DOCSLIB.ORG

Liming and Fertilizing Ornamental Plants ANR-0388

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Liming and Fertilizing Ornamental Plants ANR-0388 ALABAMA A&M AND AUBURN UNIVERSITIES Liming and Fertilizing Ornamental Plants ANR-0388 ime and fertilizers are applied to encourage When soil test recommendations call for more than healthy, vigorous plants. Too much lime or 1 ton per acre, space applications 6 months to a year L apart to avoid a band of concentrated lime moving fertilizer can actually harm or kill plants. Therefore, down through the soil. Too much lime can cause plant soil testing is necessary to determine the soil nutrient nutrient deficiencies. You will need 7 or 8 pounds of status and provide recommendations for applying lime basic slag to equal the liming action of 5 pounds of and fertilizers in correct amounts. Contact your county ground limestone. Extension office for instructions and materials for Fertilizer Nutrients soil testing. Fertilizers are liquid or dry materials containing Lime plant nutrients. The three numbers found on the fertil- izer container refer to the percentage of nitrogen (N), Liming materials neutralize acid in the soil and phosphorus (P2O5), and potassium (K2O), in that order, provide some nutrients essential to plant growth. Some in the fertilizer. common materials used to lime acid soils include ground calcitic limestone, basic slag, ground dolomitic The N in many fertilizers is lost quickly from the limestone, wood ashes, and flue dust. Calcitic limestone soil. It is used by plants, washed through the soil by contains calcium. Dolomitic limestone contains calcium water, or lost to the air as ammonia or nitrogen gas. and magnesium. Basic slag contains calcium, magne- Therefore, to promote growth, apply N frequently, or sium, and a few micronutrients and is often fortified use a slow-release N source such as sulfur-coated urea, with phosphorus, potassium, and micronutrients. Wood manure, or compost. Fertilize lightly or not at all with ashes and flue dust also contain some plant nutrients, N if additional growth is not needed. particularly potassium. The primary purpose of liming, Phosphorus (P) is held very tightly by soils (except however, is to neutralize soil acidity, not to add plant pure sand) and cannot be washed out of the soil by nutrients. watering. Furthermore, high levels of P make other Lime can be applied any time of the year, but a plant nutrients, such as iron, unavailable and may result winter application will begin to neutralize soil acidity in discolored leaves and poor growth. This makes soil before spring growth. On established plants, space testing important to determine the need for P. lime and fertilizer applications at least 2 weeks apart Potassium (K) can be washed through the soil by or plants may be injured. Use finely ground lime water but not as quickly as N. In sandy soils, K may materials to assure quick neutralization of soil acidity. need to be applied once every year. In clay soils, K Most liming materials are in fine, dusty powders. A may be needed only every few years. pelleted limestone is available in some locations that will dissolve in rain, isARCHIVE dust free, and is easy to apply Slow Release Fertilizers accurately using a lawn spreader. Many commercial fertilizers release their nutrients Lime moves about 1 inch per year down through quickly, and this fast release will “burn” or kill plants the soil. This slow movement of lime makes it impor- if too much fertilizer is applied at one time. “Slow tant to mix lime deeply into the soil before planting release” fertilizers allow large applications without ornamentals. For established plants, apply a maximum hurting plants. These fertilizers are sold as granules or of 5 pounds of ground limestone per 100 square feet as spikes for houseplants, shrubs, or trees. Some have per application. This is equivalent to 1 ton per acre. a sulfur or resin coat to slow down the nutrient release. www.aces.edu Others contain synthetic substances, processed Applying Fertilizer sewage sludge, or other organic materials that take Spread fertilizer evenly under the limb spread of a a long time for soil organisms to break down into shrub or tree to avoid burning roots with concentrated usable plant nutrients. heaps. A shaker jar can be helpful. Sprinkle the fertil- Slow release fertilizers are a safe, convenient way izer on top of the soil or mulch and water lightly. Rinse to fertilize in large amounts, thus reducing the number fertilizer off leaves to prevent foliar burn. of applications per year. They are also expensive, In large areas, fertilize trees using a lawn fertilizer typically costing four or five times as much per pound spreader in February