Ethephon was applied to Deltapine 55 cotton with 35% of the bolls open. Ethephon significantly increased the percent first pick yield of the cotton. There was no significant difference in the total yield.

PIX was applied to long and short staple cotton in 5, 10 and 20 gallons of water in an incomplete factorial design involving 0.5, 1 and 2 pints of the product per acre. Plant heights were significantly shortened and the percent of lint obtained in the first picking was significantly increased when Piz was applied on the short staple cotton. No statistically significant yield differences were observed between the volumes of dilution or the rates of application for either long or short staple cotton. A factor underlying the experiment was that the monsoon rains. They kept the surface of the ground moist and the plants looking good; however, the subsurface moisture had apparently been depleted, and the plants were under some stress. This stressed condition offset what good the FIX might have done for yield.

Experiments were conducted in 1987 and 1988 to determine whether hormonal changes may be involved in the decreases in growth and boll retention commonly referred to as cutout. Nitrogen deficiency decreased the auxin content and growth of fruiting branches. The auxin contents of fruiting branches, squares, and bolls decreased during the season as the plants entered cutout. ABA in bolls increased slightly, but the ABA content of squares and fruiting branches showed no consistent changes. The results indicate that decreases in auxin (IAA) may be involved in cutout.

Four field experiments were conducted in Arizona in 1988 to evaluate the effects of various multiple application treatment combinations of PIX on the growth and development, as well as the lint yields of both upland and pima cotton. Plant height was significantly reduced (P ≤ 0.05) in some FIX treatments in comparison to the checks for short periods of time after the treatment applications. Those effects did not persist, nor did they translate into any significant positive differences among treatments in terms of lint yields for either of the upland or pima experiments.

A field study was conducted at the Marana Agricultural Center to evaluate the effectiveness of growth regulators on Deltapine 90 cotton. The Pix treatment yielded significantly higher than the check and any of the other treatments.

Water deficit increases boll shedding. Large squares, however, are much less likely to shed, possibly because they contain high concentrations of free and total auxin (indole-3-acetic acid or IAA). Our previous research indicated that much of this IAA disappears by the time the squares open as flowers and the IAA content remains low for about four days after anthesis. If water deficit decreases the IAA content, or increases the ABA conten4 of squares and flowers, then water deficit before flowering could have a carry-over effect and increase the shedding rate of young bolls that subsequently develop from them. In field plots, water deficit increased the ABA content of flowers as much as 66 %. Water deficit first decreased and later increased the concentrations of free and total IAA in squares that were analyzed about three days before anthesis. Flowers contained much less IAA than squares. Despite pronounced effects of water deficit on the IAA content of squares it is unlikely that it had any carry-over effect on the free IAA content of young bolls that subsequently developed from them. Water deficit slightly increased the total IAA content of flowers, but had no effect on their free IAA. Because water deficit increased the ABA content but did not decrease the IAAA content of flowers, any carry-over effect of water deficit on young boll shedding might have been from changes in ABA but not from changes in IAA before the young-boll stage.

No description available.

An experiment was designed to test seven treatments of PIX on both short and long staple cotton. The treatments included single applications of 1/2- and 1-pint rates and multiple applications of 1/8- and 1/4-pint rates. Because of the exceptionally good growing season with lots of early heat units, both short- and long-staple plants set fruit early, which limited their vegetative growth naturally without the need for FIX. Yields were high with lint production over 1800 and 1400 pounds of lint for short and long staple, respectively. Plant mapping also was performed on each treatment.

A four-by-four factorial experiment was performed on the Safford Agricultural Center to determine if CaZn, Foliar Triggrr or Soil Triggrr would cause increases in lint yields on short or long staple cotton. Four levels of PIX were used to see if there would be any interaction between PIX and the other materials. The results in 1989 showed that CaZn and the Trier products did not increase yields, the levels of PIX did not increase yields and there was no interaction between them. Very favorable weather conditions and good crop management kept plants from growing vegetative and prevented crop stress, thus reducing the opportunity for the plant growth regulators to increase yields. Yields were excellent with over 1700 and 1600 pounds of lint per acre for short and long staple cotton, respectively.

Field tests were conducted at the Maricopa and Marana Agricultural Centers to evaluate the effectiveness of growth regulators on Deltapine 90 cotton. With full season management, the check treatment yielded as well as any of the growth regulator treatments at both locations.