Effect of farmyard manure, mineral fertilizers and mung bean residues on some microbiological properties of eroded soil in district Swat

The present study was conducted to evaluate the efficacy of organic and inorganic fertilizers and mung bean residues on improving microbiological properties of eroded lands of District Swat, North West Frontier Province (NWFP) Pakistan under wheat-mung bean-wheat cropping system during 2006 to 2008. The experiment was laid out in RCBD split-plot arrangement. Mung bean was grown and a basal dose of 25-60 kg N-P2O5 ha^-1 was applied. After mung bean harvest, three residues management practices, i.e., R+ (mung bean residues incorporated into soil), R- (mung bean residues removed) and F (fallow) were performed in the main-plots. Sub-plot factor consisted of six fertilizer treatments for wheat crop i.e., T1 (control), T2 (120 kg N ha^-1), T3 (120-90-0 kg N-P2O5-K2O ha^-1), T4 (120-90-60 kg N-P2O5-K2O ha^-1), T5 (90-90-60 kg N-P2O5-K2O + 10 t FYM ha^-1) and T6 (60-90-60 kg N-P2O5-K2O + 20 t FYM ha^-1). The results showed that microbial activity, microbial biomass-C and-N, mineralizable C and N were highest with T6 as well as with the incorporation of mung bean residues (R+). Compared with control, T6 increased microbial biomass C, N, mineralizable C and N by 33.8, 164.1, 35.5 and 110.6% at surface and 38.4, 237.5, 38.7 and 124.1% at sub-surface soil, respectively, while R+ compared with fallow increased these properties by 33.7, 47.4, 21.4 and 32.2% at surface and 36.8, 51, 21.9 and 35.4% at sub-surface soil, respectively. Inclusion of mung bean with its residues incorporated and application of 20 t FYM ha^-1 and reducing inorganic N fertilizer to 60 kg N ha^-1 for wheat is recommended for improving microbiological properties of slightly eroded lands.