Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/15/2003
Publication Date: 4/1/2004
Citation: Pettigrew, W.T. 2004. Moisture deficit effects on cotton lint yield, yield components, and boll distribution. Agronomy Journal. 96:377-383. Interpretive Summary: Cotton lint yields in the MidSouth have become stagnant in recent years with little or no yield increases occurring. One of the phenomena limiting yield production in cotton is the effect of environmental stresses, such as drought stress. Understanding how drought stress limits cotton production provides insight to the physiological infrastructure of growth and development, and also provides insight into what aspects of growth need improvement to produce higher and more stable yields. This four year study investigated how drought stress affected cotton growth, lint yield, and fiber quality for eight different cotton varieties. Drought stress reduced the yield and fiber quality produced. Irrigation increased lint yields significantly (30 %) in two of four years. Irrigated plants were able to sustain their boll production longer during the summer. This allowed the irrigated plants to be taller, with more bolls higher on the plant and further out on the reproductive branches. All the cotton varieties responded similarly to drought stress. The transgenic varieties behaved the same as the conventional varieties. In addition to measuring the effects of irrigation on cotton yields, this study also showed that higher yields can be obtained and stabilized by adapting techniques to facilitate boll set at higher plant nodes and further out on the reproductive branches.
Technical Abstract: Understanding how moisture deficit stress alters cotton (Gossypium hirsutum L.) reproductive growth and yield component development would provide insight into the current yield stagnation problem plaguing U.S. cotton producers. The objectives were to document the effects of moisture deficit stress on reproductive growth, lint yield, yield components, boll distribution, and fiber quality for a diverse group of genotypes. Field studies were conducted from 1998 through 2001 utilizing eight genotypes of diverse backgrounds, including an okra-normal leaf-type near-isoline pair and transgenic lines paired with their recurrent parents. These genotypes were grown under both dryland and irrigated conditions. Weekly white bloom counts, nodes above white bloom, lint yield, yield components, end of season plant mapping, and fiber quality data were collected. Genotypes responded similarly to the two soil moisture regimes for essentially all of the parameters evaluated. Irrigation delayed cutout, the slowing of vegetative growth due to strong reproductive demand for assimilate, an average of 6 d. This delayed maturity enabled those plants to sustain flowering later in the growing season (after 90 days after planting) compared to dryland plants. During the years when sufficient moisture deficits occurred, the lint yield of dryland plants was reduced 25%, primarily because of a 19% reduction in number of bolls. Irrigated plants produced more bolls at higher plant nodes ( > node 10) and at the more distal positions (greater than or equal to 2) on the sympodial branches than did the dryland plants. Most fiber quality traits were not consistently affected by irrigation, but three out of four years irrigation produced approximately 2% longer fiber. Production of more bolls higher up the plant and further out the fruiting branch with irrigation indicate that these areas on the plant are where high yields need to be stabilized.