Increases in soil sequestered carbon under conservation agriculture cropping decrease the estimated greenhouse gas emissions of wetland rice using life cycle assessment

Abstract

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 to 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- ACCEPTED MANUSCRIPTpuddled 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.

Influence of non-puddled transplanting and residues of previous mustard on rice (<em>Oryza sativa</em> L.)

“…On the other hand, crop yield increase in MT might have occurred from the improved soil structure and stability. They may facilitate better water holding capacity and drainage that reduces the extremes of water logging and drought (Holland, 2004), ultimately improving soil fertility by sequestering organic carbon in farmland soils (Alam et al, 2019). This finding supports the research result of Liu et al (2010) who found 20% higher maize yield in MT than CT due to increase of soil organic carbon, soil total nitrogen and soil total phosphorus by 25, 18 and 7%, respectively.…”

Rice (Oryza sativa L.) Establishment Techniques and Their Implications for Soil Properties, Global Warming Potential Mitigation and Crop Yields

“…A schematic of the C cycle in two triple-cropped rotations in northwest Bangladesh is shown in Figure 2. The LCA for greenhouse gas emissions by monsoon rice [191], irrigated rice [192] and for the mustard-irrigated rice-monsoon rice rotation [27] have been reported. Soil respiration (emission of CO 2 ) can strongly influence net carbon uptake from the atmosphere, or net ecosystem production [193] The CH 4 emission by rice soils which results from CH 4 production in anoxic zones was the major component of the C footprint for each of the rice crops and for the annual rotation.…”

Effects of tillage practices and nutrient management on crop productivity and profitability in Jute-T. aman rice- onion cropping system

“…As the delta country has most of the cropping systems based on rice (Alam et al, 2016b), the puddling of soil for rice crop establishment causes heavy havoc on soil properties by destroying structure of soil. In addition, puddling of soil accelerates decomposition of SOM, increases greenhouse gas emissions (GHGs)and nitrogen loss (Alam et al, 2019b) and inflicts increased costs for upland crop establishment (Bell et al, 2019).In contrary, minimum or zero tillage practice increases SOM levels (Busari and Salako, 2013),enriches nutrients in soils (Alam, 2018) and water retention capacity (Aziz et al, 2013), and decreases production costs (Salahin, 2017) and GHGs (Alam et al, 2019b) by reducing fuel use for intensive tillage and irrigation requirements (Johansen et al, 2012). There are many researches on zero and minimum tillage that has been proved as a greater technique to increase SOM, microbial activity, total N, and extractable P, S, Zn and B at the soil surface compared to conventional tillage (Alam et al, 2016a;Vu et al, 2009).…”