <1.0 15

Grain Control <0.08 0.33 1.69 0.68 <0.86 16.4 Sludgea <0.08 0.52 1.57 1.05 <0.86 19.8 Fertilizerb <0.08 0.66 1.57 0.90 <0.86 16.0

Abbreviations: Cd = cadmium; Cr = chromium, Cu = copper, Ni = nickel, Pb = lead, Zn = zinc. a Sludge applied at 6 ton/a per year. b Fertilizer (N, P2O5, K2O) equivalent to that in 3 ton/a of sludge. Source: Peterson, A.E. 1990. Unpublished report. Dept. of Soil Sci., UW-Madison.

Questions 1. Why are nitrogen and phosphorus 5. How does phosphate find its way potential “environmental into surface water? How can this be pollutants”? reduced? 2. Under what conditions might you 6. Discuss the pros and cons of expect to find high levels of nitrate applying sewage sludge to in groundwater? What can be done agricultural land. to reduce leaching of nitrate? 7. What can be done to ensure that 3. Why is applying more than the heavy metals in sewage sludge recommended amount of nitrogen applied to agricultural land do not as “insurance” not a sound practice? build up to unacceptable levels? 4. List at least two reasons why irrigation scheduling is recommended. C-12 10/18/05 11:17 AM Page 135

CHAPTER 12 135 Soil testing, soil test recommendations, and plant analysis

There are a number of ways of Soil testing evaluating the nutrient status of soils Wisconsin laboratories analyze and the crops grown on them. The about 250,000 soil samples each year. most commonly used methods include The results of these tests guide “This we know: The earth the following: Wisconsin farmers in an annual does not belong to man; man ■ fertilizer trials in the field, expenditure of about 165 million ■ greenhouse experiments, dollars for lime and fertilizer. It is belongs to the earth. Man estimated that Wisconsin farmers have ■ observation of crop symptoms, did not weave the web of life; increased their collective crop income ■ plant analysis, he is merely a strand in it. by over 400 million dollars as a result ■ tissue testing in the field, and of using lime and fertilizer. To harm the earth is to heap Even though these statistics point ■ soil testing. out the importance of soil testing, some contempt upon its creator.” Each method has limitations. confusion exists as to the meaning and Fertilizer trials are expensive and time- usefulness of soil test results. Some Chief Seattle, 1852 consuming so they cannot be run on people view the soil test as only a (Reply to United States Government wanting to very many fields, and the results from purchase Indian tribal lands in the Northwest) “gimmick” to sell more lime and one field cannot be transferred easily to fertilizer. Others regard it as an another. Greenhouse experiments infallible and almost magical method of require specialized facilities and are predicting exactly how much of each costly, and the yield response is often plant nutrient needs to be supplied to quite different from that which occurs the crop. In fact, the soil test is neither in the field. Visual symptoms indicate a gimmick nor an exact science but an only severe deficiencies, and they often estimate. The accuracy of the estimate appear so late that any remedial action depends on how well the soil sample may be only partially successful. Plant represents the field, the quality of the analysis and tissue tests are conducted lab analysis, and the accuracy of the during the growing season to help calibrations used to interpret the data. identify problems, but they generally A sound soil testing program cannot be used to predict the amount requires a tremendous amount of field, of fertilizer or lime needed. Of the greenhouse, and laboratory research. methods mentioned above, soil testing Scientists must identify the various is the only rapid and inexpensive forms of the available nutrients in the method which can be used to reliably soil, find chemical extractants that will estimate lime and fertilizer needs in remove an amount of the nutrient advance of when the crop is grown. Soil proportional to that extracted by crops, tests are the only truly predictive tests and determine the response to different available. C-12 10/18/05 11:17 AM Page 136

136 MANAGEMENT OF WISCONSIN SOILS

rates of lime and fertilizer at various characteristic of the entire field. For determine how many are needed and soil test levels. Furthermore, this these reasons, multiple composite where to sample. For example, if the research has to be conducted over a samples composed of several soil cores intent is to fertilize the entire field wide range of soil, crop, and climatic need to be taken from a given field. using a single application rate, fewer conditions. The value of a soil testing Goals of a soil sampling samples will need to be collected than if program is directly proportional to the program a variable rate of fertilizer application quality and quantity of its research When sampling soils for testing was planned within the field. The backing. and obtaining fertilizer and lime second application strategy, known as A soil testing program is usually recommendations, the most common site-specific management, requires divided into four phases: objectives are to: special equipment to change rates of manure, lime, or fertilizer on the go. To 1. Collecting the sample. 1. Obtain samples that accurately select between the sampling strategies, 2. Analyzing the soil. represent the field from which they consider analytical costs, field were taken; 3. Interpreting the results. fertilization history, and the likelihood 4. Making the recommendations. 2. Estimate the amount of nutrients of response to variable fertilization. With representative sampling of that should be applied to provide the Each approach is outlined in the the field, accurate analysis of the soil, greatest economic return to the following text. grower; and correct interpretation of the test Sampling fields for results, the lime, phosphorus and 3. Provide some estimate of the a single recommendation potassium requirements can be variation that exists within the field With conventional sampling, predicted with a relatively high degree and how the nutrients are a single set of soil test results and of accuracy. Also, while not as precise, distributed spatially; and associated fertilizer and lime soil tests can serve as a guide for 4. Monitor the changes in nutrient recommendations will be based on nitrogen and some of the secondary status of the field over time. sample averages. The sampling and micronutrients. Soil testing does The ultimate goal of a soil fertility guidelines in table 12-1 are based on have some limitations, but it is the only program needs to be considered before when the field was last tested (more or practical way of predicting crop taking any samples, as that will less than 4 years) and whether the field response to lime and fertilizer. was responsive or non-responsive the Soil sampling Soil samples are taken to provide Table 12-1. Recommended sample intensity for uniform fields. an estimate of the fertility status of a field and to show the size and location Field Field size Suggested characteristics (acres) sample numbera of any variability that may exist. A fertilizer or lime recommendation Fields tested more than based on soil analysis is good only if the 4 years ago and fields testing all fields 1 sample/ soil sample analyzed is representative of in the responsive range 5 acres the field from which it was taken. If a Non-responsive fields 5–10 2 sample does not represent the general tested within past 4 years 11–25 3 soil conditions of the field, the 26–40 4 recommendations based on this sample 41–60 5 will be useless, or worse, misleading. 61–80 6 An acre of soil to a 6-inch depth weighs 81–100 7 about 1,000 tons, yet less than 1 ounce a Take a minimum of 10 cores per sample. of soil is used for each test in the laboratory. Therefore, it is very important that the soil sample is C-12 10/18/05 11:17 AM Page 137

Chapter 12. Soil testing, soil test recommendations and plant analysis 137

last time it was tested (if within 4 years). Figure 12-1. Recommended W-shaped sampling pattern The responsive range is considered to be for a 15-acre field. Each sample should be composed of at least 10 cores. where either soil test phosphorus or potassium levels are in the high Sample 1 Sample 2 Sample 3 category or lower. A nonresponsive field is one where both soil test phosphorus and potassium levels are in the very high or excessively high categories. To assure accurate representation of the nutrient needs of the field, each sample should be made up of a mini- mum of 10 cores. Research has shown that taking 10 to 20 cores provides a more representative sample of the area than when samples are made up of fewer cores. Use a W-shaped sampling pattern (figure 12-1) when gathering composite Samples should be taken within a selected is a compromise between cost samples. Be sure to thoroughly mix the relatively small radius (10 feet) of a and desired accuracy. Most commercial cores before placing approximately known point within a field rather than samples are collected on a 1 to 2.5 acre 2 cups in the soil sample bag. as a composite of cores taken over a grid (200 to 330 foot spacing). The broader area. This method is known as most simple grid pattern is the uniform Sampling fields for grid-point soil sampling. The points are pattern; however, unaligned grid site-specific (grid sampling) management most conveniently and accurately patterns (figure 12-2) ensure that the located with differentially corrected soil sampling points are staggered or Site-specific management, or grid global positioning systems (GPS) that randomized within the grid to prevent sampling, requires a more intensive soil use satellite radio signals to find biasing the results by previous nutrient sampling scheme that differs from positions with a repeatable accuracy of applications (fertilizer bands, manure sampling for single rate applications. 3 to 10 feet. The area or grid size strips, etc.).

Figure 12-2. Examples of grid sampling patterns for site-specific fields.

UNIFORM UNALIGNED

2 2

3 3

5 5

4 4

5 5

2 4253 2 4253 C-12 10/18/05 11:17 AM Page 138

138 MANAGEMENT OF WISCONSIN SOILS

Soil test data are mathematically the value of that accuracy must be 5. Take at least 10 soil cores or borings manipulated to create management weighed against both the expense and for each composite sample. maps showing areas having different the practicality of taking more samples. 6. Avoid sampling nonrepresentative fertilizer needs. These methods How to collect soil samples areas of a field such as dead and back interpolate expected values between the Guidelines for sampling soil in furrows, fence lines, lime, sludge or known sample points and create Wisconsin are given below: manure piles, rows where fertilizer contoured boundaries that are used to 1. Use a soil sample probe or soil auger was band-applied, eroded knolls, low variably apply fertilizer materials. spots, etc. Variable-rate fertilizer equipment to take samples (figure 12-3). 7. Avoid sampling any area that varies directly reads the information from the 2. If manure or crop residues are on the widely from the rest of the field in management map and changes the rate soil surface, push these aside and do color, fertility, slope, texture, of application as the spreader drives not include in the sample. drainage, or productivity. If the across the field. 3. Insert the probe or auger into the distinctive area is large enough to Grid soil sampling is best suited to soil to plow depth or at least 6 inches. receive lime or fertilizer treatments fields that are expected to have 4. For non-responsive fields larger than different from the rest of the field, significant areas in the responsive soil 5 acres, obtain, at a minimum, the sample it separately. test range. An example would be a number of samples specified in table relatively large field near the barn that 8. Place the sample (about 2 cups) in a 12-1. For responsive fields that have has received differential applications of soil sample bag. Sample bags are not been sampled in the past 4 years, manure. available from all soil testing labs. take one composite sample for every Regardless of the sampling strategy 5 acres. Collect at least two 9. Identify the bag with name, field used, soil must be collected from several composite samples for every field. identification, and sample number. locations within the defined sampling Cores from two or three small 10. Record the field and sample area. Fertilizer recommendations contour strips may be combined if location on an aerial photo or sketch become increasingly accurate as the they are cropped and fertilized the of the farm and retain for future number of cores per sample and the same. reference. number of samples increases. However, 11. Fill out the soil information sheet and submit it along with the soil Figure 12-3. Soil sampling tools. The soil sample probe (left) samples to a soil testing laboratory. povides a uniform sample to the depth of tillage. The soil auger The more completely and carefully (right) works best when collecting samples in stony soil. this sheet is filled out, the better the recommendations will be. A sample of the soil information sheet is attached. For samples to be useful in tracking changes in a field from one sampling period to the next, it is essential that all

plow depth 6–7 inches Soil & Plant Analysis Lab Department of Soil Science Soil & Forage Analysis Lab 8452 Mineral Pt Rd College of Agricultural and Life Sciences 8396 Yellowstone Drive Verona, WI 53593 University of Wisconsin - Madison/Extension Marshfield, WI 54449 (608) 262-4364 (715) 387-2523

Date Rec'd Soil Information Sheet for Field, Vegetable and Fruit Crops Lab No (Lab Use Only) County FSA No. Method of Payment Name Account ID Address Amount paid City State Zip Cash County Code Email Address Check No. TOTAL NUMBER PLOW Credit Card No______-______-______-______OF SAMPLES DEPTH Exp Date ______/______VISA ____ MC ____ FERTILIZER CREDIT INFORMATION 4-YEAR CROP ROTATION Previous Legume Crop Manure Applied to Field Since Last Crop Acres FIELD SAMPLE SOIL NAME Slope Check if in Legume Manure Consecutive ID NO(S) (if known) % Sequence to Legume more than Application Application Field Forage Code Years of be Grown Yield Goal Crop 8" Rate T/a Method % stand (See Application (crop code) Tillage (crop code) regrowth gal/a (Circle one) Check if Irrigated (circle) below) (circle)

Ck if Conserv in fall

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+

< 30 Surface 1 30-70 Incorp. 2 > 70 Injected 3+ Special Soil Tests (additional fee) Manure Code List (List field or sample identification) Solid Liquid Calcium/Magnesium Zinc 1 Dairy 11 Dairy Boron Sulfate 2 Beef 12 Veal calf Manganese Other 3 Swine 13 Beef Soil tests recommended if: 4 Duck 14 Swine, indoor pit growing corn (field or sweet) Zn and SO4-S 5 Chicken 15 Swine, outdoor pit growing legume forage B and SO4-S 6 Turkey 16 Swine, farrow-nursery growing small grain or soybean (with soil pH >7.0) Mn 7 Sheep indoor pit growing potato or apple (with pH < 5.5) Ca/Mg 8 Horse 17 Duck growing specialty or vegetable crops B, Zn, and Mn 18 Poultry acid or sandy soil with high amounts of applied K Ca/Mg 8/03 INSTRUCTIONS NAME AND ADDRESS - Print clearly Fill in the FSA Farm No (optional) and County from which the sample(s) were taken. Fill in the e-mail address if you would like results emailed.

METHOD OF PAYMENT Fill in your Account ID (if applicable), cash, credit card, or check payable to: UW Soil Testing Lab

FIELD ID and SAMPLE NO(S) Record the field and sample identification for each field on the same line. Please number samples consecutively. . Field ID Sample No(s) EXAMPLE 1 1-4 2 5 3 6-8 SOIL NAME Write the soil name (not the abbreviation) from an FSA farm plan or county soil survey map. Example: Fayette silt loam, write “Fayette”. If the field has more than one soil type, use the most predominant soil found in the field. A more precise soil test recommendation can be given if the soil name is included.