according to soil test recom- of fertilizer nutrient. They are a good alternative mendations. Early spring rain will move the fertilizer for special plants, such as a prize rose. Follow the into the root zone. Only fertilize trees in February if manufacturer’s recommendations on the use of these they are not surrounded by turf (this is too early for fertilizers. warm-season turf). The recommended lawn fertiliza- Liquid Fertilizers tion programs will benefit trees, but this precaution must be considered. If applying fertilizer to lawns, do There is no magic to liquid fertilizers. They work not fertilize warm-season lawns before May 1. Do not the same as dry fertilizers, except the liquid may reach use lawn “weed-and-feed” fertilizers under trees or the roots more quickly. A dry fertilizer can be mixed shrubs unless the label says it is safe. Some of these with water and applied as a liquid. Or, a dry fertilizer can damage trees and shrubs. can be watered lightly and dissolved after it is applied. One advantage to liquid fertilizer is that it can be Timing Applications used for foliar feeding, that is, spraying weak nutrient To stimulate growth, fertilize three times a year. solutions directly on a plant’s leaves. The leaves then Normally, the first fertilization is made in February for take up some of these nutrients. Foliar feeding may trees and in March or April for shrubs. Space later fertil- be needed to supply a plant with micronutrients, such izations 2 months apart. If the trees or shrubs are large as iron or zinc. If soil P is very high or, if soil acidity enough, fertilize only once or not at all. Do not fertilize is very low (high soil pH), soil micronutrients may be later than mid-August with N, or the new growth is unavailable to plant roots. A leaf burn is likely from likely to be injured by cold weather. foliar feeding if the nutrient solution is too strong. For roses and annuals, follow soil test recommen- Some houseplant fertilizers and specialty fertilizers dations for lime, P, and K, then fertilize with N monthly for particular plants, such as azaleas and camellias, are from March through August at half the rates recom- sold as liquids. Follow the manufacturer’s recommen- mended for shrubs. Perennial herbaceous ornamentals, dations for these products. such as tulips, irises, daffodils, dahlias, peonies, and Plants growing outside in tubs, pots, window daylilies, can be fertilized at the same rates as shrubs. planters, or raised planters might best be fertilized with However, one N application per year is usually suffi- houseplant fertilizers or slow release fertilizers. Replace cient. Disease and insect infestations are more likely this soil every year or two to avoid build-up of P typi- when lush growth is stimulated by high rates of N. cally present in high levels in these fertilizers. Examples: Amount Per Application 1. An established bed of daylilies, about 10 feet If soil test results indicate a need for P or K, select a wide and 15 feet long. fertilizer containing appropriate amounts of these nutri- Soil test recommendations: no lime, 120 pounds ents. Soil test recommendations will provide an example N per acre, 40 pounds P O per acre, and 120 pounds ARCHIVE2 5 of a fertilizer or fertilizers that can be used. Other fertil- K2O per acre. The comment on the soil test report izers may also correct soil nutrient deficiencies if used suggests: per 100 square feet, in March apply 2.5 cups at the proper rate. Call your county Extension office if 8-8-8; in May and July apply 1.3 cups 15-0-15. you need help in deciding whether another fertilizer can The bed is 150 square feet (10 x 15 = 150). There- be substituted for the recommended fertilizer. Use the fore, half again as much fertilizer as suggested per 100 same percentage of N in the fertilizer to determine the square feet will be needed (150 ÷ 100 = 1.5) in each maximum amount per application. The size of the plant application: or the area of soil to be fertilized also determines the amount of fertilizer to apply. 2 Alabama Cooperative Extension System 2.5 cups 8-8-8 x 1.5 = 3.75 cups 8-8-8 and May apply 1.25 cups 8- 8-8; in April and June apply 0.65 cups 15-0-15; and in July and mid-August 1.3 cups 15-0-15 x 1.5 = 1.95 cups 15-0-15 apply 0.3 cups ammonium nitrate. However, 8-8-8 and 15-0-15 are not available in You already own a lawn fertilizer with a 24-8-16 the local garden store! A 13-13-13 fertilizer, ammonium analysis. No pesticides are in this product, so it is safe nitrate (33-0-0), and muriate of potash (0-0-62) are to use if used at the proper rate. Also this fertilizer available. The 13-13-13 can be substituted for the 8-8-8 contains the same ratio of nitrogen, phosphorous, and if the right amount is used.
