Dry matter allocation and fruiting patterns of cotton grown at two divergent plant populations

Reduced plant populations frequently occur in the northern Cotton Belt of the USA because of poor seed germination and early seedling damage. A field study was conducted at Clayton, NC, on a Dothan sandy loam (fine-loamy, siliceous, thermic Plinthic Paleudult) to investigate the response of cotton (Gossypium hirsutum L.) vegetative and reproductive development to two plant populations. Cotton plants, grown at 2 and 12 plants m(-2) in 1.0-m rows had every flower tagged with week-specific, color-coded tags. Dry matter partitioning, power development, flower retention, and bell development patterns were determined. Plants at the low population exhibited large increases in the vegetative dry weight of individual plants at maturity; however, all parameters of vegetative growth were reduced on a land area basis. Reproductive development of the 2 plants m(-2) treatment was prolonged because of fewer early fruiting sites per unit land area and there was an average 16-d delay in flowering maxima. No differences in total flowers per meter or flower retention occurred between treatments at final harvest. Slight differences in total bells per meter occurred in 1993 (13% fewer bells at 2 plants m(-2)); however, the low population plants had more bells on monopodia, more late-season hewers, and greater retention of these late bells. Replanting low populations would not be advisable because the delay in maturity would probably be more injurious to bell production than the low population per se.