(一) 在生产上每推广种植一个棉花良种,总是体现了新的产量水平和品质指标。建国以来,我国主要棉产区曾进行四次大面积的品种更换,每次换种,都促进了棉花生产的发展。第一次(1950～1955年)换种,使棉花单产提高15%左右,绒长增长2～4 (I) Planting a cotton seed for each promotion in production always reflects the new output level and quality indicators. Since the founding of the People’s Republic of China, four major varieties of cotton have been changed in major cotton producing areas in our country. Every change of varieties has promoted the development of cotton production. The first change (1950 ~ 1955), so that cotton yield increased by about 15%, cashmere growth of 2 to 4