NITROGEN-FERTILIZATION AND PLANT DEVELOPMENT OF COTTON AS DETERMINED BY NODES ABOVE WHITE FLOWER

Early maturation is very beneficial in successfully harvesting a high- quality, high-yielding cotton (Gossypium hirstum L.) crop. If harvest is delayed until inclement weather patterns are established, both yiel d and fiber quality may be lost. The objective of these studies was to determine the maturity differences that occur in cotton differentiall y fertilized with nitrogen (N). Field experiments with irrigated cotto n were conducted in 1990 and 1991 in three locations to study the effe cts of soil applied N rates on cotton maturity as estimated by nodes a bove white flower (NAWF) measurements. The test sites and soils were a production field near Manila, AR, on a Dundee sandy loam (fine-silty, mixed, thermic Aeric Ochraqualfs), the Southeast Branch Experiment St ation (SEBES) near Rohwer, AR, on an Hebert silt loam (fine-silty, mix ed, thermic Aeric Ochraqualfs), and the Northeast Research and Extensi on Center (NEREC) near Keiser, AR, on a Sharkey silty clay (very fine, montmorillonitic, nonacid, thermic Vertic Haplaquepts). Criteria used as indicators of crop maturity and earliness in these studies were th e time in days after planting (DAP) and the accumulated heat units (HU ) for the crop to reach NAWF=5. Increasing N rates delayed maturity at SEBES both years and at Manila in 1991 but not at NEREC either year. Differences in maturity between N treatments of 168 and 224 kg N/ha we re minimal at all locations both years. Smaller differences in time fo r the plants to achieve NAWF=5 were observed in the cotton grown at Ma nila in 1990 and at NEREC both years. The smaller differences at Manil a are assumed to be due to high levels of residual N from previous cro ps. Early-season vegetative growth was indicated by NAWF extrapolated to first flower (60 DAP or 945 HU). A trend of higher NAWF at the extr apolated first flower stage with increasing N rate was observed, but g enerally differences were minimal. The NAWF values at DAP=60 were lowe r in 1991 than in 1990 for all locations.