IMPACT OF THRESHING ON HARD RED SPRING WHEAT SEED VIGOR

Improper handling of seed during harvesting may result in severe seed vigour loss. The objective of this study was to determine, under field conditions, the effect of threshing on wheat seed vigour. A conventio nal combine and an axial flow rotary combine were used at three cylind er speeds. The proportion of visually damaged seeds was assessed for a ll samples, and subsequent vigour tests were conducted using visually sound seed. Seed vigour was reduced when wheat was threshed at a high cylinder speed. Wheat kernels threshed with the rotary combine were le ss damaged than wheat kernels threshed with the conventional combine. Both seedling emergence and grain yield were reduced by 20 plants m(-2 ) and by 200 kg ha(-1), respectively, in plots seeded with kernels thr eshed at a high cylinder speed compared with kernels threshed at a low cylinder speed. Vigour of sound wheat kernels was negatively correlat ed with the number of broken kernels in samples. To maintain high vigo ur in wheat seed, it is essential to thresh at a low cylinder speed.