Load more

Recommended publications
  • AGR-5: When to Apply Lime and Fertilizer
    AGR-5 C O O P E R A T I V E E X T E N S I O N S E R V I C E U N I V E R S I T Y O F K E N T U C K Y • C O L L E G E O F A G R I C U L T U R E WHEN TO APPLY LIME AND FERTILIZER Kenneth Wells Department of Agronomy early half of all the fertilizer used in Kentucky each The mineral form of individual soil particles and the Nyear is bought by farmers during the rush of the spring extent to which these mineral soil particles have been planting season. As a result, it is often difficult for the coated with layers of oxides and organic materials also fertilizer industry to meet customer demands during this 6 affect the total soil reaction. to 8 week period. All clay particles in soil have a net negative (-) Much of the fertilizer now used during the spring rush electrical charge. Because of this negative charge, clay season could be applied during other seasons of the year. If particles will react with components of lime and fertilizer farmers scheduled fertilizer applications more evenly through- which dissolve as positively (+) charged particles (cations) out the year, dealers would be in a much better position to when added to soil. Lime materials dissolve to release provide them with the kinds and amounts of fertilizer they positively charged calcium (Ca++) and/or magnesium desire. Custom application services could be improved.
    [Show full text]
  • Choosing Effective Liming Materials ► Acidic Soils Require Lime to Maintain the Proper Ph for Growing Crops and Forage
    AGRICULTURE Choosing Effective Liming Materials ► Acidic soils require lime to maintain the proper pH for growing crops and forage. Learn how to test and maintain your soil for optimal production. Most Alabama soils are naturally low in pH and must How Lime Recommendations be limed to create soil conditions that increase plant Are Determined nutrient availability and decrease aluminum toxicity. The ideal pH for most Alabama crops is in the range The amount of liming material needed to reach a target of 6.0 to 6.5. When the pH of a soil falls below a value soil pH depends on the soil’s current pH and the soil’s of 6.0, the availability of most macronutrients (such buffer pH. Soil pH is a measurement of the acidity or as nitrogen, phosphorous, and potassium) needed for alkalinity of a soil, while buffer pH is used to measure crop and forage production begins to decrease. When the soil’s resistance to change in pH. pH increases above 6.5, the availability of most plant Soils that are high in organic matter and clay content micronutrients (such as zinc, manganese, copper, and have a higher buffering capacity. More lime is therefore iron) tends to decrease. required to raise the pH in these soils than in soils that Maintaining pH according to soil testing laboratory are sandy and low in organic matter. For example, a recommendations will ensure that the availability of sandy soil at pH 5.0 may require only 1 ton of ground all plant nutrients is maximized and that any fertilizers limestone to raise the pH to 6.5, while a clay soil at the applied to the soil will not go to waste.
