FGV-00348 UNIVERSITY OF ALASKA FAIRBANKS UNIVERSITY OF ALASKA FAIRBANKS Field Crop Fertilizer Recommendations For Alaska FERTILIZER NUTRIENT SOURCES AND LIME either from manufactured or naturally occurring sources. Nitrate is chemically the same from either CONTENTS source. Ammonium from a manufactured source is Fertilizer .......................................................1 chemically identical to ammonium from a naturally Lime .............................................................2 occurring source. The difference lies in avail- Lime Quality .................................................3 ability of manufactured versus organically bound Lime Requirement .......................................3 nutrients in manures and residues. The nitrogen in manure, fish by-products and plant residues must be converted to nitrate and ammonium by soil microorganisms. The conversion takes time FERTILIZER Numerous manufactured and natural fertilizers and depends to a large extent on the kind of crop are available in Alaska. Manufactured fertilizers residues or manures, soil temperature and mois- typically contain a high percentage of a nutrient ture. The converting process for fish by-products element or elements per unit. Natural fertilizers is usually relatively fast. include animal manures, fish by-products (e.g., Phosphorus and potassium are also supplied by fish meals) and crop residues. The nutrient levels manufactured and naturally occurring sources. in manures and other residues are usually lower Naturally occurring phosphorus sources such as than those found in many manufactured fertilizers. rock phosphate are not as readily plant available In addition, many of the nutrient elements found as manufactured sources. Potassium is taken up in manures and residues are bound to the organic by the plant as K+ ion. Potassium from naturally matter and are not immediately available to plants. occurring sources is often more plant available than Nutrient levels in manures vary substantially, nitrogen or phosphorus. Manufactured potassium depending upon the degree of decomposition and sources such as potassium chloride and potassium whether the manure has been stored under cover or sulfate are readily plant available. has been left exposed. Table 1 lists many commonly available fertilizers and their respective analyses. Sulfur behaves much like nitrogen in the soil, with nearly all sulfur occurring in the organic Nitrogen is used by the plant primarily in the fraction. If applied in elemental form, sulfur must nitrate and ammonium forms. These forms come be converted in the soil to sulfate, the form of sulfur that can be used by plants. For this reason, Although boron is essential for proper plant growth, sulfur fertilizers should be scrutinized for their it is phytotoxic in even relatively small amounts. relative plant availability. Another manufactured It is therefore important to ensure that a constant sulfur fertilizer is ammonium sulfate. Sulfur in but minute supply is available to the plant. ammonium sulfate is readily available to plants; therefore, where immediate sulfur response is LIME required, a sulfate source should be selected. In a Lime applications are required on many of Alaska's soil sulfur building program or where long term acidic soils to raise the pH. Raising the pH is sulfur availability is required (perennial crops), necessary to 1) increase soil microbial activity, 2) a combination of elemental sulfur and sulfate is increase phosphorus availability, 3) reduce micro- desirable. Care should be used when applying nutrient toxicity, 4) reduce aluminum toxicity and elemental sulfur as this material lowers soil pH 5) overcome poor plant performance. during the converting process. Lime contains calcium, or a combination of cal- Calcium, and magnesium if required, is normally cium and magnesium, and neutralizes acidity. applied in liming materials discussed in the next Agricultural lime, or ag lime, is primarily calcium section. Gypsum (calcium sulfate) and calcium carbonate. It is the most commonly used liming nitrate are sources of calcium that do not signifi- material and contains plant-available calcium and cantly raise the pH of the surrounding soil. acidity-neutralizing carbonate (see UAF Coopera- tive Extension Service publication FGV-00242A, The micronutrients required by plants include Soil Fertility Basics). zinc, manganese, copper, iron, boron, nickel and molybdenum. The term micronutrient accurately Numerous materials come under the heading of describes these nutrient elements because they are lime, including limestone, burned lime, slaked required in very small amounts for plant growth, lime, marl, oyster shells, slag, wood ashes, mine although they are just as important as macronu- tailings