Abstract: A field experiment was undertaken to evaluate the effect of conservation agriculture (CA) based management on soil biological properties, and on fungal diversity and abundance after 5 years of continuous cultivation. Treatments included four crop managements viz., conventional tillage (CT) rice-wheat (CT-RW; CT based), conventional tillage rice-zero tillage wheat and mungbean (CTR-ZTWMb; partially CA based), zero tillage rice-wheat-mungbean (ZT-RWMb; full CA based), and zero tillage maize-wheat-mungbean (ZT-MWMb; full CA based). Full rice, maize, and mungbean crop residue and anchored wheat residue were recycled in CA-based managements, while CT-based management was without any residue. Full CA-based management (ZT-MWMb) recorded 43% higher organic carbon, 56% microbial biomass carbon, 70% microbial biomass nitrogen, 73% phosphatase activity, and 40% β-glucosidase activity, than CT-RW management. Ascomycota (55-74%) was the dominant phylum followed by Basidiomycota and Glomeromycota (0 to 3%); abundance of these phylavaried amongst managements. Ascomycota abundance was in order of CT-RW< CTR-ZTWMb< ZT-RWMb< ZT-MWMb, however, Basidiomycota and Glomeromycota did not follow any trend. Diversity indices such as species richness, evenness and Shannon-Wiener diversity index were in the order: ZT-MWMb> ZT-RWMb> CTR-ZTWMb> CT-RW. This study clearly showed that CA with all three proven principles (no-tillage, residue retention and crop diversification) in maize-wheat-mungbean system resulted in higher microbial activities, fungal diversity and species richness compared to other cereal based management systems.

The present study describes the one-step purification and characterization of an extracellular cellulase-free xylanase from a newly isolated alkalophilic and moderately thermophilic strain of Bacillus subtilis ASH. Xylanase was purified to homogeneity by 10.5-fold with ~43% recovery using ion-exchange chromatography through CM-Sephadex C-50. The purified enzyme revealed a single band on SDS-PAGE gel with a molecular mass of 23 kDa. It showed an optimum pH at 7.0 and was stable over the pH range 6.0-9.0. The optimum temperature for enzyme activity was 55 ºC. The purified xylanase did not lose any activity up to 45 ºC, however, it retained 80% and 51% of its activity after pre-incubation at 55 ºC and 60 ºC, respectively. The enzyme obeyed Michaelis-Menton kinetics towards birch wood xylan with apparent Km 3.33 mg/ml and Vmax 100 IU/ml. The enzyme was strongly inhibited by Hg2+ and Cu2+ while enhanced by Co2+ and Mn2+. The purified enzyme could be stored at 4 ºC for six weeks without any loss of catalytic activity. The faster and economical purification of the cellulase-free xylanase from B. subtilis ASH by one-step procedure together with its appreciable stability at high temperature and alkaline pH makes it potentially effective for industrial applications.