Phosphorus mineralization in response to organic and inorganic amendment in a semi-arid pasture soil

Abstract

Phosphorus deficient soil was amended with compost (C) (organic source of phosphorus) and inorganic P (KH2PO4 as inorganic phosphorus) at different rates and incubated for 28 days. Six treatments were used including i) Control ii) Inorganic P (0.79 mg per 30 g of soil sample) iii) 100 % C (0.13 g) iv) 75% C (0.1 g) + 25% P (0.2 mg) v) 50% C (0.065 g) + 50% P (0.4 mg) vi) 25% C (0.03 g) + 75% P (0.6 mg). Soil respiration was recorded using Infra-red CO2 gas analyzer. MBC was determined by using fumigation extraction method. Resin P and MBP extraction was carried out by anion exchange membranes and was determined colorimetrically. P pools were determined by using DeLuca method. Cumulative respiration microbial biomass significantly increased in organic amended soil with higher increase in soil emended with 75% C +25% P rate followed by 50% C and 50% P rate. It was concluded that compost amended with high inorganic P stimulated the formation of P labile pools which supply long term slow release of P for plants and microbes.