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This study aimed to establish, calibrate and verify a discrete element method (DEM) particle model of rototilled soil particles for investigating the particle migration and machine soil interaction mechanism when forming micro-ridge seed beds by the rapeseed direct seeding machine. The soil type was rototilled yellow-brown soil, which is widely distributed in the mid)lower Yangtze River. The study consisted of two parts: parameter calibration and application verification. The parameter calibration followed these steps: (1) testing the soil plastic limit and selecting the contact model accordingly; (2) measuring the basic parameters, such as the soil particle size distribution and repose angle after rototilling; (3) using the EDEM particle filling and particle factory function to reproduce the particle bed based on the particle size distribution; (4) solving the optimal contact parameter combination by using factorial design, steepest ascent method, and quadratic orthogonal rotation regression method. The application verification test used two sets of structural parameters of a rotary-cutting micro-ridge seedbed preparation device (RMSD, which is the key device of rapeseed direct seeding machine to forming micro-ridge seed beds) to conduct DEM simulation and field tests, and compared the particles migration patterns and the landform after operation. A soil plastic limit tester was used to determine the plastic limit of the soil. The plastic limit of the sampled soil was 24.79%, which is close to the upper limit of the moisture content for rototiller operation. Hence, the Hertze-Mindlin (no slip) contact model was selected. The particle size range and mass ratio of the rototilled soil particles from the rapeseed direct seeding machine were sieved and counted. The rototilled soil particles of each particle size range were scanned and modelled using the EinScan-Pro 3D scanner. Based on the 3D models of the soil particles, the EDEM particle filling function was used to reconstruct the particles with different particle sizes and mass ratios. The soil particles bed was re-generated in EDEM according to the particles` mass ratio. The contact parameter calibration test includes a two-level factorization test, steepest ascent test, and quadratic orthogonal regression test, respectively, to perform a preliminary analysis of test factors and eliminate non-significant tone system, narrow down the range of factors, and solve the combination of contact parameters. The contact parameter calibration test uses the repose angle as an indicator. The two-level factorization test showed that the impact restitution coefficient had no significant effect on the repose angle; the rolling friction coefficient, static friction coefficient, and the interaction term of the two significantly affected the repose angle. The steepest ascent test was designed based on the model regression equation from a two-level factorization test. The steepest ascent test reduced the range of factors tested 0.20-0.60 (static friction coefficient) and 0.05-0.40 (rolling friction coefficient) to 0.32-0.51 and 0.11-0.27, a reduction of greater than 50%, providing effective support for obtaining accurate regression models. Since the restitution coefficient had an insignificant effect on the repose angle, the impact recovery coefficient was set to an intermediate level of 0.350 for the quadratic orthogonal regression test. The calibrations resulted in restitution, static friction and rolling friction coefficients of 0.350, 0.351 and 0.257, respectively. The verification consists of simulations and field tests conducted on the RMSD with two structural parameters. The field verification test used the PIVlab tool and the Trimble TX8 3D laser scanner to obtain the soil particles` velocity and the land-form. The simulation of 2 structural parameters was consistent with field experiments. The error of micro-ridge distance is 8.25%, which increases with the number of vanes of RMSD. The calibration parameters are accurate. This paper provides fundamentals for the DEM simulation and structural improvement for rapeseed micro-ridge seedbed preparation device. [ABSTRACT FROM AUTHOR]

Deep rotary tillage is a hot and difficult problem in the research field of tillage machinery. Scholars at home and abroad have made a lot of explorations on deep rotary tillage technology and theory. At present, deep rotary tillage is mainly realized through the following three methods: 1) plowing depth was increased by directly increasing the diameter of the knife roller; 2)Two-axis stratified rotary tillage. Two rows of knife rollers are set in front and back for the first rotary tillage of the former one, and then the latter one for further rotary tillage; 3) subsoil reverse rotary tillage, that is, deep tillage is achieved by sinking the knife shaft below the surface. These three methods can achieve the goal of deep rotation tillage, but they all have their own disadvantages. Considering the characteristics of oblique rotary tilling and reverse tilling, the