Study On The Infulence Of Tillage Methods And Fertilization Types On Soil Phosphorus Loss Risk

With the development of agricultural intensification,agricultural non-point sources have become an important source of phosphorus pollution in water bodies.Brittany as the spatial priorities of the development of agricultural intensification is located in western France,in which surface water is often affected by cyanobacteria blooms,and phosphorus is considered as the restrict nutrients.The agricultural protective management methods adopted in this area include ST and DS and the application of PM,which have been proven to increase the loss of soil dissolved phosphorus.Therefore,protective agricultural management is explored.The influence mechanism of different methods on the loss of soil dissolved phosphorus,it is particularly important to find and estimate the risk of soil dissolved phosphorus loss.The study took place in the typical European soil（silty non-calcareous soil）in Brittany,France.Based on sampling analysis and indoor simulated rainfall experiments,the influence of farming methods and fertilization types on soil were studied.Furthermore,the influencing mechanism of the risk of dissolved phosphorus loss was explored,and the best indicators for assessing the risk of dissolved phosphorus loss have been screened out.The main research contents and results of this thesis are shown as follows:（1）The impacts of soil management methods on the physicochemical properties of soil were studied by measuring the physicochemical properties of the surface soil.The results show that the tillage method had no significant effect on the content of Al-ox,Fe-ox and Si-ox.Moreover,DS treatment increased the content of N,C,P,and increased slightly fine particles and p H value in the surface soil.Compared with MF,application of PM increased the content of N,C and P in the surface soil.The application of PM with ST and DS increased the p H value,Al-ox,Fe-ox and Si-ox in the surface soil due to the content of N,C and P in PM was higher than that of MF.（2）The influence mechanism of tillage methods and fertilization types on the loss of dissolved phosphorus in surface soil was explored by the adsorption isotherm experiment.The dissolved phosphorus release risk shown DS>ST>CT,and the phosphorus release risk of different fertilization treatments was DS/PM>ST/PM>CT/PM>ST/MF>DS/MF>CT/MF,which indicates that DS treatment and application of PM significantly increased the risk of soil phosphorus release.The DS treatment and the application of PM increased the phosphorus content in the surface soil lead to the increase of the soil DPS.At the same time,although the phosphorus content of the DS treatment was higher than other soils,but the DPS was lower.The EPC₀ and WSP have a significant positive correlation with the soil phosphorus content.（3）The rule of the variation of dissolved phosphorus in runoff during rainfall was studied by using indoor simulated rainfall experiments.The results show that SRP was the main component of DTP in runoff,and its proportion was higher than68.03%,and which decreases with the increase of surface soil phosphorus content.The average concentration and flux of DTP,SRP and MURP in runoff were DS/PM>ST/PM>CT/PM>DS>ST>CT/MF>CT.Therefore,DS treatment and application of PM are not effective measures to reduce the loss of dissolved phosphorus from the soil.The MURP concentration was very high at the beginning of rainfall and the proportion of DTP in DS/PM（31.97%）and ST/PM（22.16%）treatments with high contents of soil C and P.Meanwhile,the the progress of decreased sharply of MURP concentration only was observed in DS/PM,ST/PM,and DS due to high contents of soil C and P.However,the concentration of SRP in runoff was relatively stable or slowly decreases,indicating that MURP was easier to release,and which cannot be ignored,especially in the soil with the high content of C and P.（4）The optimal indicators for evaluating the risk of the loss of dissolved phosphorus were selected combining the physicochemical properties of the soil and the simulated rainfall experiments.Compared with Q_max and DPS,EPC₀ and WSP,which directly characterize the phosphorus release from soil into water bodies.The WSP is optimal indicators because determination method was simple,and which is sensitive to the reaction of excessive fertilizers.In addition,the use of WSP can ignore the type of soil.Moreover,soil Dyer-P and Olsen-P content can be used as auxiliary parameters for phosphorus release risk assessment.