Experimental Methods and Research on the Physical Charac-Teristics of Green Manure Seeds

To enhance the operational performance of green manure sowing, seed harvesting, and processing equipment, as well as to obtain the physical characteristic parameters required for equipment simulation analysis, it is necessary to carry out the seed physical properties such as dimensions, bulk density, and frictional characteristics. This study focuses on the main cultivated varieties of green manure in China—milk vetch, hairy vetch, and sesbania—and innovatively proposes three low-cost, convenient, and high-precision experimental methods of geometric size for small-sized seeds. The measured results show that geometric dimensions of the seeds for milk vetch were 2.60mm-3.40mm in length, 1.90mm-2.40mm in width and 0.71mm-0.97mm in height, the pod dimensions of hairy vetch were 23.03mm-32.83mm in length, 7.39mm-9.74mm in width, 4.06mm-6.15mm in height, and seed diameters were 3.04mm-4.10mm, the seed dimensions of sesbania were 3.81mm-4.29mm in length, 1.98mm-2.37mm in width, 1.85mm-2.08mm in height. Using Python programming language and open-source AI algorithms, we innovatively developed an image-based seed counting experimental method. This cost-effective approach requires no specialized instruments while significantly saving time and labor. Based on the counting results, the thousand-seed weights of milk vetch, hairy vetch, and sesbania seeds were determined to be 3.40g, 26.50g and 15.58g, with respective seed moisture contents of 7.18%, 9.81% and 8.73% at the time of measurement. The instruments and methods for measuring bulk density and angle of repose of green manure seeds were defined. The bulk densities of milk vetch, hairy vetch, and sesbania seeds were determined to be 732 g/L, 761 g/L and 845 g/L, by using the electronic grain densitometer. Meanwhile, the angles of repose of milk vetch, hairy vetch, and sesbania seeds were determined to be 31.66°, 28.15°and 29.82°, by using the angle of repose tester. Based on the principle that the indexing head can accurately determine the angle, the sliding friction angles of milk vetch, hairy vetch, and sesbania seeds were determined to be 25.85°, 23.55°and 24.03°, by using the di-viding head. The testing methods developed in this study, along with the results of measuring the physical properties of green manure seeds, provide valuable reference data for the measurement of the physical properties of small-seeded crop (e.g., green manures) as well as other small or irregularly-shaped particles.