Phosphorus in fertilizers

Phosphorus in Fertilizers 20.10 The Group 6A Elements The Chemistry of Oxygen The Chemistry of Sulfur Sulfur Oxides Oxyacids of Sulfur... 

Millions of tons of ammonia are used worldwide each year to supply crops with nitrogen. Ammonia is either added to irrigation water or injected directly into the ground. Many other nitrogen fertilizers are synthesized from ammonia. Phosphorus in fertilizers originates from phosphate (P04 ) in rock deposits. Potassium in fertilizers comes from evaporated ancient seabeds in the form of potassium oxide (K2O). 

This is the principal linkage between cyanobacterial blooms and eutrophication. Avoidance of cyanobacterial production does not necessarily depend upon eliminating all phosphorus inputs, but upon ensuring that optimum physical and chemical conditions for these organisms do not coincide. It is easy to understand why the biggest blooms in the UK have been in fertile lakes and reservoirs after prolonged spells of warm, dry weather in summer. 

Molten CaSi03 is less dense than molten iron and floats on top of it. An average furnace that produces about 750 tons of iron per day, will also yield 410 tons of slag. The slag is sometimes useful in the manufacture of cement and, when it contains sufficient phosphorus, in the manufacture of fertilizer. 

C21-0082. Calcium dihydrogen phosphate is a common phosphoras fertilizer that is made by treating fluoroapatite with phosphoric acid. Hydrogen fluoride is a by-product of the synthesis. Write a balanced equation for the production of this fertilizer and calculate the mass percent of phosphorus in the fertilizer. 

J. C. Tarafdar and A. Jungk, Phosphatase activity in the rhizosphere and its relation to the depletion of. soil organic phosphorus. Biol. Fertil. Soils J 199 (1987). 

The global phosphate system is described in Figure 7.10 (Lasaga, 1980). Table 7.1 gives the amounts held by each reservoir, and Table 7.2 the fluxes between reservoirs. Assuming steady-state, calculate the evolution of the world phosphate system if 10000 x 109 kg of phosphorus from fertilizer (mined from an isolated reservoir) were dumped on land in a short period of time. 

Phosphorites are hydrogenous precipitates with phosphorus concentrations greater than 5% w/w P2O5. Concentrations as high as 40% have been observed. In comparison the phosphorus content of most sediments is aroimd 0.3%. Phosphorites represent an important economic ore deposit as shown in Table 18.3, supplying phosphorus for fertilizer use. The United States is the leading supplier of processed phosphates in the world, accounting for about 45% of world trade. 

Phosphorus in the subsurface originates from a natural parent material or anthropogenic application on land surface (e.g., fertilizers, pesticides, surfactant products, sludge, and effluents). This element may be found in inorganic or organic forms, which are in a dynamic equihbrium with dissolved P in the subsurface liquid phase. 

Several phenolic acids and many nonspecific allelopathic conditions have been shown to alter the mineral content of plants, and certainly phenolic allelochemicals may perturb cellular functions in a number of ways that are of importance to plant nutrition (34,35). However, raising fertility does not always suppress allelopathic inhibition, and the interrelationships between these two factors are still not clear. Bhowmik and Doll (36) showed that allelopathic inhibition of corn and soybeans by residues of five annual weeds was not alleviated by supplemental nitrogen or phosphorus. Similarly, an increase in fertilizer did not overcome inhibition of corn by quackgrass or circumvent the autotoxicity of berseem clover Trifolivm alexandrium L.) (37,38). Even when raising nutrient levels releases Inhibition, it does not mean that allelopathy was inoperative under the original conditions. These instances simply illustrate the importance of the Interaction of the two stress conditions. 

Plant nutrient sulfur has been growing in importance worldwide as food production trends increase while overall incidental sulfur inputs diminish. Increasing crop production, reduced sulfur dioxide emissions, and shifts in fertilizer sources have led to a global increase of crop nutritional sulfur deficiencies. Despite the vital role of sulfur in crop nutrition, most of the growth in wodd fertilizer consumption has been in sulfur-free nitrogen and phosphorus fertilizers (see Fertilizers). 

N was one-quarter that of conventional farms, organic N mineralisation potential was three times larger. Similarly, Oberson et al. (1993) concluded that routine soil tests would not have been sufficient to predict phosphorus (P) fertility due to increased mobility of P ions in a biodynamic system. 

Cereals and meats are the major sources of phosphorus in human diets. Phosphorus deficiencies in most regions have not been a serious problem in human nutrition. Insofar as food is concerned, the primary value of phosphorus fertilizers is that they generally increase the total food production not die content of phosphorus in the food per se,... 

When phosphorus fertilizers are added to soils deficient in available forms of the element, increased crop and pasture yields ordinarily follow. Sometimes the phosphorus concentration in the crop is increased, and this increase may help to prevent phosphorus deficiency in the animals consuming the crop, but this is not always so. Some soils convert phosphorus added in fertilizers to forms that are not available to plants. On these soils, very heavy applications of phosphorus fertilizer may be required. Some plants always contain low concentrations of phosphorus even though phosphorus availability from the soil may be good. See also Fertilizer. 

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