| Under the background of global warming,lack of water resources and social structure change of human resources,rice production mode in China is gradually developing to water-saving,light and simplified cultivation mode.Northeast China has become one of the most obvious areas of global warming.Due to the advance of rice phenology,direct rice cultivation has become a rice cultivation measure for saving water,reducing emissions and increasing efficiency to cope with global warming in northern China.However,there are still some management problems in direct seeding rice cultivation in north China,such as unstable yield,uncertain sowing density,nitrogen fertilizer application,and growth and development regulation.Therefore,in this study,the northern japonica rice variety Beijing 3(BJ3)was used as test material.On the basis of determining the appropriate sowing amount,the effects of EBRs spraying and combined application of organic fertilizer at different growth stages on the yield and greenhouse gas emissions of direct-seeding rice were studied,which laid a practical research foundation for the formation of standardized and sustainable direct-seeding rice cultivation technology.In order to achieve emission reduction and efficiency of direct seeding rice production,the greenhouse gas emission was reduced while the yield was stable.The main results are as follows:(1)Three seeding rates of 60 kg/hm~2,90 kg/hm~2 and 120 kg/hm~2 were set for direct seeding rice variety Beijing 3,and the optimal seeding rate was selected as 60 kg/hm~2 according to yield,greenhouse gas and other indicators.Under this seeding rate,the rice population structure was good,the dry matter accumulation at the stage of full panicle to maturity was the largest,the effective panicle number was higher than that of 90 kg/hm~2,and the grains per panicle and1000-grain weight were also significantly higher than those of the other two groups.Compared with the other two groups,the rice yield was increased by 12.91%and 8.82%,respectively.The combined warming potential decreased by 7.56%and 8.79%,respectively.(2)Spraying 1μmol/L EBR at tillering stage,elongation stage and flowering stage of direct seeding rice Beijing 3,respectively,to screen the optimal spraying time.The results showed that the activities of SOD and POD antioxidant enzymes were significantly increased by 25.24%and 21.10%,respectively,and the chlorophyll content of the top three leaves was increased and leaf senescence was delayed after spraying EBR in the high temperature period of the field at flowering stage.The seed setting rate and 1000-grain weight of rice were increased,and the final dry matter accumulation of rice was increased by 4.58%compared with CK.Greenhouse gas emissions have not changed significantly.(3)Set the total nitrogen application rate as 200 kg/hm~2 and apply it with N amount.According to the different ratio of organic and inorganic fertilizers,select the best fertilization program according to the yield,growth and development indexes.The results showed that compared with CK,inorganic urea(CT)and organic fertilizer:In the four fertilization treatments of inorganic fertilizer 3:7(MT)and OT(organic fertilizer),MT combined application significantly increased the yield by 3.54%,and the greenhouse gas comprehensive warming potential increased by 3.69%compared with CT treatment,but the difference was not significant,and significantly decreased by 17.06%compared with OT.Therefore,the combined application of inorganic N and organic fertilizer N is expected to achieve the goal of increasing production and reducing emissions under the premise of promoting high yield.In conclusion,on the basis of suitable sowing rate,the stable and increased yield of direct seeding rice could be guaranteed and greenhouse gas emission could be controlled by spraying1μmol/L EBR and applying organic fertilizer at flowering stage.It laid the theoretical foundation for the cultivation measures to ensure the stable yield of direct-seeding rice in northern China and inspired us to ensure the maximum environmental benefit while ensuring the economic benefit. |
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