Effects Of Different Land Use Pattern On Organic Nitrogen Fractions

Nitrogen transformation and cycling is not only the most important dynamic process of nutrient cycling in farmland ecosystem,but also an important component of geochemical cycling.Organic nitrogen is the main component of soil nitrogen,which is of great significance to plant growth and farmland ecological environment.Therefore,this paper combines field survey,chemical experiment detection and data analysis to obtain the spatial distribution characteristics of soil organic nitrogen fractions under different land use patterns in Jinhua area,discusses the occurrence state and transformation and migration of organic nitrogen in soil-environment system,and analyses the correlation between organic nitrogen fractions and influencing factors in natural environment,and uses multiple lines.Sex regression equation fitted the effects of soil properties and nutrient elements on organic nitrogen fractions,which provided scientific basis for maximizing nitrogen utilization rate,reducing the loss probability of nitrogen loss and leaching,improving farmland soil production function,improving soil nutrient status and healthy development of ecological environment.The main results are as follows:（1）The content of organic nitrogen fractions in surface soil of vegetable field,orchard,nursery field,tea garden and paddy field was 0.93².70 g·kg^-1,the content of organic nitrogen fractions in wasteland was the lowest,and the content of organic nitrogen fractions in paddy field was the highest.The content of acidolysis organic nitrogen is higher in total nitrogen.Ammonia nitrogen and amino acid nitrogen are the main fractions of acidolysis organic nitrogen,the contents are 0.27⁰.75 g·kg^-1 and 0.34⁰.93 g·kg^-1,respectively.Aminosaccharide nitrogen is the least,and the content of non-acidic nitrogen is close to or more than unknown nitrogen.On the whole,the contents of acid-soluble nitrogen fractions in different types of farmland were ranked as amino acid nitrogen>ammonia nitrogen>hydrolysable unidentified nitrogen>amino sugar nitrogen.The content of soil organic nitrogen fractions was significantly different under different land use patterns（P<0.05）,which was greatly affected by land use patterns.（2）The ratio of soil organic nitrogen to total nitrogen in the different land use patterns changed significantly.The ratio of acid-soluble organic nitrogen to total nitrogen ranged from68.45%to 80.55%,which was much higher than the ratio of non-acid nitrogen to total nitrogen.The content of ammonia nitrogen and amino acid nitrogen in surface soil accounted for higher than that of other acid-soluble organic nitrogen fractions.The proportion of unknown nitrogen in total nitrogen was less than 20%,and the proportion of non-acid nitrogen in total nitrogen changed significantly.In addition to tea gardens,the content of organic nitrogen in other types of farmland is ranked as amino acid nitrogen>non-acid hydrolysablenitrogen>ammonia nitrogen>hydrolysable unidentified nitrogen>amino sugar nitrogen.（3）The content of organic nitrogen fractions in different types of farmland changed obviously,and the content of organic nitrogen in paddy field and tea garden soil was higher.The content of acidolysis organic nitrogen fractions showed a decreasing trend with the deepening of soil layer,while the content of non-acidic nitrogen had no obvious regularity.Comparing the soil layers,it was found that the content of organic nitrogen in the 10²0 cm layer decreased most rapidly,and the content of organic nitrogen in the lower layer was even higher than that in the upper layer.The content of organic nitrogen fractions in different types of farmland was significantly different in the profile（P<0.05）,and changed significantly in different types of farmland in the same soil profile.（4）In the profile distribution,the content of ammonia nitrogen and amino acid nitrogen in the organic nitrogen component accounted for 18.68%²4.31%and 22.11%²9.66%,which dominated the acid-soluble organic nitrogen component.And the proportion of total nitrogen generally decreases with the increase of soil depth.The ratio of non-acid nitrogen to total nitrogen is opposite.The ratio of amino sugar nitrogen and hydrolysable unidentified nitrogen to total nitrogen has no obvious characteristics.In the same soil layer profile,the ratio of organic nitrogen to total nitrogen in different land use patterns changed significantly.（5）The change of organic nitrogen content in soil and its decomposition and transformation are complex.Overall,most of the total nitrogen conversion was allocated to acid-soluble nitrogen,ranging from 66.38%to 81.19%.The distribution of amino acid nitrogen and ammonia nitrogen in acid-soluble organic nitrogen fractions was higher than that in other fractions.The conversion ratio of non-acid hydrolysable nitrogen was fluctuated greatly,and the distribution ratio of organic nitrogen fractions in different types of farmland was different.（6）Correlation analysis showed that soil organic nitrogen fractions and impact factors,present different degree of mutual relations between the fractions of organic nitrogen,organic matter,total nitrogen and acid solution appears extremely significant positive correlation（P<0.01）,in addition to the acid nitrogen,the nitrogen composition and pH form very significant negative correlation（P<0.01）,the organic nitrogen fractions and water content,C/N were not significant（P>0.05）.Multiple linear regression analysis showed that acid solution fractions are affected by acid solution of total nitrogen,but amino acid nitrogen and total nitrogen is are factors affecting the rest of the fractions of organic nitrogen content,pH is a negative factor affecting the acid hydrolysis of ammonia nitrogen,amino acid nitrogen,amino sugar nitrogen and unknown nitrogen content.Non-acid hydrolysable nitrogen is difficult to be decomposed into organic nitrogen fractions,and pH does not participate in the establishment of multiple regression equations.