Effect of Fertilizer P and Farmyard Manure on Bioavailable P as Influenced by Rhizosphere Microbial Activities in Soybean-Wheat Rotation

ABSTRACT The efficiency of use of applied P may be improved through an understanding of soil P dynamics in relation to management practices in a cropping system. The objective of this study was to examine the influence of farmyard manure (FYM) and fertilizer P application on the activities of native arbuscular mycorrhizal fungi (AMF), inorganic P-solubilizing and organic-P mineralizing organisms, and selected enzyme activities in a soybean (Glycine max merril L.)-wheat (Triticum aestivum L.) rotation of five years duration. The results showed that the greatest microbial activities were measured when maximum crop growth occurred and that their activities increased significantly with the application of manure. AMF root colonization was twice higher in soybean than in wheat. The application of fertilizer P (44 kg P ha−1) reduced AMF colonization in roots, which was 15% lower than in control plots in both soybean and wheat. The combined application of fertilizer P and manure significantly improved the inorgan...