4-YEAR CROP ROTATION Indicate the intended crops to be grown for the next four years. Use the crop codes(s) listed in the table below. Enter a yield goal no more than 10-15% higher than the prior 5-year average for each crop. Base the yield goal for corn on yield of No. 2 corn at 15.5% moisture. Yield goal for alfalfa should be based on dry matter in T/a. Base yield of other crops on the yield unit shown in parenthesis ( ). Give yield goals to the nearest ½ T for crop units expressed in T/a. Check if conservation tillage leaves more than 50% residue cover when corn follows corn. ______Crop Crop Yield Crop Crop Yield Crop Crop Yield Code Name Unit Code Name Unit Code Name Unit 1 Alfalfa (tons) 25 Melon (tons) 48 Soybeans (bu) 2 Alfalfa, seeding year (tons) 26 Millet (bu) 49 Spinach (tons) 3 Asparagus (lbs) 27 Mint, oil (lbs) 50 Squash (tons) 4 Barley (bu) 28 Oats (bu) 51 Sunflower (lbs) 5 Beans, dry (kidney, navy) (bu) 29 Oatlage (tons) 52 Tobacco (lbs) 6 Beans, lima (lbs) 30 Oat-pea, forage (tons) 53 Tomato (tons) 7 Beets, table (tons) 31 Onion (cwt) 54 Trefoil, birdsfoot (tons) 8 Brassicas, forage (tons) 32 Pasture, unimproved (tons) 55 Triticale (lbs) 9 Broccoli (tons) 33 Pasture, managed (tons) 56 Truck crops (-) 10 Brussel sprouts (tons) 34 Pasture, legume grass (tons) 57 Vetch, hairy, crown (tons) 11 Buckwheat (lbs) 35 Peas, canning (lbs) 58 Wheat (bu) 12 Cabbage (tons) 36 Peas, chick, field, cow (tons) 59 Miscellaneous -- 13 Canola (bu) 37 Peppers (tons) 60 Apple -- 14 Carrots (tons) 38 Popcorn (bu) 61 Blueberry -- 15 Cauliflower (tons) 39 Potato (cwt) 62 Cherry -- 16 Celery (tons) 40 Pumpkin (tons) 63 Cranberry -- 17 Corn, grain (bu) 41 Reed canarygrass (tons) 64 Raspberry -- 18 Corn, silage (tons) 42 Red clover (tons) 65 Strawberry -- 19 Corn, sweet (tons) 43 Rye (bu) 66 CRP, alfalfa -- 20 Cucumber (bu) 44 Snapbean (lbs) 67 CRP, red clover -- 21 Flax (bu) 45 Sod (-) 68 CRP, grass -- 22 Ginseng (lbs) 46 Sorghum, grain (bu) 23 Lettuce (tons) 47 Sorghum, forage (tons) 24 Lupin (bu)

FERTILIZER CREDIT INFORMATION: Legume-sod plowdown or manure application may reduce nutrient need. Previous Legume Crop: Enter the crop code for the previous legume crop grown on the field. For all forage crops that were plowed down, indicate the % legume remaining in stand and check if there was more than 8 inches of regrowth in the fall before the stand is killed. Manure Applied to Field Since Last Crop: If manure was applied to the field since harvesting the last crop, choose manure code from Manure Code List on front of Information Sheet. Specify the approximate rate of application in T/a for solid or 1000 gal/a for liquid manure, the application method (surface applied, incorporated within 72 hrs or injected) and the number of consecutive years manure has been applied to this field.

SPECIAL SOIL TESTS: Special tests may be run on individual samples, or all the samples from the same field may be combined at the lab for a single field analysis. If the special test(s) is requested on a field basis only, enter the field ID. If the special test(s) is requested for each sample, enter the field ID and sample no. C-12 10/18/05 11:17 AM Page 139

Chapter 12. Soil testing, soil test recommendations and plant analysis 139

cores be taken to exactly the same depth. acid layer, take a separate sample to a dations will be. Read the instructions Small differences in sampling depth, depth of only 2 inches. When such a on the back side of the sheet. Be sure to especially from conservation or reduced sample is submitted for soil testing, include the soil series name for each tillage fields, can dramatically affect soil indicate that it is from the surface field. The soil series can be obtained test results. layer (0 to 2 inches) of a no-till field. from a farm’s conservation plan. The soil samples and a completed Tillage considerations ■ With till-plant and ridge tillage, soil information sheet can be left at any When sampling fields that have sample ridges to the 6-inch depth county Extension office for forwarding not been tilled since the last application and between rows (furrows) to a to an approved soil testing laboratory. of row fertilizer, take the soil cores depth of 4 inches. Combine soil If this is not convenient, soil samples midway between crop rows. This will cores from ridges and furrows in can be sent directly to the soil testing help avoid sampling the old fertilizer equal numbers to make up the laboratory or delivered in person. band, which would give falsely high soil composite sample. The Department of Soil Science, test results for phosphorus and Timing and frequency UW-Madison and UW-Extension, potassium. Sample freshly plowed fields Soil samples can be taken at any operates soil testing laboratories at by inserting the soil probe or auger into time; however, early fall is preferred Madison, 8452 Mineral Point Road, a footprint. This slight compaction because farmers will then have adequate Verona, WI 53593 and Marshfield, ensures extraction of a solid uniform time to plan, purchase, and apply 8396 Yellowstone Drive, Marshfield, core of soil from the plow layer. needed lime and fertilizer. When WI 54449. Private soil testing ■ With moldboard plowing, sample samples are submitted in the spring, laboratories, which are certified by the soils to 6 inches or the depth of the farmers may not receive the soil test Wisconsin Department of Agriculture, plow layer. Although subsoils do report back in time for planting. Trade and Consumer Protection contribute nutrients to a crop, the Sampling frozen soil should be (WDATCP) are also available. The phosphorus and potassium avoided unless uniform soil borings or locations of WDATCP-approved recommendations are not accurate cores can be obtained to the laboratories can be obtained from enough to justify the extra cost of appropriate depth. Normally, this county Extension offices or online at taking and analyzing subsoil requires the use of a portable power uwlab.soils.wisc.edu. Fees for the samples. Subsoil fertility is factored boring tool. Do not use a pick or spade various soil tests offered by the UW into the nutrient recommendations to remove a few chunks of frozen soil labs are also available on this web site. based on the soil type or area of the from the surface. state. For field crops, sampling the soil Analyzing the soil A routine soil test in Wisconsin ■ With chisel plowing and offset once every 4 years or once in crop includes analysis of the soil for water disking, take soil samples to 3⁄4 of the rotation is sufficient. For crops grown pH, buffer pH, organic matter, tillage depth. When possible, take on sands or for high-value crops such as phosphorus, and potassium. Upon soil samples before fall or spring potatoes, samples should be gathered request, special tests are available for tillage to avoid residual fertilizer every year. More detailed information nitrate-nitrogen, calcium, magnesium, bands and to more accurately on soil sampling is given in Extension sulfur, boron, manganese, and zinc. determine sampling depth. publication Sampling Soils for Testing (A2100). It is available from any Soil tests are not routinely done for ■ With no-till, take soil samples to a county Extension office. copper, iron, or molybdenum because depth of 6 to 7 inches. Sample Field history is needed to make application of these nutrients very between rows to avoid old fertilizer accurate recommendations. This seldom results in crop response in the bands. When nitrogen is surface- information should be reported on the field. A reliable soil test cannot be applied, an acid layer may develop soil information sheet (sample attached) developed unless the results of that test near the soil surface. Such an acid when soil samples are taken. The more are calibrated with field responses to layer could reduce the effectiveness completely and carefully this sheet is application of that nutrient. of some herbicides. If you suspect an filled out, the better the recommen- C-12 10/18/05 11:17 AM Page 140

140 MANAGEMENT OF WISCONSIN SOILS

Secondary or micronutrient soil Table 12-2. Soil conditions that favor secondary and micronutrient tests are available on request. Table deficiencies. 12-2 describes situations where such Element Where most likely needed tests may be of use. The analytical procedures used in Calcium Acid sands and soils where high calcium-demanding Wisconsin are outlined in detail in a crops are grown. publication entitled Wisconsin Procedures for Soil Testing, Plant Analysis Magnesium Acid sands and sandy soils that have been limed with marl or paper mill sludge. and Feed and Forage Analysis, which is available from either UW Soil Testing Sulfur Light-colored soils, especially sands and sandy Laboratory. loams in west central and northwestern Wisconsin.

Interpreting the Boron Sandy and low organic matter soils, all soils that will be analytical results cropped to alfalfa for a long period of time, and soils that Soil tests for the available nutrients are planted to vegetable crops. are categorized as being very low, low, Manganese Soils with a high pH (above 7.0) and high organic matter optimum, high, very high, or content, especially in eastern, southeastern and south central excessively high. Such interpretations Wisconsin. indicate the probability of response to nutrient application. Table 12-3 shows Zinc Soils with a low organic matter content, high pH, and the ranges of these probabilities. high level of available phosphorus, especially the sandy soils in central Wisconsin and high pH mucks and peats. When a soil test for phosphorus or potassium falls into the very low or low category, nutrient applications are warranted. If a soil test falls in the Table 12-3. Interpretations of the soil test levels. optimum range, no adjustment is Percent of fields needed in the current fertilizer expected to program, and future applications about Soil test give a profitable equal to the amount of nutrients level yield increase Description removed in crop harvest are % recommended. When the soil tests high or very high, apply some nutrients, but Very low >90 Buildup to optimum level should reduce the rates. If the soil tests occur over a 5- to 8-year period. excessively high, omit nutrient Low 60–90 Somewhat more nutrients are applications for 2 to 3 years or until the required than what crop removes. tests drop to the optimum or high range. Optimum 30–60 Yields are optimized at nutrient The interpretations of soil tests for additions approximately equal to crop phosphorus and potassium depend on removal. This is the economical and the crop to be grown and the environmental optimum level. contribution of the subsoil. Some High 5–30 Some nutrients are required, about subsoils supply appreciable amounts of half of that removed by the crop. phosphorus and/or potassium during the growing season; others do not. The Very high ~5 Used only for potassium; gradual Wisconsin soil testing program drawdown recommended. recognizes six subsoil fertility groups Excessively <2 No fertilizer needed or recommended and six crop demand levels for high except a small amount of row-placed starter. C-12 10/18/05 11:17 AM Page 141

Chapter 12. Soil testing, soil test recommendations and plant analysis 141

phosphorus and potassium. For sources, such as manure, legume crops, interpretations of soil tests for these Soil test or carryover from previous applications and other nutrients, see Extension recommendations of nitrogen fertilizer. Growers should publication Optimum Soil Test Levels for make allowances for these inputs, if All soil test recommendations are Wisconsin (A3030). they are present, and reduce fertilizer based on field research work that The optimum soil pH for nitrogen accordingly. See chapters 9 measures yield increase with several Wisconsin crops is given in table 6-4. and 10 for information on crediting rates of fertilizer at various soil test The soil organic matter test primarily nitrogen from non-commercial levels. As shown in figure 12-4, large measures the humus in soil and is not fertilizer sources. quantities of fertilizer have to be changed appreciably by adding manure It is important to remember that applied to a low testing soil to achieve or crop residue. When these fresh crop recovery of nitrogen decreases as optimum yields; moderate amounts of organic materials decompose, most of the rate applied increases. Also, excess fertilizer are needed on a medium the organic carbon contained therein nitrogen increases the risk of leaching. testing soil; and only a very small returns to the atmosphere as carbon Research trials conducted quantity of fertilizer is required on a dioxide (CO ). Only a very small throughout the state over many years 2 high testing soil. portion remains as a residue to become have shown that the optimum nitrogen part of the soil humus. The amount of Nitrogen rate for corn is similar in high- and organic matter a soil contains depends recommendations low-yielding years. However, plants use mainly on the original vegetation, soil Nitrogen recommendations nitrogen much more efficiently in texture, soil drainage, degree of erosion, indicate the amount of fertilizer needed good-yielding years, resulting in higher and tillage. Since the organic matter if no nitrogen is supplied from other recovery of available nitrogen by the content is an inherent characteristic of crop. Corn recovers more available the soil and cannot be changed easily, it is not possible to establish optimum soil test levels for organic matter. Figure 12-4. Theoretical yield response to increasing rates of However, the amount of organic matter fertilizer when applied to soils containing low, medium or high available nutrient levels. in a soil affects its ability to supply

nitrogen during the growing season and 140 is used in the nitrogen recommendation Soil test program. High In the past, soil testing was used 120 primarily to correct plant nutritional Medium problems. Phosphorus and potassium Low levels have been increasing gradually 100 over the years so that now the average soil tests for phosphorus and potassium are well above the optimum. Although 80 there are still soils testing very low and Relative yield low in these elements, many fields now test excessively high. Soil testing 60 currently identifies more fields where fertilizer applications should be reduced or eliminated than fields where 40 increases in current application rates are 0 12 345 required. Relative amount of nutrient applied

Source: Barber, S.A. 1973. Reprinted from Soil Testing and Plant Analysis, rev. ed., page 202, with permission from the Soil Science Society of America, Inc., Madison, WI. C-12 10/18/05 11:17 AM Page 142

142 MANAGEMENT OF WISCONSIN SOILS

nitrogen under favorable growing Phosphate and potash phosphate or potash needed to change conditions and less under poor recommendations a given soil test level a desired amount. conditions such as those caused by Phosphate and potash The amount of phosphate or potash (in drought stress or cold weather. recommendations are based on crop pounds per acre) required to change Nitrogen recommendations for demand level, subsoil fertility, crop soil test phosphorus or potassium by corn on medium- and fine-textured yield goal or soil yield potential. 1 ppm is defined as the soil buffering soils are based on soil yield potential, Wisconsin crops are placed in one capacity. The buffering capacity is organic matter content, and soil texture of six crop demand categories, always greater than 1 because (table 12-4). Every named soil in depending on their phosphate and ■ the mathematical units for added Wisconsin is assigned a yield potential potash requirements. An optimum soil fertilizer are in lb/a while the soil test ranking of very high, high, medium, or test in one category may be a low test value is in ppm, and low. This ranking is based on level in another category. Thus, a soil ■ fertilizer is sold on the oxide individual soil characteristics, such as phosphorus test of 10 ppm might be basis while soil test values are drainage, rooting depth, and water considered optimum for soybeans but reported on the elemental basis holding capacity, as well as the length low for alfalfa, and more phosphate (1 ppm P = 2.29 ppm P O , of the growing season. Sandy soils would be recommended for alfalfa. 2 5 1 ppm K = 1.2 ppm K O). (sands and loamy sands) are given Crops growing on soils testing in the 2 For example, since a 7-inch layer of separate nitrogen recommendations optimum range will give optimum a typical silt loam soil weighs which are dependant upon organic yield and profit when the quantity of 2,000,000 pounds, an application of matter content and irrigation. Non- nutrients applied approximately equals 2 pounds per acre (2 pounds fertilizer irrigated sandy soils have a lower yield the amount in the harvested part of the to 2,000,000 pounds soil) would equal potential because moisture is crop (table 12-5). 1 ppm. Therefore, 2 pounds per acre of inadequate in most years. Nitrogen The subsoil group accounts for the phosphorus (4.58 pounds of P O ) or recommendations for additional crops phosphorus and potassium supplying 2 5 2 pounds per acre of potassium are given in Extension publication Soil power of the subsoil and, thereby, the (2.4 pounds of K O) would be Test Recommendations for Field, optimum soil test level of the plow 2 required to increase the soil test by Vegetable, and Fruit Crops (A2809). layer in relation to crop needs. It is also 1 ppm if all of the added phosphorus used to determine the amount of and potassium remained available. But

Table 12-4. Nitrogen recommendations for corn.

