Design and Experiment of a Reciprocating Intermittent Chopping Device for Maize Straw Returning

Straw returning has shown great advantages in residue management and soil protection in crop planting systems. Mechanized retention of straw is the primary straw returning method, which can reduce costs and improve efficiency. It is important to increase the chopping quality in the field of straw returning, because poor chopping quality will provoke a series of problems including seeding blockage. Straw chopping pass rate (CPR) is an important indicator to measure the chopping quality. Therefore, the CPR of straw should be improved during the chopping process. This paper introduced a novel maize straw chopping device. With the ground as the support, the maize straw was chopped rapidly in the vertical direction. The key parameters of the chopping device were determined by establishing mathematical models and kinematics simulation analysis methods via ADAMS. The effects of rotational velocity, installation positions of chopping units, and the tractor forward velocity on the CPR of maize straw and soil bulk density (SBD) were examined through the Box–Behnken design method. The test factors were the rotational velocities of the chopping units (RV, 550 rpm, 650 rpm, 750 rpm), the installation distance of the two chopping units (IDTCU, 480 mm, 600 mm, 720 mm), and the velocity of the tractor (VT, 3 km/h, 4 km/h, 5 km/h). The results showed that the maximum CPR value and better value of SBD were obtained under the RV of 610 rpm, the IDTCU of 526.8 mm, and the VT of 3.96 km/h. Finally, field validation experiments were conducted under the RV of 610 rpm, the IDTCU of 550 mm, and the VT of 4 km/h. The results showed that the CPR of maize straw was 92.0%, which was superior to the requirement as stipulated in the National Standards of China (CPR ≥ 85%). In addition, in 0–50 mm and 50–100 mm soil layers, the bulk density was decreased by 25.42% and 13.24%, respectively. These results become of considerable importance for crop production in China.