| Wheat is one of the important food crops in China.Its planting area is widely distributed and its yield ranks the second place among food crops.Ensuring high and stable yield of wheat is of great significance to maintaining Chinese food safety.At present,the main problem in wheat production is poor seeding quality.Due to the poor sowing uniformity caused by the structure problem of seed metering device,the crowded wheat forms "lumps",leaving insufficient growth space for the wheat.And the missing sowing will lead to the phenomenon of seedling shortage in wheat field.The present transmission mechanism of wheat seeder makes it easy to slip when the straw is returned to the field,which affects the sowing effect,and the operation efficiency is low and the suppression effect is poor.It is difficult to fill the wheat seed in the high speed operation with the existing wheat seed metering device.Secondly,the wheat-com double cropping a year system was adopted in Huang-Huai-Hai area,and the lack of accumulated temperature before winter in wheat production resulted in insufficient tillering,which affected the number of ears per mu of wheat and limited the increase of wheat yield.Third,the production of agricultural machinery and agronomic integration is not sufficient.Through the mechanical analysis of the seeds,the structure of the seed distributor was designed,the EDEM discrete element software and Design-Expert 8.0.6 software were used to carry out simulation tests,and the parameters of different-speed single grain seed-metering device with seed-filling groove for wheat were optimized.In this paper,the optimized different-speed single grain seed-metering device with seed-filling groove for wheat was validated by bench test.Test results showed that when the speed was 60r/min,arc baffle was fixed on the metering device end cover,the filling ditch clapboard length,seed filling between the groove width,height of filling ditch were 8.00,6.00,5.00 mm,curved fender bulge angle was 42.68°,the seed spacing percent of pass was 81.67%,replay rate was 12.50%,the leakage rate was 5.83%,metering uniformity of seed variation coefficient was 32.32%,the result was consistent with the simulation test results.The narrow row spacing wheat seeder adopted an innovative different-speed single grain seed-metering deice with seed-filling groove for wheat,which improved the seed filling rate by using the principle of differential rate,and realized single seed seed-discharging by setting a partition in the furrow.The field test of the 7.5cm row spacing wheat planter was carried out,and the test results were basically consistent with the simulation test and the bench test results.The new narrow row spacing wheat seeder can achieve precise sowing of wheat at fixed row spacing,fixed dropping distance and fixed sowing depth,reduce soil water evaporation at seedling stage,increase tiller number before winter,and increase yield under the same water and fertilizer conditions.By means of mechanical analysis and structural analysis,the structure of the whole machine,the ditching device,the driving device and the line crushing device were designed and calculated respectively.Field tests of the wheat narrow row spacing seeder showed that:the wheat narrow row spacing seeder with row spacing of 7.5cm had good passability in straw returning field;the qualified rate of seed spacing,replay rate,missed rate,qualified coefficient of variation of seed spacing and qualified rate of seeding depth were all in line with the standard.On the premise of ensuring the operation quality,the optimized narrow row spacing wheat seeder can achieve a driving speed of 8.46km/h in the field,which improved the sowing efficiency.Adopting narrow row spacing wheat sowing technology can realize cover the field surface with wheat before winter,reduce soil moisture evaporation,and improve soil moisture content after winter:The average value of the soil moisture with stand distance of 7.5cm was 9.12%,and that of the wheat with stand distance of 15cm marks was 8.24%.According to the random sampling points,the number of tillers and rooting strips,dry matter weight and yield of wheat planted with row spacing of 7.5cm were all better than those of control wheat planted with row spacing of 15cm.The results of wheat field harvest test showed that the yield of 7.5cm row spacing was 9.22%higher than that of 15cm row spacing.In this paper,the field experiment of narrow row spacing wheat seeder was carried out for many years,and the increasing law of narrow row spacing wheat seeder with the change of longitude and latitude was preliminarily explored.Aiming at the problem of insufficient tillering before winter in wheat-maize double cropping area due to accumulated temperature,thus affecting the yield,this paper proposed and verified the wheat narrow row spacing sowing technique.The mechanism of wheat yield increase in narrow row spacing sowing was explored theoretically and practically,and it was verified that the wheat seeding technology of "shorten row spacing and even plant spacing" could give full play to the individual growth advantage of wheat and had the theoretical effect of "supplementing temperature with light".The field experiment of many years has proved that narrow row spacing wheat sowing technique has the remarkable effect of increasing tiller number and yield before winter.The technical model of "8×7cm row spacing for wheat+11cm row spacing for no-tillage maize planter" was put forward for wheat-maize double cropping system.By using navigation technology,precise alignment can be achieved,which can not only reduce the excessive power loss caused by root stubble breaking,but also reduce the disturbance of machines and tools to the soil during the com sowing operation,and play a positive role in improving the consistency of sowing and maintaining soil moisture.The results of field experiments show that the variation coefficient of uniformity of maize sowing depth by using navigation tractor and unmanned tractor is 7.26%. |
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