Soil Medium & fine-textured soils ——— Sandy soils ——— organic —— Yield potentiala ——— matter Low/mediumb High/very high Non-irrigated Irrigated

— % — ————————————— nitrogen, lb/ac ——————————————

<2.0 150 180 120 200

2.0–9.9 120 160 110 160

10.0–20.0 90 120 100 120

>20.0 80 80 80 80

a To determine a soil’s yield potential, see UWEX publication Soil Test Recommendations for Field, Vegetable, and Fruit Crops (A2809) or contact your agronomist or county agent. b Irrigated non-sandy soils with a medium/low yield potential should use the high/very high recommendation. c If more than 50% residue cover from a previous corn crop remains on the surface, increase nitrogen by 30 lb/acre. C-12 10/18/05 11:17 AM Page 143

Chapter 12. Soil testing, soil test recommendations and plant analysis 143

some of each of these nutrients reacts with the soil to become “fixed” or not Table 12-5. Estimates of the nitrogen, phosphate, and potash extractable by crops nor by the tests removed in the harvested portion of several Wisconsin crops. used to measure their availability. Considering both soil fixation and the ———— Nutrients removed ———— conversion factors noted above, the Nitrogen Phosphate Potash amount of phosphate and potash Crop Yield (N) (P2O5)(K2O) needed to change soil test values is per acre ———————— lb/a ——————— considerably greater than 1. The table Alfalfa 4 ton 240a 52 240 at the bottom of figure 12-5 gives the phosphorus and potassium buffering Beets, table 17 ton 210 20 120 capacities of the six subsoil groups used in the Wisconsin soil test Broccoli 5 ton 120 10 20 recommendation program. Cabbage 25 ton 200 40 180 The data presented in figure 12-5 are from laboratory studies. In the field, Carrots 25 ton 140 45 240 the amount of change in soil test phosphorus or potassium will also Corn, field depend on the degree of mixing of grain 150 bu 120 55 40 stover 51 14 150 phosphate and potash with the soil and the amount of phosphorus and Corn, sweet 7 ton 45 25 40 potassium extracted by roots from the subsoil and deposited on the soil Cucumber 350 bu 120 10 30 surface in crop residue. Lettuce 18 ton 140 40 160 The Wisconsin soil testing program divides all of the soils in the Oats 90 bu 60 30 90 state into six subsoil fertility groups according to the relative levels of Peas 5000 lb 50a 20 40 available phosphorus and potassium in Potato 400 cwt 80 60 200 the subsoil. The approximate location of these groups in the state and their Red clover 3.5 ton 140a 35 150 relative levels of subsoil fertility are shown in figure 12-5. A special group, Snapbean 7000 lb 205a 17 35 X, not shown in figure 12-5 is used for Soybean 50 bu 190a 45 50 phosphorus recommendations only. Group X soils have a pH of 7.5 or Trefoil, birdsfoot 3.5 ton 150a 45 175 higher. If the soil name is not given on the soil information sheet Wheat 65 bu 85 45 25 accompanying samples to the lab, the a Leguminous crops get most of their nitrogen from the air. soil sample is placed in a subsoil group based on its organic matter content, pH, texture, color and county of origin. The subsoil fertility groups for all 700+ Wisconsin soils are given in Extension publication Soil Test Recommendations for Field, Vegetable, and Fruit Crops (A2809). C-12 10/18/05 11:17 AM Page 144

144 MANAGEMENT OF WISCONSIN SOILS

Figure 12-5. General subsoil fertility groups, based on available phosphorus and potassium in subsoils.

Nutrient buffering Subsoil Nutrient —— capacityb —— a group Description Legend supply power P2O5 K2O A Southern, forested; medium and fine texture P high, K medium 18 7

B Southern, prairie; medium and fine texture P medium, K medium 18 7

C Red; medium and fine texture P low, K high 18 7

D Northern; medium and fine texture P medium, K low 18 6

E Sandy, coarse texture P variable, K low 12 6

O Organic soilc P variable, K low 18 5

a All data refer to subsoils (8 to 30 inch) only. Low, medium, and high ratings are relative and are not defined in absolute units. b The soil nutrient buffering capacity is the approximate amount of fertilizer in lb/a (oxide basis) required to change the soil test level (elemental basis) by 1 ppm. c Subsoil group O is for organic soils (> 10% organic matter) and is not based on subsoil fertility. C-12 10/18/05 11:17 AM Page 145

Chapter 12. Soil testing, soil test recommendations and plant analysis 145

Table 12-6. Yield goals for corn and alfalfa as influenced by soil yield potential.

Relative — Typical yields — Acceptable yield goals yield potential Corn Alfalfa Corn Alfalfa

bu/a tons/a DMa bu/a tons/a DMa

Very high 140–180 5–7 130–220 3.5–8.0

High 120–140 4–5 100–180 3.0–7.0

Medium 90–120 3–4 80–160 2.5–5.5

Low 70–90 2–3 60–140 1.0–4.0

a DM = dry matter.

The amount of fertilizer will receive recommendations less than calculated. For potassium, the rejection recommended also depends on the crop removal. No fertilizer is limit is 20 ppm. No more than two yield goal for the crop to be grown. recommended for soils testing in the samples may be rejected from fields Yield goals should be realistic—not excessively high range, except for a with five or more samples and only one more than 10 to 15% above the small amount of starter fertilizer. value from fields with three or four previous 3- to 5-year average. When Research has shown that 40 to 50% of samples. If there are only two samples the yield goal for corn or alfalfa is not soils testing in the excessively high from a field, neither will be eliminated. given on the soil information sheet, the range will still respond to starter. This The adjusted average field values are computer assigns a yield goal based on nutrient recommendation system was used to make nutrient application the soil yield potential. If the soil name established to provide the maximum recommendations. is not given, the yield potential is profit to the farmer on a year-to-year Aglime recommendations estimated based on location within the basis with soil tests maintained in the Because farmers can select any crop state (county) and soil texture. For responsive range and adequate amounts as part of their rotation, the target pH other crops, a middle yield goal range is of nutrients applied each year. for aglime recommendations is based used. The relative yield potentials and Phosphate and potash on the most acid-sensitive crop (table acceptable yield goals used are shown in recommendations for corn and alfalfa 6-4) from those selected, except when table 12-6. are given as examples in tables 12-7 and potatoes are chosen. The amount of When soil phosphorus or 12-8. Recommendations for other lime recommended is the amount potassium is in the optimum range, crops may be found in Extension needed to reach the field target pH for economic return from fertilizer publication Soil Test Recommendations that rotation. When potatoes are to be additions is maximized by applying for Field, Vegetable, and Fruit Crops grown, the pH should not exceed the nutrients at rates about equal to the (A2809). optimum pH for potatoes. amounts removed in the harvested part The soil test report averages the Because of minor fluctuations of the crop. Soils testing very low or soil test values for all samples from the inherent in soil sampling and pH low will require nutrients beyond the same field and compares the individual measurement, the lime requirement is amount removed by the crop. This will values against the average. For calculated only when the soil pH is more improve crop yields and slowly build phosphorus, if an individual value than 0.2 pH unit below the target pH. these nutrient levels to the optimum exceeds the mean by more than 5 ppm, range. Soils testing high or very high that value is rejected and a new mean is C-12 10/18/05 11:17 AM Page 146

146 MANAGEMENT OF WISCONSIN SOILS

Table 12-7. Corn fertilizer recommendations for phosphate and potash.

————— Soil test interpretation categorya ————— Yield goal VLb Lb Opt H EHc

bu/a —————————— P2O5 to apply, lb/a ——————————

71–90 0–90 50–70 30 15 0

91–110 70–100 60–80 40 20 0

111–130 75–105 65–85 45 25 0

131–150 85–115 75–95 55 25 0

151–170 90–120 80–100 60 30 0

171–190 100–130 90–110 70 35 0

191–220 105–135 95–115 75 40 0

—————————— K2O to apply, lb/a ——————————

71–90 50–80 40–65 25 15 0

91–110 55–85 45–70 30 15 0

111–130 60–90 50–75 35 15 0

131–150 65–95 55–80 40 20 0

151–170 70–100 60–85 45 20 0

171–190 75–105 65–90 50 20 0

191–220 80–110 70–95 55 25 0

a VL = very low, L = low, Opt = optimum, H= high, EH = excessively high. b The precise amount recommended varies with the subsoil fertility level. See Extension publ. Soil Test Recommendations for Field, Vegetable, and Fruit Crops (A2809) for more information. c A small amount of starter fertilizer (10-20-20) is recommended for most row crops.

The amount of aglime needed to The formulas used for calculating Aglime recommendations are made achieve the desired pH is calculated the amount of aglime needed to reach on the basis of liming materials with from the pH of the soil, the organic different pH levels are given in neutralizing indices (NI) of 60-69 and matter content of the soil as measured Extension publication Soil Test 80-89. (See chapter 6 for a discussion by loss of weight upon ignition (i.e. Recommendations for Field, Vegetable, of lime quality and neutralization burning) and the pH buffering capacity and Fruit Crops (A2809). An example index). The lime requirement can be of the soil as measured by a buffer pH of the formula used for calculating the adjusted for other lime grades using test. In reality, both organic matter lime requirement to pH 6.3 is given in table 6-8 or the following formula: content and the buffer test are chapter 6. indicators of the soil pH buffering Lime requirement of ton/a of 60–69 lime 65 = x capacity or reserve acidity. lime to be used (ton/a) recommended NI of lime to be used C-12 10/18/05 11:17 AM Page 147

Chapter 12. Soil testing, soil test recommendations and plant analysis 147

Table 12-8. Alfalfa fertilizer recommendations for phosphate and potash.

———————— Soil test interpretation categorya ———————— Yield goal VLb Lb Opt H VH EH

ton/a ————————————— P2O5 to apply, lb/a ————————————

1.5–2.5 55–75 45–65 25 10 0 0

2.6–3.5 65–85 55–75 35 15 0 0

3.6–4.5 80–100 70–90 50 25 0 0

4.6–5.5 95–115 85–105 65 30 0 0

5.6–6.5 105–125 95–115 75 35 0 0

6.6–7.5 120–140 110–130 90 45 0 0 c ————————————— K2O to apply, lb/a —————————————

1.5–2.5 135–150 125–135 100 50 25 0

2.6–3.5 185–200 175–185 150 75 40 0

3.6–4.5 235–250 225–235 200 100 50 0

4.6–5.5 285–300 275–285 250 125 60 0

5.6–6.5 335–350 325–335 300 150 75 0

6.6–7.5 385–400 375–385 350 175 90 0

a VL = very low, L = low, Opt = optimum, H= high, VH = very high, EH = excessively high. b The precise amount recommended varies with the subsoil fertility level. See Extension publ. Soil Test Recommendations for Field, Vegetable, and Fruit Crops (A2809) for more information. c If the alfalfa stand will be maintained for more than 3 years, increase topdressed potash by 20%.

Aglime recommendations are Aglime recommendations are Secondary nutrient limited to a maximum of 8 tons per calculated for a tillage depth of recommendations acre for potatoes and 12 tons per acre 7 inches. If deeper tillage is indicated Soils are not tested routinely for for other crops even though more lime on the soil information sheet, the lime secondary and micronutrients. These may be required to reach the targeted recommendation is adjusted by 1-inch tests must be requested specifically. All pH. This is done to avoid the depth increments to a maximum of secondary nutrients and micronutrients possibility of localized overliming 9 inches (table 6-9). Lime cannot be for which soil tests are available are because it is difficult to do a good job mixed effectively deeper than 9 inches, interpreted in terms of their relative of mixing more than 12 tons per acre and no research in Wisconsin has availability (table 12-9). When the soil of lime throughout the tilled (plow) shown any benefit from liming soil test falls into the very low or low range layer uniformly. deeper than that. for a given nutrient, recommendations C-12 10/18/05 11:17 AM Page 148

148 MANAGEMENT OF WISCONSIN SOILS

are made if the crop demand for that calcitic lime have been repeatedly crops such as alfalfa, canola or forage nutrient is medium or high. applied at high rates, (2) very acid and brassicas, and cole crops grown on Calcium deficiency is rare for most sandy soils where high rates of sandy soils or other soils low in organic crops and highly unlikely if aglime potassium and/or ammonium nitrogen matter and located away from recommendations are followed. Crops have been applied, and (3) calcareous urbanized areas. Available sulfur such as apples and potatoes in which organic soils. The most economical way includes sulfur in precipitation, sulfur the storage organs are not part of the to avoid magnesium deficiency is to released from soil organic matter, plant transpiration stream sometimes follow a good liming program using sulfur from applied manure and subsoil benefit from supplemental calcium in dolomitic limestone. Other suitable sulfur, in addition to the sulfate sulfur = terms of improved disease resistance or magnesium carriers are Epsom salts (SO4 ) measured by soil analysis. crop quality. Also, extra calcium is (MgSO4•7H2O) and potassium- Recent surveys have shown that often beneficial for celery. magnesium sulfate (K2SO4•2MgSO4). precipitation contains about 5 pounds The use of dolomitic limestone has A row application of 10 to 20 pounds of sulfur per acre in western and prevented magnesium deficiency in of magnesium per acre is recommended northern Wisconsin counties, as shown most Wisconsin soils. Some soils low in annually on magnesium-deficient soils in figure 12-6, and 10 to 15 pounds of this element include: (1) soils where where liming is undesirable. sulfur per acre in the remainder of the liming materials low in magnesium Sulfur deficiency is most likely to state. such as paper mill lime sludge, marl, or occur with high sulfur-demanding

Table 12-9. Interpretation of soil test values for secondary nutrients and micronutrients.

