In order to improve soil fertility and fertilizer utilization, a subsoiling variable rate fertilization machine based on conservation tillage and precision agriculture was designed and tested. The relationship between suspension parameters and penetrating distance was analyzed, and a matching model between fertilizing quantity and penetrating distance was established. The variable-rate fertilization control machine was developed based on an Advantech PCM-9363 industrial control mainboard. The machine operates under two patterns: DGPS-based positioning and straight-line path positioning based on a planar coordinate system. This machine can perform on-demand fertilization according to the spatial differences in soil nutrients and the prescription maps pre-set before the operation. Field experiments showed the machine has a subsoiling stability of 92.5%, a soil breaking rate of 61.1%, a maximum positioning relative error of 2.68% and a maximum variable rate fertilization error of 3.89%. The subsoiling performance and variable rate fertilization indices of this machine satisfy the requirements of GB/T24675.2-2009. The tested indices meet the national and industrial standards and satisfy the design requirements. The findings of the research can be used as the structural design of the subsoiling variable rate fertilization machine. Keywords: agricultural machinery, conservation tillage, precision agriculture, subsoiling; variable rate fertilization DOI: 10.25165/j.ijabe.20201304.5757 Citation: Qi J T, Tian X L, Li Y, Fan X H, Yuan H F, Zhao J L, et al. Design and experiment of a subsoiling variable rate fertilization machine. Int J Agric & Biol Eng, 2020; 13(4): 118–124.

In order to address the current deficit in research on discrete elements within the context of the cotton seed pressing process, a combination of physical tests and simulation experiments were conducted on Xinluzao 84 cottonseed. The Plackett-Burman experimental design was employed to identify the parameters that had a significant impact on the accumulation angle. Subsequently, the Box-Behnken design was employed to establish a second-order regression model for the accumulation angle and the significant parameters. This resulted in the optimal parameter combination for the maximum friction coefficient, minimum sliding friction coefficient and critical shear stress being 0.207, 0.388, and 5×10⁶ Pa, respectively. In order to calibrate the cottonseed bonding parameters, a Box-Behnken test was designed based on the results of the cottonseed particle crushing test. The optimal parameter combinations of normal stiffness, tangential stiffness, and bond radius were obtained as 1.25×10⁹ N/m², 7.57×10⁸ N/m², and 0.727 mm, respectively. The obtained parameters were verified by the simulation of stacking angle and the crushing test simulation. The relative error was 0.84% and 0.46%, respectively. This serves to validate the cottonseed bonding model and simulation parameters, thereby providing a foundation for optimising the core structural parameters of the cottonseed shelling machine.