Phosphorus fertilizers, application levels

The soil macronutrients, nitrogen (N), phosphorus (P), and potassium (K), are essential for crop growth, and the use of commercial N, P, and K fertilizers has contributed greatly to the increased yield of agricultural crops. However, excessive fertilizer applications can lead to environmental contamination, primarily of surface and ground waters.Ideally, fertilizer application should be adjusted to match the requirements for optimum crop production at each within-held location, because there can be high spatial variability in the N, P, and K levels found within helds. ° ° ... 

Parham JA, Deng SP, Raun WR, Johnson GV (2002) Long-term cattle manure application in soil. I. Effect on soil phosphorus levels, microbial biomass C, and dehydrogenase and phosphatase activities. Biol Fertil Soils 35 328-337... 

The phosphate manufacturing and phosphate fertilizer industry includes the production of elemental phosphorus, various phosphorus-derived chemicals, phosphate fertilizer chemicals, and other nonfertilizer phosphate chemicals [1-30], Chemicals that are derived from phosphorus include phosphoric acid (dry process), phosphorus pentoxide, phosphorus penta-sulfide, phosphoms trichloride, phosphorus oxychloride, sodium tripolyphosphate, and calcium phosphates [8]. The nonfertilizer phosphate production part of the industry includes defluori-nated phosphate rock, defluorinated phosphoric acid, and sodium phosphate salts. The phosphate fertilizer segment of the industry produces the primary phosphorus nutrient source for the agricultural industry and for other applications of chemical fertilization. Many of these fertilizer products are toxic to aquatic life at certain levels of concentration, and many are also hazardous to human life and health when contact is made in a concentrated form. 

The content of crude protein, fat, carotene and AA in the dry matter markedly increased on application of nitrogen (N) especially in quantities of 100 and 150 mg/kg soil (Filimonov, 1969). Largskii (1971) showed that doses of N above 60 mg/kg soil maintained the amount of total sugar and AA in the cucumber. Phosphate fertilizer increased the concentration of these substances. Sugar content and dry matter were also Increased by the fertilizer. An increase in the phosphorus level also enhanced the sugar and AA concentrations and decreased the nitrogen content in plant tissues, especially under water deficit ... 

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