    [Show full text]
  • Agricultural Lime Recommendations Based on Lime Quality E.L
    University of Kentucky College of Agriculture, Food and Environment ID-163 Cooperative Extension Service Agricultural Lime Recommendations Based on Lime Quality E.L. Ritchey, L.W. Murdock, D. Ditsch, and J.M. McGrath, Plant and Soil Sciences; F.J. Sikora, Division of Regulatory Services oil acidity is one of the most important soil factors affect- Figure 1. Liming acid soils increases exchangeable Ca and Mg. Sing crop growth and ultimately, yield and profitability. It is determined by measuring the soil pH, which is a measure Acid Soil Limed Soil Ca2+ H+ H+ Ca2+ Ca2+ of the amount of hydrogen ions in the soil solution. As soil Lime Applied H+ H+ H+ H+ Ca2+ acidity increases, the soil pH decreases. Soils tend to be + + + 2+ + naturally acidic in areas where rainfall is sufficient to cause H H H Mg H substantial leaching of basic ions (such as calcium and mag- nesium), which are replaced by hydrogen ions. Most soils in Kentucky are naturally acidic because of our abundant rainfall. Nitrogen fertilization can also contribute to soil acid- The majority of the hydrogen ions are actually held on ity as the nitrification of ammonium increases the hydrogen cation exchange sites. To effectively neutralize soil acidity, ion concentration in the soil through the following reaction: hydrogen ions must be removed from both the soil solution and the exchange sites. While soil pH only measures the solu- + - - + NH4 + 2O2 --> NO3 = H2O + 2H tion hydrogen, the buffer pH is an indication of exchangeable acidity and how much ag lime is actually needed. It is possible Periodically, agricultural limestone (ag lime) is needed to for two soils to have the same water pH but different lime neutralize soil acidity and maintain crop productivity.
    [Show full text]
  • The Liming of Soils by EMIL TRUOG
    The Liming of Soils by EMIL TRUOG A=.BOUT three-fourths of the cultivated land in our humid regions needs lime. What would happen if farmers stopped applying it? Just this : Yields on laçids where more than half of our agricultural crops are now produced would start to go down. For a few years we would not notice the decline very much. In a decade it would become quite pro- nounced. Iç 30 years or so the yields might be cut in half; in 50 years the result would certainly be hunger and disaster. And not only would har- vests drop ; control of soil erosion would become increasingly difficult. In recent years American farmers have become well aware of the need for liming: In 1944 they used nearly 25 million tons of agricultural lime, four times the amount applied just 8 years earlier and seven times more than in 1929. Calculations by C. E. Carter of the Department indicate that about 40 million tons of lime annually should be used for the next decade on our arable and pasture lands. That a usage approaching that figure may be attained in the near future seems quite probable.. Extensive educational work on liming by the State and Federal agen- cies, including hundreds of thousands of tests for acidity and numerous field demonstrations of results, has brought about a general and thorough realization among farmers of the widespread need for lime and its bene- fits. Because liming of acid soils has been shown to have a favorable effect as regards fertility on the physical, chemical, and biological properties of soils, farmers now appreciate, as never before, why liming of land is often referred to as the backbone of profitable and permanent agriculture in humid regions.
    [Show full text]
  • Lime for Acid Soils
    Prepared for the Northern and Yorke NRM Board Lime for Acid Soils Sustainable Agriculture in the Northern and Yorke NRM Region. Lime is the most effective method for the treatment of acid soils. Within the Northern and Yorke Region there are more than 270,000 hectares of land susceptible to soil acidification that degrades the soil and reduces crop and pasture growth. Soil acidification tends to occur on the sands and sandy loams in the high rainfall areas, north of Kapunda through to Jamestown and from Crystal Brook through to Melrose with a smaller area around Redhill (Figure 1). Soil acidification is caused by an accumulation of hydrogen ions in the soil through the build-up of organic matter; addition and leaching of nitrogen from fertilisers and legumes and the removal of alkaline nutrients in plant and animal products. As the amount of hydrogen ions increases then soil acidity increases. When the soil falls below a soil pH of 5.0 (CaCl2) the productivity of even tolerant crops and pastures starts to fall, toxic amounts of aluminium can be released into the soil, microbial activity starts to decline and nutrients such as phosphorus, magnesium, calcium and molybdenum become less available. Table 1 shows the tolerance of plant species to soil acidity. Table 1: Tolerance of plants of soil acidity Species Tolerance Canola, faba beans, lucerne, annual medic Very Sensitive Barley, wheat, peas, phalaris Sensitive Lupins, wheat, sub-clover, cocksfoot, vetch, Tolerant fescue, perennial rye-grass Triticale, oats, seradella Very tolerant Lime for acid soils The use of lime will raise the soil pH and increase the productivity of crops and pastures.
