Fertilisers. Also

Phosphate fertilisers also contain a number of other elements found in the parent phosphate rock (Bowen, 1979 Bockman et al., 1990 Jackson and Alloway, 1992). Cadmium originating from sedimentary rock is particularly undesirable, and processes for the removal of Cd from such fertilisers are being developed (Bockman et al., 1990). Fertilised soils have shown increases in Cd content after a number of years, but there appears to be little evidence for long-term Cd-increase in crop plants, except possibly for wheat (Jones and Johnston, 1989). Mortvedt (1984) determined the uptake of Cd and Zn by several vegetable crops heavily fertilised with triple superphosphate over a ten year period. Cd levels were found to be similar in fertilised and unfertilised snap bean seed, beet blades and roots, and in sweet corn leaves and grain. However, Zn concentrations were found to decrease with P application in all tissues except cabbage heads and cores. Claims that fertilisers promote the uptake of Al by plants have been refuted (Akerstrand et al., 1988). 

Natural sources of NO / principally chemical and bacterial denitrification in soil, account for very approximately 50% of NO in the atmosphere. One should also add that ammonia sources (principally fertilisers) also make some contribution to total NOx. 

Industrially. phosphoric(V) acid is manufactured by two processes. In one process phosphorus is burned in air and the phos-phorus(V) oxide produced is dissolved in water. It is also manufactured by the action of dilute sulphuric acid on bone-ash or phosphorite, i.e. calcium tetraoxophosphate(V). Ca3(P04)2 the insoluble calcium sulphate is filtered off and the remaining solution concentrated. In this reaction, the calcium phosphate may be treated to convert it to the more soluble dihydrogenphosphatc. CafHjPOjj. When mixed with the calcium sulphate this is used as a fertiliser under the name "superphosphate . 

Most of the phosphoms produced as the element is later converted to high purity phosphoric acid and phosphate compounds the remainder is used in direct chemical synthesis to produce high purity products. In contrast, phosphoric acid produced by the wet process is used in lower purity apphcations, especially in fertiliser and to a lesser degree in animal feed (see Feeds AND FEED ADDITIVES). More recendy, a small portion of wet acid is purified in a second process and then also used in high purity acid and phosphate compound apphcations. 

Potassium [7440-09-7] K, is the third, element ia the aLkaU metal series. The name designation for the element is derived from potash, a potassium mineral the symbol from the German name kalium, which comes from the Arabic qili, a plant. The ashes of these plants al qili) were the historical source of potash for preparing fertilisers (qv) or gun powder. Potassium ions, essential to plants and animals, play a key role in carbohydrate metaboHsm in plants. In animals, potassium ions promote glycolysis, Hpolysis, tissue respiration, and the synthesis of proteins (qv) and acetylcholine. Potassium ions are also beheved to function in regulating blood pressure. 

Markets. Industrial use of ammonia varies according to region. Eor example, industrial usage represents 20% of the ammonia production in the United States and Western Europe, 10% in the USSR, 1—10% in Asia, and 5% in Latin America and North Africa (79). Fertiliser ammonia consumed domestically in most countries is converted to straight or compound fertilisers such as urea, ammonium nitrate, diammonium phosphate, and various grades of mixed fertilisers. However, almost 29% of ammonia nitrogen in the United States is consumed as direct appHcation material. The use of nitrogen solution such as urea and ammonium nitrate (UAN) has also become popular in the United States and the USSR. 

Salt apphed as equal parts of unionised sodium chloride and calcium chloride at 20 g total per L for 1 h, three times a week, has also been used to control fungal infections on eggs. The salt combination is first appHed one day after fertilisation to the first pick of eggs. These compounds are categorized as generally recognized as safe (GRAS). 

A goal of controlled release fertiliser research since the 1940s has been the development of a product that deUvers its nutrients at a rate matching the demand rate of the plant to which it is appHed. Such a fertiliser would represent the ultimate in use efficiency agronomic performance, ie, crop yield, quahty, and appearance agronomic safety and labor savings, ie, reduced appHcation frequency. It also would minimise potential losses to the environment. 

In North America, calcium cyanamide is no longer used as fertiliser, but it has limited use in special agricultural appHcations for defoHants, fungicides, herbicides, and as a weed killer. The primary industrial use is as a chemical intermediate for the manufacture of calcium cyanide, hydrogen cyanamide solution, and dicyandiamide. Calcium cyanamide is also used to add nitrogen to steel. 

Polycaprolactones (see also Section 25.11), although available since 1969, have only recently been marketed for biodegradable purposes. Applications include degradable film, tree planting containers and slow-release matrices for pharmaceuticals, pesticides, herbieides and fertilisers. Its rate of biodegradability is said to be less than that of the polylactides. 

Nitrogen compounds These also arise from both natural and synthetic sources. Thus ammonia is formed in the atmosphere during electrical storms, but increases in the ammonium ion concentration in rainfall over Europe in recent years are attributed to increased use of artiflcial fertilisers. Ammonium compounds in solution may increase the wettability of a metaland the action of ammonia and its compounds in causing season cracking , a type of stress-corrosion cracking of cold-worked brass, is well documented. 

Manufacturers and specialist materials development associations publish extensive corrosion data in the form of monographs, and this form of presentation is also used in national standards. The most recent comprehensive text in this category is perhaps the publication by the Zinc Development Association . The work is important in that the section on chemicals also deals with common, though complex, chemical formulations, e.g. Are-extinguisher fluids, soaps and syndets, agricultural chemicals such as pesticides and fertilisers. This publication also demonstrates the mammoth task of recording all the available data for just one material. A comparable book for mild steel would probably be much larger, whereas for many other materials the information has not yet been determined. Thus at best, only very incomplete data are available in this form. 

Typical applications in the inorganic field are the analysis of minerals, metals (including alloys), fertilisers, natural waters, industrial effluents and polluted atmospheres. The technique can also be used to establish the formulae of various complexes,... 

The higher elastic modulus (a measure of structure in solution) of rhamsan suggests that it should be superior to xanthan as a stabiliser. Rhamsan also has improved salt compatibility and is used in fertiliser suspension (high polyphosphates) and explosives (high ammonium nitrate). 

Basic slag used to be a popular fertiliser for supplying phosphate, but it also had liming value and contained some trace elements. However, the older steel-making processes are now out-of-date and basic slag is much less freely available. The consequence of this is that soils in Britain are becoming more acidic. 

Large quantities are used as a raw material in the chemical process industry, especially for urea across C02 reaction with NH3 and later dehydration of the formed carbamate. Urea is the product most used as agricultural fertiliser. It is used in feed for ruminants, as carbon cellulose explosives stabiliser in the manufacture of resins and also for thermosetting plastic products, among others. 

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