Tensile properties of foxtail millet leaf sheath, leaf and leaf collar

Abstract: Millet stalk has high strength and toughness, and is not easy to break. The mature millet has thin stalk wall, long leaves and heavy ear head, which is easy to bend in the internode of ear head and entangle easily during harvest. In order to solve the problem that the stalks and leaves are easy to wind in the process of mechanical harvesting of millet, Jingu 21 and zhangza 10 were chosen as the testing objects, tensile properties of stalks, leaf sheaths, leaves and leaf collars at different internode locations were tested. The test data were analyzed by SAS statistics software. The variation laws of mechanical parameters along stalks, such as elastic modulus, strength and tension resistance, were investigated. The results showed that at the bottom and top internode locations, elastic modulus, strength and tension resistance for both of the two species were significant differences(P<0.05). It was found that at 3 height locations along the stalk(bottom, middle, top) of Jingu 21, the elastic modulus was 4.15-6.64 GPa, the tensile strength was 67.65-130.13 MPa, and the tensile resistance was 343.97-1 598.37 N. While for the stalks of Zhangza 10, the elastic modulus was 4.54-7.98 GPa, the tensile strength was 73.22-136.50 MPa, and the tensile resistance was 167.66-567.54 N. The influence of internode and locations(leaf sheaths, leaves and leaf collars) on the tensile strength and tensile resistance were highly significant(P<0.01). The mean tensile strength of leaf sheathes, leaves and leaf collars on the upper half of Jingu 21 was 13.30, 10.13 and 4.18 MPa, and the mean tensile resistance was 122.16, 41.23 and 25.80 N, respectively. Whereas for Zhangza 10, the mean tensile strength of leaf sheathes, leaves and leaf collars was 13.30, 11.77 and 4.24 MPa, and the mean tensile resistance was 104.30, 59.48 and 22.87 N, respectively. The results showed that the connected collar was the weakest part to separate the leaf from stalk. In the mechanical harvesting of millet, stalk leaf separation should be carried out at the leaf collars position between the upper half of stalk and below the second internode of earhead, and the application range of force should be controlled within 20-25 N. The results can provide basis for the design and optimization of foxtail millet harvesting equipments.