Study On Soil Mechanical Compaction By Harvesting Machinery Under Rice-wheat Rotation

With the continuous improvement of the level of agricultural mechanization and the development of science and technology,the quantity of agricultural machinery in China increases every year,which greatly enhances the efficiency of agriculture.However,the extensive use of agricultural implements will cause one or more soil compaction,which will lead to changes in the soil cultivation structure,which will result in compaction of the soil.The effect of compaction caused by agricultural machinery is much greater than the self-recovery of the soil.Capability has led to a reduction in soil productivity.However,most of the existing soil compaction studies are concentrated on sand and loam,therefore,few people in the clay compaction research,Jiangsu region rice harvest season rainy,resulting in paddy soil moisture content high,viscous,soil carrying capacity is far lower than in the north,agricultural machinery in such soil in the work,track or tyre subsidence seriously,caused serious damage to the soil.Therefore,based on the field survey,the physicalp:irameters and mechanical parameters of the soil were irieasured,and the spatial distribution of soil parameters in Jiangsu area was described,and the relationship between several and the subsidence quantity of the harvester was analyzed.The main content of the thesis is as follows;In order to accurately measure the damage of harvesting machinery to soil micro-landform5 in this study,the general design scheme of the laser micro-topography tester based on the contact micro-geomorphology test method is proposed,and the three-dimensional drawing and the mapping of the third-dimension diagram Processing and selection of key components and the preparation of data acquisition procedures.The results show that the concentration of subsidence in summer is within 3cm,the subsidence in winter is concentrated in the 4?1 Ocm,and the winter distribution and subsidence are obviously higher than that in summer.The selection of sampling points,scientific and reasonable dispatched are important ways to improve the efficiency of field investigation.So this paper compares and analyses the five-point sampling method in soil sampling method,the 21-point sampling method based on five-point method and the nine-point sampling method based on grid method.The results show that the five point method can only meet the requirement of sampling point error less than 5%,but can not achieve the goal of describing the spatial variability of subsidence of the whole block,however,the 21 and nine-point method can satisfy the sampling precision to describe the spatial variability,but considering the labor cost and time synthetically,Finally,a more easily nine-point sampling method was selected as a sampling methodology for the field survey of micro-geomorphology.In order to reflect the compaction effect of harvester on farmland soil,the soil physical parameters(water content,bulk density,total porosity)and mechanical parameters(soil compaction)and the compaction area of the plots were studied before and after the harvester operation.The results showed that the soil bulk density was bigger,the total porosity decreased,and the water content decreased after compaction.The soil parameters of two seasons in winter and summer are obviously different,in which the water content in winter is concentrated in the 30%?40%,and the summer is mainly distributed between 10%?20%,It can be seen from the soil compaction that the bottom of the plow appears near 12.5cm,and the soil compactness of the plow is increased more than 25%after the winter harvester walking,and the increase in summer is not obvious due to the high soil bearing capacity.The statistical results of the walking compaction area of the harvester show that over 45%of the farmland area is affected by the compaction of the harvester in the whole plot.In order to study the bearing capacity of field soi1,the relationship between subsidence quantity and soil parameters was analyzed by linear and exponential method,and the stress-strain curves and the pre-consolidation pressure of different plate diameters were carried out by the field in-situ plate subsidence test platform.The results show that both the subsidence and soil parameters conform to the exponential fitting,and the determining coefficients are in accordance with the requirements.From the results of the flat subsidence test,the phase consolidation pressure decreases with the increase of the plate diameter and finally stabilizes.This paper provides a preliminary theoretical basis for explaining the severe soil compaction subsidence caused by harvesting machinery.