Forms and Function of Essential Plant Nutrients - Valley Crops Home

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Forms Nitrogen fertilizer is available to the plant from several different sources, including fertilizers, manures and legumes. The amount of nitrogen from organic forms varies depending on the origin, how it was handled and stored and the decomposition rate of the material. Common inorganic fertilizer forms of N available in Virginia include: - Ammonium nitrate (33-0-0) - Ammonium sulfate (21-0-0-24S) - Diammonium phosphate or DAP (18-46-0) - Urea (46-0-0) - Urea ammonium nitrate or UAN (liquid form containing 30% N by weight) Nitrogen Deficiency Plants that are deficient in N typically show stunted growth and their foliage is pale green. Symptoms generally appear on the bottom leaves first, and lower leaves will sometimes have a “fired” appearance on the tips, turn brown and fall off. In crops such as vegetables, forage and pasture, low N results in low yield and quality. With grain crops, such as corn and small grains, deficiency results in yellow leaf tips, stunted growth with spindly stalks and low yields of poor quality grain. Too much N causes excessive vegetative growth, delays maturity, increases lodging risk and promotes plant diseases. Phosphorus Function Plant growth will not occur without phosphorus (P). Concentration of P in most plants is between 0.1 and 0.4%, lower than either N or potassium. Plants absorb P either as H 2 PO 4 - or HPO 4 2- orthophosphate ions, depending on the pH. Plants may also absorb organic phosphate forms, made available as soil organic matter is decomposed. The most essential function of P in plants is in energy storage and transfer. Nucleic acids, phospholipids, coenzymes DNA and NADP, and most importantly ATP rely on P for the energy required to function. ATP is the source of energy that powers practically every energy-requiring biological process in plants. Phosphorus is also required for other essential metabolic processes, such as photosynthesis, glycolysis, respiration, and fatty acid synthesis. Phosphorus: 1. Enhances seed germination and early growth 2. Is associated with increased root growth 3. Stimulates blooming and bud set 4. Improves straw strength 5. Increases disease resistance 6. Aids in seed formation 7. Hastens plant maturity 8. Provides winter hardiness 2
Forms Phosphorus is made available to the plant through fertilizer or organic forms. Some common forms of P fertilizer in Virginia include: - Monoammonium phosphate, or MAP (11-48-0) - Diammonium phosphate, or DAP (18-46-0) - Triple super phosphate (0-46-0) - Various liquid forms, including 10-34-0 or 9-18-9 Phosphorus Deficiency Plants deficient in P typically have stunted growth. Leaves in some cases may be dark green with a leathery texture, with reddish purple leaf tips and margins. In corn, reddish purple leaf margins are characteristic of P deficiency. Deficiency symptoms may appear even when soil P levels are adequate, particularly if soil temperatures are less than 60°F. When soil is cool, less P is made available for plant uptake. These symptoms will generally disappear as soils warm. Potassium Function Potassium has many functions in plant growth, but primarily acts as a regulator for the many metabolic processes required for growth, fruit and seed development. Potassium (K) is actively taken up from the soil solution by plant roots. Potassium concentrations in most plants range from 1 to 4% by weight. Plants require a good deal of K to properly function. Unlike the other primary nutrients, K forms no other compounds in the plant, but remains a lone ion. Potassium is also vital for animal and human nutrition, and thus healthy fruits, vegetables and grains must have adequate levels of K. Potassium: 1. Adds stalk and stem stiffness 2. Increases disease resistance 3. Increases drought tolerance 4. Gives plumpness to grain and seed (increasing kernel and test weight) 5. Improves firmness, texture, size and color of fruit crops 6. Increases oil content of oil crops 7. Regulates opening and closing of cell stomata, increasing water use efficiency 3
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Forms and Function of Essential Plant Nutrients - Valley Crops Home

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