Microbial biomass phosphorus and alkaline phosphomonoesterase activity in the rhizosphere of different wheat cultivars as influenced by inorganic phosphorus and farmyard manure

Abstract

Wheat cultivars C 306, PBW 175, HD 1553, and HD 2329 were grown in an alkaline soil with and without inorganic P fertilizer and/or farmyard manure in a pot culture experiment. Microbial biomass P (MBP) and alkaline phosphomonoesterase (APM) activities were studied in rhizosphere soils of the above wheat cultivars at different physiological stages. Root weight and P uptake were also estimated simultaneously. Higher microbial biomass P was observed at crown root initiation (CRI) stage while APM activities were higher at panicle initiation (PI) stage. The HD cultivars showed higher MBP and APM activities at PI stage, while at CRI stage, the reverse was true. Though the application of inorganic P apparently showed higher APM activity, the ratio of APM activity and microbial biomass P (APM to MBP) decreased in the presence of inorganic fertilizer P. Inorganic P compared to FYM was the more dominant factor in reducing the APM to MBP ratio. Root weight did not correlate with grain yield. From step-wise regression analysis, it was revealed that microbial biomass P at both CRI and PI stages was a significant factor in influencing the P uptake in relation to grain yield of wheat.