Effects Of Different Fertilization Measures On Crop Yield And Soil Comprehensive Fertility In Purple Soil During 39 Years

Fertilization measures are the main anthropogenic factors affecting crop productivity and soil fertility quality in agricultural fields.To explore the effects of long-term different fertilization measures on the spatial-temporal evolution patterns of soil fertility and crop productivity in purple soil areas,this study used the data from 39 a(1982～2021)located fertilization trials as the basis,and applied factor analysis method,correlation coefficient method,Nemoro index method,principal component cluster analysis method and gray correlation analysis method to comprehensively evaluat the soil fertility quality of CK(no fertilization),N(nitrogen fertilization),NP(nitrogen and phosphorus fertilization),NPK(nitrogen,phosphorus and potassium fertilization),M(organic fertilization),MN(organic fertilization+nitrogen fertilization),MNP(organic fertilization+nitrogen and phosphorus fertilization)and MNPK(organic fertilization+nitrogen,phosphorus and potassium fertilization),and the quantitative relationship between soil comprehensive fertility index(IFI)and crop productivity was established to clarify the best fertilization measures and the evaluation methods to the comprehensive fertility of purple soils in southwest China.The main research results are as follows:(1)Long-term fertilization significantly increased crop yield compared to no fertilization treatment(P<0.01).The rice yield,wheat yield,and system productivity(sum of rice and wheat yields)all showed MNPK>MNP>NPK>NP>MN>M,N>CK.The rice yield and system productivity of M were significantly greater than those of N(P<0.05).The evolution process of crop yield for N,M,MN and CK shows an increasing trend,and the growth coefficient of system productivity were N(69.7)>M(55.6)>MN(44.3)>CK(36.4).The purple soil under rice-wheat rotation system has a strong self-recovery ability,and the rice yield and its stability are significantly greater than that of wheat.(2)The soil p H,total potassium and available potassium were in a decreasing trend,while organic matter,total nitrogen,available nitrogen and total phosphorus were in an increasing trend under long-term different fertilization measures;The soil organic matter,total nitrogen,available nitrogen,total phosphorus and available phosphorus of MNPK,NPK and MNP had similar increasing trends,and their contents and increasing trend coefficients were larger.With the increase of soil depth,the contents of organic matter,total nitrogen and available nitrogen showed a gradual decrease process,and the contents of all nutrients in the soil of the profile layer showed the highest in MNPK and the lowest in CK;There is a highly significant negative correlation between soil available phosphorus and p H(R=-0.595**).There were highly significant correlations(P<0.01)among soil p H,organic matter,total nitrogen,available nitrogen,total phosphorus and available phosphorus,while total potassium showed a highly significant positive correlation(P<0.01)with soil p H,available nitrogen and available potassium.The purple soil in southwestern China has abundant potassium content,and long-term non-application of phosphorus fertilizer is the main reason for soil phosphorus deficiency,and the response of available phosphorus to phosphorus fertilizer is more sensitive than that of total phosphorus.(3)The IFI evolution trend coefficients evaluated by factor analysis,correlation coefficient method,and Nemoro index method all showed MNPK>NPK>MNP,NP>M>CK,MN>N.the trend coefficient of IFI evolution by Nemoro index method was NP>MNP,and the trend coefficient of IFI evolution by correlation coefficient method was MN>CK.Nitrogen fertilizer is the main factor of crop yield increase,but long-term single application of nitrogen fertilizer is not conducive to soil fertilization.Soil organic matter,total nitrogen,available nitrogen,total phosphorus,available phosphorus had extremely significant positive correlation with rice yield,wheat yield,system productivity and IFI(P<0.01);There is a highly significant negative correlation between soil p H and IFI(P<0.01),and a significant negative correlation with rice yield(P<0.05).The IFI of the three evaluation methods showed a highly significant positive correlation with crop yield(P<0.01),and the IFI of the Nemoro index method was consistent with the evolution trend of crop yield and soil fertility quality,making it more suitable for evaluating the comprehensive fertility of purple soil in southwestern China.(4)With the Nemoro index method was used to evaluate the soil comprehensive fertility,the IFI of CK,N,and MN(IFI of 1.33,1.34 and 1.41)for low fertilizer and low yield showed a decreasing trend;the IFI of M(IFI of 1.48)for low fertilizer and low yield,NP(IFI of 1.62)for medium fertilizer and medium yield,MNP,NPK and MNPK(IFI of 1.69,1.73,and 1.80)for high fertilizer and high yield showed an increasing trend.The comprehensive scores of various principal components of soil quality under long-term different fertilization measures are MNPK(214.56)>NPK(139.00)>MNP(99.81)>M(15.50)>NP(6.33)>MN(-118.49)>CK(-171.20)>N(-185.50).Grey correlation analysis was conducted on soil quality evaluation indicators,and the soil quality evaluation results of MNPK,NPK and MNP were the best,belonging to the level of I(excellent);The soil quality evaluation results of M take second place and belong to the level of III(general);The soil quality evaluation results of NP are poor,belonging to the level of IV(poor);The soil quality evaluation results of CK,N and MN are the worst,belonging to the level of V(extreme).Long-term balanced application of chemical fertilizers or chemical fertilizers with organic fertilizers can not only achieve high and stable crop yields,but also fertilize the soil,and the best effect of chemical fertilizers with organic fertilizers.