Research On Decomposition Law Of Green Manure In Fragrant Pear Orchard Of Southern Xinjiang By Different Mechanical Returning Methods

Southern Xinjiang is the main production area of forest fruit industry,which promotes the development of local rural economy and the construction of ecological environment.For a long time,non-standard management mode existed in the orchard planting process in southern Xinjiang,resulting in soil degradation,fruit quality and yield decline,poor economic benefits and other problems,which is not conducive to the healthy development of forest fruit industry.Therefore,the orchard in southern Xinjiang gradually adopted the management model of green manure planting and green manure returning to the field to improve such problems.The orchards in southern Xinjiang have a large area and a wide range.At present,the orchards in southern Xinjiang have a variety of mechanical methods of green manure return,such as shallow rotation by rotary tiller,deep rotation,crushing and overturning,etc.The soil improvement and fertilizer cultivation effects of green manure return to the field under different returning methods are different.Therefore,in order to explore the decomposition characteristics and soil nutrient change rule of different green manure overturning and pressure returning methods,this experiment will select three common green manure returning machinery in southern Xinjiang orchard,and use nylon mesh bag method to artificially simulate the length and depth of green manure returning during the three mechanical returning to explore the decomposition and nutrient release characteristics of rape.The experimental soil after mechanical return of rapeseed was collected regularly to analyze the dynamic changes of soil nutrients after rapeseed return to field,providing theoretical reference for efficient return and full utilization of green manure in orchards in southern Xinjiang in a short period of time.The main research results are as follows:（1）The net bag method was used to simulate the decomposition process of rapeseed under different returning treatments.It was found that the cumulative decomposition rate of rapeseed was proportional to the returning time,and the decomposition rate was inversely proportional to the returning time.The decomposition process of rape under each treatment can be divided into three stages:rapid decomposition stage（0-14d）,moderate decomposition stage（14-56d）and slow decomposition stage（56-150d）.Under different treatments,the rapeseed decomposition rate was the fastest when the length of rapeseed was 6cm（F1）and the depth of rapeseed was 10cm（S2）,and the cumulative decomposition rate of rapeseed was the highest when the length of rapeseed was 6cm（F1）and the depth of rapeseed was 10cm（S2）at the end of 150d.（2）The net bag method was used to simulate the decomposition process of rapeseed under different returning treatments.It was found that the release law of various nutrients in the decomposition process of rapeseed was similar to that of dry matter in rapeseed,with the characteristics of fast release in the early stage and slow release in the later stage.When the length of field was 6cm（F1）and the depth of field was 10cm（S2）,or the length of field was6cm（F1）and the depth of field was 18cm（S3）,the cumulative release rate of all nutrients in rape was higher.The release rates of all nutrients in rape showed the order of K>N>C>P,and the release of K was basically complete in the early stage of decomposition.（3）The first-order kinetic equation Y_t=a(1-e^-bt),compared with the power function equation and logarithmic equation,could better fit the change law of cumulative decomposition rate and nutrient cumulative release rate of rape with time under different returning methods.（4）In the short term,the contents of soil organic matter,alkali-hydrolyzed nitrogen,available phosphorus,available potassium and soil pH value changed in different degrees after the rape was returned to the field by different mechanical methods.The pH value decreased first and then increased,and the contents of other indexes increased first and then decreased.Compared with the 0d,the increase and decrease range of each index was in the order of available potassium>alkali-hydrolyzed nitrogen>available phosphorus>organic matter>pH value.There were significant differences between the indexes of each treatment and the control group（P<0.05）,among which,the increase and decrease range of soil indexes was more obvious under the treatment of green manure grinding rotary tillage integrated machine（T3:length of returning 9cm,depth of returning 10cm）.Based on the integration of the results of the mesh bag simulated rape decomposition test and the rapeseed return test with different mechanical methods,it can be seen that when the mechanical return method of green manure to the field of rapeseed in fragrant pear orchard of southern Xinjiang is present,the operation requirements are as follows:When the length of returning field is 6cm（F1）or 9cm（F2）and the depth of returning field is 10cm（S2）,the decomposition and nutrient release of rape are the best.The results of this study can provide theoretical reference for the subsequent improvement and development of green manure returning machinery in orchards in southern Xinjiang.