Development of deep fertilizing no-tillage segmented maize sowing opener using discrete element method

Openers in no-tillage can confer a yield benefit via disruption of pathogenic hyphae, particularly when crop rotations lack species diversity in extremely cold climates, like in northeast China. However, it is still urgent to improve the uniformity of seedling depth, while alleviating large working resistance and soil disturbance on the deep fertilizing no-tillage planter after returning crop stalks to the field. In this study, a novel opener was designed for corn seeds in a segmented flow for deep fertilizing and no-tillage using a Discrete Element Method (DEM). Six types of stubble cutter-fertilization shovel devices were selected on the soil to explore the effect mechanism in the simulated analysis. First of all, a soil-corn stubble-corn straw DEM model was established to achieve the uniform seed-to-soil contact. Three kinds of stubble cutters (including plane, notched and corrugated stubble cutter) were then randomly combined with two kinds of fertilization shovels (including sharp and arc-type fertilization shovel) in the DEM simulation test. After that, a respective analysis was carried out for the motion trail of soil particles in the six types of stubble cutter–fertilization shovel devices after the operation. The location and direction of soil particles were finally extracted to obtain six fitted curves representing the maximum force in the falling process. As such, the curve of the opener was designed in the buried part. Specifically, the opener curve Ⅰ was set as the fitted falling curve of soil particles after the combination operation of three kinds of stubble cutters and sharp-cornered fertilization shovel devices. The opener curve Ⅱ was that of three kinds of stubble cutters and arc-type fertilization shovel devices. The opener curve III was that of six kinds of stubble cutters and fertilization shovel devices. At the same time, the inclined edge of the opener in the unburied part was also designed to improve the passing ability, particularly for the sliding frictional angle under the minimum power consumption when cutting straw. In addition, the buried clearance angle of the opener was set as 6° with the traverse width of 20 mm and inclined edge angle of 30°. Finally, the optimal spacing between the fertilization shovel and the opener was determined as 374 mm, according to the time and advanced speed for the soil particle falling back to the maximum force. Besides, a field test was performed on three kinds of segmented openers to verify the feasibility of the developed device. Curve III was finally chosen in the buried part for more extensive applicability of the segmented opener. The field comparison test indicated that the variable coefficient of seedling depth in the segmented opener dropped 14.24%, 27.31%, and 33.63%, respectively, while the working resistance dropped 27.56%, 16.93%, and 1.23%, respectively, as well as 11.67%, 28.34%, and 49.34% in the soil disturbance area, compared with the sharp-cornered, the sliding knife and double disk opener. Consequently, a high operation performance was achieved in the segmented opener, including high uniformity of seedling depth, small working resistance, and soil disturbance for deep fertilizing and no-tillage.