principle of oblique submerged reverse rotary tillage is put forward in this paper, which can not only destroy the soil by “pull” but also reduce the heaping soil as well as make the central transmission box easy to sink subsoil, and realize low energy consumption deep tilling with short knife. The back-up amount of tilting rotary tilter directly depends on the performance of tilting rotary tilter. Oblique submerged reverse rotary tillage is put forward in this paper. It is important to study the mechanism of throwing soil to optimize the design of this machine. Oblique submerged reverse rotary tillage is a new type of rotary tillage. It is important to study the mechanism of throwing soil to optimize the design of inclined subterranean reversal rotary tiller. In this paper, a simulation model of SPH (Smoothed Particle Hydrodynamics) is established on the LS-DYNA platform. The model is used to reverse the rotary tillage in different working conditions. The simulation results show that the post-soil rate of different layers in the reverse rotation of different parameters under different parameters is obtained. The post-soil rate of different layers obtained under the same conditions and the post-casting of different layers obtained by the indoor soil trough test are obtained. The soil rate was compared and analyzed. The verification results show that the maximum simulation error is 12.50%, the minimum simulation error is 0.20%, and the average error is 3.09%. Applying the corrected simulation model, the oblique angle, the forward speed, the depth of the submerged soil and the speed of the cutter roll were taken as the four factors of the test, and three levels were taken for each factor. Afterwards, the throwing rate was measured and the tilt was set. The virtual orthogonal experiment of reversing the rotary tillage and throwing soil was conducted. The test results were analyzed by the range analysis method, the variance analysis method and the regression analysis method. The data analysis results show that the primary and secondary order of the impact rate after the impact is the subsoil depth and the oblique angle, the forward speed and the knife roll speed. The influence on the post-lost rate is not significant, and the mathematical relationship model of the subsoil depth, the oblique angle and the post-lost rate is obtained. According to the results of virtual experiment, the physical prototype of the inclined submersible soil reverse rotation tillage machine was optimized and the field experiment was carried out. The field test results showed that the reverse rotation of the inclined subterranean soil successfully solved the problem of the rotary tiller bracket and the central transmission box. And with the R175 standard rotary cultivator, the tilling depth of 20 cm was achieved, and deep tilling using short knife was realized in this paper. [ABSTRACT FROM AUTHOR]

As a kind of rural residential regions, scattered residential regions in the fields are the inevitable outcome of large-scale habitat-based regions that cannot meet the needs of agricultural planting activities. The rapid development of scattered residential regions in the fields would reduce the effective cultivated land region and cause waste of land resources. Therefore, in order to clarify the influence mechanism of scattered residence pattern in Heilongjiang reclamation region, taking 859 Farm under the jurisdiction of Jiansanjiang Administration Bureau of Heilongjiang reclamation area as the research region, this paper used spatial analysis, coupling degree model, multivariate statistical analysis to explore the influence mechanism of scattered residence pattern. The results show that: 1) 859 Farm has both large-scale habitat-based regions and scattered residential regions in the fields. The number of habitat-based regions is relatively small and the land use mode is relatively intensive. However, some farmers still own scattered residential regions in the fields while owning large-scale habitat-based regions, and the number is relatively large, about 15 times that of large-scale habitat-based regions. It also shows the spatial differentiation characteristics of dense central region and sparse east and west, resulting in extensive residential land use in the study region, reducing the effective cultivated land region and intensifying the contradiction between supply and demand of farm land resources. 2) The average value, the maximum value and the median value of the coupling degree between scattered residential regions in the fields and agricultural planting activities in the study region are 0.52, 1.00 and 0.60, respectively. The coupling degree between the systems is relatively high. Moreover, the spatial differentiation characteristics of coupling degree between scattered residential regions in the fields and agricultural planting activity system and the distribution state of kernel density show spatial consistency. Agricultural planting activities are related to scattered residential regions in the fields to a certain extent, so cultivated land structure, cultivated land region, field fragmentation, tillage radius and deviation distance are the influencing factors of scattered residential regions in the fields in the study region. 