良种在生产使用过程中要不断退化和混杂,逐步丧失其生产能力。据调查,退化种与原种相比较,每亩可减产皮棉10—20％,衣分和绒长也相应降低,为了保证品种的纯度和丰产性,发挥良种的增产潜力,必须坚持更换和使用良种。 1990年由于育苗阶段遭受阴雨寡照天气影响,烂种死苗十分严重,导致多次补育棉苗。除良种用完外,也用上了备荒种,造成棉种混杂、种性退化,丰产性大大降低, Seed production in the use of the process should continue to degenerate and mixed, and gradually lose its production capacity. According to the survey, compared with the original degenerated species, the lint yield can be reduced by 10-20% per mu and the lint percentage and cashmere length can be reduced accordingly. In order to ensure the variety purity and high yield, Good seed. In 1990 due to the nuisance-tolerant weather, the dead seedlings are very serious, resulting in multiple cotton seedlings. In addition to running out of seeds, but also spent on prepared waste species, resulting in cotton hybrids, species degradation, greatly reduced yield,