and many more. There are four categories trients. For this reason, micronutrients are often into which these materials are grouped: carbon- applied with seeds or in foliar sprays. Table 2 lists ates, oxides, hydroxides and by-product materials. various inorganic micronutrient sources and their Carbonates solubility in water. Carbonates are widely available and are the most Metallic micronutrients (manganese, copper, commonly used liming materials. Mined high- iron and zinc) are also commercially available in grade calcitic limestone, when ground, is almost chelated forms. Chelates are designed to hold the pure calcium carbonate. This is an excellent lim- micronutrient atoms in solution for increased plant ing material because of its relatively low cost and availability. These forms are important agricultur- availability and its effectiveness in neutralizing soil ally since micronutrients are often plant unavailable acidity. Dolomitic limestone (a naturally occurring because of soil physical and chemical limitations or combination of magnesium carbonate and calcium are relatively water insoluble and therefore difficult carbonate), although more costly, is also widely to apply in foliar sprays. Four important chelates used in areas with low soil magnesium levels are EDTA (ethylenediaminetetraacetic acid), DTPA, because it provides both calcium and magnesium (diethylenetriaminepentaacetic acid), CDTA (cy- along with its acidity-neutralizing capabilities. clohexanediaminetetraacetic acid) and EDDHA Marls come from naturally occurring deposits (ethylenediaminedi [o-hydroxyphenylacetic acid]). of calcium and magnesium carbonates, clay and Although these chelates act similarly and their ef- shell remnants and can be used to increase soil pH. fectiveness is fairly uniform, their individual activity Oyster shells are pure calcium carbonate which, varies with soil chemical conditions. when finely ground, increase soil pH. 2 Oxides LIME QUALITY Oxides, liming materials commonly known as Chemical composition (purity) and particle size burned lime, quicklime and unslaked lime, are are the two attributes which define the potential made by baking or roasting crushed calcitic or effectiveness of liming materials. dolomitic lime in an oven or furnace, which drives off carbon dioxide and leaves a pure oxide. These Chemical Composition oxides are the most efficient liming materials on a Calcium carbonate equivalence (CCE) is used pound-for-pound basis and react rapidly with the to measure the relative effectiveness of liming soil to increase pH. materials. The CCE scale (Table 3) compares all liming materials to pure calcium carbonate, which Oxides are powdery, caustic and reactive with is assigned a value of 100. Note that on a per-pound moisture so they are usually sold in bags. Because basis, marl, slags, sludges and wood ashes have of the large amount of energy required to remove considerably less acid-neutralizing power than the carbon dioxide, oxide materials are more expensive oxides, hydroxides or carbonates because of their to manufacture than carbonate materials. high level of impurities. Hydroxides Physical Composition Hydroxides are hydrated oxides, or simply, oxides Because agricultural limestone is produced by mixed with water. Hydroxide limes, also known crushing limestone rock, particle sizes vary. Particle as slaked lime, hydrated lime or builder’s lime, size is important because it is related to the speed react similarly to oxides in the soil and are also of the acid-neutralizing activity. Finely ground powdery and unpleasant to handle. materials (smaller particle size) react more rapidly By-product Materials in soil than coarsely ground materials (large particle Mining, refining, processing and manufacturing size). Most ground limestone will pass through a industries produce numerous by-products useful U.S. Standard No. 8 sieve (8 wires per inch, each for increasing soil pH. Slags from blast and elec- opening 0.0937 by 0.0937 inches) and as much tric furnaces, along with fly and bottom ash from as 40 percent passes through a 100 mesh sieve. coal burning plants, are used in agricultural lim- LIME REQUIREMENT ing. Wood ashes from wood stoves and fireplaces The lime requirement is the amount of lime needed can also be used to increase soil pH. Carbide lime to increase soil pH to a desired level. The amount is from acetylene production is nearly pure Ca(OH)2 determined by testing the soil. Lime recommenda- and used to be an important lime source in Alaska. tions are established by comparing individual soil Probably the major problems with by-product lime test values to values from calibration experiments. sources involve variability in quality (purity) and Crops differ in their sensitivity to soil acidity. See