3) The main factors influencing the pattern of scattered residential regions in the study area are the attributes of cultivated land (tillage radius, cultivated land region, fragmentation degree of cultivated land) and the status of cultivated land use (cultivated land structure), while the influence of deviation distance is slightly small and is not the main factor. Cultivated land structure and tillage radius are the direct factors, while cultivated land region and field fragmentation are the indirect influencing factors. The mismatch between cultivated land structure and tillage radius makes the study region show the regional characteristics of gathering in the middle and dispersing in the east and west. [ABSTRACT FROM AUTHOR]

Evaluation of the healthy productivity of cultivated land in China, analysis of key problems of different regions that endangers cultivated land health is of great significance to explore sustainable cultivated land utilization path and safeguard national food security and ecological security. The evaluation of cultivated land healthy productivity should be executed base on integration of existing evaluation indicators system and evaluation method achievements and clarification of key factor states and driving processes that affecting cultivated land health from the perspective of cultivated land components. And interaction characteristics between cultivated land health and cultivated land productivity should be analyzed by coupling them with each other. In this paper, we selected 65 counties (cities) nationwide as research regions with considering the difference of climate conditions in different regions of China, and used 5 categories of indicators including topographic characteristics, soil properties, tillage conditions, environmental conditions and biological characteristics to present the cultivated land health status. And on that basis, we defined critical health threshold and critical sub-health threshold of different indicators by analyzing counties’ indicator standard deviation convergence characteristics and scoring rules. We divided all pilot counties into three statuses: Health, sub-health and unhealth, and analyzed spatial distribution features of counties with different health status. Furthermore, regional climate conditions indicator, cultivated land natural conditions indicator and tillage technique level indicator had been synthetically integrated to evaluate the productivity of cultivated land, and regional cultivated land health-productivity interaction characteristic had been analyzed. Experimental result showed that counties whose cultivated land in sub-healthy or unhealthy status expressed significant regional features, and the key factors of limiting cultivated land health were different among pilot counties. On the one hand, the sub-health status cases caused by inferior farming conditions indicator were more common (accounting for nearly 40% of pilot counties) than other indicators, which was not only manifested by serious fragmentation of cultivated land and imperfect farmland infrastructure, but also reflected the urgent requirement for promoting high-standard farmland construction. On the other hand, the form of biological characteristics was severe, indicating that under the interaction of climatic conditions, soil structure and tillage technology, the ability of cultivated land to guarantee the healthy growth of animals was facing degradation. Furthermore, through coupling analysis of cultivated land health and cultivated land productivity, we divided the cultivated land healthy productivity characteristics of pilot counties into six categories: “health-high productivity”, “health-low productivity”, “sub-health-high productivity”, “sub-health-low productivity”, “unhealth-high productivity” and “unhealth-low productivity”, and respectively analyzed the regional farmland protection directions for each category. “Sub-health/unhealth-high productivity” type was widely distributed, which was the core region for implementation of “storing grain on land and storing grain in technology” strategy in China. Therefore, it is necessary to give consideration to the health and productivity of cultivated land in this region, and strengthen the research and practice on methods to improve the health of cultivated land. This study provides scientific basis for improving cultivated land healthy productivity and provides effective support for designing protection paths of cultivated land resources in different regions. [ABSTRACT FROM AUTHOR]

