International Journal of Plant & Soil Science

Aims: The aim of the investigation was to see the long-term effect of integrated nutrient management (INM) on chemical and microbiological properties of soil after 17 cycles of a rice-wheat cropping system.

Place and Duration of Study: This study was carried out in an on-going long-term fertilizer experiment initiated during 1991 at CSK Himachal Pradesh Agricultural University, Palampur, Himachal Pradesh, India.

Methodology: The experiment comprised of 8 treatment combinations viz., N, P and K fertilizer application as individual component and use of chemical fertilizers in conjunction with different organic sources i.e. farm yard manure (FYM), wheat straw (WS), and green manure (GM) with Sesbania aculeata to substitute 25 or 50% N through organics.

Results: The highest grain yield was 43.37 q ha^-1 in treatment receiving 50% NPK + 50% N through FYM and lowest of 26.70 q ha^-1 under control. The highest increase of organic carbon of about 55.2 per cent over control was observed under treatment receiving 50% N substituted through FYM during summer every year. Similarly, the highest soil microbial biomass carbon (248.50 mg kg^-1), microbial biomass nitrogen (38.25 mg kg^-1) and respiratory activities (153 mg kg^-1) was observed in the same treatment.  Total nitrogen was highest (928 mg kg^-1) under 50% NPK + 50% N through green manure in summer followed by 100% NPK in winter.

Conclusion: Application of 50% N through organics plus 50% NPK through chemical fertilizers was better than other treatments in improving chemical and microbiological properties of soil and in sustaining the crop yields.