Soil Enzymes and Microbial Biomass Carbon under Rice-Toria Sequence as Influenced by Nutrient Management

Abstract

Soil enzymes and microbial biomass carbon (Cmic) were assessed to understand the influence of integrated nutrient management (INM) under rice-toria sequence during 2008 and 2009. Fluorescein di-acetate (FDA), phosphomonoesterase (PMEase) and dehydrogenase (DHD), involved in energy flow and nutrient cycling showed significantly higher activities under INM treatments. Enriched compost (EC) application @ 2 t ha−1 demonstrated clear increase in FDA (10.75 μg fluorescein g−1 soil h−1) and PMEase (393.5 μg p-nitrophenol g−1 soil h−1) activities with only 25% of recommended nitrogenous (N) and phosphatic (P) fertilizers under the sequence. The DHD activity however, showed significantly maximum quantity (287.6 μg TPF g−1 24 h−1) on application of compost (2 t ha−1) and biofertilizers with 25% NP fertilizers. The enzymes assayed showed significant correlation with build-up of Cmic and organic carbon (Corg) of the soil. Among the organic inputs, compost (2 t ha−1) coupled with biofertilizers revealed the highest Cmic (222.8 μg g−1soil) in the study. Likewise, maximum Corg (10.96 g kg−1) accumulation was observed under the INM treatment which had received EC @ 2 t ha−1 continuously under the sequence. Available P status of the soil also increased (28.64 kg ha−1) significantly on application of rock phosphate (RP) with EC. The multifaceted effects of INM treatments that facilitated beneficial soil conditions were reflected in terms of significant increase in the grain yield of both rice (3.87 t ha−1) and toria (1.04 t ha−1) even over the 100% NPK.