potassium guidelines for field crops in new york - Purdue Agriculture

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Potassium Guidelines for Field Crops in New York. Second Release. June 12, 2003.BACKGROUND LITERATURE 21APPENDIX:Appendix Table A:Cornell crop codes. 22Appendix Table B:Potassium recommendations for corn silage, grain corn, millet,sorghum forage, sorghum grain, sorghum sudan hybrids,sudangrass and sunflowers. 23Appendix Table C:Soil management group and alfalfa yield potential for undrainedand artificially drained New York soils. 25Appendix Table D:Potassium recommendations for spring barley, winter barley,oats and wheat. 34Appendix Table E:Potassium recommendations for buckwheat and rye cover crop. 35Appendix Table F:Potassium recommendations for triticale peas. 36Appendix Table G:Potassium recommendations for alfalfa, birdsfoot trefoil,clover, pasture, and rye seed. 374
Potassium Guidelines for Field Crops in New York. Second Release. June 12, 2003.1. INTRODUCTIONAfter nitrogen and phosphorus, potassium (K) is the nutrient most likely to limitplant productivity. It is commonly applied to soils as a fertilizer. Potassium acts as anactivator for cellular enzymes involved in processes such as energy metabolism, starchsynthesis, nitrate reduction, photosynthesis, nitrogen fixation, and sugar degradation.Potassium plays an important role in lowering cellular osmotic potentials, allowing plantsto reduce transpiration from leaves and to increase uptake through the roots. Plants withoptimum potassium levels are known to be more resistant to environmental stressesincluding drought.Presently, K is not considered a contaminant in water or a threat to water quality.However, K should be managed appropriately to improve crop production economics,reduce its loss, and to prevent excessive build up in soils. Excessive soil K may cause anaccumulation of K in the feed ration and pose a health risk for transition cows.2. POTASSIUM FORMS AND PLANT AVAILABILITYSoil K can be divided into three major pools of availability. Unavailable ornonexchangeable potassium is contained in soil minerals (micas and feldspars). Theseprimary minerals are the original source of potassium. Plants cannot use K in thesecrystalline insoluble forms. However, over long periods of time, these soil mineralsweather and decompose, thereby releasing K. Most of the soil K is contained in thisprimary non-exchangeable mineral form.Readily available K is composed of exchangeable and soil solution K. The totalamount of K in this pool is relatively small (one or two percent of the total K in the soil).Potassium is a positively charged ion (cation). It does not leach readily because of itsattraction to the soil's negative charge. However, K can leach in very sandy soils with alow cation exchange capacity.Slowly available or exchangeable K is part of the internal structure of clayminerals of the soil. Some of the readily soluble K applied in fertilizer and manure maybe temporarily converted to a more slowly available form within the clay structure.Much of the K required for crop production can be derived from the pool ofexchangeable K. Some potassium may be returned to the soil as a result of leaching fromplant foliage by rainwater or irrigation.3. SOIL MANAGEMENT GROUPSNew York agricultural soils are divided into five mineral soil management groupsand a sixth group that includes organic (muck) soils, urban soils, the AdirondackMountains, Tug Hill, and primarily rock land (Figure 1). There is a good correlation5
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