What economically viable alternates, a farmer is left with, for paddy straw management, when its in-situ incorporation leads to higher emissions of Methane (CH4), a gas about 25 times more potent than Carbon-di-oxide (CO2) in causing global warming? Is it still right to advise farmers to incorporate paddy straw back into their fields, as most of the State Agricultural Universities highly emphasize on this approach without knowing its consequences in long-run?
https://m.tribuneindia.com/article/ploughing-straw-back-into-soil-won-t-do-experts/662354/amp
Ploughing back rice straw can have its issues. Rice straw can be a valuable source for food production through a mushroom industry. The repatriation of the spent mushroom compost allows the soil to be improved as compost is more stable from loss of the soil organic matter. The coupling of the removal of straw its beneficial use of highly nutritious food resource and its strategic return as organic amendment has economic environment and energetic advantages. When the harvest field planted to winter cover legume can produce the nitrogen for a subsequent rice crop without dependence on high carbon footprint fertilizer nitrogen will large negative environmental footprint. An integrated mixed farming system approach can be fundamental for regenerating soil and having improved food system results.
In addition to mushroom culture that Paul mentions, another practice is to compost the straw for fertilizer. Another practice that has huge potential to reduce Methane emission is mid-season drainage. The study is conducted in paddy field of China and published in Nature - https://www.nature.com/news/2009/090818/full/news.2009.833.html
One problem is that it might increase nitrous oxide, another GHG. The main intention of incorporation of paddy straw insitu is for adding organic matter for nutrient management. The Methane emissions from decomposition of straw from previous season is an issue in such semi-aquatic crop. While there are other options like alternative varieties, dry seeding, concern is tradeoff in yield and sometimes crop requirements of nutrients. There is always tradeoffs. Reducing organic sources of nutrients may need fertilization to compensate for it; which is nutrient runoff issues.
I suspect composting could cause methane emission under anaerobic conditions, hence the composting method (anaerobic digestion process can be avoided by regular turning and mixing of compost during the process) is critical in determining whether converting straw into compost is a sustainable practice.
I understand flooded paddy fields are drained/dried before harvest hence once harvesting is completed straw can be incorporated in soil for it to decompose over the fallow season without any flooding. This should enable straw decomposing into organic matter and CO2.
Composting can be performed aerobically to avoid methane generation. The use of direct seeding can be eliminate the anaerobic conditions mostly responsible for paddy rice methane genesis. The rice cultivation of direct planting will require preventive weeding strategies. The ability of incorporating a off season winter legume could provide the platform for supply rice nitrogen need without depending on ammoniated fertilizer the biggest carbon footprint for rice production system. The heavy production of a vetch crop would be important for eliminating most of the weed issue. The use of legume in the winter would give control of many of rice diseases.
Now days paddy straw can be used various ways livestock feed with manipulation of straw with other animal feed, mushroom culture, composting, straw for basket, packaging material, composite wood, paper board, etc but the only cost involved in removal of straw from filed.
There is a great potential for using such crop residues in paper and board industry as mentioned in this research:
https://www.researchgate.net/publication/315427845_Agricultural_Residues_Wastes_for_Manufacture_of_Paper_Board_and_Miscellaneous_Products_Background_Overview_and_Future_Prospects?_sg=JP33FaKJp6S_UahMaQ59XEG2vIpL_xujuTFgnDiscbOY_n_Y5oJ1HDkKvnOfATxanPK83ZpvZR0j7YCeig3cV3iX_f7SltMLfVHvc0Ub.mSuBWZuVuXkAcRggfuuTFmdWdyEW3r-_X4OCL32gjQkfbsStC8uOACYaytdHy3wIhYyPGUsZrppEXhaVdDZ_XQ
The generation of mushrooms from rice straw allows a value added product which is nutritionally complementary to rice to generate a diet which avoids most issues related to rice dominated culture. The ability to generate a stabilized humic material also for soil improvement and its targeted use for vegetable production. The use of mixed culture like this has health, environment and economic incentives.
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