Evaluation of the healthy productivity of cultivated land in China, analysis of key problems of different regions that endangers cultivated land health is of great significance to explore sustainable cultivated land utilization path and safeguard national food security and ecological security. The evaluation of cultivated land healthy productivity should be executed base on integration of existing evaluation indicators system and evaluation method achievements and clarification of key factor states and driving processes that affecting cultivated land health from the perspective of cultivated land components. And interaction characteristics between cultivated land health and cultivated land productivity should be analyzed by coupling them with each other. In this paper, we selected 65 counties (cities) nationwide as research regions with considering the difference of climate conditions in different regions of China, and used 5 categories of indicators including topographic characteristics, soil properties, tillage conditions, environmental conditions and biological characteristics to present the cultivated land health status. And on that basis, we defined critical health threshold and critical sub-health threshold of different indicators by analyzing counties’ indicator standard deviation convergence characteristics and scoring rules. We divided all pilot counties into three statuses: Health, sub-health and unhealth, and analyzed spatial distribution features of counties with different health status. Furthermore, regional climate conditions indicator, cultivated land natural conditions indicator and tillage technique level indicator had been synthetically integrated to evaluate the productivity of cultivated land, and regional cultivated land health-productivity interaction characteristic had been analyzed. Experimental result showed that counties whose cultivated land in sub-healthy or unhealthy status expressed significant regional features, and the key factors of limiting cultivated land health were different among pilot counties. On the one hand, the sub-health status cases caused by inferior farming conditions indicator were more common (accounting for nearly 40% of pilot counties) than other indicators, which was not only manifested by serious fragmentation of cultivated land and imperfect farmland infrastructure, but also reflected the urgent requirement for promoting high-standard farmland construction. On the other hand, the form of biological characteristics was severe, indicating that under the interaction of climatic conditions, soil structure and tillage technology, the ability of cultivated land to guarantee the healthy growth of animals was facing degradation. Furthermore, through coupling analysis of cultivated land health and cultivated land productivity, we divided the cultivated land healthy productivity characteristics of pilot counties into six categories: “health-high productivity”, “health-low productivity”, “sub-health-high productivity”, “sub-health-low productivity”, “ill-health-high productivity” and “ill health-low productivity”, and respectively analyzed the regional farmland protection directions for each category. “Sub-health/ill-health-high productivity” type was widely distributed, which was the core region for implementation of “storing grain on land and storing grain in technology” strategy in China. Therefore, it is necessary to give consideration to the health and productivity of cultivated land in this region, and strengthen the research and practice on methods to improve the health of cultivated land. This study provides scientific basis for improving cultivated land healthy productivity and provides effective support for designing protection paths of cultivated land resources in different regions. [ABSTRACT FROM AUTHOR]

Warming climate has been a global concern. Methane is an important greenhouse gas. Double rice cropping system in Hunan province contributes a large proportion of the national rice production. In this study, we studied the effect of agricultural managements of rice on methane emissions from double cropping paddy fields in Hunan Province, China based on Meta-analysis method. Only studies designed as side-by-side paired field experiments were included in this study. Field management practices, treatments, and controls were described in detail in each study, and the location of the experiment was provided. If seasonal accumulative CH4 emission fluxes were not directly provided, these values were calculated by multiplying time and mean CH4 emissions by the measurement period. A total of 53 published peer-reviewed papers published before 2018were obtained by reference retrieval. From them, 840 groups of data were drawn. The management measures included crop rotation, symbiosis ecosystem, tillage, nitrogen fertilizer input, organic manure and residue retention. The control and treatment groups were fallow versus winter crops, paddy-rice system versus rice-duck and rice-fish systems, conventional versus no tillage, no fertilizer-N input versus fertilizer-N input, no manure input versus fertilizer-N and manure input, and fertilizer-N input versus residue retention. Natural log of response ratio was used as the effect size in the random effect meta-analysis. Results showed that CH4 emissions from both early and late rice accounted for 97.9% of annual CH4 emissions, and more CH4 emissions from late rice was observed than that for early rice. In the double rice cropping