Fertlizer part 2

FERTILIZER PART 2 Last week we discussed fertilizers, their solubility and pH, this week we are discussing the salt index. All fertilizers come in salt form. This is not the same a calcium chloride or sodium chloride. Salt index. Seedling injury or "fertilizer burn" occurs when the soil solution in contact with the seed or root contains a high concentration of salts. The plant seedling, because of the high salt concentration, is unable to absorb moisture from the soil solution. Salt injury may result from a high rate of salt-forming fertilizers, improper placement of fertilizers, irrigation with saline water, or farming on saline soils. Determination of the salt index of a fertilizer is a means of measuring its tendency to cause seedling injury or plant "burn." The lower the salt index of a fertilizer, the less likely it is to cause damage. Fertilizers with the highest salt indexes generally supply nitrogen as the primary nutrient, high potash materials have intermediate salt indexes, and phosphate materials have the lowest. Salt Index of Some Fertilizer Materials Material Salt Index ________________________________________________________________________ ammonium sulfate (21% N) 53.7 ammonium nitrate (35% N) 49.3 muriate of potash (50% K) 26.7 sulfate of potash (45% K) 14.1 anhydrous ammonia (82% N) 9.4 diammonium phosphate (21% N, 23% P) 7.5 monoammonium phosphate (12% N, 27% P) 6.7 superphosphate (9% P) 6.4 superphosphate (21% P) 3.5 ________________________________________________________________________ Research results. Here is a summary of some research about fertilizers: • Anhydrous ammonia, whether dissolved in irrigation water or not, causes a surface "sealing" when applied to a calcareous soil. The symptoms of the seal are similar to a sodium-affected soil-poor drainage, which causes water to pool or stand on the soil surface. Not recommended for Eddy County. • Phosphates move very little in the soil, and the secondary orthophosphate (HPO4) is the phosphorus form used most by plants in our soils. Should be applied in the fall or incorporated in the soil pre plant. • Phosphates are readily and rapidly "fixed" by our alkaline soils. Liquid phosphates are fixed much more rapidly than the dry or granulated forms. • The polyphosphates seem to be no better or no worse than the usual phosphate forms. There is speculation that the polyphosphates serve as a chelating agent. If so, they would have decided advantages. Cost per unit of nutrient. Several factors cause fertilizer nutrients to vary in cost, such as the different manufacturing processes required in their manufacture, shipping and handling costs are greater per unit of nutrient in low analysis fertilizers than in high analysis fertilizers, the physical form of the fertilizer, whether gas, liquid or solid affects handling cost. The size of purchase also affects unit cost. In general a low-analysis fertilizer in a small package is expensive in comparison with high-analysis fertilizers in ton lots in bulk form. The farmer who uses several tons of fertilizer each year has more options in buying fertilizer than the person with a lawn, garden, or flower bed. The home owner usually has the choice of buying a pound or two of low-analysis fertilizer or a 50-pound bag of high-analysis fertilizer. Soil sample, information sheets, and instructions for taking samples are available from your local county extension office. Special instructions and information sheets are available for soil tests for lawns, vegetables, and ornamentals; orchard, fruit, and nut trees; and cropland. Subscribe to Eddy County Ag news at: http://nmsueddyag.blogspot.com/ Eddy County Extension Service, New Mexico State University is an equal opportunity/affirmative action employer and educator. All programs are available to everyone regardless of race, color, religion, sex, age, handicap, or national origin. New Mexico State University, U.S. Department of Agriculture, and the Eddy County Government Cooperating.