Nitrogen mineralisation and the activity and populations of microflora in a high producing yellow-brown loam under pasture

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Abstract
At 25°C, optimum N-mineralisation in a topsoil sample from a yellow-brown loam under high-producing pasture was observed in the laboratory at 80% moisture (by weight). Populations of ammonium-oxidising bacteria and moulds did not differ significantly at soil moisture levels of 20%, 40%, 80%, and 140% by weight, but 20% moisture reduced the populations of total aerobic bacteria, gram negative bacteria, fluorescent Pseudomonas spp., and nitrite-oxidising bacteria. Liming with Ca(OH)2 (equivalent to 2500 kg.ha–1, pH 7.0) did not increase N-mineralisation but increased CO2 evolution. Liming also increased total aerobic bacteria, gram negative bacteria, and the biomass carbon level.