system, adding winter crops could significantly increase CH4 emissions from double rice season by 43.88% (P < 0.05) compared to winter fallow. Moreover, the increase in methane emissions from early rice was significantly higher than that from late rice. Symbiosis ecosystem of rice (i.e., with ducks or fishes) and adopting no-till significantly decreased CH4 emissions by 37.02% and 26.84% (P < 0.05), respectively. The decrease in the emission from early rice field was much higher than that from late rice field. As for yield-scaled emission, application of N fertilizer decreased yield-scaled CH4 emissions by 40.01% (P < 0.05) mainly due to the yields increased by 73.87% (P < 0.05). Additionally, organic fertilizer application and residue retention increased 68.11% and 71.80% (P < 0.05) of yield-scaled CH4 emissions without impacting the rice yield. The results suggested adopting symbiosis ecosystem rice production or no-till along with optimized N input is conducive to balancing rice yield and CH4 emissions from fields with double rice cropping system in Hunan province. [ABSTRACT FROM AUTHOR]

Warming climate has been a global concern. Methane is an important greenhouse gas. Double rice cropping system in Hunan province contributes a large proportion of the national rice production. In this study, we studied the effect of agricultural managements of rice on methane emissions from double cropping paddy fields in Hunan Province, China based on Meta-analysis method. Only studies designed as side-by-side paired field experiments were included in this study. Field management practices, treatments, and controls were described in detail in each study, and the location of the experiment was provided. If seasonal accumulative CH4 emission fluxes were not directly provided, these values were calculated by multiplying time and mean CH4 emissions by the measurement period. A total of 53 published peer-reviewed papers published before 2018were obtained by reference retrieval. From them, 840 groups of data were drawn. The management measures included crop rotation, symbiosis ecosystem, tillage, nitrogen fertilizer input, organic manure and residue retention. The control and treatment groups were fallow versus winter crops, paddy-rice system versus rice-duck and rice-fish systems, conventional versus no tillage, no fertilizer-N input versus fertilizer-N input, no manure input versus fertilizer-N and manure input, and fertilizer-N input versus residue retention. Natural log of response ratio was used as the effect size in the random effect meta-analysis. Results showed that CH4 emissions from both early and late rice accounted for 97.9% of annual CH4 emissions, and more CH4 emissions from late rice was observed than that for early rice. In the double rice cropping system, adding winter crops could significantly increase CH4 emissions from double rice season by 43.88% (P < 0.05) compared to winter fallow. Moreover, the increase in methane emissions from early rice was significantly higher than that from late rice. Symbiosis ecosystem of rice (i.e., with ducks or fishes) and adopting no-till significantly decreased CH4 emissions by 37.02% and 26.84% (P < 0.05), respectively. The decrease in the emission from early rice field was much higher than that from late rice field. As for yield-scaled emission, application of N fertilizer decreased yield-scaled CH4 emissions by 40.01% (P < 0.05) mainly due to the yields increased by 73.87% (P < 0.05). Additionally, organic fertilizer application and residue retention increased 68.11% and 71.80% (P < 0.05) of yield-scaled CH4 emissions without impacting the rice yield. The results suggested adopting symbiosis ecosystem rice production or no-till along with optimized N input is conducive to balancing rice yield and CH4 emissions from fields with double rice cropping system in Hunan province. [ABSTRACT FROM AUTHOR]

Potato is one of the fourth staple food crops in China. Medium tillage operations such as loosening soil, crushing soil, soil cultivation and weeding during the early seedling and middle growth stages of potatoes have a great influence on potato yield. The main functions of mid-tillage include loosening soil, enhancing soil permeability, preserving soil moisture and drought resistance, improving soil physical properties, improving soil fertility and eliminating weeds, and mid-tillage can resist lodging and increase crop yield. Potato mid-tillage production has a large amount of work and its operation process is limited by growing crops. Therefore, it is of great significance to develop a potato mid-tillage machine with high working efficiency and good operation effect. Aiming at the problems of low soil breaking rate, weeding rate and poor soil cultivation effect of traditional hoe-shovel type cultivator under the condition of soil cohesion and compaction, a driving potato cultivator which integrates the functions of deep loosening and crushing soil, weed eradication, side deep fertilization, soil cultivation and ridging is designed in this paper, the key parts of the machine and the structure of the deep