Pasture soils, microbial phosphorus

Fig. 12.2. The increase in water-soluble organic phosphorus after soil drying as a function of soil microbial phosphorus in a wide range of permanent pasture soils from England and Wales (Turner and Haygarth, 2001). Water-soluble phosphorus was determined by extracting soils at field moisture capacity with water in a 4 1 solution/soil ratio for 1 h. Subsamples were air-dried for 7 days at 30°C and extracted in an identical manner.

Table 7.5. Microbial phosphorus concentration in the topsoil layer of permanent grassland and pasture soils. 

Microbial phosphorus concentrations between 4 and >100 mg P/kg have been determined in grassland soils (Table 7.5). Concentrations decrease with increasing soil depth in parallel with decreasing soil organic matter concentrations. Tropical pasture soils containing little available and total phosphorus have a similar proportion of total phosphorus in the soil microbial biomass as temperate grassland soils, except for the excessively fertilized sites sampled by Scharer (2003). In a fertilization experiment, farmyard manure and phosphorus fertilization resulted in the largest microbial phosphorus concentrations, whereas ammonium sulphate decreased microbial phosphorus in... 

He ZL, Wu J, O Donnell AG, Syers JK (1997) Seasonal responses in microbial biomass carbon, phosphorus and sulphur in soils under pasture. Biol Fertil Soils 24 421 128... 

McLaughlin, M.J., Alston, A.M. and Martin, J.K. (1988) Phosphorus cycling in wheat-pasture rotations. II.The role of the microbial biomass in phosphorus cycling. Australian Journal of Soil Research 25, 333-342. 

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