Global Maize Project in India: Dharwad, Karnataka - Site Specific Nutrient Management in Maize-Wheat cropping system in Northern Karnataka

Evaluation of ecological intensification (EI) and farmer's practice (FP) in the maize-wheat cropping system during the third year of this trial revealed that EI with application of 180 kg N, 90 kg P₂O₅ and 100 kg K₂O/ha resulted in maize grain and stover yields of 3.9 and 7.2 t/ha, respectively. These yields were 27 and 30% higher, respectively, than the yields obtained in the FP treatment with application of 115 kg N, 52 kg P₂O₅ 45 kg K₂O/ha. However, pooled data for three years indicated 24% higher grain yield in EI than FP. Compared to EI and FP treatments, there was a steep reduction in maize grain yields in the EI-N (64%) and FP-N (53%) treatments over a period of three years. Net returns of INR 25,969/ha were obtained in the EI treatment, which were 26% higher than the net returns obtained with FP (INR 19,099/ha). In wheat, EI resulted in higher grain and straw yields of 3.6 and 6.5 t/ha, respectively, which were 12 and 5% higher than the grain and straw yields obtained with FP. Data averaged over three years also indicated higher wheat grain and straw yields in EI as compared to FP.

Rate and application studies revealed yield responses of 9, 7.6 and 4.3 t/ha in maize-wheat cropping system (MWCS) with applications of 390, 260 and 130 kg N/ha, respectively, over the no-N treatment. Even though the yield increase due to N fertilization was substantial (248% at 390 kg N/ha and 118% at 130 kg N/ha), the AEN (kg grain/kg N) decreased from 32.9 to 23.1 with increasing N rates from 130 to 390 kg N/ha. This indicated lower N use efficiencies at higher N application rates. Also, with increasing N rates, return on investment (ROI) for N fertilizer in the MWCS, decreased from 20.4 to 12.7, with a mean return of 16.6 INR/INR invested. The results indicated that although the net returns increased with increasing N rates, they also came at the cost of increased risk level for the farmer. These studies also gave an indication that, in addition to crop response, AEN and ROI also need consideration while deciding on the N application rate in the MWCS. A relatively better AEN (30.7) and ROI (17.7) were noticed with N application in three splits using a leaf color chart. IPNI-23