Search Results (3)

Subsoiling can break the plough pan and improve the root growth environment. The effect of the traditional subsoiler is poor, as it relies only on the chisel tine, but pneumatic subsoiling can improve the soil structure more efficiently through the negative pressure generated by the jet hole. This research used computational fluid dynamics and the discrete element method to optimize the biomimetic structure of the jet hole, model the pneumatic subsoiling process at a depth of 330 mm, and observe the movement of soil particles as airflow passes through. The effect of the jet hole at different positions and sizes on the plough pan soil was analyzed, and fluid domains and measurement areas were set up to observe the upward movement, diffusion, stabilization, and settling of soil particles under the action of airflow. The results of the soil bin experiment validated the accuracy of the simulation model through draft force and vertical force, and the average error between the simulation and experimental data was 2.8%. The study revealed that the increase in the rate of soil porosity reached a maximum of 3.65% when the jet hole was positioned above the chisel tine with a radius of 4 mm. The biomimetic jet hole pneumatic subsoiler designed in this study, along with the established CFD-DEM coupled simulation model capable of predicting pneumatic subsoiling performance, can provide references for the design and application of a pneumatic subsoiler. Furthermore, it also provides a theoretical basis for understanding the mechanism of airflow on soil during pneumatic subsoiling operations. Full article

Subsoiling is an effective tillage method for breaking up the plough pan and reducing soil bulk density. However, subsoilers often encounter challenges such as high draft resistance and excessive energy consumption during operation. In this study, the claw toes of the badger and the scales of the pangolin were selected as bionic prototypes, based on which coupling bionic subsoilers were designed. The discrete element method (DEM) was used to simulate and analyze the interactions between soil and both the standard subsoiler and coupling bionic subsoilers. Field experiments were conducted to validate the simulation results. The simulation results showed that the coupling bionic subsoilers reduced the draft force by 7.70–16.02% compared to the standard subsoiler at different working speeds. Additionally, the soil disturbance coefficient of the coupling bionic subsoilers decreased by 5.91–13.57%, and the soil bulkiness was reduced by 2.84–18.41%. The field experiment results showed that coupling bionic subsoilers reduced the average draft force by 11.06% and decreased the soil disturbance area. The field experiments validated the accuracy of DEM simulation results. This study provides valuable insights for designing more efficient subsoilers. Full article

Straw return is a common cultivation to improve soil fertility and realize sustainable agricultural development. However, the effect of returning interval on the corn straw humification process in northeast China is little known. In this study, a four-year field trial was conducted to investigate the characteristics of soil carbon sequestration under the annual deep straw return (T1), the biennial deep straw return (T2), and the non-straw return (T3) in Jilin Province, China. In order to precisely evaluate the soil organic carbon density (SOCD), each soil horizon was divided differently according to the actual situation, rather than a fixed thickness. The results show that both the annual and the biennial deep straw return had a significantly positive influence on the content of soil organic carbon (SOC), humic acid, fulvic acid, and humin in the plough pan (straw-applied horizon), compared to the no-straw return. SOC of the cambic horizon and the C horizon in annual straw return was 28.78%, 47.44% higher than the biennial straw return, but it was 27.58% lower in the plough pan. The SOCD in the plough pan in the biennial straw return was higher than the annual straw return, but their difference in the entire soil profile was not significant. However, the conversion rate of straw carbon to SOC was 18.42% in the annual straw return and 21.05% in the biennial straw return. The straw return amount was not a key factor affecting the SOC sequestration in the cold area; it was restricted by the comprehensive effects of the cold weather, the intensity of soil disturbance, C/V and the initial SOC content. In conclusion, the biennial deep straw return was a better management tool, as it generally had an identical quality and quantity of soil organic carbon and a higher straw conversion rate relative to the annual deep straw return. Full article