Greenhouse Gas Mitigation by New Crop Rotations Together with Good Management Practices.

New cropping systems and good management practices for different environments were evaluated to maximize crop and input productivity and explore opportunities for greenhouse gas mitigation. In a field trial (clay with 1.27% total C and 0.075% total N) in South India, we compared crop productivity and greenhouse gas (GHG) emissions of a conventional (rice-rice-black gram) and an intensive “futuristic” (maize-rice-maize) cropping systems with four levels of N fertilizer. The conventional system included farmers’ practices of tillage and water management whereas intensive system had minimum tillage and need based water application. Total productivity of one year rotation with fertilization, of the intensive system was about 50% higher than that of conventional with about 3 fold reduction in global warming potential. Significant N₂O (9.98 kg N₂O ha^-1) was emitted during early stage of rice (dry season) in conventional system due to nitrate accumulation from the previous black gram crop. In maize under intensive system, N₂O emission increased from 2.47 to 8.07 kg N₂O ha^-1 with increasing levels of N (0 to 300 kg N ha^-1). In wet season rice, CH₄ emission in intensive system was lower by 10 fold as compared to that of conventional system.  Our results show that replacing conventional crop rotation with an intensive system can lead to improvement in total productivity and significant greenhouse gas mitigation.