Soil texture ———————— Soil test interpretation categoryb ———————— Element codea VL L Opt H EH

———————————————— ppm ————————————————

Calcium 1, 4 0–200 201–400 401–600 >600 — 2, 3, 4 0–300 301–600 601–1000 >1000 —

Magnesium 1, 4 0–25 26–50 51–250 >250 — 2, 3, 4 0–50 51–100 101–500 >500 —

Boron 1, 4 0–0.2 0.3–0.4 0.5–1.0 1.1–2.5 >2.5 2, 4 0–0.3 0.4–0.8 0.9–1.5 1.6–3.0 >3.0 3, 4 0–0.5 0.6–1.0 1.1–2.0 2.1–4.0 >4.0

Zinc 1, 2, 3, 4 0–1.5 1.6–3.0 3.1–20 21–40 >40

Manganese OM <6.1% 1, 2, 3, 4 — 0–10 11–20 >20 — ———————— Soil pHc ———————— OM >6.0% 1, 2, 3, 4 — >6.9 6.0–6.9 <6.0 —

Sulfur availability Low Medium High indexd 1, 2, 3, 4 — <30 30–40 >40 —

a Soil texture codes: 1 = sands, 2 = silts and clays, 3 = organic soils, 4 = red soils. b Soil test interpretation categories: VL = very low, L = low, Opt = optimum, H= high, EH = excessively high. c When soil organic matter exceeds 6.0%, manganese availability is based on soil pH; the manganese soil test is not used. d Sulfur availability index includes estimates of sulfur released from organic matter, sulfur in precipitation, subsoil sulfur and sulfur in manure if applied, as well as S04-S determined by soil test. C-12 10/18/05 11:17 AM Page 149

Chapter 12. Soil testing, soil test recommendations and plant analysis 149

Sulfur contributed by organic Table 12-10. Sulfur fertilizer recommendations. matter is estimated by multiplying the percent organic matter content by 2.8. Crop Sulfur to apply (lb/a) Sulfur in manure, if applied, depends Forage legumes on the kind of animal and application rates. Subsoil sulfur is estimated from Incorporated at seeding 25–50 data collected from surveys of subsoil sulfur and ranges from 5 pounds per Topdressed on established stand 15–25 acre on sandy soils to 20 pounds per Corn, small grains, 10–25 acre on organic soils. vegetable and fruit crops A sulfur availability index (SAI) is calculated by summing the available sulfur inputs as shown below. This SAI has been calibrated against 600 alfalfa plant tissue samples. Figure 12-6. Sulfate sulfur in precipitation. If the SAI is less than 30, sulfur Source: National Atmospheric Deposition Program. 1999. should be added; if it is greater than 40, no sulfur is needed; and if it is between

30 and 40, the need for sulfur is BAYFIELD borderline and should be confirmed DOUGLAS with plant analysis. If needed, apply the IRON

amount of sulfur shown in table 12-10. VILAS

WASHBURN SAWYER ASHLAND

PRICE FOREST FLORENCE ONEIDA Calculating the sulfur BURNETT MARINETTE availability index (SAI) POLK BARRON RUSK LINCOLN LANGLADE SAI = (OM-S) + (manure-S) + (pptn-S) OCONTO TAYLOR + (subsoil-S) + (soil test SO4-S) CHIPPEWA ST. CROIX DUNN where: MENOMINEE MARATHON CLARK ■ OM-S (sulfur in organic matter) SHAWANO PIERCE EAU CLAIRE DOOR = % organic matter x 2.8 lb/a PEPIN WOOD PORTAGE WAUPACA OUTAGAMIE ■ manure-S = ton/a of manure x BUFFALO BROWN lb available S per ton KEWAUNEE JACKSON

■ pptn-S (sulfur in precipitation) JUNEAU WAUSHARA C WINNEBAGO

TREMPEALEAU OWO

= 5, 10, or 15 lb/a depending on county MONROE ADAMS IT

CALUMET

AN M ■ subsoil-S = 5, 10, or 20 lb/a LA CROSSE depending on soil GREEN-

VERNON MARQUETTE LAKE FOND DU LAC

■ SHEBOYGAN soil test SO -S = ppm S (from lab test) x 4 SAUK DODGE 4 WASHING- RICHLAND TON

CRAWFORD COLUMBIA OZAUKEE DANE JEFFERSON WAUKESHA IOWA

GRANT MILWAUKEE

GREEN ROCK WALWORTH RACINE LAFAYETTE

KENOSHA

5 lb/a 10 lb/a 15 lb/a C-12 10/18/05 11:17 AM Page 150

150 MANAGEMENT OF WISCONSIN SOILS

Micronutrient molybdenum are rarely ever deficient in Crops vary in their micronutrient recommendations Wisconsin so soil tests have not been requirements (table 12-11). If the soil Plants need only very small adequately calibrated for these tests low or very low in a amounts of micronutrients for good elements. Plant analysis can be used to micronutrient, response to application growth. While a deficiency of any evaluate the status of copper and iron, of that nutrient (1) likely will occur if nutrient will reduce crop yields, the and is often used to confirm soil tests the crop has a high requirement for overuse of micronutrients can produce for boron, manganese, and zinc as well. that nutrient, (2) probably will occur if a harmful level in the soil which may be Use of micronutrients is the crop has a medium requirement, or more difficult to correct than a recommended when the soil test is low (3) most likely will not occur if the crop deficiency. or very low, when verified deficiency has a low requirement for the nutrient. Soil tests are available from symptoms appear in the plant, or when Wisconsin labs for boron, manganese, certain crops have very high and zinc. Copper, iron, and requirements such as boron for beets.

Table 12-11. Relative micronutrient requirements of Wisconsin crops.

Crop ————————————— Micronutrienta ———————————— code Crop Boron Copper Manganese Molybdenum Zinc

1 Alfalfa High Medium Low Medium Low 2 Alfalfa seeding High Medium Low Medium Low 3 Asparagus Medium Low Low Low Low 4 Barley Low Medium Medium Low Medium 5 Bean, dry (kidney, navy) Low Low High Medium Medium 6 Bean, lima Low Low High Medium Medium 7 Beet High High Medium High Medium 8 Brassica, forage High — — High — 9 Broccoli Medium Medium Medium High — 10 Brussels sprout Medium Medium Medium High — 11 Buckwheat Low ———— 12 Cabbage Medium Medium Medium Medium Low 13 Canola High Medium Medium Medium Medium 14 Carrot Medium Medium Medium Low Low 15 Cauliflower High Medium Medium High — 16 Celery High Medium Medium Low — 17 Corn, grain Low Medium Medium Low High 18 Corn, silage Low Medium Medium Low High 19 Corn, sweet Low Medium Medium Low High 20 Cucumber Low Medium Medium Low Medium 21 Flax ————— 22 Ginseng ————— 23 Lettuce Medium High High High Medium 24 Lupin Low Low Low Medium Medium (continued) C-12 10/18/05 11:17 AM Page 151

Chapter 12. Soil testing, soil test recommendations and plant analysis 151

Table 12-11. Relative micronutrient requirements of Wisconsin crops (continued).

Crop ————————————— Micronutrienta ———————————— code Crop Boron Copper Manganese Molybdenum Zinc

25 Melon Medium ———— 26 Millet Low ———— 27 Mint, oil Low Low Medium Low Low 28 Oat Low Medium High Low Low 29 Oatlage Low Medium High Low Low 30 Oat-pea forage Low Medium High Low Low 31 Onion Low High High High High 32 Pasture, unimproved Low Low Medium Low Low 33 Pasture, managed Low Low Medium Low Low 34 Pasture, legume-grass High Medium Low High Low 35 Pea, canning Low Low Medium Medium Low 36 Pea (chick, field, cow) Low Low Medium Medium Low 37 Pepper ————— 38 Popcorn ————— 39 Potato Low Low Medium Low Medium 40 Pumpkin ————— 41 Reed canarygrass Low Low Medium Low Low 42 Red clover Medium Medium Low Medium Low 43 Rye Low Low Low Low Low 44 Snapbean Low Low — — — 45 Sod Low Low Medium Low Low 46 Sorghum, grain Low Medium High Low High 47 Sorghum-sudan forage Low Medium High Low Medium 48 Soybean Low Low High Medium Medium 49 Spinach Medium High High High High 50 Squash ————— 51 Sunflower High High — — — 52 Tobacco Medium Low Medium — Medium 53 Tomato High High Medium Medium Medium 54 Trefoil, birdsfoot High ———— 55 Triticale Low Low Medium — — 56 Truck crops Medium Medium — — — 57 Vetch (crown, hairy) Medium ———— 58 Wheat Low Medium High Low Low 66 CRP, alfalfa High Medium Low Medium Low 67 CRP, red clover Medium Medium Low Medium Low 68 CRP, grass Low Low Medium Low Low — = no data a Iron (Fe) and chloride (Cl) deficiencies have not been noted on field crops in Wisconsin. C-12 10/18/05 11:17 AM Page 152

152 MANAGEMENT OF WISCONSIN SOILS

Table 12-12 gives fertilizer chelates (0.2% solution). Soil No recommendations have been recommendations for boron, applications with the chelate FeDDHA formulated for chlorine because this manganese, and zinc based on relative have also been successful. Follow the element has never been reported to be crop requirements and soil test results. manufacturer’s recommendations. deficient in Wisconsin. Copper recommendations (table 12- Deficiencies of molybdenum can Soil test report 13) are based on plant analysis or the often be corrected simply by liming. If An example of a soil test report is appearance of visible deficiency liming does not correct the deficiency shown on the following page. symptoms. Deficiencies of iron can be or if the pH must be kept low, apply Field information is reported in corrected by foliar applications of 1.0 ounce per acre of ammonium or the upper left section of the soil test ferrous sulfate (1% solution) or iron sodium molybdate as a seed treatment.

Table 12-12. Soil test recommendations for boron, manganese, and zinc.

—————— Manganese —————— Crop —— Row —— —— Foliar —— —————— Zinc —————— a b b requirement Soil test Boron MnSO4 MnEDTA MnSO4 MnEDTA Row Broadcast Foliar

————————————————————— lb/a —————————————————————

High Low 2 5 0.8 1 0.15 2 6 1.0/0.15c

Very low 3 —d —d —d —d 2 8 1.0/0.15c

Medium Low 1 3 0.5 1 0.15 1.5 4 1.0/0.15c

Very low 2 —d —d —d —d 2 5 1.0/0.15c

LowLow0****** *

Very low * —d —d —d —d ** *

a Apply broadcast or topdress. b Recommendations are for ZnSO4; use one-fourth these rates if applied as zinc chelate. c Apply 1.0 lb/a zinc sulfate or 0.15 lb/a ZnEDTA. d There is no very low category for manganese. * Confirm the need for micronutrient with plant analysis before applying fertilizer.

Table 12-13. Copper fertilizer recommendations.a

Crop ——— Sands ——— — Silts and clays —— Organic soils — requirement Broadcast Band Broadcast Band Broadcast Band

————————————— lb/a —————————————

High 10 2 12 3 13 4

Medium 4 1 8 2 12 3

Low * * * * * *

a Recommendations are for inorganic sources of copper. Apply copper chelates at one-sixth the above rates. * Confirm the need for micronutrient with plant analysis before applying fertilizer. soil test report (QX) 10/19/05 8:39 AM Page 1 soil test report (QX) 10/19/05 8:39 AM Page 2 C-12 10/18/05 11:17 AM Page 153

Chapter 12. Soil testing, soil test recommendations and plant analysis 153

report. The field history given on the soil test for phosphorus and potassium problem. For example, plant analysis information sheet when the soils are are shown in the center section of the might show a corn plant being low in submitted for analysis is the same report. Lines of repeated “P”s and “K”s phosphorus even though the soil test information reported in this section of extend into the appropriate shows there is sufficient soil the report. interpretation level for each crop. phosphorus. Only on-site inspection Field nutrient recommendations The laboratory analysis results for will reveal that the deficiency is due to for fertilizer and lime are presented in each sample are located in the lower cold weather, rootworm damage, or the upper portion of the report. These portion of the report. Routine soil tests some other factor. recommendations are based on the include soil pH, buffer pH (reported in Identification of nutritional average results of all samples from one the buffer code column), organic disorders. The main use of plant field and are presented for the 4-year matter, phosphorus, and potassium. analysis is the identification of crop rotation selected. If no specific Organic matter results are reported in nutritional disorders. For that reason, crop rotation is selected, percent and nutrient tests in ppm. carbon, hydrogen, and oxygen are not recommendations for a corn-soybean- analyzed because they come from the alfalfa seeding-alfalfa rotation are given. air or water and virtually never limit Aglime recommendations for the Plant analysis plant growth. Molybdenum is analyzed specific crop sequences are presented only on request because it is difficult to directly beneath the fertilizer Uses of plant analysis analyze, is seldom deficient, and is used recommendation for each option. The Plant analysis is used to measure as an internal standard on some amount of aglime needed to raise the the concentration of essential elements analytical equipment. Chlorine is not soil pH for the most acid-sensitive crop in plant tissue. It is a more precise analyzed because it is always sufficient in the sequence is shown for lime diagnostic tool for identifying under Wisconsin field conditions. grades with neutralizing indexes of nutritional disorders than soil tests or Plant analysis is also used to test for 60-69 and 80-89. observations of visual deficiency aluminum and sodium, even though The fertilizer recommendations on symptoms. Plant analysis can accurately they are not essential elements, because the soil test report form are adjusted for identify deficiencies of macronutrients aluminum can be toxic in acid soils, previous legume crops or applied and most micronutrients. In fact, for and sodium improves the quality of manure if this information is given on some nutrients, such as copper and some crops, such as beets and celery. the information sheet. These iron, plant analysis is the only practical Plant analysis is unique from other adjustments are also shown in the diagnostic tool available. In addition, crop diagnostic tests in that it gives an upper portion of the report. Below the plant analysis can be used to evaluate overall picture of the nutrient levels fertilizer recommendations is additional fertilizer efficiency, to study nutrient within the plant at the time the sample information for modifying the interactions, and to identify or confirm was taken. This picture shows the recommendations based on crop nutrient toxicities. It is also used to concentration levels for each of the management practices. The total make fertilizer recommendations for analyzed nutrients. Figure 12-7 shows nutrient requirement can be applied as perennial shrubs and trees. the relationship between nutrient a combination of manure, legume, Plant analysis and a good soil test concentration levels and crop growth. commercial fertilizer, or other nutrient can furnish a guide to more efficient Increasing the concentration of a source. Applications can be made as a crop production. Soil tests provide a deficient nutrient will increase crop row treatment, a broadcast treatment, good estimate or prediction of lime and growth until it reaches a maximum or as a combination of the two. The fertilizer needs. Plant analysis records yield. Further additions of the element decision on how to apply the required the actual uptake of plant nutrients and will cause the concentration of that nutrients depends largely on the total allows an evaluation of fertilizer and element in the plant to rise more amount needed, soil type, crop to be management practices by providing a rapidly because it is not being diluted grown, and personal preference. nutritional “photograph” of the crop. by added dry matter accumulation. A graphic presentation of the Soil tests and plant analyses often Eventually, toxicity of that element may interpretations of the adjusted average need to be used in combination with occur. on-site inspection to help pinpoint a C-12 10/18/05 11:17 AM Page 154

