Comparison Among Different Rice Establishment Methods:Grain Yield, Water And Nitrogen Utilization Efficiencies And Greenhouse Gas Emissions

Labor shortage, water scarcity and climate change threaten the sustainability and profitability of traditional transplanted-rice. With the advantages of saving water and labor, increasing system productivity, direct-seeded rice has been proposed to be a promising option for rice production. To evaluating the potential of shifting from traditional transplanted rice to direct-seeded rice. Rice growth, yield performance, water and nitrogen use efficiency, lodging resistence and greenhouse gases emissions were compared among three different establishment methods. Two-year experiments were conducted including these three establishment methods, i.e. dry direct-seeded rice(Dry direct-seeded rice), wet direct-seeded(Wet direct-seeded rice) rice and transplanted-rice(TR).Our results show that the grain yield of wet direct-seeded rice was 10.8 % higher than transplanted rice when averaged across cultivars and both years, grain yield of dry direct-seeded rice and transplanted rice was close. Water productivity in dry direct-seeded rice and wet direct-seeded rice were also 11.6 % and 13.4 % higher than that in transplanted rice, respectively.Seasonal total CH4 emissions were highest in transplanted rice, followed by wet direct-seeded rice and dry direct-seeded rice was the lowest. The seasonal total N2 O emissions among three establishment methods displayed contrary tendency to seasonal total CH4 emissions. Compared with transplanted rice, global warming potential from dry direct-seeded rice and wet direct-seeded rice was decreased significantly(76.2 % for dry direct-seeded rice and 60.4 % for wet direct-seeded rice averaged across both years).Wet direct-seeded rice is more susceptible to lodging, lodging index in wet direct-seeded rice was 29.0 % and 32.1 % higher than that in dry direct-seeded rice and transplanted rice, respectively. The distribution of roots in wet direct-seeded rice was mostly in a shallow soil layer, and the distribution of roots in dry direct-seeded rice and transplanted rice were mostly in the deep soil layer. In wet direct-seeded rice, 54.2 % of total root lenghth were distributed in the shallow soil layer(0-15 cm underground), the distribution of roots in dry direct-seeded rice and transplanted rice in deep soil layer(15-45 cm underground) were up to 59.8 % and 61.9 % respectivity.Over all, wet direct-seeded rice is a competitive establishment method in Central China due to its higher grain yield, water productivity, and lower global warming potential. Dry direct-seeded rice may also be suitable for some regions where water is scarce for soil puddling during land preparation.