Cotton Lint Yield Accumulation Rate and Quality Development

Wanjura, D.F. and Barker, G.L., 1985. Cotton lint yield accumulation rate and quality development. Field Crops Res., 10: 205--218. Crop production management during the period of boll setting and maturation of cot ton (Gossypium hirsutum L.) is critical in determining lint yield and quality. A field investigation conducted at Lubbock, Texas, during 1977--1980 included three cultivars to study the effect of temperature on factors that influence the rate of cotton yield accumulation and the development of lint quality parameters. A linear regression of physiological days (heat units) explained 93% of the variation in prebloom period expressed in days. The number of physiological days needed to complete the prebloom period was negatively related to average daily temperature in a linear manner and included a significant cultivar effect. The length of the boll setting period was determined by temperature and plant moisture stress. In the absence of plant water stress, 20--25 physiological days were needed to complete boll setting. The length of time to fully mature bolls was related to air temperature in a negative exponential manner (r 2 = 0.85) with little direct influence of plant water stress or effect of cultivars. Average boll weight of crop increments fluctuated, but the only trend across years was for the mean boll weight of the last two crop increments to be smaller than the average for the total crop. However, there was a direct correlation between the percentage of total bolls set and percentage of final yield. Fiber micronaire was correlated with temperature in a positive linear manner. In the absence of significant plant water stress, temperature explained 80--90% of the micronaire values of individual cultivars compared with 60% when moisture stress conditions were included. An average crop boll temperature of 27°C appears adequate to achieve maximum development of fiber micronaire. Fiber strength also displayed a linear increase as boll period temperature increased, with coefficients of determination ranging from 0.60 to 0.77 among cultivars. Plant water stress significantly reduced micronaire values but had little effect on fiber strength. Fiber length was not affected by the range of environmental conditions during the four-year period of the study.