Temporal responses of soil biological characteristics to organic inputs and mineral fertilizers under wheat cultivation in inceptisol

A 2-year field experiment was conducted in wheat ecosystem to assess the key soil biological characteristics in inceptisols of northeastern region of India. Nine treatments using organic inputs (farmyard manure and vermicompost) and mineral fertilizers were applied by modulating the doses of organics and mineral N fertilizer. Soil enzymes (urease, phosphatase, dehydrogenase, fluorescein diacetate (FDA) and arylsulphatase), microbial biomass carbon (MBC), bacteria and fungi populations were measured before seed sowing (GS(1)), at flowering stage (GS(2)) and after harvest (GS(3)) of wheat, whereas total organic carbon (TOC) was studied at GS(3). GS(2) recorded significantly higher soil enzyme activities, except FDA, which increased considerably at GS(3). Enzyme activities, available N and TOC significantly (p0.05) enhanced with application of organic inputs even with reduced (50%) mineral N. Except urease and phosphatase, other enzymes did not respond significantly to mineral fertilization. Vermicompost application increased mean enzyme activities, MBC, microbial growth and TOC fractions (particulate organic carbon, humic acid and fulvic acid carbon) than farmyard manure. Significant (p0.05) positive correlations (r=0.61-0.87) were obtained between TOC and its fractions with studied soil enzymes. Thus, in conclusion, 5 tha(-1) organics incorporation (especially vermicompost) in wheat fertility programme can uphold soil biological health, reduce (50%) N application and would be a sustainable option for wheat grown in inceptisols of northeastern region of India.