Fertiliser compound fertilisers

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. 

Parrish, P. and OGILVIE, H. Calcium Superphosphates and Compound Fertilisers. Their Chemistry and Manufacture (Hutchison, 1939). 

Coarsely pulverised dolomitic limestone in the size range 0.2 to 1mm is frequently added to compound fertilisers at levels of up to about 10 %. It confers several benefits ... 

Compound fertilisers (including calcium nitrate and calcium ammonium nitrate) sometimes contain 1 to 2 % of dolomitic hydrated lime. The lime confers similar benefits to pulverised dolomitic limestone (see section 10.3). 

Abundant supplies of the macronutrients C, H and O are available from water and atmospheric carbon dioxide, while nearly all the other essential elements are supplied via the soil solution supplied by the root system. Commercial fertilisers are used primarily to supply the elements N, P and K. Soils are not usually deficient in Ca, Mg and S, but these elements are in any case present in many types of commercial fertiliser. Fertiliser compounds of leading importance are... 

Other fertiliser compounds which can satisfactorily provide phosphorus and nitrogen are urea phosphate, CO(NH2)2 H3PO4, ammonium polyphosphate, [(NH4)P03] and phosphazenes such as P3N3(NH2)g (Table 12.4). Red phosphorus is slowly oxidised in damp soil and has been considered as a possible fertiliser [32,33]. 

The nitrogen in many straight and compound fertilisers is in the ammonium (NH cation) form but, depending on the soil temperature, it is quickly changed by bacteria in the soil to the nitrate (NOj anion) form. Many crop plants, e.g. cereals, take up and respond to the NO3 anions quicker than the NH cations, but other crops, e.g. grass and potatoes, are equally responsive to NH and NO ions. 

It should be noted that a significant proportion of the nitrogen now supplied to farm crops comes from compound fertilisers in which it is usually present mainly as monammonium phosphate (MAP) or diammonium phosphate (DAP), as described in the section on phosphate fertilisers. 

Muriate of potash (potassium chloride). As now sold, it usually contains 60% K O. It is the most common source of potash for farm use and is also the main potash ingredient for compound fertilisers containing potassium. As a straight fertiliser it is normally granulated, but some is marketed in a powdered form. KCl is found in vast quantities all over the world and is mined from rock deposits left by dried-up oceans. It is nearly always found in conjunction with NaCl and the two are separated by a flotation process. 

The main constituents for compound fertihsers used in the United Kingdom are urea, mono and diammonium phosphate and potassium chloride. These compound fertilisers, or compounds, supply two or three of the major plant foods (nitrogen, phosphoms and potassium). Other plant foods, e.g. trace elements, as well as pesticides, can also be added, although this is not commonly done now. The exception to this is sulphur which is increasingly being offered as part of compound fertilisers to overcome the deficiencies in certain parts of the country. 

Sulphur deficiency can be a problem in second and subsequent silage cuts. Compound fertilisers should be used to apply about 40 kg/ha SO if deficiency is confirmed by herbage analysis. 

NPK compound fertilisers for farmers who want nitrogen, phosphoms, and potassium. These are usually a mixture of ammonium nitrate, ammonium phosphate, and potassium chloride. 

This diagram shows the raw materials the factory needs to make 1000 tonnes of straight and 1000 tonnes of compound fertiliser a day, and the steps in the production process t/day stands for tonnes per day. 

While the trace-element content of guano and, to a lesser extent, of mined mineral salts, could make some contribution to the nutrient requirements of crops, these materials are no longer adequately available. We have now become largely dependent on highly purified compound fertilisers containing only nitrogen, phosphorus and potassium as nutrients, so that the rate of depletion of essential trace elements has been greatly accelerated. The natural cycle... 

The equivalent quantities of sulfur dispersed are considerably greater than the amount needed to produce enough sulfate-based compound fertiliser to meet the whole UK requirement. 

Fluorine is another potentially-toxic trace element which is dispersed by atmospheric pollution and it has long been recognised that damage to plants occurs and that there is a hazard to man and farm stock, in the vicinity of industrial plants processing fluoride-containing minerals. Such plants include factories for the production of aluminium, superphosphates and compound fertilisers based on the liberation of phosphoric acid from rock phosphate. In October 1976, ten cows had to be destroyed on two farms in the vicinity of the British Aluminium Company s aluminium smelter at Invergorden in the north of Scotland, and problems of fluoride toxicity have been commonly associated elsewhere with the production of aluminium. 

Uses of ammonia and ammonium compounds. Most of the ammonia produced is used in the manufaeture of nitrogenous fertilisers such as ammonium sulphate. Other uses include nitric acid and synthetic fibre and plastic manufacture. 

Phosphorus [7723-14-0] is a nonmetaUic element having widespread occurrence in nature as phosphate compounds (see Phosphoric acid and phosphates). Fluorapatite [1306-03-4], Ca F(P0 2> is the primary mineral in phosphate rock ores from which useful phosphoms compounds (qv) ate produced. The recovery from the ore into commercial chemicals is accompHshed by two routes the electric furnace process, which yields elemental phosphoms and the wet acid process, which generates phosphoric acid. The former is discussed herein (see Furnaces, electric). Less than 10% of the phosphate rock mined in the world is processed in electric furnaces. Over 90% is processed by the wet process, used primarily to make fertilisers (qv). 

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. 

There are a considerable number of stable crystalline salts of the ammonium ion [14798-03-9] NH. Several are of commercial importance because of large scale consumption in fertiliser and industrial markets. The ammonium ion is about the same size as the potassium and mbidium ions, so these salts are often isomorphous and have similar solubiUty in water. Compounds in which the ammonium ion is combined with a large, uninegative anion are usually the most stable. Ammonium salts containing a small, highly charged anion generally dissociate easily into ammonia (qv) and the free acid (1). At about 300°C most simple ammonium salts volatilize with dissociation, for example... 

Sodium nitrate is used as a fertiliser and in a number of industrial processes. In the period from 1880—1910 it accounted for 60% of the world fertiliser nitrogen production. In the 1990s sodium nitrate accounts for 0.1% of the world fertiliser nitrogen production, and is used for some specific crops and soil conditions. This decline has resulted from an enormous growth in fertiliser manufacture and an increased use of less expensive nitrogen fertilisers (qv) produced from synthetic ammonia (qv), such as urea (qv), ammonium nitrate, ammonium phosphates, ammonium sulfate, and ammonia itself (see Ammonium compounds). The commercial production of synthetic ammonia began in 1921, soon after the end of World War I. The main industrial market for sodium nitrate was at first the manufacture of nitric acid (qv) and explosives (see Explosives and propellants). As of the mid-1990s sodium nitrate was used in the production of some explosives and in a number of industrial areas. 

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). 

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. 

Related to chemical pollution - referring to all kind of contamination (mineral and organic) - there is a clear distinction between point-source pollution and diffuse pollution. It appears that it is easier to take measures for point-source pollution, for instance, the improvement of the wastewater treatment plants, even if the treatments for specific compounds (pesticides, emerging compounds, etc.) still need further research. Measures for diffuse pollution can be more complex because some of them require real political decisions, for instance to interfere on agricultural practices to reduce inorganic and organic fertilisers. 

Application of sludge on agricultural soils could result in these organics entering the food chain. As many of these compounds are toxic to humans or animals, their presence could be a constraint for the use of sludges as fertilisers. Some food companies have set soil limits above which crops grown on such contaminated soils are rejected [11] Aldrin/Dieldrin, 0.1 DDT, 0.75 and Diuron, 0.3mg/kg soil. 

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