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LOGO: Journal of Cotton Science


Fertilizer Additive Rate and Plant Growth Regulator Effects on Cotton

Authors: Donald D. Howard, C. Owen Gwathmey, Gary M. Lessman, and Roland K. Roberts
Pages: 42-52
Agronomy and Soils

In-furrow applications of plant growth regulators (PGRs) and starter fertilizers have been used to improve cotton (Gossypium hirsutum L.) yields. Information about the effects of plant growth regulators and fertilizer additives on cotton production is limited. Field research was conducted from 1995 through 1997 on a Loring silt loam (fine-silty, mixed, thermic, Typic Fragiudalf) to evaluate two commercial products, Asset RTU and PGR-IV, for cotton growth. The experimental design was a randomized complete block (RCB) with treatments replicated five times. In-furrow treatments at planting included ammonium polyphosphate (11-16-0) applied at 2.33 L ha-1; Asset plus 11-16-0 applied at 0.15 and 2.33 L ha-1, respectively; Asset RTU applied at 1.17, 1.75, and 2.33 L ha-1; PGR-IV applied at 0.07 L ha-1 followed by two foliar applications of 0.28 L ha-1; and a check. Treatments were applied to disk- and no-till-produced cotton. Soil samples were collected from three positions (0, 10, and 20 cm) from the row and three soil depths (0-10, 10-20, and 20-30 cm) of selected treatments to evaluate early root development. Soil samples were collected at pinhead square and again 21 d later to evaluate root lengths. Relative to the check yield, first-harvest disk-till yields were increased 104 and 124 kg ha-1, while total yields were increased 103 and 140 kg ha-1 from in-furrow applications of 1.75 and 2.33 L ha-1 Asset RTU, respectively. Total disk-till yields were increased 67 kg ha-1 by PGR-IV. First-harvest no-till lint yields were 122, 123, and 176 kg ha-1 higher than the check while total lint yields were increased 97, 124, and 172 kg ha-1 from in-furrow applications of 11-16-0 and 1.75 and 2.33 L ha-1 Asset RTU, respectively. Although the treatment effects on disk- and no-till cotton differed slightly, in-furrow applications of 1.75 and 2.33 L ha-1 Asset RTU consistently increased yields produced by both tillage systems. Early root growth response to treatments (pinhead stage) was inconsistent and varied with sample position and soil depth. Roots evaluated at pinhead square plus 21 d showed Asset RTU applied at 1.75 L ha-1 was the most consistent treatment for increasing root lengths.