154 MANAGEMENT OF WISCONSIN SOILS

Figure 12-7. Relationship between nutrient supply, corn yield and can cause potassium to accumulate. In nutrient concentration in ear leaf tissue. addition, plant analysis usually detects only the one element that inhibits plant corn yield 100 ➡ growth the most. Rarely are two or more elements acutely deficient at the sufficient same time. A corn plant, for example, 75 may be deficient in potassium; but, low high because potassium is limiting growth, 50 there may be sufficient phosphorus for the reduced amount of dry-matter production even if soil phosphorus is deficient ➡ excessive nutrient nutrient low. When potassium is added as a 25 concentration in tissue concentration remedial treatment, dry-matter Corn yield, % of maximum production increases sharply; then 0 phosphorus becomes deficient. nutrient supply Decomposition of plant tissue, due Source: Adapted from Brown, 1970. to aging or damage such as that caused by wind, hail, or frost, will result in a loss of carbon (as CO2 through Evaluation of fertilizer Limitations of respiration and microbial activity). This efficiency. Another use of plant plant analysis dry matter loss will tend to concentrate analysis is to evaluate fertilizer Interpreting plant analysis results is most nutrient elements, thereby giving efficiency. Soil scientists use plant difficult because of the many variables erroneously high readings. analysis to study nutrient uptake from that influence nutrient concentrations. Collecting plant samples fertilizer and organic amendments and In general, good relationships can be A critical aspect of plant analysis is to evaluate different methods of developed between soil nutrient supply, sample collection. Plant composition application and other nutrient nutrient levels in the plant, and crop varies with age, the portion of the plant management practices. Adding yield for a given location in any one sampled and many other factors. nutrients to the soil is no guarantee year. However, differences in location, Therefore, it is important to follow a that they will be assimilated by the plant variety, time, and management standard sampling procedure. plant. Added nutrients might be often cause variations in these Plants need to be sampled at unavailable to plants, or they might relationships and make them more specific times during the growing react with a particular soil to form difficult to interpret. Nutrient levels in season to interpret the analytical results unavailable compounds. Plant analysis plants differ depending on the plant accurately. These results are compared can also be used to show the effect of part sampled, stage of maturity, hybrid, against a set of calibrated standards that lime on the availability of native and and climatic conditions. So, are linked to a given stage of crop applied elements. interpretation of the results of plant growth. The back of the plant analysis Interactions among plant analysis must take these factors into information sheet (attached) outlines nutrients. Nutrient interactions can consideration. the proper stage of growth, plant part, also be studied using plant analysis, Another limitation of plant and number of plants to sample for sometimes revealing unknown analysis is knowing how the factor that major agronomic and horticultural relationships among essential elements. is limiting plant growth affects other crops. If a crop is sampled at any other While plant physiologists sometimes nutrients. For example, nitrogen point in the growing season, an make these interactions a deliberate deficiency can limit the uptake of accurate interpretation of the analysis study, more often they discover these phosphorus and some of the will be more limited. Do not take relationships when they summarize micronutrients to the extent that they samples after flowering, silking, and/or results of many plant analyses. appear to be “low.” At the same time it pollination. 3/04 PLANT ANALYSIS INFORMATION SHEET Department of Soil Science UW Soil & Plant Analysis Laboratory College of Agricultural and Life Sciences 8452 Mineral Point Road University of Wisconsin-Madison/Extension Verona, WI 53593 (608) 262-4364

NAME AND ADDRESS METHOD OF PAYMENT Date Rec'd (Lab Use Only)

Name Amount paid or Acct. ID Lab No. Address Cash or Check No. PO#

City State Zip Credit Card

County Code ______County sample(s) came from: Credit Card No______-______-______-______Exp_____/_____ Stage of growth Soil submitted for Sample Interpretations only Plant part sampled routine test No. Field ID for those listed. (Choose letter on back) Crop Plant appearance (pH, OM, P and K) (Choose number on back) (Circle one) (Circle one) Normal Abnormal Yes No Normal Abnormal Yes No Normal Abnormal Yes No Normal Abnormal Yes No Normal Abnormal Yes No Normal Abnormal Yes No Normal Abnormal Yes No Normal Abnormal Yes No Normal Abnormal Yes No Normal Abnormal Yes No

In addition to routine test (pH, organic matter, phosphorus, and potassium), check soil special test(s) if requested: There is an added charge per test. Report will list fields individually unless designated otherwise: DRIS indices available for: alfalfa, apple, corn, celery, lettuce, millet, oat, potato, grain sorghum, tomato and wheat Check special test(s) desired: List fields § PASS indices available for: alfalfa, corn and soybean Calcium/Magnesium (Ca/Mg) ______§ Best information for non-diagnostic stage of growth/plant part Boron (B) ______can be obtained by comparing good and bad appearing plants Manganese (Mn) ______from the same field. Report will list fields Sulfur singularly (SO4-S) ___unless designated______If you would like to have results emailed please provide email address below: Zinc (Zn) ______Email to: ______Comments, special instructions, billing information (if different from above):

Field Crops Stage of Growth Plant Part Sampled Number of Plants

Alfalfa, red clover, birdsfoot trefoil, crown vetch 1 Bud to first flower A Top 6” 30-40 Alfalfa hay, red clover hay 2 Harvest B Whole plant 15-20 Corn, field 3 12” tall C Whole plant 10-15 4 Pre-tassel D Leaf below whorl 15-20 5 Tassel to silk E Ear leaf 15-20 6 Ensiled/chopped F Whole plant 10-15 Corn, sweet 7 Tassel to silk G Ear leaf 15-20 Beans, soybeans, dry lima, snapbeans, 8 Prior to or at initial H 4th petiole and leaflet 20-25 peas (canning, chick peas) flowering or 4th petiole only Potato 9 Prior to or at initial flowering I 4th petiole and leaflet or 4th petiole only 40-50 10 Tuber bulking J 4th petiole and leaflet or 4th petiole only 40-50

Wheat 11 Tillering K Newest fully developed leaf 30-40 Wheat, barley, rye, canary grass, triticale, 12 Prior to heading L Newest fully developed leaf 30-40 brome grass, oat, orchard grass Sorghum, grain 13 Prior to heading M 2nd fully developed leaf 15-20 Sorghum-sudan 14 Prior to heading N Newest fully developed leaf 15-20

Fruits Stage of growth Plant part sampled Number of Plants

Apple, cherry (sour) 15 Current season’s shoots O Fully developed leaf at midpoint of new shoots 10-20 Strawberry 16 At renovation before mowing P Fully developed leaflets and petioles 10-20 Raspberry 17 August 10 to September 4 Q 6th and 12th leaf blade and petiole from trifoliate10-20 Cranberry 18 August 15 to September 15 R Current season’s growth above berries 35-50

Vegetables Stage of growth Plant part sampled Number of Plants

Onion 19 Midseason S Tops, no white 10-20 Carrots, celery, ginseng, cauliflower 20 Midseason T Youngest mature leaves 10-20 Tomato 21 Midseason U Newest fully developed leaf 10-20 Cabbage, lettuce 22 Midseason V Wrapper leaf 10-20 Pepper 23 Prior to or at early fruit W Petiole and leaflet 10-20 development

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Chapter 12. Soil testing, soil test recommendations and plant analysis 155

To minimize economic losses, since plant tissue molds more readily in Nutrient ranges representing sample plants as soon as they show any such bags. It is not necessary to air dry deficient, low, sufficient, high, and abnormality, even if it is earlier than the samples that will be delivered to the lab excessive concentrations for corn and stage of growth shown on the plant within a day after collection of the alfalfa used by the University of analysis information sheet. In such a sample. Refrigerate these samples if Wisconsin Soil and Plant Analysis case, collect and submit the entire possible. Laboratory are shown in table 12-14. above-ground portion of the plant for A soil sample should be submitted For some nutrients, excessive levels analysis. Avoid any diseased or insect- along with all plant analysis samples. have not been well-defined because damaged plants. When taking samples The soil sample should be taken from growth is not depressed by excessive for trouble-shooting in a field, be sure the same area as the plant sample. For uptake. These ranges are useful to include a healthy specimen from the some problems, the soil sample results guidelines for interpreting plant same area. If normal and abnormal will substantially improve analyses, but they must not be used plants are tested, comparison of the interpretations of the plant analysis. dogmatically. Knowledge of hybrid results between the two can often For example, plants suffering from requirements, unusual soil or climatic diagnose the problem. A comparison manganese toxicity are often associated conditions, or other extenuating sample is particularly helpful in the with low pH soils. information should be considered. analysis of some plants such as flowers Interpretation of DRIS or nutrient ratio approach and shrubs where a large database is not plant analyses The Diagnosis and available for interpreting the results. Recommendation Integrated System Critical value and sufficiency Prepare a plant sample for (DRIS) simultaneously considers range approaches shipment by removing any roots and nutrients on a ratio basis in relation to For most diagnostic purposes, foreign material from the sample. Plant crop growth. The DRIS approach to plant analyses are interpreted on the samples contaminated with soil interpreting the results of plant analysis basis of “critical” or “sufficiency” levels particles will have erroneously high involves creating a database from the for each nutrient. The critical level has results for iron, aluminum, and analysis of thousands of samples of a been defined as that concentration manganese. To remove soil particles, specific crop. The nutrient ratios below which yields decrease or shake or dust off the plant tissue— corresponding to the highest yielding deficiency symptoms appear. For many DO NOT WASH tissue since soluble portion of the population are nutrients, yield decreases even before nutrients will be leached out of the established as the standard (norms) and visible deficiency symptoms are sample. used as the basis for comparison. A observed. Because the exact Complete a plant analysis ratio of plant nutrient concentrations concentration of a nutrient below information sheet (sample attached) by itself cannot be used to diagnose which yields decline is difficult to available from University laboratories, plant problems, but combinations of determine precisely, some define the county Extension offices or different nutrient ratios can be critical level as the nutrient uwlab.soils.wisc.edu/madison. The combined mathematically to determine concentration at 90 or 95% of Extension office will also have names what nutrients are most likely to limit maximum yield. and addresses of private laboratories yield. The results of such calculations As previously mentioned, the that offer plant analysis services. are the “DRIS indices.” nutrient composition of a plant If the tissue sample is to be mailed, An index of 0 is considered changes as the plant matures and with air-dry the sample for at least 1 day to optimum; however, although finer- the portion of the plant sampled; avoid mold growth during shipment. tuning may be possible, DRIS indices therefore, critical levels are defined for a Never mail samples on Thursday, are normally calibrated so that those specific plant part at a specified stage of Friday, or Saturday since the tissue may within the range of about –15 to +25 maturity. For most crops, there is a deteriorate in the post office over the are considered normal and “in fairly broad optimum range of weekend. Place the plant sample in a balance.” A DRIS index less than –25 concentration over which yield will be large paper envelope for shipment. Do indicates a likely deficiency, whereas maximized rather than a single point. not use plastic or polyethylene bags those between –15 and –25 represent a C-12 10/18/05 11:17 AM Page 156

156 MANAGEMENT OF WISCONSIN SOILS

Table 12-14. Interpretive plant nutrient ranges for corn and alfalfa in Wisconsin.

—————————— Tissue nutrient interpretive level —————————— Nutrient Deficient Low Sufficient High Excessive

CORN—ear leaf at tasseling to silking

Nitrogen, % <1.75 1.75–2.75 2.76–3.75 >3.75 —

Phosphorus, % <0.16 0.16–0.24 0.25–0.50 >0.50 —

Potassium, % <1.25 1.25–1.74 1.75–2.75 >2.75 —

Calcium, % <0.10 0.10–0.29 0.30–0.60 0.61–0.90 >0.90

Magnesium, % <0.10 0.10–0.15 0.16–0.40 >0.40 —

Sulfur, % <0.10 0.10–0.15 0.16–0.50 >0.50 —

Zinc, ppm <12 12–18 19–75 76–150 >150

Boron, ppm <2.0 2.0–5.0 5.1–40.0 40.1–55.0 >55.0

Manganese, ppm <12 12–18 19–75 >75 —

Iron, ppm <10 10–49 50–250 251–350 >350

Copper, ppm — <3 3–15 16–30 >30

ALFALFA—top 6 inches of plant at first flower

Nitrogen, % <1.25 1.25–2.50 2.51–4.00 >4.00 —

Phosphorus, % <0.20 0.20–0.25 0.26–0.45 >0.45 —

Potassium, % <1.75 1.75–2.25 0.26–3.40 3.41–4.25 >4.25

Calcium, % — <0.70 0.70–2.50 >2.50 —

Magnesium, % <0.20 0.20–0.25 0.26–0.70 >0.70 —

Sulfur, % <0.20 0.20–0.25 0.26–0.50 >0.50 —

Zinc, ppm — <20 20–60 61–300 >300

Boron, ppm <20 20–25 26–60 >60 —

Manganese, ppm <15 15–20 21–100 101–700 >700

Iron, ppm — <30 30–250 >250 —

Copper, ppm — <3.0 3.0–30.0 >30.0 — C-12 10/18/05 11:17 AM Page 157

Chapter 12. Soil testing, soil test recommendations and plant analysis 157

possible deficiency. Values greater than Plant Analysis with Tissue testing +100 may be an indication of possible Standardized Scores (PASS) Tissue testing offers a quick field nutrient excess. The greater the The Plant Analysis with test of plant sap. Unlike plant analysis, magnitude of the nutrient index, either Standardized Scores (PASS) system was which is a quantitative laboratory positive or negative, the more likely developed at the University of analysis of plant tissue, a tissue test is that element is out of balance in the Wisconsin to combine the strengths of semi-quantitative. Results are plant. the sufficiency range (SR) and DRIS interpreted as high, medium, low, or The principal advantages of the methods. The SR provides easily deficient rather than in exact DRIS system are that stage of maturity, interpreted, categorical, independent percentages or parts per million. Most plant part, and cultivar are less nutrient indices. The DRIS gives test kits analyze only nitrogen, important than they are for the critical difficult to calculate, easily interpreted, phosphorus, and potassium. A soil pH level or sufficiency range approaches to numerical, dependent nutrient indices, kit is a useful supplement to the tissue- interpreting plant analyses. Thus, by and a ranking of the relative testing kit in areas with low or high pH using DRIS as an interpretive deficiencies. The strengths of the SR soils. approach, it is possible to sample alfalfa are the weaknesses of the DRIS and Tissue testing can help interpret at the pre-bud stage and obtain vice-versa. The PASS system combines plant growth problems in the field. meaningful results, rather than waiting an independent nutrient section and a Even if it does not identify nitrogen, until first flower. dependent nutrient section. Both types phosphorus, or potassium as deficient, DRIS norms are not available for of indices are expressed as a these nutrients can be ruled out, and all crops and some users of the DRIS standardized score and can be attention can be focused elsewhere. For system tend to interpret the results too combined to make more effective questionable test results and for results dogmatically. Some regard every interpretations. Research has needing to be verified, submit samples negative index as representing a demonstrated that PASS results in to a laboratory for complete plant deficiency and pay no attention to more correct diagnoses than either of analysis. positive indices. Since not all of the the other two systems. To date, Tissue test kits can give false results nutrient norms used to develop DRIS however, the PASS system has been if the reagents deteriorate or become indices have been evaluated under field developed only for alfalfa, corn, and contaminated. conditions, experience has shown that soybean. the evaluations should not be made disregarding nutrient concentrations altogether. The University of Wisconsin recommends that the two interpretive approaches—DRIS and critical value/sufficiency range—be used together. C-12 10/18/05 11:17 AM Page 158

