Parameter optimization and experiment of the negative pressure precision seed-metering device for wheat

In order to ensure the most reasonable distribution of wheat seeds in the field to improve seeding quality and uniformity,a set of negative pressure precision seed-metering device was designed,which shares a hollow shaft.Every seed-metering device can sow two rows of wheat.By the STAR-CCM+,the analysis of nephogram,vectogram and streamline graph showed that more ideal structural parameters of the seed-metering device are 0.5 mm width of the slit sucking seed(WSS),150-200 mm diameter of the seed-metering disc(DSD),2.0 mm axial depth of air chamber in the seed-metering disc(ADS),and arc-shaped cross-section shape of the ring groove sucking seed(CSGS).Single-factor test on the JPS-12 test-bed analyzed the influence of the CSGS,WSS,DSD,and ADS on the qualified index(Iq),multiple index(Imul),miss index(Imiss)and coefficient of variation of qualified seed spacing(CV).Through the orthogonal on the JPS-12 test-bed,it is found that the influence of vacuum negative pressure and seed-metering device shaft speed is significant on the Iq,Imiss and Imul.Based on these,the structural parameters of the seed-metering device were optimized.The DSD is 180 mm,the WSS is 0.7 mm,the ADS is 2.5 mm,and the CSGS is arc-shaped.The optimization seed-metering device was tested on the JPS-12 test-bed.The Iq is 86.66%,the Imiss is 5.09%,the Imul is 8.25%,and the CV is 24.50%.These testing results fully coincide with the standard JB/T 10293-2013 Specifications of single seed drill(precision drill).The seed-metering device meets fully the requirements for wheat precision seeding.

Soil physical properties,nutrients,and crop yield with two-year tillage rotations under a winter wheat-summer maize double cropping system

Winter wheat and summer maize were planted from 2015-2017 to study the effects of different rotational tillage patterns on soil physicochemical properties,crop yield,water content,and fertilizer utilization.The tillage treatments were designed as wheat subsoiling-maize no tillage(WS-MN),wheat rotary tillage-maize subsoiling(WR-MS),wheat subsoiling-maize subsoiling(WS-MS),and conventional wheat rotary tillage-maize no tillage(WR-MN)as a control.Among the four treatments,WS-MN and WR-MS were single-season subsoiling treatments,and WS-MS was a two-season subsoiling treatment.The average soil bulk density decreased by 7.6%in the single-and double-season subsoiling groups compared to the WR-MN group,and the total porosity and noncapillary porosity increased by 10.7%and 12.2%,respectively.Single-or double-season subsoiling treatment was not conducive to water storage in the 0-20 cm soil layer but increased the water content of the 20-140 cm soil layer,and the average soil water content of the 0-140 cm layer was increased by 11.6%in the two-growing season treatment groups compared with the WR-MN group.In WS-MS and WS-MN groups compared with the WR-MN group,the soil ammonium nitrogen content was increased by an average of 18.6%in 0-20 cm soil and 16.8%in 20-100 cm soil;soil nitrate-nitrogen content was decreased by 13.5%in 0-100 cm soil;total organic carbon and microbial carbon contents in the 15-30 cm soil were increased by 18.1%and 12.7%,respectively;and soil urease,catalase,and alkaline phosphatase activities were increased by 46.1%,15.2%,and 23.1%,respectively.Annual crop yield and water use efficiency increased by 8.9%and 15.0%,respectively,in both the single-and double-season subsoiling treatment groups.This study demonstrated the advantages of subsoiling tillage and suggested that it is suitable for crop cultivation in the Haihe Plain,China.

Study on positive-negative pressure seed metering device for wide-seedling-strip-seeding

In order to solve the problem of poor uniformity of wheat strip sowing,this paper designs a positive-negative pressure wheat wide-seedling-strip-seeding precision seed metering device,which adopts the roller structure with the principle of combined positive-negative pressure.Through theoretical analysis and relevant data,the structure of the seed metering device and the structure of the positive-negative pressure air chamber were designed.The internal flow field conditions were simulated by Fluent software under different structural parameters.The design of the seed holes was completed by analyzing the pressure cloud diagram and the flow velocity vector diagram,and the optimal combination of parameters was obtained and the influence law of negative pressure on the flow field was obtained.The effect of rotational speed on the flow field was studied by EDEM-Fluent coupling technique.In this paper,a three-factor and three-level response surface test was conducted on a JPS-12 test bench with Liangxin-99 wheat as the research object.The experiment was conducted with the rotational speed of seed metering device,the negative pressure of seed suction and the seeding height as factors,and the qualified index,the reseeding index and the miss-seeding index as evaluation indicators.Through the test,the optimal structure and working parameters of the seed metering device were determined as follows:the diameter of the seed hole was 2 mm,and the number of seed holes per row was 28,negative pressure was−3.5 kPa,rotational speed of seed metering device was 19 r/min,and seeding height was 180 mm.Validation test was carried out on the optimized seed metering device:the qualified index was 80.62%,the reseeding index was 9.22%,and the miss-seeding index was 10.16%,which reached the parameter indicator in JB/T 10293-2013 Technical conditions of single seed(precision)seeder and met the agronomic requirements for wheat wide-seedling-strip-seeding.

Effects of nitrogen fertilizer on root-shoot characteristics,grain yield and nitrogen use efficiency of different maize varieties in North China Plain

Excessive nitrogen(N)fertilizer application in crop production has resulted in a series of environmental issues in North China Plain(NCP).Breeding N-efficient maize varieties is one of the effective strategies to improve the N use efficiency of maize and reduce environmental pollution.This study designed an experiment for two maize varieties(‘Xian-Yu 335’[XY335]and‘Hua-Nong 138’[HN138])with three N-level treatments(0 kg/hm^(2),180 kg/hm^(2),300 kg/hm^(2),i.e.N0,N180,N300).The aim of the study was to determine the response characteristics of maize canopy structure,root morphology,and anatomical structure,as well as N uptake and utilization of N fertilizer.Results showed that grain yield,N use efficiency,and N harvest index of XY335 were higher 5.20%-13.68%,11.86%-19.11%,and 6.07%-3.33%than those of HN138,respectively.Compared with HN138,XY335 had a higher leaf area index and photosynthetic nitrogen-use efficiency.The root length,root length density,root absorption area,root absorption area,and root active absorption area of XY335 in each period were higher than that of HN138.The proportion of RCA of XY335 was significantly higher than that of HN138,which was 14.64%higher on average.In the future breeding process,the high N and low N double-high-efficiency varieties should pay more attention to the improvement of root cortex aeration tissue.