Evaluating Principles of 4R Nutrient Stewardship in the Rice-Maize-Green Gram Cropping System for Improved Productivity and Profitability of Farmers in Odisha

This study was aimed at developing nutrient management guidelines and evaluating 4R principles for the newly proposed rice-maize-green gram cropping system in Puri and Cuttack Districts of Odisha. The soils of the experimental sites were sandy to loamy sand in texture, with acidic soil reaction (pH 4.8 to 6.9), low organic carbon (4.4 to 7.4 g/kg), low available N (155 to 189 kg/ha), low to high available P (8 to 64 kg/ha), low to high available K (30 to 140 kg/ha), low available S (8 to 12 kg/ha), low available B (0.24 ppm) and low available Zn (0.41 ppm). A soil test-based treatment (i.e., Balanced Fertilizer Treatment, BFT with NPK, S, Zn, B, and lime) was formulated considering this list of limiting nutrients, which was then compared with omission plots, one absolute control and one farmers' fertilizer practice (FP).

Results reveal that rice grain yield with BFT was 4.2 t/ha, which was 33% higher than FP, 69% higher than the absolute control and 20% higher than the BFT yield in the previous year. Yield reduction due to omission of N, P, K, S, B, Zn, and lime were 31, 14, 20, 17, 13, 11, and 15%, indicating that N is the most limiting nutrient. Choosing the right fertilizer source that includes these limiting nutrients will help improve the productivity of rice in this region. The highest maize yield (6.5 t/ha) and green gram yield (0.9 t/ha) were recorded using the BFT. Comparing rice-equivalent yield of the entire rice-maize-green gram cropping system, the highest system yields of 13.4 t/ha were recorded with BFT, which was 73% higher than FP. Use efficiency of N, P and K (kg grain/kg nutrient applied) with BFT was 24, 138 and 61, which were 118, 176 and 134% higher than FP.

Among the nutrients studied, the critical nutrients influencing the productivity of rice-maize-green gram cropping system were (in order): N > S > Ca > P > B = Zn > K. Further investigations are in progress for determining 4R nutrient management guidelines for this rice-maize-green gram cropping system.