Other transformations in soil

Phosphorus is necessary for all organisms as a constituent of nucleic acids, phospholipids and other organic phosphate compounds. Its frequent deficiency in soils must be supplemented with phosphate fertilizers. Phosphorus is liberated from organic matter during ammonification. Phosphate is also made available to plants as a result of the formation by microorganisms of organic acids which dissolve insoluble inorganic phosphate compounds in the soil. 

Organisms require smaller amounts of other biogenic elements including trace elements such as iron, manganese, molybdenum, magnesium, zinc and copper. Little is known about the cycles of these elements in the soil. 

Soil microorganisms may play a key role in modification of heavy metals added to the soil as a result of man s industrial and agricultural activity. For such modification to occur, soils must contain populations of microorganisms resistant to the toxic effects of a given metal and capable of altering the chemical form of the added metal. Drucker et al. [30] determined that the order of toxic effect (from the greatest to the least) was Ag, Hg, Cr, Cd, Cu, Ni, Zn, Tl, Fe, Sn, W, Mo, Mn, As, Co, Sb, Pb. 

Allison, F. E. Soil Organic Matter and its Role in Crop Production. Elsevier, Amsterdam 1973. 

In Microbial Growth. P. M. Meadow and S. J. Pirt (eds). Cambridge University Press, Cambridge 1969, p. 15. 

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