Effect Of Chemical Fertilizer Reduction On Soil Fertility Under Winter Wheat-Summer Sorghum System

At present,the amount of chemical fertilizers applied by farmer households in China has far exceeded the global average,and the problem of soil degradation is very serious.Therefore,it is imperative to control the amount of chemical fertilizers applied in our country.This experiment use the winter wheat-summer sorghum system as the research object,the effect of fertilizer reduction on the distribution of soil aggregate and its stability,soil physical and chemical properties and crop yield were analyzed,to find the best fertilizer amount for the central region of Shanxi Province,provide reference for reducing agricultural production cost,and provide a theoretical basis for further study of the impact of fertilizer reduction on soil degradation.The experiment set the conventional dosage(CK),75%of conventional dosage(UA75%),50%of conventional dosage(UA50%),25%of conventional dosage(UA25%)and no fertilization(NF).The main conclusions are as follows:(1)After winter wheat or summer sorghum harvested,the reduction of chemical fertilizers increased soil mechanical macroaggregates and water-stable macroaggregates(?0.25 mm)to a certain extent.NF and UA25%treatment significantly increased water-stable agglomeration.The MWD value and GMD value of the body significantly reduced the D value(fractal dimension);there was no significant difference in soil bulk density between UA25%(10-20cm)and UA75%(10-30cm)and CK treatment;NF and UA25%The treatment significantly increased the aerated porosity,total porosity and volumetric water content;the reduction of fertilizer application increased soil organic matter and total phosphorus content to a certain extent;NF and UA25%treatment reduced the available phosphorus content in 0-20cm soil layer;NF and UA50%treatment increased total nitrogen content.After harvesting of winter wheat,UA75%treatment significantly increased the MWD(mean weight diameter)value and GMD(geometric mean diameter)value of the 20-30cm soil layer;UA50%treatment reduced the gas-filled porosity and capillary pores of the 10-20cm soil layer.Degree and field water capacity;UA25%and UA50%increase the available nitrogen content;UA25%,UA50%and UA75%increase the content of available phosphorus and available potassium in 20-30cm soil layer.After harvesting in summer sorghum,UA75%treatment significantly increased the MWD,GMD,and available potassium content of 0.20cm soil mechanical stability aggregates.(2)NF,UA25%and UA50%treatments reduced the wheat kenel,and UA75%treatment increased the ear number,while UA75%treatment had no significant difference in wheat kenel,1000-kenel weight,actual yield and theoretical yield compared with CK.There was no significant difference in kenel weight per ear and theoretical yield between UA75%and CK in summer sorghum,but significant increase in 1000-kenel weight and actual yield(P<0.05),while the 1000-kenel weight and actual yield under other treatments were significantly lower than CK(P<0.05).(3)In summary,UA75%for the optimum fertilization treatment,not only to ensure soil fertility and crop yields,but also reduce the use of chemical fertilizers.But in order to further explore whether the amount of fertilizer can improve long-term soil fertility and increase Crop yields,the need Long-term positioning test for verification.