Long-term studies on soil physico-chemical properties and productivity of rice-wheat system as influenced by integrated nutrient management in inceptisol of Chhattisgarh

A long-term permanent plot field experiment was conducted from 1991–92 to 2002–03 to develop suitable integrated nutrient supply system for rice-wheat cropping system. The study was aimed to find out the effect of organic sources of nitrogen integrated with chemical sources on rice and their residual effect on succeeding wheat in rice-wheat cropping system at the Raipur Inceptisol. The initial fertility status of the soil was 234 kg N, 11.5 kg P and 280 kg K ha⁻¹, respectively. Initial bulk density and infiltration rate of experimental field were 1.51 Mg m⁻³ and 1.63 cm ⁻¹, respectively. Over the 12 years of study period, highest rice yield was obtained when 50% of nitrogen was supplied through green manuring (GM). When 50% N was supplied through farmyard manure (FYM), it produced rice yield at par with the treatment where, 100% NPK had been applied through chemical fertilizers. Significant residual effect of GM was observed on the following wheat yield during rabi. Incorporation of organic sources considerably improved the soil properties such as decrease in bulk density and increase in infiltration rate and available NPK status of the soil. Study showed that wherever, nitrogen was substituted through GM, FYM or crop residue (rice straw) in rice, bulk density was significantly lowered as compared to the initial status and control plot at the time of wheat harvest. Corresponding decrease in bulk density favourably enhanced the infiltration rate and it was found to be highest in the green-manured plot and lowest in control. Sustainability of rice-wheat system is possible either by providing 50% of recommended N through GM to rice and 50% through chemical fertilizers or even with 100% of recommended NPK through chemical fertilizers to rice and wheat.