我国棉花良种现已基本普及,在增加产量和提高品质上,均起了巨大的作用。但是不少地区由于种植年久,表现不同程度上的退化现象,据1958年,在湖北天门县调查,岱字棉15号田间杂株数为10——20%,纤维降低约2毫米,衣分降低2—3%,铃和种子变小,生产力变低,如果以减产5%计算,每100万亩棉田就有5万亩没有产量,这个无形的损失是很大的.在另一方面看,出于我国棉区广大,自然环境复杂,因此棉种的变异也是多种多样的,同一块棉田,纤维最长的可达32毫米以上,最短的只有21毫米左右,衣分高的在40%以上,最短的只有27—28 China has basically popularized cotton varieties in increasing output and improve quality, have played a huge role. However, due to years of cultivation in many areas, the performance of various degrees of degradation, according to 1958, Tianmen County, Hubei Province survey, Dai Zi Cotton 15 field hybrid number of 10 - 20%, about 2 mm lower fiber, Reduce 2-3%, bell and seed smaller, lower productivity, if the 5% reduction in production, every 100 million mu of cotton fields have 5 million mu without yield, this intangible loss is great .On the other hand, look , Out of China’s vast cotton area, the natural environment is complex, so cotton varieties are also varied, the same piece of cotton, the longest fiber up to 32 millimeters or more, the shortest of only about 21 millimeters, 40 points in 40 % Above, the shortest only 27-28