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The lowering of the groundwater table caused by increased groundwater use in the dry, Barind region has prompted sustainability concerns. In this study, water-table (WT) scenarios were simulated by the MODFLOW model under different crop rotations in Barind, a dry region of Bangladesh, to examine the effects of crop rotations on groundwater level. The studied crop rotations and recharge conditions were: with existing cropping pattern; 100, 30 and 50% of present Boro rice is replaced by Aus rice; existing cropping pattern, but with reduced recharge to 90 and 80% of present recharge. A calibrated MODFLOW model was used to develop WT scenarios. According to the modeling results, the declination of WT will be lessened and the situation with regard to WT will therefore be improved with the gradual substitution of Boro by Aus and Rabi (30, 50 and 100%). The simulated WT scenario will be useful for policymakers to set policies about cropping patterns or groundwater withdrawal amounts targeting the area's long-term sustainability of groundwater. HIGHLIGHTS Sustainable agricultural production in the Barind area is under threat due to unsustainable groundwater use.; A calibrated MODFLOW model was used to predict the water-table (WT) under different cropping patterns.; With the gradual substitution of Boro rice by Aus rice (e.g. 30%, 50%, and 100%), the situation for WT will be improved.; The simulated WT scenario will therefore be useful for the policymakers.;

Wetland rainfed rice (Oryza sativa L.), which covers 60 million hectares in South Asia, contributes significantly to agricultural greenhouse gas (GHG) emissions. Mitigation strategies for GHG emissions by wetland rice production are of considerable importance. Life cycle assessment of GHG emissions can be used to assess the mitigation potential of new rice production practices such as seedling establishment on non-puddled soil. The aim of the study was firstly to determine the GHG mitigation potential of rain-fed rice production by changing to non-puddled transplanting and increased crop residue retention and secondly to determine the addition contribution of soil carbon sequestration to net GHG emissions with the altered crop establishment approach. A cradle to farm-gate Life Cycle Analysis was used to calculate GHG emissions associated with monsoon rice production in rice-based intensive cropping systems of Northwest Bangladesh. The non-puddled transplanting and low residue retention decreased the net life cycle assessment GHG emissions (CO 2 eq) by 31% in comparison with the current puddled transplanting and increased crop residue retention. By contrast, non-puddling with increased residue retention reduced emission of the net GHG by 16% in comparison with current puddling and low residue retention. Regardless of rice establishment practices, CH 4 was the most prevalent GHG emission comprising 63–67% of the total GHGs, followed by 17–20% from CO 2 emissions from the field. The GHG emissions tonne−1 rice after accounting for soil carbon storage ranged from 1.04 to 1.18 tonne CO 2 eq for non-puddling with low and increased crop residue retention, respectively. The inclusion of soil carbon in the footprint equation represents a 26% reduction of estimated GHG emissions under non-puddled soil with increased residue retention. Overall, non-puddled transplanting with increased crop residue retention was an effective GHG mitigation option in wetland monsoon rice production because the increased yield and extra soil organic carbon storage more than offset its higher CH 4 emissions than with low residue retention. Image 1076 • Life cycle greenhouse gas emissions (LCA GHG) of monsoon rice calculated with sequestered C under CA. • Non-puddling (NP) with minimal residue retention was the most effective option of mitigation. • NP with residue retention offered yield benefit and greater GHG savings with extra C sequestration. • On-farm CH 4 and soil CO 2 emissions were the major GHG emission sources. • The exclusion of C sequestration overestimates the LCA GHG emissions by ̴ 16% to ̴ 31%. [ABSTRACT FROM AUTHOR]

Wetland rice ( Oryza sativa L.) production contributes 55% of agricultural greenhouse gas (GHG) emissions in the world. Hence any new technology with the potential to reduce the GHG emissions of wetland rice could make a significant contribution to total global warming mitigation by agriculture. We applied a streamlined life cycle assessment to the effect of a novel unpuddled transplanting of rice and of increased crop residue retention on GHG emissions from rice fields in the Eastern Gangetic Plains. We compared them with the conventional puddling of soils and current residue retention for transplanting. The GHG emissions from one tonne of rice production for the following four cropping practices were studied: a) conventional puddled transplanting with low residue retention (CTLR); b) conventional puddled transplanting with high residue retention (CTHR); c) unpuddled transplanting following strip tillage with low residue retention (UTLR) and; d) unpuddled transplanting with high residue retention (UTHR). The emissions recorded on-farm and emissions related to pre-farm activities were converted to CO 2 -eq using Global Warming Potential (GWP) values of GHGs for 20-, 100- and 500-year time horizons. The GHG emissions of 1 tonne of rice varied from 1.11 to 1.57 tonne CO 2 -eq in the 100-year horizon. For all four treatments, soil methane (CH 4 ) was the predominant GHG emitted (comprising 60–67% of the total) followed by emission from on-farm machinery use. The UTLR was the most effective GHG mitigation option (it avoided 29%, 16% and 6% of the total GHG emissions in comparison with CTHR, CTLR and UTHR, respectively) in wetland rice production. The novel minimum tillage establishment approach for rice involving strip tillage followed by UT has potential to increase global warming mitigation of wetland rice in the Eastern Gangetic Plains, but further research is needed to assess the role of increased residue retention. [ABSTRACT FROM AUTHOR]