Analysis of Phenotypic and Tensile Mechanical Properties of Seed Rope and Its Impact on Plant Root Growth

Seed rope direct-seeding is an advanced precision sowing technique that involves encapsulating seeds within rope materials, adhering to specific spacing and quantity, and then deploying these ropes in the field as an alternative to conventional direct-seeding. This method offers the dual benefits of minimal sprout damage and precise control over row-to-seed spacing. The mechanical properties of the seed rope material and the integrity of the wrapped seeds are critical factors that influence the growth and development of the plants’ root system, which in turn is a key determinant for the optimization of the seed rope automatic seeder. This paper employed uniaxial tensile testing to investigate the mechanical properties and tensile failure characteristics of seed ropes across various materials, seed wrapping techniques, and seed soaking methods. Additionally, scanning electron microscopy was utilized to scrutinize the microstructural features of the tensile fracture surfaces of the seed ropes. The results showed that the tensile strength of paper-based seed ropes ranged from 1.80 to 2.89 N/mm, with elongation at the break between 31.4% and 47.5%, and a critical stress range of 5.67 to 9.06 N. In contrast, non-woven fabric ropes exhibited a tensile strength range of 0.91 to 1.23 N/mm 2 , an elongation at break range of 160.3 to 284.2%, and a critical stress range of 2.86 to 3.86 N. Electron microscope scanning imagery analysis indicated that the broken fibers were disordered, and the fibers of the soaked ropes showed minor surface damage, which is attributed to the decline in tensile strength observed in soaked ropes. Regarding the phenotypic study of root growth and development, the root growth and development phenotypes of two types of rope materials across four different vegetable varieties were explored; the results indicated that the influence of the seed rope material on the root system was pronounced in the early stages of growth and development. As plants progressed to the middle stage of growth, the trend in root length mirrored that of the early stage, with the seed rope material continuing to significantly impact root system development. In the late stage of growth, the effect of the seed rope material on root growth gradually diminished as the seed rope material decomposed. Interestingly, the root length under non-woven fabric wrapping not only caught up to, but in some instances, surpassed the root length of unwrapped seeds. This research provides valuable theoretical insights and data to support the optimization of the parameters for the automatic seed rope direct-seeder.