    [Show full text]
  • Liming Acid Soils in Tennessee
    PB 1096 (Available online only) Liming Acid Soils in Tennessee Hubert Savoy Jr., Associate Professor, Biosystems Engineering and Soil Science and Debbie Joines, Manager, UT Soil, Plant and Pest Center What is Soil Acidity? Soil acidity refers to the level of acids present in soils. As acid levels increase, the pH of the soil decreases. While the pH scale ranges from 0-14, most Tennessee soils range in value from 4.5 to 7.5. Soils with pH values greater than 7.0 are alkaline or sweet, and those with values of less than 7.0 are acid or sour (Figure 1). As the soil pH decreases below 7.0, the amount of acidity rapidly increases. For example, a pH of 5.0 is 10 times more acidic than 6.0 and 100 times more acidic than a pH of 7.0. Soil test results indicate that approximately 40 to 60 percent of the cropland in Tennessee is too acidic for optimum crop production. Because of this, determining the need for lime by soil testing should be the first step in developing a sound crop fertilization program. Figure 1. The pH Scale (Source: NCSA). Lime neutralizes excess soil acids and increases soil pH which is a measure of soil acidity. Levels of Causes of Soil Acidity extractable aluminum (Al) and manganese (Mn) are Several factors contribute to soil acidity. Acid levels reduced to a nontoxic range as soil pH increases. If increase as basic nutrients (calcium, magnesium and not limed as needed, soils continue to become more potassium) are replaced by hydrogen through soil acidic, reducing the potential for production of healthy erosion, leaching and crop removal.
    [Show full text]
  • Pond Fertilization and Liming in Georgia by Gary J
    Pond Fertilization and Liming in Georgia By Gary J. Burtle, Extension fisheries specialist, University of Georgia, Department of Animal and Dairy Science Introduction Georgia pond owners who want to maximize fish production should be ready to start fertilization as winter ends and water temperatures begin to rise. Fertilization increases productivity of pond water by providing nutrients for fish food organisms. Increasing food supply for forage fish species, like bluegill sunfish, results in an increase in food supply for predator fish like largemouth bass. The end result should be more and larger bass and bream to catch. However, starting a fertilization program, without a plan to catch more fish, could be a mistake. Phosphorus and nitrogen, added by pond fertilization, increase the potential for algal blooms, algal scums, filamentous algal growth, and aquatic weed growth in the pond and perhaps downstream from the pond. Fertilization should be combined with more fishing and observation of algal bloom density. Also, once fertilization is begun, it should be maintained on a regular schedule or conditions may develop that are favorable to aquatic weed growth. Ponds in Georgia usually need to be limed to improve fish culture conditions. Many areas in Georgia have acidic soil characteristics that do not provide adequate amounts of hardness or alkalinity for fish production unless the pond is limed. In some cases, the ponds are filled with water from deep wells, and that well water contains enough calcium and magnesium to improve the hardness of the pond water. Other ponds have spring water supplies that originate in limestone formations. However, ponds that depend on rainfall or stream water supply usually need to be limed before fertilizing.
