• Energy Research

AbstractSequestration of soil organic carbon (SOC) is an important strategy to improve soil quality and to mitigate climate change. To investigate changes in SOC under conservation agriculture (CA), we measured SOC concentrations after seven years of rice (Oryza sativa L.)–wheat (Triticum aestivum L.) rotations in the eastern Indo‐Gangetic Plains (IGP) of India under various combinations of tillage and crop establishment methods. The six treatments were as follows: conventional till transplanted rice followed by conventional till wheat (CTR‐CTW), CTR followed by zero‐till wheat (CTR‐ZTW), ZT direct‐seeded rice followed by CTW (ZTDSR‐CTW), ZTDSR followed by ZT wheat both on permanent raised beds with residue (PBDSR‐PBW+R), and ZTDSR followed by ZTW both with (ZTDSR‐ZTW+R) and without residues (ZTDSR‐ZTW). We hypothesized that CA systems (i.e. ZT with residue retention) would sequester more carbon (C) than CT. After seven years, ZTDSR‐ZTW+R and PBDSR‐PBW+R increased SOC at 0–0.6 m depth by 4.7 and 3.0 t C/ha, respectively, whereas the CTR‐CTW system resulted in a decrease in SOC of 0.9 t C/ha. Over the same soil depth, ZT without residue retention (ZTDSR‐ZTW) only increased SOC by 1.1 t C/ha. There was no increase in SOC where ZT in either rice or wheat was followed by CT in the next crop (i.e. CTR‐ZTW and ZTDSR‐CTW), most likely because the benefit of ZT is lost when followed by tillage. Tillage and crop establishment methods had no significant effect on the SOC stock below the 0.15‐m soil layer. Over the seven years, the total carbon input from above‐ground residues was ca. 14.5 t/ha in ZTDSR‐ZTW+R and PBDSR‐PBW+R, almost sixfold greater than in the other systems. Our findings suggest that the increased biomass production achieved through a combination of ZT and partial residue retention offers an opportunity to increase SOC whilst allowing residues to be used for other purposes.

Abstract Conservation agriculture (CA) based best-bet crop management practices may increase crop and water productivity, while conserving and sustaining natural resources. Therefore, we evaluated kharif maize performance in 2014 under long-term tillage practices [permanent bed (PB) and zero tillage (ZT)] with conventional till (CT) as main plots and four irrigated maize based systems [maize-wheat-mungbean (MWMb), maize-chickpea- Sesbania (MCS), maize-mustard-mungbean (MMuMb) and maize-maize- Sesbania (MMS)] in sub plots under an ongoing trial established in 2008. In seventh kharif season at fixed plots the growth parameters, yield attributes, yield, water and energy-use efficiency of maize was maximum in ZT plots. The maize growth parameters were significantly ( p ) superior under ZT and PB compared to CT plots. Maize yield attributes viz. cobs m −2 (7.8), cob length (0.183 m), grain rows cob −1 (13.8) and grains row −1 (35.6) were significantly higher in ZT over to CT, however no-significant effect of cropping systems was found on maize growth and yield attributes. ZT registered maximum maize productivity (4589 kg ha −1 ). However, among the cropping sequences, MCS registered highest maize productivity (4582 kg ha −1 ). In maize, the water-use was reduced by 80.2-120.9 mm ha −1 in ZT and PB plots compared to CT which ultimately enhanced the water-use efficiency by 42.0 and 36.6%, respectively. ZT and PB plots registered increased soil organic carbon (SOC) by 3.5-31.8% in different depths (0-0.45 m) and energy productivity by 32.3-39.9% compared with CT. Overall, our long-term results showed that CA based ZT and PB practices coupled with diversified maize based cropping systems found effective for enhancing the maize yield, soil organic carbon, water and energy-use efficiency in North-Western India.

AbstractSouth Asian countries will have to double their food production by 2050 while using resources more efficiently and minimizing environmental problems. Transformative management approaches and technology solutions will be required in the major grain‐producing areas that provide the basis for future food and nutrition security. This study was conducted in four locations representing major food production systems of densely populated regions of South Asia. Novel production‐scale research platforms were established to assess and optimize three futuristic cropping systems and management scenarios (S2, S3, S4) in comparison with current management (S1). With best agronomic management practices (BMPs), including conservation agriculture (CA) and cropping system diversification, the productivity of rice‐ and wheat‐based cropping systems of South Asia increased substantially, whereas the global warming potential intensity (GWPi) decreased. Positive economic returns and less use of water, labor, nitrogen, and fossil fuel energy per unit food produced were achieved. In comparison with S1, S4, in which BMPs, CA and crop diversification were implemented in the most integrated manner, achieved 54% higher grain energy yield with a 104% increase in economic returns, 35% lower total water input, and a 43% lower GWPi. Conservation agriculture practices were most suitable for intensifying as well as diversifying wheat–rice rotations, but less so for rice–rice systems. This finding also highlights the need for characterizing areas suitable for CA and subsequent technology targeting. A comprehensive baseline dataset generated in this study will allow the prediction of extending benefits to a larger scale.