Author: Cotton Group, Research Institute of Crops Breeding and Cultivation, Shanghai Agricultural Academy
J Integr Plant Biol 1976, 18 (1): -.
The different development stages of cotton plant require different exterior conditions. Once the broad masses have mastered the developmental law for high yield of cotton they can display boundless creativeness. In order to obtain high yield, they undertake various agricultural measures, such as digging ditchs to drain out water, irrigation, applying fertilizer early in the seedling stages, suitable fertilizer during flower buds formation and a heavy fertilizer for the balls formation stage. Furthermore, decapitation should be done in time. A reasonable pruning and de- foliating will adjust the micro-climate in the cotton field. To overcome unfavourable environmental conditions such as dying of seedlings in chilly spring, overgrowth of plant in rainy spell, shedding of ball or reducing of ball weight in draught of dogdays and rotting of balls in autumn rain, they have to handle correctly the relation between an indivitual plant and the plant stand. 2. Developmental laws of high yield cotton are: a fast growth in the seedling stage, a steady growth in the bud formation and to prevent early deterioration in ball stage. For specific requirements, they are to ensure a full stand of seedlings by the end of April, flower buds should appear in the mid June and the cleavage of the fruit in the later part of August. The technical key link is "seizing of time and sunshine, promote a strong growth of roots and to maintain a steady growth. According to the systematic analysis of materials of 28 mu high yield cotton fields from 1967 to 1974, for yield of 200 catties ginned cotton per mu, the density is 4,500 plants, plant height is about 100em; fruiting spurs are more than 15; fruits per plant are about 50; total number of cotton balls are about 65,000; average hundred balls weight of the three sections (top, middle, bottom) amount to 458 gm; average lint percentages of mid-stage balls is 39.4%. On scorching heat day (23 July), an individual plant bears 0.7 cotton balls. Before "limit of heat day" (23 August), the number of grown balls comprise 78.6% of the total balls and the leaf area index in the maximum flowering stage is about 3.5. 3. The cotton plants of normal growth, undergrowth or overgrowth are different in their external morphology and internal nutritional conversion. Therefore, we should master such indexes as plant height; growth rate per day; red-stem ratio; width of the middle part of fourth leaf (from the top); colour of leaf; carbon-nitrogen ratio of different varieties of cottons in the different growth stages, thus undertake cultural measures during seedling-bud stage (later part of June), bud-flower stage (later part of July) and cotton-ball stage (later part of August) respectively, in order to enable the growth and development of the cotton plants coordinate with the high yield morphological index and thus obtain a high yield of cotton.