Phenotypic alterations and crop maturity differences in ultra-narrow row and conventionally spaced cotton

Ultra-narrow row cotton (Gossypium hirsutum L.) production is considered a potential strategy for reducing production costs by shortening the growing season. A 2-yr field study was conducted near College Station, TX, on varyi ng soil types to document phenotypic alterations and crop maturity differen ces for cotton grown in 19-, 38-, 76-, and 101-cm row spacings. In the 19-c m rows, the plant densities were 12.2, 18.8, and 40.5 plants m(-2). Densiti es of 11.3 and 19.5 plants m(-2) were established in the 38-cm rows. In the 76- and 101-cm rows, plant densities of 11.7 and 7.4 plants m(-2), respect ively, were evaluated. Plant height and node counts were reduced in the nar row (19 and 38 cm) row spacings in only I yr. The narrow row spacings at th e higher plant densities consistently accumulated leaf area index more rapi dly than the conventional (76 and 101 cm) row spacings. In 1998, when the s tudy was conducted on a heavy clay soil, the higher plant densities in the 19- and 38-cm row spacings tended to partition more biomass to reproductive structures and yielded more than the conventional row spacings. In 1999, t he test was conducted on a lighter silty clay loam soil and yields were una ffected by the row-spacing treatments. In 1998, the higher plant densities in the 19- and 38-cm row spacings had a greater percentage of harvestable b olls at the first fruiting positions on lower nodes, a boll distribution pa ttern that contributed to earlier crop maturity. Narrow row spacings and hi gh plant densities did not consistently alter fiber quality. No conclusive differences for crop growth and development could be ascertained between th e medium and high plant densities in the 19- and 38-cm row spacings. Howeve r, ultra-narrow row cotton may be more advantageous to producers when grown on heavier soils that typically do not promote excessive vegetative growth .