loosening shovel, soil crusher and soil cultivator are designed and analysed. On the basis of design and analysis, field experiments are carried out. The machine is mainly composed of deep loose soil device, soil conservation device, fertilization device and transmission system. Eight blade dishes are installed symmetrically on the left and right sides of the blade shaft. Each blade dish is fixed with two soil breaking blades. The length of the soil breaking blade is 242 mm, the width of the soil breaking blade is 40 mm and the thickness of the soil breaking blade is 10 mm. In order to adapt to different kind of soil conditions, the adjustment range of the subsolier is 150-250 mm, the height of the subsolier is 560 mm. The test results show that the soil breaking rate of driving-type cultivator is 95.1%, weeding rate is 96.3% and the injury rate is 1.2%, the soil bulkiness is 49.3%, and the fuel consumption is 13.2 kg/hm2, which met the relevant performance evaluation indicators. Compared with the traditional hoe-shovel type cultivator, the soil breaking rate of, weeding rate and soil bulkiness of the driving-type cultivator increase by 3.3%, 3.1% and 7.8%, injury rate and fuel consumption decrease by 1.6% and 28%. The operation effect of the driving-type cultivator has been improved significantly, exceeding the national standards and meeting the requirements of potato cultivation and agronomy. This research results can provide a reference for the development of potato cultivators. [ABSTRACT FROM AUTHOR]

In order to reduce tillage resistance, ameliorate the soil layer structure and improve soil breaking rate of soil crushing roller, a combined tillage machine which has function of subsoiling, rotary tillage and soil breaking was designed in this paper. The machine mainly consists of a fixed mount to connect the subsoiler, rotary and soil crushing roller with the machine frame, the self-excited vibration subsoiler breaks the bottom of the plow pan, the rotary tiller flattens the soil and further shreds the soil, the soil crushing roller further breaks the soil thus creating a seedbed suitable for plant growth. 2 major components of machine are optimized to solve the problem of large tillage resistance and poor soil breaking effect. Firstly, the self-excited vibration subsoiler with controllable penetration angle was designed, which can avoid the problem of poor drag reduction effect and stability of tillage depth when the penetration angle of subsoiler is too large. The subsoiler produces a vibration to loosen the soil to achieve the purpose of drag reduction because of resistance changes in soil operation. In addition, the penetration angle of subsoiler is controlled to a range to maintain the stability of subsoiling depth. To ensure the compression spring can not be tilted during the subsoiling operation, and considering the problem of large load and limited installation space, the combination spring is selected as the self-excited vibration spring. Through the kinematics and mechanical model of self-excited vibration subsoiler, the deflection is 15 mm and the minimum and maximum loads are 7 500 and 15 000 N respectively, then the parameters of the combined spring was determined. Secondly, in order to realize the secondary soil-broken function, a caged soil crushing roller was designed by staggered welding of rhombic soil-broken teeth on a cylindrical drum with clearance. The soil is first broken by the outside teeth of soil-broken tooth, and the large soil will enter the cylindrical drum inside through the gap and will broken under the action of inside teeth, which can’t adhere to the cylindrical drum. The caged soil crushing roller diameter and thickness of soil-broken teeth is calculated according to the design formula of the disc harrow. To study the drag reduction effect and tillage quality of self-excited vibration subsoiler, the experiment in the soil bin is carried out, and the field experiment of operation performance of the machine is carried out. The soil bin experiment results showed that the self-excited vibration subsoiler has obvious effect on drag reduction, and the average drag reduction is 9.22%, and the soil fluffy degree and disturbance coefficient is 26.16% and 77.21% respectively. The field experiment results showed that the stability coefficient of subsoiling depth, stability coefficient of depth of soil preparation, surface flatness, vegetation coverage and soil breaking rate is 94.92%, 92.50%, 1.17cm, 93.36% and 84.18% respectively. The soil breaking rate of ordinary soil crushing roller is 71.41%, which indicates that the caged soil crushing roller can effectively improve the soil breaking effect. Moreover, the caged soil crushing roller did not appear soil adhesion and congestion during the test. All parameters meet the requirements of the work quality standards. Therefore, the machine has obvious effect of reducing resistance and quality of the soil preparation. This study can provide a theoretical reference for further research of combined tillage machine of subsoiling and rotary. [ABSTRACT FROM AUTHOR]