Phosphorus fertilisation

Cadmium is readily taken up by most plants. The occurrence of cadmium in motor oils, car tyres, phosphorus fertilisers and zinc compounds explains its... 

Phosphorus fertilisers applied in seedbed for arable crops placement in bands near or with the seed is more efficient broadcast on grassland... 

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 . 

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). 

In hospitals, chemical analysis is widely used to assist in the diagnosis of illness and in monitoring the condition of patients. In farming, the nature and level of fertiliser application is based upon information obtained by analysis of the soil to determine its content of the essential plant nutrients, nitrogen, phosphorus and potassium, and of the trace elements which are necessary for healthy plant growth. 

The method can be applied to the determination of phosphorus in a wide variety of materials, e.g. phosphate rock, phosphatic fertilisers and metals, and is suitable for use in conjunction with the oxygen-flask procedure (Section 3.31). In all cases it is essential to ensure that the material is so treated that the phosphorus is converted to orthophosphate this may usually be done by dissolution in an oxidising medium such as concentrated nitric acid or in 60 per cent perchloric acid. 

An unusual example of a process that produces a lot of waste is the intensive rearing of pigs. They need additional phosphorus in their feed for healthy growth, and this is usually added as inorganic phosphorus in the form of monocalcium phosphate (calcium dihydroxy-oxido-oxo-phosphorane). Unabsorbed phosphorus passes through into the manure, and if spread onto fields as a fertiliser can lead to excess phosphorus run-off into rivers and lakes leading to eutrophication. 

X. L. Li, E. George, and H. Marschner, Phosphorus depletion and pH decrease at the root-soil and hyphae-soil interfaces of VA-mycorrhizal white clover fertilised with ammonium. New Phytologist 119 397 (1991). 

Figure 16 Cumulative phosphorus uptake curves (per unit root length) predicted for two tomato cultivars Knox and C37 ) grown in a soil fertilised to two P-levels. (From Ref. 28.)...

Grant C.A., Bailey L.D. Effects of phosphorus and zinc fertiliser management on cadmium accumulation in flaxseed. J SciFood Agri 1997 73 307-314. 

Sulphuric acid is used to manufacture other nitrogen-containing fertilisers such as ammonium sulphate, (NH4)2S04. Phosphorus-containing fertilisers, derived from rock phosphates such as Ca3(P04)2, are also manufactured using sulphuric acid. 

Giisewell S (2004) N P ratios in terrestrial plants variation and functional significance. New Phytol 164 243-266. doi http //www.blackwell-synergy.com/doi/abs/10. Ill 1/j. 1469-8137.2004.01192.x Giisewell S, Bailey KM, Roem WJ, Bedford BL (2005) Nutrient limitation and botanical diversity in wetlands can fertilisation raise species richness Oikos 109 71-80. doi http //www.black-well-synergy.com/doi/abs/10.1111/j.0030-1299.2005.13587.x Halsted M, Lynch J (1996) Phosphorus responses of C3 and C4 species. J Exp Bot 47 497-505. 

Sewage sludge contains significant concentrations of nutrients, particularly N and phosphorus and is recognised as having considerable potential as a fertiliser material and soil conditioner. Concentrations of nutrients vary considerably between sludges. Sommers [4], reported ranges of <0.1-17-6% for total N, <0.1-14.3% for total P, and 0.02-2.64% for total potassium. 

Craven, P. and Schwer, E.W. (1950) The determination of phosphorus. In Joint Symposium on Fertiliser Analysis. Proceedings No. 52, The Fertiliser Society, London, pp. 139-175. Discussion, pp. 175-183. 

Eppendorfer, W. H., Bille, S. W. (1996). Free and total amino acid composition of edible parts of beans, kale, spinach, cauliflower and potatoes as influenced by nitrogen fertilisation and phosphorus and potassium deficiency. Journal ofthe Science of Food and Agriculture, 71,449M58. 

The aroma compounds from the tropical fruits described in this chapter can be very important for consumers and industry as they are exotic and extremely pleasant however, the production of these compounds by biotechnological processes should be emphasised since the extraction from the fruits is a hard task. Many tropical soils contain less nitrogen and phosphorus, have lower capacity to absorb fertilisers, and therefore have lower conventional productive capacity, but some tropical soils have been very intensively farmed and further intensification is possible in other areas. Thus, the evaluation of a sustainable agriculture in tropical regions requires a sophisticated approach including the estimation of the risk of microbial or insect infestations. As many fruits go directly to fresh markets or to immediate processing, a continuing supply of the flavour manufacturers in the future is not completely assured. 

Ryan, M.H. and Ash, J. 1999. Effects of phosphorus and nitrogen on growth of pasture plants and AM fungi in SE Australian soils with contrasting fertiliser histories (conventional and biodynamic). Agriculture Ecosystems and Environment 73 51-62. 

Some of the ammonia produced by the Haber process is used to produce nitric acid. If ammonia is then reacted with the nitric acid, we have the basic reaction for the production of many artificial fertilisers. The use of artificial fertilisers is essential if farmers are to produce sufficient crops to feed the ever-increasing world population. Crops remove nutrients from the soil as they grow these include nitrogen, phosphorus and potassium. Artificial fertilisers are added to the soil to replace these nutrients and others, such as calcium, magnesium, sodium, sulfur, copper and iron. Examples of nitrogenous fertilisers (those which contain nitrogen) are shown in Table 11.7. 

Artificial fertiliser A substance added to soil to increase the amount of elements such as nitrogen, potassium and phosphorus. This enables crops grown in the soil to grow more healthily and to produce higher yields. 

Phosphorus in the form of phosphate is the principal source of P for plants. Phosphorus is commonly applied in fertilisers although its uptake by plants is much less than that of N and K and its availability is one of the most common nutritional limitations to crop yield (Bould etal., 1983). Some of the P in soils and soil solutions may be present in organic compounds. However, it is unlikely to be available to plants in its organic form and decomposition of organic matter releases P in its available... 

Hypophosphites and phosphates, e.g. calcium hypophosphite and glycerophosphate, are used in considerable quantities as patent medicines and in medicine generally as accessory foods. Acid phosphates are used extensively in baking powders and various manufactured foods. The phosphorus requirements of the animal body are stated on p. 4, and also the supply of the element in certain vegetable products, while the probable role of phosphates in some biological processes is indicated on p. 169. From their intimate connection with life it will be gathered that by far the most important use of phosphorus compounds is in the manufacture of fertilisers (see Chap. XV.). 

The phosphates of lime are the most valuable natural fertilisers and raw material of the fertiliser and phosphorus industry, which uses also to a less extent phosphates of aluminium and the apatites. Over 80 per cent, of the easily decomposible phosphorites mined are used in the preparation of superphosphate or other fertilisers (1980). 

Since the phosphorus compounds which are used in the arts, as well as phosphatic fertilisers, are derived from the decomposition of phosphates of lime, and the interactions of these are also of importance in biochemistry, a short account of the best investigated of these compounds will be given here. ... 

---