Fertilizer use

Commercial urea generally contains a small amount of the compound biuret [108-15-0] NH2CONHCONH2. For fertilizer use other than foflar apphcation, biuret contents of about 1.5% or less are not harmful, and under usual production conditions it is not difficult to avoid higher biuret levels. For most fohar apphcation, however, the level should not exceed 0.1%, and special production modifications are usually requited to ensure such a low level. 

Essentially all the ammonium sulfate fertilizer used in the United States is by-product material. By-product from the acid scmbbing of coke oven gas is one source. A larger source is as by-product ammonium sulfate solution from the production of caprolactam (qv) and acrylonitrile, (qv) which are synthetic fiber intermediates. A third but lesser source is from the ammoniation of spent sulfuric acid from other processes. In the recovery of by-product crystals from each of these sources, the crystallization usually is carried out in steam-heated sa turator—crystallizers. Characteristically, crystallizer product is of a particle size about 90% finer than 16 mesh (ca 1 mm dia), which is too small for satisfactory dry blending with granular fertilizer materials. Crystals of this size are suitable, however, as a feed material to mixed fertilizer granulation plants, and this is the main fertilizer outlet for by-product ammonium sulfate. 

Wet-Process Phosphoric Acid. As indicated in Figure 7, over 95% of the phosphate fertilizer used in the United States is made by processes that require an initial conversion of all or part of the phosphate ore to phosphoric acid. On a worldwide basis also, the proportion of phosphate fertilizer made with phosphoric acid is very high. Thus processes for production of phosphoric acid are of great importance to the fertilizer industry (see PHOSPHORIC ACID AND THE PHOSPHATES). 

World consumption of potassium salts presentiy exceeds 28 million t of K O equivalent per year. About 93% of that is for fertilizer use (see POTASSIUM compounds). The potash [17353-70-7] industry is essentially a mining and beneftciation industry. The two main fertilizer materials, KCl and K SO are produced by beneftciating ores at the mine sites. The upgraded salts then are shipped to distributors and manufacturers of mixed goods. 

Iron. World reserves are placed at 236 x 10 t of ore containing 90 x 10 t of iron world resources are estimated at 180 x 10 t of iron. Only a small fraction of world production is required for fertilizer use. 

Fertilizer Use. The worldwide use of fertilizers has an important, positive effect on the environment. Conservative estimates (112) iadicate that about 30% of world food production is direcdy attributable to fertilizer use. Without fertilizer, therefore, at least 30% mote virgin land would have to be devoted to agriculture, and 30% more labor and other resources would have to be expended. Even more serious would be the effects of land tillage and cropping without nutrient replenishment. Past experience has shown that, under such a condition, crop yields progressively decrease, the land eventually becomes barren, and forces of wiad and water erosion prevail. 

Possible negative environmental effects of fertilizer use are the subject of iatensive evaluation and much discussion. The foUowiag negative effects of fertilizer usage have been variously suggested (113) a deterioration of food quaUty the destmction of natural soil fertility the promotion of gastroiatestiaal cancer the pollution of ground and surface water and contributions toward the destmction of the ozone layer ia the stratosphere. 

The fertilizer iadustry, through its various trade organizations, supports continued iatensive study of the effects of fertilizer use on the environment. Support is also given to educational programs that promote pmdent use of fertilizer. 

The ammonia values can be recycled or sold for fertilizer use. The most important consideration ia this process is the efficient elimination of the phosphoms from the product, because as Htfle as 0.01% P2 5 electrolyte causes a 1—1.5% reduction ia current efficiency for aluminum production (28). 

Dinitrogen is fixed either by natural processes or by industrial ammonia (qv) production (1,8,9). The estimates for the aimual biological contribution range around 100-200 x 10 t. Industrial fixation contributes about 50 x 10 t/yr for fertilizer uses (see Fertilizers). Other processes, eg, lightning and combustion, are estimated to fix about 30 x 10 t/yr. Thus the biological process represents the majority (ca 65%) of the total aimual fixation rate, contributing about three times as much as the commercial production of fertilizer. 

For agricultural uses, a fully hydrated calcium cyanamide powder containing 2% oil is used for dusting appHcations for general fertilizer use, the hydrated material is granulated with water in rotary dmms and dried giving a 2.38 x 0.32 mm (8 x 48 mesh) product. 

Economic Aspects. A peakia calcium cyanamide production was probably reached ia 1962 when the world production for fertilizer use was of the order of 1,000,000 metric tons of calcium cyanamide per year, and for iadustrial use approximately 300,000 t (excluding the then USSR). In 1990, the total production of cyanamide products was about half that of 1962. The largest producers are ia Japan, Germany, and Canada. 

Nitrate is one of the facts of life. It is essential for the growth of many plant species, including most of those we eat, but it becomes a problem if it gets into water in which it is not wanted. It is perceived mainly as a chemical fertilizer used by farmers, but much of the nitrate found in soil is produced by the microbes that break down plant residues and other nitrogen-containing residues in the soil. There is no difference between nitrate from fertilizer and that produced by microbes, but, whatever its origin, this rather commonplace chemical entity has now become a major environmental problem and is also treated as a health hazard. 

Nitrate (measured as Nitrogen) 10 10 "Blue baby syndrome" in infants under six months -life threatening without immediate medical attention. Symptoms Infant looks blue and has shortness of breath. Runoff from fertilizer use leaching from septic tanks, sewage erosion of natural deposits... 

Calcium phosphate, Ca3(P04)2, is a water-insoluble mineral, large quantities of which are used to make commercial fertilizers. Use the values for Ca3(P04)2 from Table 16.1 to answer the following questions. 

The liquid in which the SAH swelling takes place in real soil (the soil solution) always contains a more-or-less wide set of dissolved salts. Their nature and amount depend on the soil composition, the degree of its salinity, the nature of water entering the soil (rainfall, irrigation, river, or groundwater), the fertilizers used. As a rule, alkali cations, Ca2 +, Mg2+, Fe3+, Al3+, and anions CP, CO, SO4, etc. are the main components of the soil solution there exist various models of soil solution and nutrient mixtures employed in research, including SAH testing. 

Fertilization using animal products has been practiced since ancient times. Animal manure returns nutrients to the soil, replenishing elements that are depleted as crops are grown and harvested. It is likely that the use of animal fertilizers quickly followed the domestication of goats, sheep, and cattle. 

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