Strategic double cropping on Vertisols: A viable rainfed croppingoption in the Indian SAT to increase productivity and reduce risk
tOur study suggests the possibility for transformational change in the productivity and risk profile of someof India’s rainfed cropping systems. In the semi-arid regions of Southern India, farmers traditionally cropsorghum or chickpea on Vertisols during the post-rainy season, keeping the fields fallow during the rainyseason. This practice avoids land management problems, but limits the potential for crop intensifica-tion to increase systems productivity. A long-term (15 year) experiment at ICRISAT demonstrated thatcropping during the rainy season is technically feasible, and that grain productivity of double croppedsorghum + chickpea (SCP–SCP) and mung bean + sorghum (MS–MS) sequential systems were higher thantheir conventional counterparts with rainy season fallow, i.e. fallow + post-rainy sorghum (FS–FS) and fal-low + post-rainy chickpea (FS–FCP). Without N application, mean grain yield of post-rainy sorghum in theMS–MS system was significantly greater (2520 kg ha−1per two-year rotation) than in the FS–FS system(1940 kg ha−1per two-year rotation), with the added benefit of the mung bean grain yield (1000 kg ha−1per two-year rotation) from the MS–MS system. In the SCP–SCP system the additional grain yield ofrainy sorghum (3400 kg ha−1per two-year rotation) ensured that the total productivity of this systemwas greater than all other systems. Double cropping MS–MS and SCP–SCP sequential systems had sig-nificantly higher crop N uptake compared to traditional fallow systems at all rates of applied nitrogen(N).The intensified MS–MS and SCP–SCP sequential systems without any N fertilizer applied recorded amuch higher median gross profit of Rs. 20,600 (US $ 375) and Rs. 15,930 (US $ 290) ha−1yr−1, respectively,compared to Rs. 1560 (US $ 28) ha−1yr−1) with the FS–FS system. Applying 120 kg of N ha−1considerablyincreased the profitability of all systems, lifting median gross profits of the sorghum + chickpea systemover Rs. 60,000 (US $ 1091) ha−1yr−1and the conventional system to Rs. 20,570 (US $ 374) ha−1yr−1. Thegross profit margin analysis showed that nitrogen is a key input for improving productivity, particularlyfor the double cropping systems. However, traditional systems are unviable and risky without N appli-cation in the variable climates of the semi-arid tropics. Together, our results show that on Vertisols insemi-arid India, double cropping systems increase systems’ productivity, and are financially more pro-fitability and less risky than traditional fallow post-rainy systems while further benefits can be achievedthrough fertilizer application.