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 evaluating 4R nutrient management guidelines in the rice-maize-green gram cropping system in a strongly acidic soil in Odisha. The experiment consisted of ten treatments: 1) Site-Specific Nutrient Management (SSNM) with application of all limiting nutrients based on 4R principles; 2) SSNM with no nitrogen (N); 3) SSNM with no phosphorus (P); 4) SSNM with no potassium (K); 5) SSNM with no sulfur (S); 6) SSNM with no boron (b); 7) SSNM with no zinc (Zn); 8) SSNM with no calcium (Ca); 9) absolute Control with no fertilizer; and 10) farmers' practice.

The experiment, conducted over a period of three years, revealed that the cumulative biomass production and the economic yield in terms of rice equivalent yield (REY) with SSNM were 98 and 49 t/ha, respectively. Omission of N, P, K, S, B, Zn, and Ca from SSNM resulted in a cumulative yield loss of 40, 25, 15, 26, 14, 11, and 19% respectively in three years, indicating that omission of any of the limiting nutrients could significantly reduce the productivity of the rice-maize-green gram system. No addition of fertilizer (absolute control) resulted in 58% yield loss, while farmers' practice of unbalanced and inadequate application of fertilizers resulted in a yield loss of 28% over SSNM.

The agronomic efficiencies (kg grain/kg of nutrient applied) across the treatments ranged between 19 to 35 for N, 50 to 161 for P, and 24 to 79 for K, while the apparent recovery efficiencies of N, P, K, and S varied from 39 to 70, 21 to 71, 49 to 139, and 6 to 19%, respectively. Both the agronomic efficiency and apparent recovery efficiency of nutrients were highest in SSNM. Post harvest soil properties indicated an improvement in soil pH as a result of lime addition under SSNM, which also reported a slight increase in organic carbon status from 0.41 to 0.49%. However, post harvest assessment of soil fertility under SSNM indicated a decline in the available K fertility status and reported a net negative balance of K by 428 kg/ha, while the negative balance of N and P were 90 and 20 kg/ha, respectively.

The study conducted over three years indicated that SSNM practice based on the 4R Nutrient Stewardship principles exhibited overall net return of Rs. 60,000/ha, which was four times higher than the farmers' practice (Rs. 15,000/ha). The K rates suggested under SSNM practice was inadequate for the three crops sequence, and may require application of K fertilizer in green gram that was previously grown on residual fertility, in order to overcome K depletion from soil. The study was concluded in 2017.