Study On Leaching Of Nitrogen And Phosphorus From Different Layers Of Typical Cinnamon Soil In Shanxi Province

Excessive application of nitrogen(N)and phosphate(P)fertilizers have increasingly caused nonpoint source pollution in agricultural production.Understanding N and P leaching is critical for reducing environmental pollution.The isotherm adsorption and desorption test using the typical cinnamon soil layers(cultivation,leaching,calcium,clay,and parent)of Shanxi Province as the research object was adopted.The phosphorus adsorption and desorption capacity of different layers was analyzed by the determination of the adsorption and desorption strength and the Langmuir equation fitting.Indoor soil column simulated leaching test was used.The migration characteristics and dominant factors of nitrogen and phosphorus in five different occurrence layers and three different types of cinnamon soils were identified by measuring the amount of nitrogen and phosphorus leached under the same conditions of fertilization and irrigation.In addition,the leaching differences of nitrogen and phosphorus in different types of cinnamon soils had also been determined.The main findings were as follows:(1)The Langmuir isothermal adsorption equation fitted the isothermal adsorption curves of phosphorus in the five soil layers,and the amount of phosphorus absorption was calcium layer > clay layer > parent layer >cultivation layer > leaching layer.The calcium layer had the highest phosphorus fixation capacity and the lowest desorption rate.The desorption capacity and desorption rate of the leaching layer were the highest.(2)There was the largest phosphorus pool in the calcium layer,and the clay layer had the largest adsorption binding energy and buffer capacity.The phosphorus pool,adsorption binding energy and buffer capacity of the leaching layer were the minimum.The cultivation layer had the highest adsorption saturation,so it was at risk of phosphorus leaching.(3)The clay content was significantly positively correlated with the maximum phosphorus adsorption amount and negatively correlated with the phosphorus adsorption saturation.The organic matter content was negatively correlated with soil adsorption binding energy.(4)The leaching amount of total soluble nitrogen was parent layer > clay layer > leaching layer > cultivation layer > calcium layer.The leaching amount of total phosphorus was cultivation layer > leaching layer > parent layer > clay layer > calcium layer.The risk of nitrogen leaching in the clay layer and parent material layer was higher than that in the other three layers,while phosphorus leaching was more likely to occur in the cultivation layer.(5)The leaching amount of total soluble nitrogen in the three types of soil was leaching cinnamon soil > leaching-calcium cinnamon soil > calcium cinnamon soil,and the leaching of nitrogen was more likely to occur in leaching cinnamon soil.The total phosphorus leaching amount of calcium,leaching-calcium and leaching cinnamon soil was 0.57 mg,0.57 mg and 0.56 mg,respectively,which did not reach the significant level.(6)Nitrate nitrogen was the main leaching form of nitrogen in soil.Soluble phosphorus was the main leached form of soil phosphorus,and orthophosphate was the main leached component of soil phosphorus.(7)The soil organic matter content,cation exchange capacity(CEC),and clay content affected the migration and transformation of soil N and P.There was a significant positive correlation between organic matter and N and P leaching.The CEC and clay content were negatively correlated with N and P leaching.