    [Show full text]
  • Reviewliming Impacts on Soils, Crops and Biodiversity in the UK: a Review
    Science of the Total Environment 610–611 (2018) 316–332 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Review Liming impacts on soils, crops and biodiversity in the UK: A review J.E. Holland a,⁎, A.E. Bennett a, A.C. Newton a, P.J. White a,B.M.McKenziea,T.S.Georgea,R.J.Pakemanb, J.S. Bailey c,D.A.Fornarac,R.C.Hayesd a The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK b The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK c Agri-Food and Biosciences Institute, Newforge Lane, Belfast BT9 5PX, UK d New South Wales Department of Primary Industries, Wagga Wagga Agricultural Institute, Pine Gully Road, Wagga Wagga, NSW 2650, Australia HIGHLIGHTS GRAPHICAL ABSTRACT • Liming has numerous far reaching im- pacts on soil and plant processes and function. • Liming impacts on soils are positive such as increased nutrients and biota. • Liming crops and grassland is beneficial to yield and quality and for grazing stock. • Liming impacts on biodiversity vary sig- nificantly with evidence of positive ef- fects. • A qualitative framework shows how liming impacts change with time. article info abstract Article history: Fertile soil is fundamental to our ability to achieve food security, but problems with soil degradation (such as Received 5 May 2017 acidification) are exacerbated by poor management. Consequently, there is a need to better understand manage- Received in revised form 14 July 2017 ment approaches that deliver multiple ecosystem services from agricultural land. There is global interest in sus- Accepted 2 August 2017 tainable soil management including the re-evaluation of existing management practices.
    [Show full text]
  • Fertilizing and Liming Forage Crops1 Y
    SS-AGR-176 Fertilizing and Liming Forage Crops1 Y. C. Newman, C. Mackowiak, R. Mylavarapu, and M. Silveira2 micronutrients, but often the supply of one or more of the nutrients is insufficient for optimum growth. Nitrogen is the nutrient that grass pastures use the most, and when used in a balanced fertilization, it often results in increased forage quality and production. Phosphorus may be deficient in some soils, but other Florida soils are high in native P. Some forage crops may extract sufficient P from the subsoil, even when the P level in the surface soil is low. Potassium (K) may be needed by some forage crops. Under intensive hay or silage production where nutrients are removed from the land, annual applications of N, P, and K are typically required. Potassium is fairly mobile in sandy soils and can quickly become deficient. Calcium, magne- sium, sulfur, and some micronutrients may also become Plants require many essential nutrients for growth. To be deficient in the soil if soil fertility is overlooked. specific, they require 17 of them. Those nutrients required by plants in large quantities are called macronutrients, While routine soil tests do not include a micronutrient and they can be either primary or secondary. Primary analysis, it is suspected that in some areas of Florida S macronutrients are required in high quantities and they deficiency may be seen in some years and on some crops. are nitrogen (N), phosphorus (P), and potassium (K). Sulfur deficiency may be seen under intensive hay or Those required in moderate quantities are called secondary silage production.
    [Show full text]
  • Interaction of Liming and Earthworm Humus in Detoxification of Soil Contaminated with Excess Copper
    Pol. J. Environ. Stud. Vol. 20, No. 6 (2011), 1611-1616 Original Research Interaction of Liming and Earthworm Humus in Detoxification of Soil Contaminated with Excess Copper Stanisław Wróbel*, Karolina Nowak-Winiarska Institute of Soil Science and Plant Cultivation, National Research Institute in Puławy, Department of Weed Science and Tillage Systems in Wrocław, Orzechowa 61, 50-540 Wrocław, Poland Received: 2 November 2010 Accepted: 23 June 2011 Abstract The effect of liming on uptake of copper by white mustard (Sinapis alba L.) was evaluated when applied alone or in conjunction with earthworm humus in detoxification of light (sandy) soil polluted with excess cop- per. The study consisted of two-factor pot trials (first-rate factor – degree of soil contamination: 0, 75, 150, -1 300, and 450 mg Cu·kg of soil; second-rate factor – variants of application of CaCO3 and earthworm humus (EH)). In the absence of any remedial treatment, phytotoxicity of copper at a concentration of 75 mg Cu·kg-1 decreased the mustard yield by 60%, while at 150 mg Cu·kg-1 the loss of yield was over 90% compared to nat- ural soil. Both CaCO3 and EH reduced Cu uptake. High effectiveness of liming with a CaCO3 dose according to double hydrolytic acidity (2 Hh) in detoxification of the analyzed soil was demonstrated. Simultaneous introduction of EH in the amount of 1.5% of soil weight resulted in Cu uptake reduction and the same metal concentration decrease in plant foliage tissues. The highest value of plant tolerance index (yield on polluted soil/yield on control soil), was obtained under joint application of CaCO3 according to 2 Hh+EH 1.5%.
