Phosphorus Pool Characteristics And Risk Assessment Of Phosphorus Leaching In Soils Under Two Crop Systems In North China

As one of the three elements of fertilizer,phosphorus can participate in the synthesis of nucleic acid,phospholipid and ATP in plants and is an indispensable element of lives.At present,the imbalance between supply and utilization of phosphate fertilizer resources still exists.On the one hand,however,there is a finite amount of phosphorus in the world,and at current levels of exploitation,the world's phosphorus reserves would last a maximum of 50 to100 years.On the one hand,according to the current mining scale,the world's limited phosphorus reserves can only support agricultural production for 50 to 100 years at most.The shortage of natural resources of phosphate fertilizer will be an important factor restricting the future agricultural development.On the other hand,since 1961,the application amount of phosphate fertilizer in the soil has been increasing year by year.Phosphorus has poor mobility in the soil,and is easy to interact with other substances in the soil and immobilize,resulting in its low utilization rate in the current season.This not only results in the waste of phosphorus resources,but also poses a great threat to the ecological environment.In order to improve the utilization rate of soil phosphorus fertilizer,solve the problems of resource consumption and environmental pollution simultaneously,and realize the rebalancing of supply and demand and utilization of phosphorus fertilizer resources,it is necessary to carry out the analysis of soil phosphorus reservoir characteristics and the risk assessment of soil phosphorus leaching.This study with winter wheat-summer maize and potato two cropping systems under the system of four soil types?chestnut soil in Inner Mongolia,fluvo-aquic soil in Hebei province,cinnamon soil in Henan province and loessial soil in Shaanxi province?as the research object,using the Meta-analysis combined with experimental study,explores the overall on behalf of the north area of typical soil phosphorus library?total phosphorus,Olsen-P,Ca Cl₂-P?characteristics,and evaluates reasonably the risk of phosphorus leaching.The main research results are as follows:?1?The contents of total phosphorus,Olsen-P and Ca Cl₂-P in chestnut soil of Inner Mongolia,fluvo-aquic soil in Hebei province,cinnamon soil in Henan province and loessial soil in Shaanxi province were obtained quantitatively,and the change characteristics of typical soil phosphorus pools in north China and their relationship with soil chemical properties were clarified.The average value of total phosphorus content in four types of typical soils under two crop systems was 0.82 g?kg^-1,the average value of Olsen-P content was 26.13 mg?kg^-1,the average value of phosphorus activation coefficient was 3.2%,and the average value of Ca Cl₂-P was 0.46 mg?kg^-1.Compared with the second soil survey,the average total phosphorus content increased by 17%,and the average Olsen-P content increased by 2.9 times.For example,the average total phosphorus content of chestnut soil in potato growing areas was0.56 g?kg^-1,the average Olsen-P content was 19.87 mg?kg^-1,the average phosphorus activation coefficient was 3.4%,and the average Ca Cl₂-P content was 0.37 mg?kg^-1.Compared with the second soil survey,the average total phosphorus content increased by 47%,and the average Olsen-P content increased by 5.17 times.The average value of total phosphorus content in fluvo-aquic soil under the winter wheat-summer maize crop system was 0.78 g?kg^-1,the average value of Olsen-P was 29.86 mg?kg^-1,the average value of phosphorus activation coefficient was 3.7%,and the average value of Ca Cl₂-P was 0.63 mg?kg^-1.Compared with the second soil survey,the mean values of total phosphorus and Olsen-P increased by 28%and444%,respectively.Similarly,the average contents of total phosphorus and Olsen-P in cinnamon soil,loessial soil increased by 14%and 140%,46%and 342%,respectively.It indicates that the total phosphorus content of soil increases continuously with the passage of time,especially the Olsen-P content.Phosphorus activation coefficient is an important index of soil phosphorus availability.It was found that there was a significant negative correlation between soil p H and phosphorus activation coefficient,and an extremely significant negative correlation between soil p H and Ca Cl₂-P.On the contrary,organic matter was positively correlated with total phosphorus,Olsen-P and Ca Cl₂-P contents of soil.?2?Meta-analysis was used to verify the change characteristics of soil phosphorus reservoir,and the effects of different fertilization patterns on phosphorus reservoir characteristics were investigated.Using meta-analysis to analyze the characteristics of soil phosphorus pool under the influence of fertilization measures and fertilizer types,it was found that compared with no fertilization,fertilization significantly increased soil total phosphorus and Olsen-P contents by 50%and 308%,respectively.The results are consistent with those obtained in?1?,which confirm that fertilization has a positive effect on soil phosphorus storage capacity.It was found that the increase of total phosphorus content of soil by applying chemical fertilizer and organic fertilizer?single application or organic and inorganic application?was 32.5%and 63.5%respectively.Application of organic fertilizer can increase the Olsen-P content of soil by 298%,which is 2.4 times higher than that of chemical fertilizer.It indicates that the increase of phosphorus storage capacity by applying organic fertilizer is higher than that of single application of chemical fertilizer,and the increase of Olsen-P content is more significant.?3?The critical value of phosphorus leaching loss in typical soils in north China was quantitatively characterized by using the double-line model.According to the relationship curve between Olsen-P and Ca Cl₂-P contents,the critical values of phosphorus leaching in each soil were obtained.The results showed that the critical values of phosphorus leaching for chestnut soil,fluvo-aquic soil,cinnamon soil and loessial soil were 25.35,54.25,26.79 and65.28 mg?kg^-1,respectively.When the Olsen-P content of soil was greater than the critical value of phosphorus leaching,phosphorus leaching was found in 18.3%chestnut soil,11.4%fluvo-aquic soil,14.7%cinnamon soil,and 7.8%loessial soil.