158 MANAGEMENT OF WISCONSIN SOILS

Questions 1. What is the minimum number of 5. Assume a soil test for available composite soil samples that should potassium (K) is 60 ppm in a be taken from a 35-acre field that Miami silt loam and that a farmer has not been tested in the past 10 broadcasts and thoroughly years? How many cores or borings incorporates the 300 pounds per should be in each composite acre of 0-0-60 (180 pounds of sample? K2O) recommended for this field in the fall. If this field was 2. To what depth should the soil be resampled and tested again in the sampled in the following tillage spring, what would be the expected systems: 1) moldboard plow, level of available potassium (K) on 2) chisel plow, 3) ridge tillage, the new soil test? 4) no-till? 6. If a toxicity is suspected, such as 3. If a farmer has soil that boron toxicity, which of the consistently tests in the excessively following diagnostic aids will more high range for phosphorus and accurately define the problem: soil potassium, what fertilizer test, plant analysis, or a tissue test? recommendations should be made Why? for corn? for established alfalfa? 7. A soil sample from an alfalfa field 4. Assume a farmer has a field of tests “low” in available zinc, but no continuous corn in Dubuque silt recommendations for zinc are loam that tests 10 ppm in available given on the soil test report. Why? phosphorus (P). Also, assume that enough row fertilizer is applied 8. Why is sulfur rarely recommended each year to replace what is being for a Tama silt loam soil in Grant removed when the ear corn is County? harvested. About how much 9. What is the difference between broadcast phosphate (P O ) would 2 5 plant analysis and tissue testing? have to be applied to increase the When would each be used? available phosphorus (P) in the soil to 20 ppm? C-13 10/18/05 11:18 AM Page 159

CHAPTER 13 159 Economics of lime and fertilizer use

Corn yields in Wisconsin, like In Wisconsin, fertilizer use on corn other states, were almost constant for increased steadily until the early 1980s. 800 years prior to 1940 (figure 13-1). Since then, rates have remained Much of the increase between 1940 constant or declined somewhat. “Farm people are not… and 1955 can be attributed to the However, this does not mean that high indifferent to economic introduction of hybrids. Most of the rates of fertilizer are always profitable. opportunities to improve their lot. sustained increase from 1955 on is A summary of over 650,000 soil attributed to the use of fertilizers and samples analyzed by Wisconsin soil They are calculating economic pesticides and improved agronomic testing labs during 1995 through 1999 agents who reckon marginal costs practices. Future yield increases will found that soil test phosphorus and and returns to a fine degree.” rely not only on science and technology potassium averaged excessively high or but also on better management practices high, respectively, for most field crops. Theodore W. Schultz, to identify and then eliminate produc- This means that most growers would “Knowledge is Power in Agriculture” in tion constraints while maintaining or be unlikely to see profitable response to Challenge, September–October 1981 improving environmental quality. more than recommended amounts of

Figure 13-1. Wisconsin corn yields from 1866 to 2000.

140

120

100

80

60

40 Grain yield (bu/a)

20

0 1860 1880 1900 1920 1940 1960 1980 2000

Source: United States Department of Agriculture (USDA). C-13 10/18/05 11:18 AM Page 160

160 MANAGEMENT OF WISCONSIN SOILS

Figure 13-2. Net profit for one and two rotations (alfalfa- ■ Study and observe research and alfalfa-corn-soybean-corn) in Plano and Withee silt loams demonstration trials conducted on limed from pH 5.0 to 6.8. nearby experimental farms. Plano silt loam ■ Set up trials to determine whether 2 rotations 1 rotation treatment response pays for the cost 800 of the treatment. The best way to evaluate 600 expenditures on various inputs is to estimate the relative return from 400 incremental investments. Usually the return per dollar invested in lime and Profit, $/a Profit, 200 fertilizer is higher than for most other inputs, such as additional breeding 0 stock, new buildings, or new 4.8 5.2 5.6 6.0 6.4 6.8 machinery. Also, the money invested in lime and fertilizer is turned over much Soil pH faster than with investments such as Withee silt loam machinery. As a result, the purchase of 2 rotations 1 rotation lime and fertilizer should have a high 800 priority, especially on farms with low or optimum fertility soils. 600 Another reason why the return on lime and fertilizer is quite favorable is 400 that prices for these items have not risen as much as most other farm

Profit, $/a Profit, inputs. For example, while the price of 200 fertilizer increased by about 250% from 1950 to 1985, the costs of wages, 0 machinery, and land have increased by 4.8 5.2 5.6 6.0 6.4 6.8 700, 725, and 1,000%, respectively. Soil pH Returns from phosphate and potash. Nevertheless, recommended rates. Some waste aglime there are still some soils testing less money by failing to credit the nutrients Liming is considered a capital than optimum in pH, phosphorus or contributed by previous leguminous investment because it improves the potassium, and it is on these soils where crops or manure. Before applying more inherent productivity of the soil and, the greatest response to lime and than the recommended amount of lime therefore, has value for more than 1 fertilizer can be expected. or fertilizer, make sure that such year. Once the optimum soil pH is One of the keys to profitable crop practices are profitable by considering achieved, it will be several years before response is to base lime and fertilizer the following: lime is needed again. Therefore, when applications on soil test ■ Check soil test levels and keep them considering the return from liming, an recommendations. A few farmers within the optimum range. See estimate of the value of crop yield forego potential profitability by not Extension publication Optimum Soil increases over a 5- to 10-year period will applying recommended rates of Tests for Wisconsin (A3030). be needed. As shown in figure 13-2, fertilizer and lime, while others cut raising the soil pH above 5.0 resulted ■ Give credits to manure and previous their profits by using more than the in substantial profits when the values of leguminous crops. C-13 10/18/05 11:18 AM Page 161

Chapter 13. Economics of lime and fertilizer use 161

the yield increases were calculated for pH 6.5. If alfalfa were kept for 3 or 4 Because of the uncertainty of two 5-year rotations (alfalfa-alfalfa- years, as it often is on Withee soil, the weather, prices, etc., many of these corn-soybean-corn). Only modest maximum profit for a long rotation factors have to be estimated at the profits were realized in one rotation. would shift toward pH 6.8. beginning of the growing season or Research plots on Plano silt loam when the fertilizer is being applied. In had a maximum profit at about pH 6.0 spite of the difficulties involved, for one rotation and at pH 6.8 for two Returns from the estimating these variables and con- rotations. Results were different on use of fertilizer ducting field trials can help determine Withee silt loam because of the Farmers often want to know the the most profitable fertilizer rate. difference in the amount and cost of most profitable rate of fertilizer to One way of finding the most aglime, and the difference in the apply. This is not an easy question to profitable rate of fertilization is to magnitude of the crop response. (Prices answer because of the various factors determine the added (marginal) return were $12 per ton for aglime on Plano which must be considered including: from incremental additions. Compare and $20 per ton for aglime on Withee, added fertilizer costs with the added ■ $75 per ton for alfalfa plus $1 per ton expected yield increase from each crop value for each increment of for each 0.1 pH above 5.0, $2 per increment of fertilizer, fertilizer. Table 13-1 illustrates how to bushel for corn, and $7 per bushel for ■ level of management, determine marginal returns. In this soybean.) Although crop yields on ■ price of fertilizer, study, increasing nitrogen applications Withee silt loam are generally lower from 0 to 200 pounds per acre resulted ■ price of commodity, than on Plano silt loam, response to in a yield increase from 93 to aglime is higher because manganese ■ added cost of handling the extra 145 bushels of corn per acre. The first toxicity at low pH is more of a problem crop yield, and two 40-pound increments gave the in the Withee soil. The maximum ■ value of residual carryover of highest return per dollar invested. profit for both one and two rotations fertilizer. However, the greatest profit was on the Withee soil occurred at about obtained when 160 pounds of nitrogen

Table 13-1. Yield of corn and return from added nitrogen (Janesville, WI).

—— Profit per acre —— Return Cost of Nitrogen Cost of Yield Value of yield From each From all per dollar producing added 40 lb Na Yield increase increaseb N increment N added spentc extra corn

lb/a $ ———bu/a——— $ ————————$/a ———————— $/bu

0 — 93 — — — — —

40 13.20 115 22 44 30.80 30.80 2.33 0.60

80 9.20 131 16 32 22.80 53.60 2.39 0.58

120 7.87 138 7 14 6.13 59.73 1.78 1.12

160 7.20 144 6 12 4.80 64.53* 1.67 1.20

200 6.80 145 1 2 –4.80 59.73 0.29 6.80

* Maximum profit a Nitrogen applied as anhydrous ammonia at $0.15/lb + prorated share of an $8/a application fee. b Corn valued at $2/bu. c Calculated by dividing the value of the additional yield by the cost of each additional 40 lb of nitrogen. Source: Adapted from Bundy et al., 1992. Nutrient Management: Practices for Wisconsin Corn Production and Water Quality Protection. University of Wisconsin-Extension publication A3557. C-13 10/18/05 11:18 AM Page 162

162 MANAGEMENT OF WISCONSIN SOILS

was applied per acre. (This is the because the second 40-pound that moderate changes in corn prices or amount that would be recommended increment of nitrogen returns $2.39 nitrogen fertilizer costs do not cause on the basis of a soil test.) Application per dollar invested. Farmers with major changes in optimum nitrogen of either 120 or 200 pounds of limited capital should concentrate on recommendations. Corn:nitrogen price nitrogen per acre would have resulted starter applications of phosphorus and ratios in the range of 10:1 or greater in a loss of $4.80 per acre in profit potassium and moderate levels of have little impact on economic when compared to the 160 pound per nitrogen on second-year corn, optimum rates (table 13-2). At these acre rate. especially where manure is not applied. price ratios, the greatest return from Note that the yield response of When topdressing hay, priority should nitrogen applied to the two soils shown fertilizer follows the “law of be given to the lowest testing fields in in table 13-2 was at university diminishing returns.” Based on the the first or second production years. recommended rates. The reason for value of corn at $2.00 per bushel, the little if any change in optimum Price changes first 40 pounds of nitrogen gave a return nitrogen fertilizer rates for corn with Changes in the price of fertilizer or of $30.80 per acre; the second 40-pound historically typical variations in prices is in the value of the crop can change increment returned $22.80 per acre; due to the broad plateau of the profit returns. However, if the response the third increment returned $6.13 per corn:nitrogen response curve. Because to fertilizer levels off abruptly at higher acre; the fourth increment returned of the relative flatness in this region of rates of fertilization as it does in the $4.80 per acre; but the yield increase the curve, shifts in corn or nitrogen nitrogen data presented in figure 13-4 for the fifth increment did not pay for prices at corn:nitrogen price ratios and table 13-1, then minor price the nitrogen application. The highest higher than 10:1 do not have major fluctuations will have little effect on the profit, in this example, was at the effects on optimum nitrogen rates. optimum fertilization rate. 160 pounds per acre application rate. Increases in the cost of nitrogen Crops such as corn respond well to fertilizers, have reduced corn:nitrogen Availability of capital fertilizer up to a certain point and then price ratios to the point that economic Whenever financially possible, a response abruptly levels off. These optimum nitrogen rates for corn are grower should try for the highest net crops seem to hit a “yield barrier” now being affected. This is also return per acre for fertilizer, where the because of weather, variety, and other illustrated in table 13-2. At last dollar invested in fertilizer is just limiting factors. For these crops, the corn:nitrogen price ratios of 8:1 or less returned in the value of the additional optimum rate of fertilization usually is (i.e. when nitrogen costs $0.25 per production. If a grower is unable to not affected by modest year-to-year pound or greater and corn sells for invest enough money in fertilizer to price changes. For other crops and $2.00 per bushel), the economic obtain optimum yields, try for a yield nutrients, such as alfalfa response to optimum rate drops from traditional where the last dollar invested in potash, the response curve is more values to levels below current university fertilizer gives a return equal to what it gradual and continuous. In this case, recommendations. would give if invested elsewhere in the the value of the feed largely determines The impact of corn:nitrogen price business. the optimum rate of fertilization. ratios on the optimum rates for corn on For example, suppose that the Due to recent substantial increases southern Wisconsin silt loam soils is purchase of additional protein in the cost of nitrogen, economic shown in figure 13- 3. Similar to supplement will return $2.00 per dollar optimum rates for corn are now being nitrogen fertilizer response curves, the invested. Based on the data from table affected by major increases in nitrogen curve in figure 13-3 has a broad 13-1, it would be more profitable to prices. As stated repeatedly in this plateau. Thus, economic optimum use limited money for the protein book, the goal of the University of rates for corn are relatively stable at supplement rather than applying the Wisconsin fertilizer recommendation corn:nitrogen ratios higher than 10:1. third 40-pound increment of nitrogen program is to provide nutrients at rates At corn:nitrogen ratios below 10:1, because it returned only $1.78 per that produce the greatest economic economic optimum rates drop dollar invested. In this situation, return. Using typical corn and nitrogen significantly. however, at least 80 pounds of nitrogen fertilizer prices during the 1980s and per acre should always be applied 1990s, Wisconsin researchers found C-13 10/18/05 11:18 AM Page 163

Chapter 13. Economics of lime and fertilizer use 163

Residual carryover Substantial amounts of phosphorus and potassium are carried over from one year to the next. Also, some carryover of nitrogen can occur, Figure 13-3. Relationship between corn:nitrogen price especially in a dry year. The residual ratios and economic optimum nitrogen rate for corn on effect of any carryover fertilizer should southern Wisconsin silt loam soils (1991–2003). be considered when calculating the profitability of a fertilizer treatment. For example, the cost of a corrective application of phosphorus and potassium may not be returned the first year following application, but this treatment may also increase the yield of subsequent crops. Corrective applications are profitable as long as the added yield from all the crops in the rotation, discounted for time, will return more than the cost of the

fertilizer. The Wisconsin soil test Economic optimum N rate, lb/a recommendation program suggests building very low and low soil tests over an 8- to 10-year period. However, Corn : nitrogen price ratio do not make corrective applications if residual fertilizer will cause environmental problems.

Table 13-2. Net return from fertilizer nitrogen at recommended, higher, and lower rates for corn production at various corn : nitrogen price ratios on two Wisconsin soils. (Shaded values indicate maximum profit and economic optimum nitrogen rate.)

