Physical-mechanical properties of onion seeds and soil

The physical and mechanical properties of the soil and onion seeds, such as the size, shape, mass, density, and the static coefficient of friction on various surfaces play an important role in the development of the dosing working bodies of the seeder. Uzbekistan has recently created various new varieties of onions. Therefore, there is a need to study the physical-mechanical properties of onion seeds of the new varieties to substantiate the parameters of the dosing devices of seeders. Currently, in Uzbekistan, onions are grown as both primary and secondary crops. The development of new technologies and technical means that ensure high-quality soil preparation and sowing onion seeds is impossible without determining the patterns of changes in the physical and mechanical properties of the soil and onion seeds. However, in the conditions of Uzbekistan, the physical and mechanical properties of the soil and onion seeds have not been sufficiently studied. The purpose of the study is to study and analyse the physical and mechanical properties of the soil and onion seeds cultivated in Uzbekistan. The results determining the moisture content, density, and hardness of the soil and geometric dimensions, the weight of 1000 seeds and the static coefficient of friction of onion seeds of the varieties ‘Sumbula’, ‘Istikbol’ and ‘Zafar’, the most common in Uzbekistan, are presented. The main physico-mechanical properties of the soil during the period of planting onion seeds were studied according to GOST 20915-2011. The geometric dimensions of the seeds (length, width, and thickness) were determined using a micrometre, and their mass was measured on an electronic scale MN-390. According to the results of the research, the soil prepared for planting onion seeds has a moisture content of 13.4 in 0–5, 5–10, 10–15, and 15–20 cm layers, respectively; 15.1; 17.4 and 18.6%; density: 1.10; 1.14; 1.22 and 1.25 g·cmE−3, and the hardness 0.50, 0.64, 0.76, and 0.89 MPa. The minimum value of the natural slope angle of the soil (300) was observed at values of 7–8% of the soil moisture. As the soil moisture increases or decreases from this value, the natural slope angle increases. The coefficient of static friction of the seeds was determined by the method determining the minimum slope angle at which they slide on the friction surface. The coefficient of friction of seed grades ‘Sumbula’, ‘Istiqbol’ and ‘Zafar’ consists of: for painted steel correspondingly 16°03´, 17°03´ and 16°48´, for neopainted steel — 18°15´, 19°42´ 18°24´, aluminium — 20°00´, 20°45´ and 20°27´, plastic – 26°00´, 27°33´ and 26°42´, rubber — 24°15´, 24°42´ and 24°24´. The seeds of earlyearly ‘Sumbula’ and mid-early ‘Istiqbol’ and ‘Zafar’ onion varieties have the following main physical and mechanical properties: the length from 3.0 mm to 3.2 mm, width from 2.1 mm to 2.3 mm up to 1.8 mm to 1.9 mm thick. The mass of 1000 onion seeds, depending on the variety, ranges from 3.79 to 3.83 g. On a plastic surface, the maximum friction angle measured for the onion seeds was 2658, while the lowest value measured in cast steel was 1651. Friction angles of the seeds of the prospect variety are higher than those of the Sumbula and triumph types on all surfaces.