Experimental Study On Straw-barriers Removing Technology By Crushed Straw Inter-row Mulching Under Full Straw Croplands

In the rice-wheat rotation area with two crops a year,the residual straws in the field after rice harvest have the characteristics of large content and strong toughness,which leads to the problems such as seeds being planted on the straw,seeds being covered by the straw,and grass hanging in the soil parts of the machinery,when returning straw to the field and sowing.In this paper,based on the agricultural requirements of wide-width planting without straw barriers,the technology of removing straw barrier by inter-row mulching of crushed straw under full straw croplands was studied,and the key devices of were designed.Based on the evaluation index of the straw cleaned rate,the coefficient of the strip width and the stubble pass rate,combined with theoretical analysis and discrete element numerical simulation,the movement law,force and velocity changes of the straws in the process of straw crushing and inter-row mulching were studied.The effect of various factors on the performance of equipment were studied,and the feasibility and rationality of the device structure were verified by field experimentsThe main research work and conclusions of this topic are as follows:1.An electronic universal testing machine,an electric blast drying oven,and an external friction angle measurement test bench,et al were used to test the dimensions,density,external friction characteristics,moisture content and shear mechanical properties of crushed straw under full straw croplands.The reference range of the physical and mechanical properties of the stubble is obtained,which provides a theoretical basis for the subsequent discrete element simulation test..Based on the characteristics of crushed straw under full straw croplands and the conventional process of returning straw to the field and sowing,the technical scheme of removing straw barriers by inter-row mulching of crushed straw under full straw croplands was put forward.2.The structure and parameters of straw crushing device and straw diversion device were designed respectively.The structure of the slicer was determined to be 2 L-shaped knives and 1 straight shaped knife.There are 36 groups of crushing knives,the sliding cutting Angle of the fixed knife is 45 degrees,and the rotating speed of the knives shaft is 2000r/min;The influence of the radial matching distance between the straw diversion device and the straw crushing device on the performance of the equipment was analyzed theoretically.The kinematic analysis and the dynamic analysis were carried out for the slip-shear coupling motion of the crushed straws on the diversion device.Influence laws of the motion parameters and assembly parameters of the devices on the operation performance of the equipment were studied by single factor test.3.The DEM(Discrete Element Method)numerical simulation model of the inter-row process of crushed straw was established,combined with the Box-Behnken combined test design method,the straw removal rate and the coefficient of variation of the width of the seed belt were used as evaluation indicators.The straw diversion device carried out a virtual straw cleaning and straw performance test,studied the influence of key parameters on the movement of crushed straw particles during the inter-row covering process,and established two regression optimization models for each evaluation index and each factor.The results show that: as the diversion length of the device increases,the straw removal rate increases and the variation coefficient of the seed width decreases;as the radial distance increases,the straw removal rate increases first and then decreases,and the seed width varies The coefficient increases;as the diversion width of the device increases,the straw removal rate of the seed zone increases first and then decreases,and the coefficient of variation of the seed zone width decreases first and then increases.When the diversion length of the device is 300 mm,the radial distance is 19 mm,and the diversion width of the device is 298 mm,it has the best performance of straw cleaning and straw covering.The theoretical values of the straw cleaned rate and the variable coefficient of the strip width were 92.60% and 9.77% respectively,which were in agreement with the simulation results after parameter optimization.4.Combined with the current situation of the field of full straw retention,the rotary tilling device and the wheat sowing device were designed respectively,and the field experiment was carried out.The field experiment shows that the average straw cleaned rate was 92.58%,the variable coefficient of the strip width was 10.91%,and the average stubble pass rate was 91.47%,which is basically consistent with the simulation results.The results of growth comparison and yield measurement showed that compared with the conventional straw returning method,there was no obvious weak seedling phenomenon and the yield of the two methods was basically the same,which proved the feasibility of the technology of removing straw barrier by inter-row mulching of crushed straw under full straw croplands.