Effects Of Tillage Method And Straw Turnover On Yield Formation,Nitrogen Utilization And Distribution Characteristics Of Double Cropping Rice

In this study,the experimental design of field splitting was adopted,with the main treatment of straw full return（S）and straw non-return,and different tillage methods were used:Double turning（TT）,double turning（RR）,double free（NN）,early turning and late turning（RT）,and early turning and late avoiding（RN）were used as auxiliary treatments to study the effects of straw returning and tillage on the yield formation,nitrogen utilization and distribution characteristics of double cropping rice,in order to provide reference for the analysis of environmental benefits of double cropping rice production.The main findings are as follows:（1）Rice yield under rotary tillage treatment was slightly higher than that under tilling treatment.Compared with rotary tillage,the yield of TTS treatment in early rice season was the highest,and that of RNS treatment was the lowest,and the yield of TTS treatment in early rice season was significantly increased by 45.6%.The yield of RTS treatment in late rice season was the highest,and the yield of RN treatment was the lowest,and the yield of RTS treatment in late rice season was significantly increased by 33.4%compared with RN treatment.The RRS treatment of rice annual effective ear was the lowest.The annual leaf area index of rice treated with TTS was the highest,and the leaf area of rice treated with RR was the lowest,and the leaf area of rice treated with TTS was significantly increased by42.3%compared with RR.The photosynthetic characteristics of rice under TTS treatment were the highest,and those under RRS treatment were the lowest.（2）Straw weighing significantly increased nitrogen use efficiency of rice,but tillage method had little effect.Nitrogen accumulation under NNS treatment was the highest in early rice season,and nitrogen accumulation under RRS treatment was the lowest,and NNS treatment was significantly increased by 37.0%compared with RRS treatment.In late rice season,nitrogen accumulation under TTS treatment was the highest,and nitrogen accumulation under RN treatment was the lowest,and the nitrogen accumulation under TTS treatment was significantly increased by 25.8%compared with RN treatment.The nitrogen allocation index of RNS treatment was the highest in early rice season,and the nitrogen allocation index of RNS treatment was significantly increased by 46.0%compared with NNS treatment.The nitrogen allocation index of RTS treatment was the highest in late rice season,and the nitrogen allocation index of RTS treatment was significantly increased by42.4%compared with RNS treatment.The nitrogen use efficiency of TTS treatment was significantly higher than that of RRS treatment in early rice season,and the nitrogen use efficiency of TTS treatment was significantly increased by 19.3%compared with RRS treatment.The nitrogen use efficiency of RRS treatment was significantly higher than that of RNS treatment in late rice season,and the nitrogen use efficiency of RRS treatment was significantly increased by 48.2%compared with RNS treatment.（3）Both rotary tillage and tilling are beneficial to improve soil physical structure.The total nitrogen content in 0-10cm soil layer of early rice season under RNS treatment was higher than that under TTS treatment,which was significantly increased by 17.1%.The total nitrogen content in 10-20cm soil layer under NNS treatment was higher than that under RNS treatment,and significantly increased by 33.0%compared with RNS treatment.The total nitrogen content in 0-10cm soil layer in late rice season under RNS treatment was higher than that under RRS treatment,and significantly increased by 30.3%.The total nitrogen content in 10-20cm soil layer treated by TTS was higher than that treated by RNS,and was significantly increased by 45.1%.（4）Cultivation methods had significant effects on greenhouse gas emissions in early and late rice seasons.In early rice season,greenhouse gas N₂O emission fluxes showed a general trend of first decreasing,then increasing and then decreasing with time.N₂O emission under RNS treatment was the highest,and N₂O emission under TTS treatment was the lowest.In late rice season,greenhouse gas N₂O showed a general trend of first increasing and then decreasing over time.NNS treatment had the highest N₂O emission,while TTS treatment had the lowest N₂O emission.In summary,according to the yield of double-cropping rice and the characteristics of nitrogen accumulation and distribution,the results showed that the rice yield was the highest under total straw return tillage,followed by rotary tillage.Therefore,the straw return tillage and sub-tillage treatment were beneficial to the growth and development of rice plants.No tillage treatment had the best effect on nutrient accumulation,absorption and utilization.The content of total nitrogen in different soil layers was the highest in early treatment and late treatment.The N₂O emission from paddy field under rotary tillage treatment was the lowest.In conclusion,straw returning+tilling and straw returning+rotary tilling have obvious advantages in improving rice yield,nitrogen use efficiency and reducing N₂O.The adoption of these two tillage systems is conducive to the efficient production of rice and the reduction of greenhouse gas N₂O emissions.