| In order to solve the problems of low fertilizer utilization rate and serious agricultural nonpoint source pollution caused by the unreasonable application of chemical fertilizers and herbicides in the process of rice planting,this paper innovatively proposed a fertilizer and drug reduction mode of "one-time centralized reduction and deep application of slow-release fertilizer&mechanical weeding"(hereinafter referred to as "SFDM mode"),and carried out the study on the application effect and applicability of SFDM mode.In view of the poor operation effect of the existing fertilization and weeding equipment,the independent fan pneumatic fertilizer discharge system and wedge-shaped rake wheel mechanical weeding device were studied and designed,the accurate line operation control system was developed,the rice line fertilization and weeding machine was developed,the four-year positioning test is carried out.and the soil environmental quality evaluation system was constructed.The main work and achievements of this paper were as follows:(1)The effects of different weeding methods and different fertilizer and drug application modes on Rice Yield and quality were studied,the planting economic benefits were calculated and analyzed,and the applicability of SFDM mode in drill-seeded rice production was explored,which showed that it had certain advantages in stabilizing rice yield,improving rice quality and controlling cost.(2)The pneumatic fertilizer discharge system of independent fan was developed.Using FLUENT simulation,the inclination angle of branch pipe θf and the height from the branch road to the bottom of the main pipeline h was optimized with the goal of air flow velocity and air distribution uniformity,after optimization θf was 30° and h was 20 mm.The mechanical weeding device of wedge rake wheel was designed,the simulation of mechanical soil interaction effect based on ADAMS-EDEM coupling was carried out,and the included angle of wedge tooth surface was optimized θα was 130°.(3)A path tracking control method based on Pure Pursuit-Cascade PID control was proposed.The state equation of the total heading deviation of agricultural machinery at the preview point was constructed by using the Pure Pursuit control theory.The stability of the expected angle tracking control was improved by setting the Cascade PID control loop.The path tracking test results showed that this method has good adaptability and robustness to different paddy field environments.The variation range of transverse deviation was all within±4 cm at the working speed of 3 km/h,4 km/h and 5 km/h,and the standard deviation of lateral deviation were less than 1.5 cm.(4)A method for extracting the center line of seedling row suitable for drill rice was proposed.The difficulty of image segmentation was reduced by the region of interest extraction method based on average gray statistics.The image filtering method based on area threshold and "close first and then open" was adopted to effectively eliminate the inter row noise of seedlings,improved the edge detection accuracy of subsequent seedling rows,and improved the fitting accuracy of seedling row centerline by screening the edge feature points of seedling rows.The results of extraction accuracy test showed that this method shows good seedling row extraction accuracy in each weeding operation period,and the average error was less than 1.7 cm.Based on the principle of planar four-bar mechanism,the executive device of row deviation correction was designed,and the construction of row deviation correction control system was completed by using PID algorithm and hydraulic servo control technology.(5)A row-controlled fertilizing&weeding machine for rice cultivation was developed and a field experiment was carried out.The results of fertilization performance test showed that the coefficient of variation of fertilizer discharge consistency in each row was less than 3%in the range of 10 r/min～30 r/min motor speed.When the target fertilization rates were 150 kg/hm2,250kg/hm2 and 350 kg/hm2,the deviation of fertilization rate was less than 5%;During the test,there was no fertilizer strip breaking area,and the qualified rate of lateral distance and depth of fertilization met the standard requirements.The results of weeding performance test showed that the weeding rate of machines and tools was more than 80%and the seedling injury rate is less than 4%under different weeding periods and different working speeds(3 km/h,4 km/h and 5 km/h).(6)The soil environmental quality evaluation system based on multi method fusion at the field scale was constructed,and six soil environmental quality evaluation indexes including soil bulk density,organic matter,pH,total nitrogen,microbial biomass carbon and quinclorac acid were determined.A soil environmental quality evaluation scheme combining fuzzy comprehensive evaluation method based on factor analysis and hierarchical cluster analysis method based on Ward method was proposed.The results showed that compared with the conventional fertilizer application mode,SFDM mode can improve the soil environmental quality by improving the soil physical,chemical and biological indexes and reducing pesticide residues. |
PDF Full Text Request