Investigation of Seed Movement Within the Delivery System of a Planter Sowing Unit Opener

Abstract

The aim of the work is to develop a scientifically grounded methodology for determining the rational design parameters of the retaining heel of a sowing unit furrow opener, based on a comprehensive theoretical study of the physical and mechanical processes of seed-soil interaction and the force interaction between the soil flow and the working surfaces of the heel. The study is aimed at addressing the issue of non-uniform seed placement depth, which leads to a 10–12% reduction in grain crop yields when deviations from the target seeding depth occur. The relevance of the work is driven by the need to ensure the effective operation of sowing machines under minimum and zero tillage conditions, where traditional disc openers demonstrate critically unsatisfactory sowing quality indicators that exceed permissible agrotechnical requirements severalfold.

The study analyzes the physical nature of non-uniform seed placement, which involves multiple seed bounces from the furrow bottom (3–5 rebounds at a height of 8–45 mm) with simultaneous soil sloughing from the furrow walls at a velocity of 0.08–0.15 m/s, leading to chaotic seed entrapment by the soil at various horizons. A sowing unit design with a retaining heel has been developed, incorporating a parallelogram linkage, a coulter (disk cutter), a packing roller, an opener with an integrated heel, and an adjustment rod with a spring element. The rational design parameters of the heel were theoretically justified through an analysis of the balance of dynamic pressure, friction, and soil adhesion forces during soil movement along the inclined surface of the heel. It was established that the inclination angle of the heel plane to the horizon is directly proportional to the specific soil adhesion force and inversely proportional to the square of the sowing unit's operating speed. For typical soil-technological conditions (moisture content 20–22%, specific adhesion force F = 1471 Pa, speed 1.5–3.0 m/s), a rational angle value of α = 15° was determined. The heel parameters in the horizontal plane were justified based on the condition of bifurcating the soil flow into two symmetrical streams, and it was confirmed that variations in soil density within the range of 1200–1600 kg/m³ do not significantly influence the optimal heel inclination angle.

The developed methodology for determining the design parameters of the retaining heel allows for adapting the geometric characteristics of the working tool to specific soil and technological operating conditions. It provides a theoretical framework for designing sowing units capable of operating effectively under minimum and zero tillage conditions with crop residue densities of up to 6–8 t/ha. The proposed sowing unit design ensures seed fixation at the furrow bottom for the duration required for complete soil coverage, reducing the coefficient of variation of seeding depth to agrotechnically permissible levels (not exceeding 20%). The theoretical relationships established between the heel design and the operating parameters of the sowing unit form the basis for further experimental research and the industrial implementation of the results. These findings can be applied to the modernization of existing seeding machinery and the development of new designs for resource-saving grain production technologies.