Effect Of Long-term Different Fertilizer Application Methods On Rice Yield And Soil Fertility In Yellow Clay Paddy Soil

In order to study the effects of long-term different fertilization methods on rice yield,soil nutrients,soil enzyme activity,soil carbon fraction,soil aggregate composition and the contents of carbon and nitrogen distribution in yellow clayey paddy soil,four treatments were conducted,including unfertilized control,chemical fertilizer alone(NPK),NPK plus cattle manure,and NPK plus rice straw.The results are as follows:1.Large macroaggregate(>0.25 mm)fraction contributed the largest percentage at different fertilizer treatments and soil depths.The proportion of>0.25 mm aggregate fraction was greater in the surface soil than in the subsurface soil.The proportion of large macroaggregate in the soil was significantly higher with NPK plus cattle manure than with NPK alone,while there was no difference between NPK and NPK with rice straw.Chemical fertilizer with cattle manure significantly improved the contents of carbon and nitrogen within all sizes of aggregates compared to the NPK alone.2.Compared withthe NPK alone,the NPK plus cattle manure increased the particulate organic carbon content of the surface soil and deep soil by 98.3%and 31.4%,respectively.The POC/SOC in the surface soil ranged from large to small:chemical fertilizer with cattle manure>chemical fertilizer with straw>chemical fertilizer alone≈unfertilized control.3.The NPK with cattle manure resulted in the highest contents of soil organic carbon,total nitrogen,available P,and NH4+.In addition,compared with chemical fertilizer alone,the combination of chemical fertilizer and cattle manure for 10 consecutive years increased the pH of the surface soil by 0.19 units.The NPK plus cattle manure increased soil available Fe,Mn,Cu,Zn and K+,Ca2+,Na+,Mg2+contents compared to chemical fertilizer alone.4.Fertilizer with straw significantly improved the surface soil sucrase activity by 23%(P<0.05)compared to chemical fertilizer alone,which was better than the fertilizer with cattle manure treatment.For 10 consecutive years,fertilizer with cow manure significantly improved surface soil urease,polyphenol oxidase,acid phosphatase and β-glucosidase activities by 9.2%,22.7%,24.5%and 23.2%,respectively,compared with fertilizer alone.Considered together,chemical fertilizer with cattle manure was the optimal fertilization mode for improving soil enzyme activities in low and medium yielding yellow clayey paddy soil.5.The fertilizer with cattle manure treatment was the most effective among the fertilizer application treatments from 2017 to 2020,with the highest average yield of 10.2 t/hm2.Compared with the fertilizer application treatment alone,the fertilizer with cow manure treatment increased the average rice yield by 10.4%(P<0.05),and the yield increase was higher than that of the fertilizer with straw treatment.Compared with other fertilizer treatments,the fertilizer with cattle manure treatment increased the SYI value of rice yield and reduced the coefficient of variation(CV).Overall,chemical fertilizer with cattle manure is the most effective fertilization mode for low and medium fertility yellow clayey paddy soil to improve rice yield,soil nutrients,organic carbon active fraction,aggregate composition,trace elements,saltbased ions and soil enzyme activity.