—————— Net economic return from fertilizera ————— ————— Corn : nitrogen price ratio ($/bu and $/lb) ————— Yield increase 13.3 :1 10.0 :1 8.0 : 1 6.7 : 1 5.7 : 1 Soil N rate from fertilizer N ($2.00/15¢) ($2.00/20¢) ($2.00/25¢) ($2.00/30¢) ($2.00/35¢)

lb/a bu/a ——————————————— $/a ———————————————

Plano 130 50.1 75.60 69.10 62.60 56.10 49.60

160b 54.4 79.80 71.80 63.80 55.80 47.80

190 56.1 78.60 69.10 59.60 50.10 40.60

Withee 90 24.3 30.10 25.60 21.10 16.60 12.10

120b 27.5 32.00 26.00 20.00 14.00 8.00

150 28.2 28.90 21.40 13.90 6.40 –1.10

a Calculated as: (value of yield increase from N) – (cost of N) – (cost of N application (assumed $5/acre)). b Recommended (base) N rate prior to taking legume/manure N credits. C-13 10/18/05 11:18 AM Page 164

164 MANAGEMENT OF WISCONSIN SOILS

Figure 13-4. Acreage required to produce 144 bushels of corn at different rates of applied nitrogen. Optimum rate 150 1.6 • Corn yield

125 1.4

100 1.2

Acres Corn yield, bu/a required 75 • 1.0 Acres required to produce 144 bu to produce required Acres

50 0.8 0 50 100 150 200 Nitrogen applied, lb/a Source: Bundy et al., 1992. Nutrient Management Practices for Wisconsin Corn Production and Water Quality Protection. University of Wisconsin-Extension publication A3537.

Substituting fertilizer it is more economical to increase crop would be more profitable than extra for land production by applying more fertilizer fertilizer only where corn could be An important economic principle on existing acreage than by buying or grown for less than $1.20 per bushel on is that fertilizer and land can be renting more land. Also, there are fixed the additional land. substituted for one another to produce costs that have to be met regardless of a given quantity of feeds or forages. yield, such as costs of tillage, planting, Figure 13-4 charts the data from table taxes, and herbicides. It is usually better Calculating the 13-1 to illustrate the relationship to concentrate these fixed costs on cost of plant between fertilizer rates and acreage. fewer acres and use part of the savings nutrients In this example, the optimum rate for inputs such as fertilizer that increase No appreciable difference exists in of nitrogen of 160 pounds per acre per-acre yields. crop response among different forms or produced a yield of 144 bushels per Table 13-1 also provides analysis of fertilizer when the same acre. To produce the same amount of information on the question of whether amounts of plant nutrients are applied. corn while decreasing the fertilizer to invest in more fertilizer or more Therefore, money can be saved by requires more acreage. For example, if land. At the optimum fertilization rate, determining the cost per pound of only 50 pounds of nitrogen had been 160 pounds per acre of nitrogen, the plant nutrient in various fertilizers and applied per acre, then 1.2 acres would last 40-pound increment of nitrogen purchasing one that supplies the have been needed to produce produced corn at a cost of $1.20 per needed plant nutrients at lowest cost. 144 bushels. Since land costs are high, bushel. In this example, extra land C-13 10/18/05 11:18 AM Page 165

Chapter 13. Economics of lime and fertilizer use 165

Single nutrient fertilizer Example 2: determine what proportion of the total Calculating the cost per pound of a. Calculate the pounds of phosphate price is for each nutrient. Using a price a nutrient in a single element fertilizer of $0.20 per pound for nitrogen sold as (P2O5) per ton of triple is relatively easy. Examples are superphosphate (0-46-0). urea or 28% N solution, $0.20 per illustrated below for anhydrous pound for P2O5 as triple superphosphate, 2,000 lb/ton x 0.46 = 920 lb P2O5 ammonia (82-0-0) and triple and $0.12 per pound for K2O as superphosphate (0-46-0). b. Calculate the cost per pound of muriate of potash, the ratio of these P2O5, assuming triple costs is 2:2:1.2. A procedure for Example 1: superphosphate costs $280 per ton. calculating the cost per pound of each nutrient in a mixed fertilizer is outlined a. Calculate the pounds of nitrogen $280 ÷ 920 lb P2O5 = $0.30/lb P2O5 below using 5-14-42 at $162 per ton or (N) per ton of anhydrous ammonia Mixed fertilizer (82-0-0): $8.10 per 100 pounds as an example. Mixed fertilizers contain more High analysis fertilizers are usually 2,000 lb/ton x 0.82 = 1,640 lb N than one nutrient. An example is less expensive per pound of plant b. Calculate the cost per pound of diammonium phosphate (18-46-0). nutrient. The higher concentration nitrogen, assuming anhydrous When determining the cost per pound translates to savings in transportation, ammonia costs $330 per ton: of the two or three nutrients (N, P2O5, handling, and storage because less and K O) in a mixed fertilizer, first $330 ÷ 1,640 lb N = $0.20/lb N 2 weight is handled per pound of plant

a. Determine the nutrient units: Multiply the N by 2, P2O5 by 2, and K2O by 1.2; then add up the products obtained.

Nutrient Analysis Price factor Nutrient units

N5x2=10 P2O5 14 x 2 = 28 K2O 42 x 1.2 = 50 Total 88 b. Take the total nutrient units for each nutrient, divide by the total for all nutrients, and multiply by the price per 100 lb of the mixed fertilizer. This gives the division of the cost of the mixed fertilizer among the N, P2O5 and K2O.

Total Price of Cost of Nutrient Nutrient units nutrient units 100 lb of 5-14-42 nutrient per 100 lb

N (10 ÷ 88) x $8.10 = $0.92 P2O5 (28 ÷ 88) x $8.10 = $2.58 K2O (50 ÷ 88) x $8.10 = $4.60 Total $8.10 c. Divide the cost of each nutrient by its analysis to get the cost per pound of each plant nutrient.

Cost of Cost per lb Nutrient nutrient per 100 lb Analysis of nutrient

N $0.92 ÷ 5 = $0.18 P2O5 $2.58 ÷ 14 = $0.18 K2O $4.60 ÷ 42 = $0.11 C-13 10/18/05 11:18 AM Page 166

166 MANAGEMENT OF WISCONSIN SOILS

Table 13-3. Effect of rotation on corn yields. Sources of increased returns Previous —— Nitrogen applied to corn, lb/a —— Increased returns resulting from Crops 0 75 150 300 improved soil management may be due ————— corn yield, % of control ————— to any of the following items:

Corn-corn control +46 +60 +49 ■ the market value of increased crop yields, Corn-soybeans +60 +69 +72 +63 ■ a larger proportion of high-return Alfalfa-alfalfa +70 +76 +77 +69 crops grown in the rotation, ■ a permanent increase in the value of the farm (as with increased tillable acres due to drainage). nutrient. The cost of application must reduced costs and added returns Comparison of net returns also be considered because some resulting from such a practice. This Some management practices cost materials such as anhydrous ammonia allows farmers to calculate the impact little to implement but can improve can be relatively costly to apply. of a management practice change on crop yields substantially. These include Other ways to cut fertilizer costs net farm income. Added costs and include buying fertilizer in bulk and returns are most easily figured on an ■ timeliness of tillage, planting, and buying during the off-season. Bulk annual basis. harvesting, fertilizer is less expensive than bagged ■ variety selection, Annual costs for long-term fertilizer. However, the convenience capital investments ■ plant population, and superior storing quality of bagged Some soil management practices ■ fertilizer for a starter application crop rotation, require a capital investment which sometimes makes it the most practical ■ equipment adjustment (seed depth, benefits crops for more than 1 year. choice. Bulk spreading is virtually fertilizer calibration, spray Examples include terraces, tile and always used for broadcast and topdress calibration), surface drainage, lime, and corrective applications; bagged fertilizer is used ■ applications of fertilizer. The annual uniform spreading of manure, and mainly for starter fertilizer. Buying cost of capital improvements consists of ■ taking appropriate credits for manure fertilizer in the fall or winter usually annual depreciation, interest on and previous leguminous crops. offers an advantage in terms of off- investment, repair and up-keep costs (if Corn yields, for example, decrease season discounts. any), insurance, and possible increased by roughly 1 buhels per acre for every taxes because of the improvement. day planting is delayed beyond May 5 Calculating profits Annual depreciation can be in southern Wisconsin. If tillage is not computed by dividing the total costs of completed and the planter ready to go from improved the improvement by the number of on time, weather can delay planting soil management years it is estimated to last. An interest further. If weeds are not sprayed or Farmers cannot afford to adopt charge should be included since the cultivated on time, they can get out of improved soil management practices capital invested could earn interest in control and cause serious yield losses. unless those practices increase farm some other use. A study of various crop rotations income. Each group of related practices When evaluating profitability any on the Lancaster, WI Research Station can best be evaluated by means of a cost sharing available through various showed that corn invariably yielded partial farm budget. A partial farm county, state, or federally funded better following a rotation crop than in budget compares the added costs and programs should be deducted from the continuous corn regardless of the reduced returns of a proposed cost of the practice. amount of nitrogen applied management practice against the (table 13-3). This is probably due to C-13 10/18/05 11:18 AM Page 167

Chapter 13. Economics of lime and fertilizer use 167

the influence of the rotation crop in The returns from farming soils to An increase in livestock can also be breaking the life cycles of some insect their productive capacity is illustrated accomplished by purchasing feeds or by and disease pests. Corn following in table 13-4. These data show an purchasing or renting additional land. alfalfa rarely responds to more than a increase in net return of 35 to 80% However, these alternatives are often small application of nitrogen. Corn when crops are grown under a high less economical than improving crop following soybeans without added level of management compared to production on present land. nitrogen produced as much as average management. In summary, there are many ways continuous corn receiving 150 pounds to increase profits through crop or of nitrogen per acre. Corn following livestock production. The key to alfalfa yielded even more. Most states Feeding higher making the most of each dollar spent give a soybean nitrogen credit of about crop yields lies in careful analysis of the value of 40 pounds nitrogen per acre, which is each farm input. Select the most worth about $10 per acre at a nitrogen through livestock profitable inputs first, followed by cost of $0.25 per pound. Alfalfa Improved soil management those inputs that are likely to give less nitrogen credits are typically two to practices are usually the least expensive return per dollar invested but which three times this amount. way to get the feed needed for livestock should still be profitable. Increasing plant population can expansion. Many Wisconsin farmers often increase yields with only a slight limit their livestock production to the increase in the cost of seed. Adjusting reliable amount of feed that can be the planter for the proper depth of produced on their farms. On these planting takes a few minutes of time farms, increased livestock expansion is but can make a big difference in closely tied to the additional feed that germination and, ultimately, in the can be produced through improved yield. crop and soil management.

Table 13-4. A comparison of net returns per acre for corn, oats, and alfalfa under average and high- level management on a Fayette silt loam.

——— Corn ——— ——— Oats ——— ——— Alfalfa ——— Average High Average High Average High

Return Yield per acre 100 bu 140 bu 75 bu 100 bu 3.0 ton 4.0 ton Price per unit, $ 2.00 2.00 1.25 1.25 75.00 85.00*

Gross value per acre, $ 200.00 280.00 93.75 125.00 225.00 340.00

Costs Power & machinery 31.44 35.44 15.72 17.72 69.00 74.10 Seed 17.00 20.00 3.00 4.00 9.45 13.40 Fertilizer 39.40 43.90 25.70 31.60 26.50 36.00 Spraying 19.81 19.81 — 5.00 — 5.00 Hauling & storage 20.00 28.00 15.00 20.00 15.00 20.00

Total cost 127.65 147.15 59.42 78.32 119.95 148.50

Net value per acre $72.35 132.85 34.33 46.68 105.05 191.50 (Return costs)

*With improved management, the alfalfa is assumed to be of higher quality. C-13 10/18/05 11:18 AM Page 168

168 MANAGEMENT OF WISCONSIN SOILS

Questions 1. Why should aglime be considered 6. Which of the following fertilizers is as a capital investment? the least expensive in terms of cost per unit of plant nutrient: 2. Would you lime alfalfa to a pH of 3-13-33 at $140.00 per ton; 6.5 or 6.8 on rented land? Why? 7-17-27 at $142.00 per ton; or 3. Explain why the returns from 5-10-30 at $128.00 per ton? liming are much greater over two Assume that N and P2O5 are 5-year rotations of corn-oats- selling for $0.21 per pound and alfalfa-alfalfa-alfalfa, as compared K2O for $0.13 per pound. to only one 5- year rotation. 7.. Would it be more profitable to 4. What is the cost per pound of N, apply 160 pounds per acre of P2O5 and K2O in a 15-40-5 nitrogen on 50 acres of corn or priced at $220.00 per ton if the 80 pounds per acre on 100 acres? nutrient:price ratio is 1.6:1.9:1.0? Why? 8. 5.. Use of incremental rates of K2O Using figure 13-4, estimate how gave the following alfalfa yields: much acreage will be required to produce 144 bushels per acre of K2O application Yield corn if only 75 pounds per acre of

lb/a ton/a nitrogen are applied? 9. The use of a certain herbicide is 0 2.5 expected to increase the yield of 50 3.2 corn by 12 bushels per acre. If the herbicide costs $10.00 per acre, 100 3.7 when is it more profitable to apply the herbicide than another 40 150 4.0 pounds per acre of nitrogen? Use 200 4.1 the data in table 13-1 for the cost of nitrogen and the value of corn. 250 4.2 10.Why, in general, is it more What is the return per dollar spent profitable to increase production for fertilizer and the profit per acre on a farm by increasing yields per for each 50-pound increment of acre rather than by increasing K2O, assuming that K2O costs acreage under production? What $0.11 per pound and that alfalfa is can be done to increase yields per worth $80.00 per ton? In this acre when there is no more land example what is the optimum rate available to put into production. of application? Index (qx) 10/18/05 11:19 AM Page 169

