Analysis Of Soil Chemical Fertility Index And Crop Yield Evolution And Influencing Factors In North China Under Long-term Fertilization

The level of soil fertility plays a decisive role in the growth and development of crops and agricultural production.Based on the data of the long-term monitoring of national cultivated land quality in North China in the past 31 years,this study analyzes the evolution of soil fertility at different monitoring stages in North China under conventional fertilization and the relationship between soil nutrient balance and soil fertility,and further analyzes the factors affecting crop yield.Provide a basis for scientific and rational fertilization in North China.The main results are as follows:1.Through data analysis of monitoring points in North China,we can see that after 31 years of evolution,the contents of organic matter,total nitrogen,available phosphorus and available potassium in the soil all showed an increasing trend.The contents of soil organic matter,total nitrogen,available phosphorus,and available potassium in the later period of monitoring?2004-2018?were significantly higher than those in the early period of monitoring?1988-1997?,and the changes in available phosphorus content were the most significant.Under the condition of long-term fertilization,the comprehensive soil fertility index of North China showed an increasing trend,among which,the soil fertility of Chao soil and cinnamon soil also showed an increasing trend throughout the monitoring period.The change of soil fertility in Chao soil is more significant,while the change trend of cinnamon soil is not obvious.The order of the score coefficients of the five fertility indicators in North China from large to small is:TN>SOM>AK>Olsen-P>pH,indicating that soil total nitrogen and organic matter content are the key factors affecting soil comprehensive fertility;monitoring soil comprehensive fertility attributes in the later period The score increased to 0.32,indicating that the soil comprehensive fertility in the late monitoring period has been significantly improved.Under the conditions of regular fertilization by farmers,after 31 years of long-term cultivation,soil fertility in North China has been significantly improved in the later period of monitoring.2.The nitrogen,phosphorus and potassium nutrients of farmland soils in North China are in a surplus state,and show an increasing trend as the year increases.The correlation between nitrogen balance and the change of soil total nitrogen is not significant.The annual change of available phosphorus is positively correlated with the annual average phosphorus surplus.The increase of available phosphorus in soil per 100 kg of phosphorus surplus is 4.33 mg.kg^-1.The annual change of available potassium has a positive correlation with the annual average potassium surplus.The increase of soil available potassium per 100 kg of potassium surplus is 2.76 mg.kg^-1.The relative yield of wheat and corn relative to soil Olsen P linear platform model in North China is 16.5 mg.kg^-1 and 12.69 mg.kg^-1,respectively.For soils with Olsen P content higher than 16.5 mg.kg^-1?agronomic threshold?but lower than 40 mg.kg^-1?environmental threshold?,the phosphorus level of Olsen should be maintained in these places,and the annual Phosphate application rate.There are three points in Shandong and Henan where the Olsen phosphorus content is higher than 40 mg.kg^-1,which may cause environmental pollution.Therefore,no phosphate fertilizer or a small amount of phosphate fertilizer should be added.3.The yield of wheat and maize under conventional fertilization in North China's farmland increased significantly compared with no fertilization,with the overall trend of increasing with time.Wheat yield reached 6651kg·hm^-2 in the later period of monitoring,which was a significant increase of27.58%?P<0.05?compared with the initial period of monitoring;maize yield was relatively stable throughout the monitoring period,and reached 8851 kg·hm^-2 in the latter period of monitoring.Using random forests to analyze the influencing factors of yield in North China,the quantitative relationship between climate factors,soil fertility and nutrient gains and losses on wheat and maize yields was initially clarified.The results showed that the major factors affecting wheat were nitrogen fertilizer 15.75%,pH14.83%,temperature 13.81%,and total nitrogen:13.15%.The most influential factors of maize are 16.28%of potassium fertilizer,15.55%of nitrogen fertilizer,11.76%of temperature and 11.24%of total nitrogen.