ORGANIC SULPHUR AND NITROGEN IN PASTURE-CEREAL MIXED CROPPING SOILS AND RELATED FACTORS -A REVIEW

Haque, M.A., Mclaren, R.G., Condron, L.M., Williams, P.H. and Francis, G.S. 2007. Organic Sulphur and Nitrogen in PastureCereal Mixed Cropping Soils and Related Factors –A Review. J .Soil .Nature .1(2): 39-54 A detailed review was carried out to report the published information on the forms of S and N present in soils as well as their accumulation and mineralisation in a grazed pasture ecosystem under New Zealand condition. Sulphur and N present in soil are mostly in organic forms (about 90% of total). Accumulation of N under intensive heavily stocked grass-clover pastures occurs mainly from the biological N fixation of the legume component of pastures, residue return from pasture crops and return of grazing animal excreta whereas, the build up of organic S in soils is mainly attributed to the addition of fertiliser S as but indirectly it also helped build up of organic N. Cultivation of arable crops, on the other hand, decreased soil organic matter. Mineralisation of S from decomposing organic materials depends on the S content of the decomposing materials in much the same way as mineralisation of N depends on the N content. Although considerable research work has been done on the accumulation and mineralisation of organic S and N in soils under various conditions, there is still considerable uncertainty regarding the biological turnover of organic S and N in soil plant ecosystems.