Assessing the Contribution of Nutrients to Yield of Hybrid Rice and Maize through Omission Plot Techniques in Bihar

This experiment was conducted at five on-farm locations in each of Samastipur and Muzaffarpur districts of Bihar as well as at one plot at the Research Farm, Rajendra Agricultural University, Pusa, Samastipur, Bihar, under a hybrid rice-maize cropping system during 2013-15. Hybrid rice was grown as a kharif (rainfed) crop while hybrid maize was grown during the rabi (winter) season. The project studies the role of primary, secondary and micronutrients in the yield improvement of the hybrid rice-hybrid maize cropping system. Nine treatment combinations included: 1 (NPKSZn), 2 (-N), 3 (-P), 4 (-K), 5 (-S), 6 (-Zn), 7 (local variety under unfertilized check), 8 (local variety with ample NPKSZn), and 9 (hybrid variety under unfertilized check). In hybrid rice (Arize 6444), the fertilizer was applied by fixing the target yield at 7 t/ha (175-70-80 kg N-P₂O₅-K₂O/ha) and in local rice (Rajshree) at 5 t/ha (125-50-60 kg/ha). For the hybrid maize (DKC 9081), fertilizer was applied based on yield target of 10 t/ha (210-140-200 kg/ha) and for the local maize variety (Laxmi) at yield target of 6 t/ha (150-70-120 kg/ha). Sulfur was applied at 30 kg/ha through bentonite-S and Zn through 25 kg Zn-EDTA/ha in both rice and maize as per treatment combinations.

After two cropping cycles, the average hybrid rice grain yield decreased due to N, P, K, S, and Zn omissions, and the reductions compared to yield achieved with ample NPK were 40, 16, 12, 9, and 7%, respectively. The average hybrid rice grain yield in the ample NPKSZn plots was 6.1 t/ha, while in the control plot (no fertilizer) the average grain yield was 3 t/ha. The average grain yield in the control plot decreased over the previous year (3.4 t/ha), while there was increase in grain yield in ample NPK plot over the previous year (5.4 t/ha).

During rabi, the average hybrid maize yield was 8.9 t/ha, while the control plot (no fertilizer) average grain yield was 2.1 t/ha. Omission of N, P, K, S, and Zn resulted in 69, 28, 23, 15, and 16% yield decrease, respectively. Although maize yield in ample fertilized plots did not increase over last year (9.1 t/ha), the yield in omission plot decreased compared to last winter (4.5 t/ha).

Soil testing before planting and after harvest indicates that an ample dose of NPKSZn not only improved the yield but also improved the available nutrient status in post-harvest soil.