Study On Technology And Equipment For Direct-seeded Rice Using Film Mulching In Dryland

Direct-seeded rice is a simple and convenient cultivation method that saves water and labour without reducing grain yield,especially in case of dry direct-seeded rice.However,dry direct-seeded rice is susceptible to the effects of low temperature and grass damage.In this regard,dry direct-seeded rice mulching film has been widely studied with promising results;however,some problems remain.By analysing the problems in the technology and equipment employed for production of dry direct-seeded rice mulching film,this study investigated micro-ridge-furrow rainwater harvesting utilising degradable mulching film planting patterns.Moreover,it addressed the development of seeders for direct-seeded rice with film mulching in dryland,thus yielding novel techniques and equipment for the cultivation of dry direct-seeded rice.The main achievements of this study are as follows:(1)The micro-ridge-furrow rainwater harvesting with a degradable mulching film planting pattern eliminated white pollution and utilised natural rainfall.Field experiments were performed to evaluate traditional plastic film and degradable plastic film;additionally,a traditional flat-cropping planting pattern was examined along with a micro-ridge-furrow rainwater harvesting system employing a mulching planting pattern.The two planting patterns adopted the following row spacing configuration: a large row spacing was 250 mm,a small row spacing was120 mm,and the ridge height of the micro-ridge-furrow was 30–40 mm.Among the four experimental groups and one control group,the micro-ridge-furrow rainwater harvesting with the degradable mulching film planting pattern exhibited the best comprehensive performance;compared to the traditional flat-cropping mulching with a traditional plastic film,the soil temperature,germination rate,plant height,leaf area,dry mass in shoot,dry mass in root,and grain yield were increased by 10.91–19.5%,6.54-78.46%,59.38%,45.21%,34.3%,54.41% and14.28%,respectively.Therefore,the micro-ridge-furrow rainwater harvesting technique utilising degradable mulching film is the recommended planting method for dry direct-seeded rice.(2)The discrete element method,which is an important means of bulk material simulation and device design,was used in this study.In this method,the accuracy of the simulation parameters directly affects the reliability of the results.The discrete element simulation parameters of the interaction between the materials(stone,soil,and rice seed)and machine involved in the device design were measured and calibrated.A hand-held 3D scanner was used to construct an accurate particle model.The obtained simulation parameters and particle models could simulate the operating process of the device effectively.The difference between the simulation results and actual experiment results was less than 10%,indicating that the model was reliable,and the simulation results were credible.(3)The combined ‘micro-shovel + telescopic tube' seeding method proposed in this study realised the function of opening holes on the film and seeding under the film;it effectively curtailed the seeding blockage,reduced the missing seeding and reseeding rates,and improved the seeding quality.The operating mechanism of the device was examined,and the theoretical calculations and design of the device were completed.The diameter of the drum of the device was 410 mm,and 12 groups of micro-shovels and telescopic tubes were evenly distributed on the circumference of the drum.The length of the micro spade was 70 mm,and the contact degree of the device was 2.7868,which effectively reduced the slip rate during roller operation and ensured the stability of hole spacing.The kinematics of the device were simulated and analysed using the Solid Works Motion software.To further explore the seeding mechanism of the device,the Design Expert software was used to conduct a three-factor and three-level discrete element simulation experiment on the central composite design.Meanwhile,a regression model was established with the seeding depth as the response value;the forward velocity V,extension length of the telescopic tube h1,and oblique cutting height h2 were the model variables.The optimal combination of operating parameters was found to be V = 0.5 m/s,h1 = 15 mm,and h2 =15 mm,according to the agronomic requirements.The field experiment results under the optimal combination of operating parameters were 100%,4.84%,95%,83.33%,and 3.23% of the right rate of hill distances,stagger rate of film hill and hill,right rate of depth of sowing under film,right rate of seeds per hill,and rate of no seed hill,respectively,which met the industry standards and the requirements of low-speed sowing.(4)The fragmentation of soil clods in the seeding layer and the discharge of hard materials,such as stones,provided a good seedbed environment for the sowing and growth of rice.The diameter of the roller of the device was 210 mm,and the length of the stirring tooth was 100 mm.The stirring tooth was evenly distributed on the roller at a pitch of 1200 mm and a spacing of 40 mm,and the stones were discharged from the middle to the two ends of the device.In this study,the Box–Behnken design experiment was implemented using Design Expert,and discrete element method simulation experiments were performed.Mathematical models of the stone discharge rate,stone discharge efficiency,horizontal working resistance,and torque were established;the order of importance of the three influencing factors,i.e.soil depth,forward speed,and rotational speed,on the stone discharge rate,stone discharge efficiency,horizontal working resistance,and torque,respectively,were as follows: soil depth > forward speed >rotational speed,soil depth > rotational speed > forward speed,soil depth > forward speed >rotational speed,and soil depth > forward speed > rotational speed.The optimal combination of working parameters in the simulation experiments was as follows: forward speed V = 0.5 m/s,soil depth H = 61 mm,and rotate speed n = 110 r/min.Under the optimal combination of working parameters,the simulation verification experiment results revealed the following: stone discharge rate y1 = 85.65%,stone discharge efficiency y2 = 35.47 pieces/m,horizontal operation resistance y3 = 719.23 N,and torque y4 = 174.89 N·m.The field experiment for verification of the optimal combination of working parameters indicated a stone discharge rate of 77.23%,which was consistent with the simulation verification experiment results;thus,the model was determined to be reliable.(5)Soil covering is an important part of dry direct-seeded rice in northern China.To ensure a good lighting rate of the mulching film,the method of covering the soil in the rows was adopted.The drainage ring was transformed into hollow drainage holes to reduce large soil blocks or stones falling over the seeds.The size of the drainage holes was adjustable within a certain range,as per the requirements.To perform continuous experimental design and construct the soil quantity model in this study,the forward speed,working angle,and soil depth were considered the factors and the soil quantity was considered the response value.Field experiments were conducted to obtain the soil covering amount in each experimental group.According to the analysis of the soil quantity model,the order of importance of the influence of each factor on the response value was as follows: working angle >soil depth > forward speed.Under the condition wherein the soil quantity requirement was satisfied and forward speed V was 0.5 m/s,the combination of operating parameters obtained was as follows: working angle = 21° and soil depth = 50 mm.Under this combination of operating parameters,the qualified rates of the soil quantity on the film edge and on the seed hole were 93% and 96%,respectively,both of which met the agronomic requirements and design objectives.(6)To verify the operating performance of the device and provide a basis for its improvement,field performance and seedling emergence experiments were carried out.The average soil compactness of the 0–100 mm soil layer and soil moisture content during sowing were 133.18 k Pa and 15.35%,respectively.During operation,the combination of working parameters of the device was as follows: the forward speed was 0.5 m/s,the rotate speed of the stone roller was 110 r/min,the soil depth was 61 mm,and the extension length of the telescopic pipe was 15 mm.The field experiment results showed that the right rate of soil covered on film side,right rate of hill distances,stagger rate of film hill and hill,right rate of depth of sowing under film,right rate of seeds per hill,and rate of no seed hill were 91.67%,95.56%,4.26%,95.56%,91.11%,and 3.23%,respectively,which met the application requirements.Seedling information was collected 23 days after sowing,and the average emergence rate was 76.73%.In summary,the micro-ridge-furrow rainwater harvesting technology with a degradable mulching film planting pattern alleviated white pollution,improved the utilisation rate of natural rainfall,and increased the grain yield.The developed seeder for dry direct-seeded rice mulching film achieved the design objectives and met the relevant industry standards as well as the agronomic requirements of actual production.