Source‐to‐Sink Manipulation Effects on Cotton Lint Yield and Yield Components

Abstract Cotton (Gossypium hirsutum L.) yields can vary considerably among years and locations, even under levels of water and nutrients considered adequate. Since photosynthesis is one of the principal components in determining reproductive yield, the objectives of this study were to determine how manipulations of the ratio of photosynthetic source to reproductive sink affect cotton lint yield and yield components (boll mass, seed mass, seed per boll, lint percentage, and bolls per square meter). Field studies were conducted in 1991 and 1992 on a Bosket fine sandy loam with six source‐to‐sink ratio manipulations (partial fruit pruned, partial leaf pruned, reflectors, open canopy, shaded plots, and an untreated control) imposed on three cotton genotypes: ‘DES 119’, ‘DPL 5690’, and ‘Prema’. White blooms were tagged twice in both years, and fruit were subsequently harvested after bolls had opened. These bolls were ginned and boll mass, lint percentage, and seed mass were determined. Overall lint yield and yield components were determined for the reflector, open canopy, shaded plot, and control treatments. The partial fruit pruned treatment had a 16% greater boll mass and a 10% greater seed mass than the control. Percentage lint was not affected by any of the treatments. In 1992, bolls at the first sympodial position (fruit at all other positions were pruned from the sympodial branches) had a 25% greater boll mass and 8% greater seed mass than bolls at the second sympodial position (fruit at all other positions were pruned from the sympodial branches) and control treatment bolls from the first tagging. Position 1 and Position 2 bolls did not differ in boll or seed mass during the second tagging period (both greater than the control) or in percent fruit abortion during either tagging period (both lower than the control). Lint yields from the open canopy and reflector treatments were 17% and 6% greater than the control, respectively, and the shaded plot yielded 20% less than the control. Boll number was the component of yield that accounted for these differences. Cotton canopies bred for increased light penetration to lower leaves or for better utilization of the intercepted light may lead to lint yield increases.