What are the causes of cotton abortive development and the remedial measures

Cotton abortive development occurs every year. So-called abortive development means that cotton has lost its normal reproductive function, that is, it only flowers but does not set bolls, or it flowers heavily but sets few bolls. The causes are first of all climatic factors, secondly the blind and indiscriminate introduction of cotton varieties, and thirdly cultivation methods that are incompatible with climate change.

According to records, when the temperature exceeds 35°C, pollen development becomes deformed and normal pollination cannot occur; sustained drought then intensifies the shedding of squares and bolls. In addition, in mid-August some cotton areas experience a continuous week of rainy weather, which also makes it difficult for cotton to flower and pollinate normally.

Heat-tolerant varieties show few cases of abortive development, while northern varieties that are not heat-tolerant, when introduced and planted in southern cotton areas, show more cases of abortive development.

In terms of cultivation techniques, some late-maturing cotton varieties and late-crop cotton encounter high temperature and drought just at the peak flowering period; some cotton fields are too dense, with severe shading and a poor air and light environment; some cotton fields have been given excessive nitrogen fertilizer, causing excessive vegetative growth, which is also unfavorable for boll setting.

The following measures can be taken to rescue cotton from abortive development:

First, seize the opportunity of the second peak boll-setting period of cotton. In a normal year, late July to early August is the first peak boll-setting period, and when the temperature drops to 25-30°C, a second peak boll-setting period appears. Therefore, losses in summer bolls can be compensated by autumn bolls, and the boll-setting rate of autumn bolls is about 15 percentage points higher than that of summer bolls.

Second, strengthen management according to the differences in seedling condition. For cotton fields lacking fertilizer, apply urea as a topdressing, 5-10 kg per mu; for general cotton fields, spray 1% urea and 0.2%-0.3% potassium dihydrogen phosphate solution on the leaves; for cotton fields with high density and heavy shading, thoroughly prune and remove old leaves; for cotton fields with excessively vigorous growth, spray mepiquat chloride or chlormequat on the leaves, 3-5 g or 12-20 ml per mu, diluted with 50 kg of water; and control pests and diseases well in the later stage.

Third, select cotton varieties suitable for planting in the local area; raise seedlings at the right time and transplant early; plant at a reasonable density; improve the water system facilities of cotton fields; and scientifically manage fertilizer and water.