Long-term effect of nutrient management on soil health and productivity of rice (Oryza sativa)-wheat (Triticum aestivum) system.

Degradation in soil health has emerged as a major factor responsible for stagnation in agricultural production. The maintenance of good soil health needs balanced fertilization, which includes application of all the required plant nutrients in proper amount and form. Long-term studies revealed that crop productivity is declining even after applying recommended doses of NPK fertilizers. Responses to N reduced greatly in rice and almost zero in wheat (Triticum aestivum L. emend. Firori & Paol.) in the absence of P fertilizer over 20 years. But the responses to P and K emerged after 8–10 and 20–22 years respectively, when their availability in soil reached below the critical limits. The response (kg grain/kg nutrients applied) to N was higher in rice (Oryza sativa L.) than in wheat, while that to P and K was higher in wheat than in rice. Amongst the nutrients, maximum response was noted with P followed by N and K. Experiments conducted on farmers’ fields revealed that 8–12% of the total increase in grain yield of various crops could be attributed to K application only. Application of zinc to both rice and wheat was found more beneficial than its application to any single crop. The results of site-specific nutrient-management experiment’s indicated that maximum grain and economic yields can be achieved by applying all the required nutrients including microand macro-nutrients (N150 P60 K120 S40 B5 Mn20 Zn25) based on soil-test values. Trends in organic farming revealed that the yield gaps between chemical fertilizers and organic manures reduced with time. Organic inputs take time to be apparently responsive in terms of productivity and soil health. The system of integrated plant-nutrient supply is emerging as the most logical concept for managing long- term soil fertility and productivity. Addition of organic manures along with chemical fertilizers sustained the yield through increased nutrients availability and nutrient-use efficiency. The combined use of organic manures and chemical fertilizers improves the physical condition of soil more effectively than continuous addition of chemical fertilizers alone.