Efects Of Different Cropping Patterns On Soil Fertility,Bacterial Diversity And Greenhouse Gas Emissions In Paddy Fields

There are many disadvantages in double cropping rice areas,such as single cropping system,declining multiple cropping index,excessive application of chemical fertilizers and pesticides,declining soil fertility,and large greenhouse gas emissions.In order to make full use of winter light,temperature,water,heat and other natural resources,give full play to the role of winter green manure and winter grain and oil crops,optimize the planting system and variety structure to form a high-yield and high-efficiency planting mode under multi-cropping and multi-crop conditions,improve the annual grain production capacity,promote the efficient use of agricultural resources,improve soil ecology,and reduce greenhouse gas emissions,the study was conducted from October 2016 to October 2018 at the Experimental Field of Jiangxi Agricultural University Science Park for 2 years.In the field trial,five different cropping modes were set:CRR（Chinese milk vetch-Rice-Rice）,CRI（Chinese milk vetch-Early Rice-Sweet Potato||Soybean）,RRR（Rape-Early rice-Late rice）,RRI(Rape-Early Rice-Sweet potato||Soybean,and PRR（Potato-Early rice-Late rice）,which aims at in-depth study on the effects of different cropping patterns on soil chemical properties,soil bacterial community,rice yield and greenhouse gas emissions in paddy fields with the purpose of screening a high yield,stable yield,greenhouse gas planting mode for emission reduction and sustainable soil development.The main conclusions of the study are as follows:（1）Chinese milk vetch-Early rice-Sweet potato‖Soybean is beneficial to the accumulation of organic matter,organic carbon,total nitrogen,alkali nitrogen and nitrate nitrogen.The Chinese milk vetch-double cropping rice model is beneficial to the accumulation of ammonium nitrogen and alkali nitrogen.Rape-Early rice-Sweet potato‖Soybean is beneficial to soil pH and effective phosphorus.The rape-double-season rice model is conducive to the accumulation of soil available potassium.（2）Winter Chinese milk vetch can increase the richness of bacterial communities,but have no significant effect on diversity.The paddy-upland rotation method can increase the diversity of bacterial communities,but reduce the richness of bacterial communities.The main environmental factors affecting the changes of bacterial community are ammonium nitrogen,nitrate nitrogen,organic matter,organic carbon,available potassium,and available phosphorus.（3）Compared with other winter treatments,winter Chinese milk vetch treatment performed better in terms of effective panicle number,grain number per panicle and 1000-grain weight of rice,and winter Chinese milk vetch and rape with paddy-upland rotation were all conducive to the improvement of seed setting rate and 1000-grain weight of early rice.Chinese milk vetch-Early rice-Sweet potato‖Soybean can effectively increase the annual yield of rice,which is 9.37%¹8.01%higher than that of other treatments.（4）The contribution of CO₂ to global warming potential is dominant,followed by CH4 and N₂O.The annual global warming potential and emission intensity of Chinese milk vetch-early rice-sweet potato||soybean decreased by 1.87%and 6.35%respectively compared to the previous year,which showed the best performance among the five models and had better emission reduction potential.