Long-term effects of fertilizer and manure application on soil quality and sustainability of jute-rice-wheat production system in Indo-Gangetic plain

A long-term fertilizer experiment was initiated in 1971 in sandy loam soil (Eutrochrept) of Barrackpore, West Bengal to study the effects of applying organic and inorganic sources of nutrients on yield of jute-rice-wheat system and soil health. The unfertilized soil supported yields of 0.8 t ha-1 of jute fibre, 1.5 t ha-1 of rice grain and 0.7 t ha-1 of wheat grain (average yield of 42 years). Application of 150% recommended NPK through chemical fertilizers produced maximum yields of jute (2.1 t ha-1), rice (3.8 t ha-1) and wheat (2.8 t ha-1). The yields obtained with 150% NPK fertilizers were 5%, 2.7% and 12% higher than that with 100% NPK fertilizers +FYM. Combined application of 100% NPK fertilizers and FYM, however, increased soil organic carbon, available nitrogen, phosphorus and potassium from 5.60 to 8.90 g kg-1, 270 to 316 kg ha-1, 40.7 to 120 kg ha-1 and 139 to 236 kg ha-1 respectively. Maximum DTPA-extractable micronutrients in soil were also observed with 100%NPK fertilizers+FYM. Applying FYM together with NPK fertilizers increased microbial biomass from 221 to 435 mg kg-1 and microbial quotient from 3.95 to 4.89 with concomitant increase in dehydrogenase, phosphatase and fluorescein-diacetate-hydrolyzing activities in the soil. The acid phosphatase activity (139 to 275 ?g PNPg-1 h-1) was much lower than alkaline phosphatase activity (479 to 616 ?g PNPg-1 h-1). The enzymes assayed showed significant correlation with microbial-C and organic C. Beneficial effects of integrated nutrient management (NPK+FYM) on soil health were reflected on the yields of all the crops.