| In recent years,environmental problems,such as soil erosion,dust and dust storm,and ecological deterioration caused by traditional farming methods have attracted more and more attention.Conservation tillage technology is one of the important measures to solve these problems.Based on the analysis of conservation tillage at home and abroad,this paper focuses on conservation tillage technology and rice seeding precision.In view of the large number of laborers in rice cultivation in China,high labor costs,high soil moisture content in southern rice region,and high toughness large straw content.Combining technology and using the idea of strip rotary tillage in conservation tillage,a double-row upright mounting driven notched disk stubble ploughing technology was proposed.The rice no tillage precision dry direct seeder has been developed,and the key technologies and components of rice no tillage precision dry direct seeder have been deeply studied,including the measurement and analysis of soil related parameters,the shear characteristics of the rice stubble-soil complex in the southern rice area.On the basis of the discrete element simulation and soil bin test for three kinds of stubble ploughing disks,a kind of double-row upright mounting driven notched disk stubble ploughing device is designed,which has parallel four-bar profiling mechanism,cell wheel type seed metering device and elastic driven ground wheel all in one.Field performance test and production test were carried out.The main research results were as follows:(1)According to the requirements of conservation tillage in the paddy field in the south,the physical characteristics parameters of soil in the southern area were determined.The shear properties of rice-stubble soil complex was tested by self-made shear test device.The test results show that the relationship between ultimate shear stress and water content of the complex,soil bulk density,the diameter of rice stubble-soil complex and the shear velocity are quadratic polynomial,power function,quadratic polynomial,and logarithmic function respectively.The farther the shear position is from the stubble center,the smaller the ultimate shear stress is,and the smaller the cutting edge angle is,the smaller the ultimate shear stress is.In the four kinds of edge cutting tools,the ultimate shear stress of concave arc cutting edge is the smallest,when the cutting speed is 450 mm/min,the moisture content is 25%,the cutting edge angle is 15 degrees,the ultimate shear stress is the smallest.It provides a basis for designing stubble ploughing ditching device for rice stubble.(2)A discrete element model of soil and rice stubble in southern rice region was built,the simulation experiments of three kinds of stubble disk cutters,of the forward speed of the vehicle and of the speed of the cutter shaft were carried out,and verified by the soil bin test,the error of this two kinds of test is 12%~30%.According to the test results,the notched disk is used as the main stubble ploughing working part,and a stubble ploughing device is designed for parallel positive drive disk.Tests have shown that when the disk diameter is 435mm,Soil moisture content is between 20~25%,the rotating speed of the cutter shaft is 350r/min,the field straw cover rate is less than 0.6kg/m~2 and the speed of advance is 3.6 km/h,the cutting rate of the cutting straw and the cutting root can reach90%.(3)A rice no tillage precision dry direct seeder is designed,which can drive stubble ploughing cutter,ditching device,precision sowing,soil covering and compaction.Experiments were conducted on the stubble ploughing ability,ditching ability,seed metering,and ground wheels of the no-tillage dry direct seeding machine for rice.Field test results showed that the cutting rate and stubble ploughing rate of rice straw decreased when the forward speed of machine increased.But when the speed of the drive shaft is 450r/min,both the cutting rate of straw and the cutting rate of stubble are 95%at the forward speed of2.8 km/h,3.6 km/h and 4.3 km/h.In the opener performance test using the acute angle opener,obtuse angle opener,standard double disk,depth limited double disk and notched double disk.The deep limit double disk can loosen soil and cut out deep 1 to 3cm width 4to 6cm ditch for rice growth with good trafficability.In the slip rate test,when the soil moisture content was 23%and the straw coverage was 0.75kg/m~2,the slip rate was 3%to12%.Taking the forward speed as the influencing factor,the bench test and field test were carried out with the cell wheel type seed metering device.When the speed of advance was2.7~3.6 km/h,the qualified rate of seeds per hill was 90.57%and the rate of qualified distance of the hill distance was 88.77%.When the tractor's forward speed exceeds 3.6 km/h,the hill spacing pass rate is only about 80%in field test.The best operation parameters of machine tools are:advancing speed 3.6km/h,tool shaft speed 350 r/min.(4)The effect of mechanical no tillage direct seeding on the growth characteristics of rice and field production experiments were carried out.Tests have shown that the seedling emergence rate of mechanical no-tillage direct seeding is 10%higher than that of artificial no-tillage sowing,and no-tillage rice was planted in an orderly manner,and culverts were planted to meet the technical requirements for rice direct seeding.Compared with mechanical transplanting and conventional tillage machinery,the yield is reduced by about3%to 5%.Compared with artificial no tillage sowing,conventional mechanical direct seeding and mechanical transplanting,rice no tillage and dry direct seeding saves 80~100yuan per mu.In 2017,by using Yongyou 4149 variety,production test were conducted at Qianshanhong Farm,Datonghu District,Yiyang City,Hunan Province,the whole rice growth is balanced,plant height and panicle type were uniform,seed setting rate was high,and no obvious diseases,an average yield was 705.88kg per mu,the average output is 5%higher than the local average. |
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