169

Index

copper, 72, 99, 100, 150–52 A C cover crop, to control erosion, 43, 45, acid rain, 53 cadmium, 73, 113, 132, 133–34 47, 129 actinomycetes, 51, 67 calcium carbonate crop demand categories, 142 adhesion, 24 equivalent, 51, 52, 58–60, crop residue, 3, 14, 15, 29–30, 33, 37, aeolian silts, 2 free, 63, 94 38, 81 aglime, 17 insoluble salt, 74 crop rotation, 43–44, 62, 166 application timing, 62–63 precipitates, 4, 68 crustaceans, 66 crop response from, 160 calcium, 17, 50, 72, 92–93, 100, 148 neutralizing index, 59–60 calcium/magnesium ratios, 92–93 recommendations, 59–61, 145–47, 153 capability classes, 8–9 D returns from, 160–61 capillary water, 26 denitrification, 39, 80–81 substitutes for, 114 carbon deposition, 42, 53, 95 See also liming and pH carbon:nitrogen ratio, 16, 116 diversions, soil, 7, 9, 43, 45, 129 algae, 66, 127 cycle, 65, 67–68 dolomitic limestone, 17, 58, 93, 148 alkaline soils, 63–64 levels in soil, 16 drainage systems, 7 alluvial soils, 2 plant analysis and, 153 DRIS (Diagnosis and Recommendation aluminum sulfate, 63 reservoirs, 68 Integrated System), 155–57 aluminum, 53, 55, 56, 63–64, 73, 86, sources, 71, 72 87, 153, 155 use by organisms, 67, 68, 154 ammonia, 78, 82–84, 126 carbon dioxide ammonification, 80 and formation of carbonic acid, 68 E anions, 73 and respiration, 68 earthworms, 15, 33, 66, 69 arthropods, 66 in atmosphere, 67 economics, 145, 159–67 atoms, 73 in organic matter and crop residues, elements available water, 22, 25 4, 15, 81, 95, 141 chemical, 73 in soils, 26, 32, 52, 68 essential, 71–72 reaction with lime, 58 non-essential, 73, 131–34 B secretion by roots, 69, 74–75 trace, 71 solubility in water, 68 See also nutrients bacteria, 15, 66 use by organisms, 27, 66, 67, 71, 77 eluviation, 3 bedrock geology, 1 cation exchange capacity (CEC), 51, 75 epsom salts, 94, 96, 148 Bedrock Geology of Wisconsin (map cations, 73 erosion insert), following 2 chelates, 4, 75 by tillage, 41, 47 biological inoculants and activators, chemical reactions in soil, 4 by water, 3, 7, 8, 41–48 118–19 chloride, 74, 91, 99, 100, 101 by wind, 3, 12, 45, 46–47 biosolids, 113–14, 131–34 chlorine, 51, 72, 99, 100, 153 control, 129 blue baby syndrome, 121 climate and soil formation, 2 estimating soil loss, 41, 46 bogs, 2 cobalt, 73, 131 factors influencing, 43 boron, 51, 72, 97–98, 100, 150–52 cohesion, 24 tolerable soil loss (T) values, 41–42, buffer capacity, 142, 144, 146 colloid, 90–91 112, 131 buffer strips, 45–46 complexation, 4 eutrophication, 127 bulk density, 12, 18, 32–33, 38, 39 conservation practices, 43–46 evapotranspiration, 22–23, 27 exudates, root, 69 Index (qx) 10/18/05 11:19 AM Page 170

170 MANAGEMENT OF WISCONSIN SOILS

marl, 58, 94, 140, 148 F I mercury, 73, 113, 132–33 FeDDHA, 99, 152 Ice Age Deposits of Wisconsin (map methemoglobinemia, 121 feldspar, 4, 16, 17, 89, 90, 92 insert), following 2 mica, 16, 17, 89 fertigation, 107 illuviation, 3 microbial activity, 75, 81 fertilizer indoleacetic acid, 98 micronutrients, 71–72, 97–99, 150–52 analysis, 101 ions, 73 mineral application methods, 85, 103–7, 138 iron, 19, 51, 63, 72, 99, 100, 150, 152 matter, 25, 73 calculating nutrient costs, 164–66 irrigation scheduling, 27, 126 nutrient sources, as soil amendments, commercial forms, 101–3 117 grades, 101–3 primary, 116 secondary, 116 liquid versus dry, 102–3 K starter, 102, 103–105 soils, 2, 16–18 kiln dust, 59 use, economics of, 159–67 weathering, 12 Know How Much You Haul! (insert), field moisture capacity, 25 mineralization, 3, 69, 87 following 112 filter strips, 45–46 mollusks, 66 fish, as soil amendment, 117 molybdenosis, 99 590 nutrient management standard, molybdenum, 51, 72, 99, 100, 150–53 112–13, 131 L montmorillonite, 18 muck soils, 2 fixation Lactobacillus bacteria, 119 muriate of potash, 91, 165 manganese, 98 land capability classes, 8–9 mycorrhiza, 67 nitrogen, 50, 55, 73, 78–79, 99, 118 laterization, 3 phosphorus, 86, 104, 143 law of diminishing returns, 162 potassium, 91, 143 law of the minimum, 71 fly ash, 59 leaching, 3, 51, 81 N fungi, 51, 67 lead, 73, 113, 132–34 nematodes, 66 legumes, 68 neutralizing index (NI), 59–61, 146 liming nickel, 51, 72, 99 G benefits of, 55–58 nitrate tests, 123–24, 125 deep plowing, 63 glacial action, 1 nitrate-nitrogen, 79–81, 121–26 materials, 58–59 gleization, 3 nitrification inhibitors, 81, 85, 126, 127 See also aglime and pH grass tetany, 93 nitrogen loess, 2 gravitational water, 22, 25 ammonification, 80 Groundwater Contamination availability, 50 Susceptibility in Wisconsin (map best management practices, 122–27 insert), following 122 M credits, 80, 84, 125, 127 cycle in soils, 78 groundwater, 22, 27, 81, 107, 121–27, magnesium, 17, 50, 72, 93–94, 100, 148 deficiency symptoms, 78 130 manganese, 51, 63, 72, 98, 100, 150–52 denitrification, 80–81 growth regulators, as soil amendments, manure fertilizer materials, 82–84 119 calibrating spreaders, 112, 131 fixation, 78–79 gypsum, 58, 93, 116–17 estimating application rates, credits, 112 function in plants, 78 management guidelines, 112, 126, immobilization, 81 128–29 in biosolids, 114 nitrogen credits, 84 H in groundwater, 121–22 nutrient availability and content, 84, heavy metals, 113, 131–34 leaching, 81, 100, 122, 124, 125, 126 89, 92, 109–11 , 125 humification, 3 mineralization, 3, 69, 87 nutrient credits, 110–12, 125 humus, 2, 15, 19, 38, 79 nitrification, 80 phosphorus credits, 88–89 hydrologic cycle, 21–22 nitrification inhibitors, 81, 85, 126, 127 potassium credits, 91–92 hydrolysis, 4 reactions in soils, 79–82 soil amendment, benefits, 109–10 hypomagnesia, 93 recovery in corn, 122 storage facilities, 126 residual carryover, 123–24, 163 sulfur credits, 96, 97 returns from, 161–62 Index (qx) 10/18/05 11:19 AM Page 171

Index 171

soil test recommendations, 141–42 perched water table, 26 precipitation sources, 82–84 percolation, 3, 22, 80, 100, 120, 127 as source of nutrients, 72, 82, 84, 96, timing of applications, 85–86, permanent wilting percentage, 25, 27 148–49 125–26, 127 pH atmospheric, 2, 21–22, 124, 125, 128, volatilization, 81–82, 127 adjusting, 55–64 chemical, 4, 107, nutrient management and nutrient availability, 50–51 preplant soil profile nitrate test, 123–24 crediting, 130 buffer pH, 60–61, 146 pre-sidedress nitrate test, 124, 125 590 standard, 112–13, 131 defined, 49 protozoa, 66 plan, 130–31 fertilizers and, 52 pyrophosphate, 88 nutrients effect on yield, 55–58 pyroxene, 17, 92, 93 amounts harvested, by crop, 143 importance of, 50 calculating costs, 164–66 optimum crop levels, 53–55, 160 chelated, 75 See also aglime and liming Q complexed, 75 phosphorus quartz, 16, 17 exchangeable, 74–75 availability, 50 micro-, 71–72, 97–99, 150–52 best management practices, 130 primary, 71–72 conversion factor, 101 reservoir, 74–75 credits, 127–28 R runoff, 127 deficiency symptoms, 86 reserve acidity, 53, 60–61, 146 secondary, 71–72, 92–96, 147–49 effect on yield, 88 residue solubility, 75–76 erosion control, 129 decomposition, 81 sources, 74–107 fertilizer materials, 87–88 estimating, 37 susceptibility to leaching, 100 fixation, 74, 86–87 management, 30, 32, 38, 43, 47 See also elements function in plants, 86 surface, 31, 33–34 index, 129–30 Rhizobium bacteria, 50, 55, 68, 78–79, in surface water, 127–30 118 O levels in soil, 72, 159–60 rhizosphere, 69 methods of application, 89 organic matter, 2, 12, 15–16, 19, 25 mineralization, 87 and nutrient availability, 74, 90 reactions in soils, 86–87 and soil erosion, 43 S residual carryover, 163 and soil texture, 12 salinization, 3 soil test recommendations, 142–47 decomposition of, 2, 69, 75, 87 salts solubility, 75, 86–88, 100 defined, 2 defined, 73–74 photosynthesis, 21, 27, 67, 98, 99 in conservation tillage systems, 33 injury, 104 plant analysis, 153–57 orthophosphate, 88 seaweed, as soil amendment, 117 plant stimulants, as soil amendment, 119 oxidation, 4, 19, 51, 53 sediment, 7, 41, 43, 46–47, 112, 129, plow depth, 31, 32 oxides, 16–17, 19 seedbed, 12, 14, 18, 29–30, 31, 34, 44 plow pan, 15 oxygen selenium, 73, 131 polarity, 24 depletion, 115, 121, 127 sewage sludge, 113–14, 131–34 polyphosphate, 88 in soil air, 2, 26, 39, 65, 71, 75, silicates, 16–18 potassium plant requirements, 68, 71, 72, 77, sodium, 73, 153 availability, 50, 90, 100 role in oxidation, 19 soil conversion factor, 101 aggregates, 2, 13, 14, 25, 29, 33, 38, deficiency symptoms, 89 42, 43, 67, 116 fertilizer materials, 91 classification, 4–5 P function in plants, 89 color, 19 paper mill lime sludge, 58, 59, 93, 109, levels in soil, 72, 159–60 compaction, 14, 38, 40 116, 140, 148 manure nutrient credits, 89 crusting, 38 parent materials, 1, 51 reactions in soils, 90–91 defined, 1 PASS (Plant Analysis with Standardized residual carryover, 163 depth, 7 Scores), 157 soil test recommendations, 142–47 drainage, 7 peat, 2, 19 sources, 91–92 fauna, 66 peds, 14 prairie soils, 2, 5, 144 flora, 66–67 Index (qx) 10/18/05 11:19 AM Page 172

172 MANAGEMENT OF WISCONSIN SOILS

horizons, 4–5 soil types, 2 names, 5 soil water, 21–27, 32, 33 U particles, 12, 14, 17, 22, 25 stratification of nutrients, 33 UAN, 82–83 pores, 18, 22, 24–26, 32, 33, 39, 45 strip cropping, 45 urea, 84–85 profiles, 5 subsoil fertility groups, 143, 144 urease inhibitors, 85, 127 slope, 7 subsoils, 14–15 solution, 74 sulfur, 51, 72, 94–96, 97, 100, 148–49 structure, 12, 14–15 sulfur availability index (SAI), 149 temperature, 19, 22, 32, 33 surfactants, as soil amendment, 118 V texture, 11–13, 18 symbiosis, 68, 78–79 vadose zone, 22 soil acidity, 49–53 vermiculite, 17, 93 soil amendments volatilization biosolids (sewage sludge), 113–14 T of nitrogen, 78, 81–82, 83, 106, carbon to nitrogen ratios, 116t 110, 127 terraces, 45 defined, 109 of sulfur, 95 textural classes of soil, 11 gypsum (wallboard), 116–17 tile drainage, 7 manure, 109–13 tillage, 15, 16, 19, 29–40 non-traditional, 117–19 deep, 34, 63 W organic, 109–16 depth, 38 water conservation soil buffering capacity, 142–44 effect on nutrient availability, 39–40 government agencies, 47 soil conditioners, as soil amendment, 117 primary, 30–31, 34 practices, 43–48 soil conservation purpose, 29 water table, perched, 26 government agencies, 47 secondary, 31 water, soil, 21–27, 32, 33 plans, 131 tillage implements, 30, 32–34 water-use efficiency, 24 practices, 43–48 chisel plow, 34–36 waterways, 45 soil fertility, 76 cultivators, 34 weathering and soil formation, 3–4 soil formation, 1–4 disk, 30, 34–36 wetting agent, as soil amendment, 118 soil maps, 5–6, 8 moldboard plow, 30–31, 35–36 whey, as soil amendment, 114–15 developing conservation plans and, 6 spring-tooth harrow, 31 white muscle disease, 131 soil nitrate tests, 123–24, 125, 127 tillage systems, 29, 39 wilt, incipient, 27 soil organisms, 2, 65–69 comparison of, 35–36 wood ash, 58, 59 Soil Regions of Wisconsin (map insert), conservation, 30, 31–34, 44 following 6 contour, 44–45 soil survey reports, 6 conventional, 30–31, 39 soil testing laboratories, 139 Y mulch till, 33–34 soil tests yield barrier, 162 no-till, 33, 35–36, 38, 39 collecting samples, 136–39 reduced, 30, 39 interpretations, 140 ridge-till, 33, 35–36, 38, 39 recommendations, 141–53 strip-till, 33, 35–36, 38, 45 Z report, 150–52 subsoiler, 38 zinc, 51, 72, 98, 100, 150–52 responsive versus nonresponsive fields, tilth, 12, 18, 31 136–38 tissue testing, 157 with plant analysis, 153 topography, 1, 3, 129 yield goals, 145 transpiration, 22, 25 TOC-FM 10/20/05 10:07 AM Page 2 TOC-FM 10/20/05 10:07 AM Page 11

Copyright © 2005 by the Board of Regents of the University of Wisconsin System doing business as the division of Cooperative Extension of the University of Wisconsin-Extension. Send inquiries about copyright permission to: Manager, Cooperative Extension Publishing, 432 N. Lake St., Rm. 103, Madison, WI 53706. Authors: E.E. Schulte, L.M. Walsh, and K.A. Kelling, professors emeriti of soil science; L.G. Bundy and W.L. Bland, professors of soil science; R.P. Wolkowski, Extension soil scientist; J.B Peters, director, University of Wisconsin Soil Testing Laboratories; and S.J. Sturgul, nutrient management specialist. All hold joint appointments with the College of Agricultural and Life Sciences, University of Wisconsin-Madison and University of Wisconsin-Extension, Cooperative Extension. Produced by Cooperative Extension Publications, University of Wisconsin-Extension. L.G. Deith, editor; S.A. Anderson, designer. Cover photo by B.W. Hoffmann, Life Sciences Communication. This material is based upon work supported in part by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture under Agreement No. 2002-51130-01950. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture. University of Wisconsin-Extension, Cooperative Extension, in cooperation with the U.S. Department of Agriculture and Wisconsin counties, publishes this information to further the purpose of the May 8 and June 30, 1914 Acts of Congress; and provides equal opportunities and affirmative action in employment and programming. This publication is available from your Wisconsin county Extension office or from Cooperative Extension Publications. To order, call toll-free 877-947-7827 or visit cecommerce.uwex.edu. A3588 Management of Wisconsin Soils R-10-2005-1.5M