Integrative Effects Of Tillage And Straw Incorporation On Crop Yield And Greenhouse Gas Emission In A Double Rice Cropping System

Rice?Oryza sativa L.?is an important cereal crop in China and forms a staple for more than 60%of the population.Meanwhile,paddy fields are an important source of methane?CH₄?emission accounting for one-quarter of global anthropogenic CH₄ emission.As demand for rice continues to increase,simultaneously achieving higher yield and low CH₄ emission has become an urgent and important scientific problem.Although reports indicate that tillage management and straw incorporation affect greenhouse gas emission?GHG?from paddy fields,the interactive effect is not clear.Therefore,based on a seven-year field experiment under a double rice cropping system,we conducted an experiment to investigate the effects of different tillage methods and straw incorporation on rice productivity and GHG emission from paddy field in Yujiang county,Jiangxi province,China.The main findings are as follow:?1?Early and late rice yields of plough tillage?PT?were slightly higher than that of rotary tillage?RT?with?S?or without straw incorporation?NS?.Compared to the rotary tillage,mean grain yield of early rice and late rice of plough tillage decreased by 8.8%.Straw incorporation increased rice yield and the yield-increasing effects varied with the method of tillage.Compared with straw removal,average grain yield over three years with straw incorporation was 5.1%higher in both RT and PT,and there are significant positive effects with 14.8%increasing on grain yield under plough tillage.However,the grain yield was susceptible to the effects of straw incorporation under rotary tillage.?2?Straw incorporation increased the nitrogen use efficiency significantly,but not tillage management.Compared to the straw removal,straw incorporation increased the N dry matter production efficiency?NUEb?and partial factor productivity of applied N?PFP?increased by 12.1%and 4.3%,respectively.In addition,the effects of straw incorporation on N use efficiency vary according to the tillage methods.In this study,the N competition was effectively alleviated by plough tillage,and compared to the straw removal,the NUEb and PFP increased significantly by 19.6%and15.1%,respectively.?3?Tillage impacts the greenhouse gas emissions significantly in both early rice season and late rice season.Greater GHG emission occurred in late rice season in double rice cropping system.The CH₄ and global warming potential?GWP?were 55.0%and 47.8%higher in late rice growing season than that of in early rice season,respectively.With or without straw incorporation,the mean CH₄emission,GWP and yield-scale GWP about these two rice growing seasons of each year decreased by30.0%,29.7%and 22.8%significantly under plough tillage when related to that of rotary tillage,respectively,but,there is no significant effects of tillage on the nitrous oxide?N₂O?during the study years.Straw incorporation significantly increased the CH₄,GWP and yield-scaled GWP of late rice season by 17.1%,17.3%and 12.2%,respectively,and varies little during the early rice season.Compared to straw removal,to a certain extent,straw incorporation decreases the N₂O in both early rice season and late rice season.The integrative effects of tillage and straw incorporation on the GHGs were observed during the study years,compared to the rotary tillage with straw incorporation,the average CH₄,GWP and yield-scaled GWP of these study years decrease significantly by 22.2%,24.3%and20.9%under plough tillage with straw incorporation,respectively.?4?The soil physical structures can be improved by tillage?i.e.rotary tillage and plough tillage?.Compared to rotary tillage,the soil layer depth increased significantly up to 30 cm,however the soil compaction at 0²0 cm depth,measured after late rice harvested in 2015,reduced significantly by25.1%.As for the soil chemical fertilizer characteristics of different layers from surface to 60 cm depth,we measured the total nitrogen?TN?,total phosphorus?TP?,total potassium?TK?,available nitrogen?AN?,available phosphorus?AP?,available potassium?AK?and soil organic matter?SOM?.The soil TN,AN,AP,TK and SOM at 0¹0 cm layer depth of rotary tillage were lower than of plough tillage,and for 10³0 cm soil layer depth,the TN,TP and TK were significantly higher.In this study,straw incorporation reduced the TN and AN content by 9.8%and 4.7%compared to straw removal,respectively,and for 10³0 cm layer depth,the TP,TK,AP and AK were significantly higher.Summarily,straw incorporation decreased the nitrogen?including TN,AN?of upper layer?0¹0 cm?,and increase the TP,TK,AP and AK content of the whole layer depth of 0³0 cm.In addition,there was no significant effect of straw incorporation on the soil physical structure.In conclusion,straw incorporation is beneficial for increasing grain yield in double rice cropping system.Combined with appropriate plough tillage,the GHGs emissions caused by the straw incorporation will decrease significantly,and the nutrient of topsoil can be distributed rationally.Thus,with straw incorporation,to a certain extent,plough tillage is a good approach to maintain high yield and to reduce emissions in paddy field in double rice cropping system.