    [Show full text]
  • Liming to Improve Soil Quality in Acid Soils
    SOIL QUALITY – AGRONOMY TECHNICAL NOTE No. 8 Liming To Improve Soil Quality in Acid Soils Soil pH is an excellent chemical indicator of soil quality. Farmers can improve the soil quality of acid soils by liming to adjust pH to the levels needed by the crop to be grown. Benefits of liming include increased nutrient availability, improved soil structure, and increased rates of infiltration. United States Department of This technical note addresses the following topics: (1) soil pH, (2) liming Agriculture benefits, (3) liming materials, and (4) practical applications. Natural Resources Soil pH Conservation Service Understanding soil pH is essential for the proper management and optimum soil and crop productivity. In aqueous (liquid) solutions, an acid is a substance that donates hydrogen ions (H+) to some other substance (Tisdale et al., 1993). Soil Quality Institute 411 S. Donahue Dr. Auburn, AL 36832 Soil pH is a measure of the number of hydrogen ions in the soil solution. 334-844-4741 However, the actual concentration of hydrogen ions in the soil solution is actually X-177 quite small. For example, a soil with a pH of 4.0 has a hydrogen ion concentration in Technical the soil water of just 0.0001 moles per liter. (One mole is equal to the number of Note No. 8 hydrogen atoms in 1 gram of hydrogen). Since it is difficult to work with numbers like this, pH is expressed as the negative logarithm of the hydrogen ion concentration, May 1999 which results in the familiar scale of pH ranging from 0-14. Therefore, pH = 4.0 = - log (0.0001).
    [Show full text]
  • The Chemistry of Pedogenic Thresholds
    Geoderma 100Ž. 2001 321–353 www.elsevier.nlrlocatergeoderma The chemistry of pedogenic thresholds Oliver A. Chadwick a,), Jon Chorover b a Department of Geography, UniÕersity of California, Santa Barbara, CA 93106, USA b Soil Science Program, Department of Agronomy, PennsylÕania State UniÕersity, UniÕersity Park, PA 16802-3504, USA Received 10 January 2001; received in revised form 23 February 2001; accepted 1 March 2001 Abstract Pedogenesis can be slow or fast depending on the internal chemical response to environmental forcing factors. When a shift in the external environment does not produce any pedogenic change even though one is expected, the soil is said to be in a state of pedogenic inertia. In contrast, soil properties sometimes change suddenly and irreversibly in a threshold response to external stimuli or internal change in soil processes. Significant progress has been made in understanding the thermodynamics and kinetics of soil-property change. Even in the open soil system, the direction of change can be determined from measures of disequilibrium. Favorable reactions may proceed in parallel, but the most prevalent and rapid ones have the greatest impact on product formation. Simultaneous acid–base, ion exchange, redox and mineral-transformation reactions interact to determine the direction and rate of change. The nature of the governing reactions is such that soils are well buffered to pH change in the alkaline and strongly acid regions but far less so in the neutral to slightly acid zones. Organic matter inputs may drive oxidation–reduction processes through a stepwise consumption of electron acceptorsŽ. thereby producing thresholds but disequi- librium among redox couples and regeneration of redox buffer capacity may attenuate this response.
    [Show full text]