Effects Of Different Nitrogen Levels And Tribenuron-methyl On Soil Properties And Crop Yields In The Growing Season Of Winter Wheat

Chemical fertilizers and herbicides are widely used in agricultural ecosystems to increase crop yields.They always coexist for a long time in farmland soils.Excessive application of chemical fertilizers and herbicides may cause soil fertility reduction,then leading to lower food production.However,previous studies were focused on their respective effects,rather than their interactive effects.In this study,field pot trials were conducted in winter wheat growing season,and the experiment used a randomized block designs with multiple levels of fertilization and herbicides to explore the following scientific issues:(1)How fertilization and herbicides and their interactions affect soil physicochemical properties,soil biological properties and crop yields.(2)Which combination of fertilization and herbicide can increase wheat yield and contribute to the sustainable development of soil health.We measured soil physicochemical properties,biological characteristics,crops and weeds performance at the growing stage of wheat.the main results as follows:(1)During the wheat harvest period,low level nitrogen chemical fertilizer and highlevel organic fertilizers significantly increased the soil organic carbon contentand the total nitrogen content,and the effect of low level nitrogen fertilizer was the highest,indicating that lower nitrogen fertilizers are more conducive to soil carbon and nitrogen accumulation than high-nitrogen fertilizers.However,the high content of available nitrogen and dissolved organic nitrogen under high-level fertilizers treatment may suggest the high risk of nitrogen loss;Low level nitrogen fertilizer,especially for low level organic fertilizer,significantly increased the soilmicrobial biomass carbon and nitrogen,which suggesting low level nitrogen are beneficial to the accumulation of available nutrient pool in the soil.Fertilization significantly affects the content of soil PLFAs: during the harvest period of wheat,low-nitrogen organic fertilizer significantly increased soil total biomass,bacterial biomass,actinomycete biomass,gram-positive and negative-bacterial biomass,and mycorrhizal fungal biomass,and significantly reduced fungal-bacteria ratio,but fertilization did not significantly affect fungal biomass.For the interaction of fertilization and herbicides,high dose herbicides significantly increased available nitrogen and dissolved organic nitrogen at high nitrogen levels,and soil available nitrogen was significantly lower under low-nitrogen organic fertilizer and low herbicide dose combinations than other treatments.Under the condition of low nitrogen fertilizer application,spraying low-dose herbicides will be beneficial to the increase of soil microbial biomass.Under high nitrogen level fertilizer application,spraying herbicides will be even more unfavorable to soil microbial biomass and thus increasing soil N losses.(2)Low nitrogen level fertilizer and organic fertilizers significantly increased wheat yield components.High nitrogen level fertilization increased wheat yield but significantly reduced wheat grain weight,which was not conducive to the formation of wheat quality.For the interactions between fertilization and herbicides,the application of herbicides,especially the application of high-dose herbicides,under low nitrogen level fertilizers will be beneficial to the formation of wheat yield and quality,Applying low dose herbicide or no herbicide under low-nitrogen organic fertilizer treatment significantly reduced the number of wheat spikes,which would be beneficial to the formation of wheat yield.(3)Herbicide treatment significantly reduced the total biomass,diversity index andrichness index of weeds.Fertilization treatment significantly increased weed density and total biomass,but high level fertilizers,compared to other treatments,significantly reduced weed diversity,evenness,and richness.Organic fertilizers,especially high-nitrogen organic fertilizers,have higher species diversity and richer weeds than high-nitrogen fertilizers.In summary,our results showed that applying low-nitrogen fertilizer or organic fertilizer can increase crop yield and soil fertility during the winter wheat growing season.Maintaining certain weed diversity in farmland ecosystems is conducive to the formation of crop yields.Therefore,in North China Plain,the farmland management measures will be recommend for winter wheat,that is,the combination of low nitrogen level chemical or organic fertilizers and low dose herbicide will be conducive to the formation of crop yields and quality and soil health.