In 1984,1985, and 1986, leaf water potentials of irrigated cotton declined markedly as the crop approached cutout. Midday transpiration rates also declined, indicating a water-stressed condition. The water stress occurred despite the fact that measurements were made only when the soil was fully charged with water. In 1986, plant hydraulic conductances were estimated. The conductance was high early in the season, declined to a low value during cutout, and increased during regrowth to the high value of the early season. It is suggested that root length and efficiency of water uptake, or both, decrease during boll filling as most assimilates are partitioned into the bolls. Daily drip irrigation prevented this susceptibility to stress during boll filling. In 1984 and 1986, drip irrigation decreased the length and severity of cutout, resulting in an increased boll load at the end of the season.

The plant regulators XE-1019 and PIX were tested at the Maricopa and Marana Agricultural Centers. Few yield responses were found in 1987, apparently due to the short stature of the crop at both locations.

Two new Dropp formulations show promise as cotton defoliants. In addition to excellent leaf drop, most squares, flowers, and young bolls were also shed, removing the food source for late season insects.

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.

An experimental site was selected at Yuma Agricultural Research Center, University of Arizona, to evaluate the effect of Messenger on melon plant growth and yield. Four treatments in completely randomized block design replicated four times were applied to melon planted on 84- inch beds. High Mark open pollinated melon variety was planted on 3-20-2001 using a commercial planter. Treatments included Messenger applied at 3-leaf stage on 5-4-2001 Messenger applied every 14 days starting on 5-15, 5-29, 6-13, 6-27-2001, standard management practices and control. Observations collected included plant mapping and yield. Results were variable, showed no significant effect of Messenger on plant growth and yield. However, there was indication that Messenger may have an effect on plant growth pattern and yield. Messenger applied at 3-leaf stage and repeated applications seemed to induce an early melon formation, increased number of nodes and yield. It was not possible to make recommendation based on one-year results. Further investigation is needed to verify the results obtained from this experiment.

Messenger applied at three timely applications at early runner, bloom, and fruiting stages of watermelon versus bi-weekly applications, showed no significant statistical differences for vine length, number of blooms, or harvestable yields. Visual observations for the watermelon plant health at the end of the season tended to indicate that the three timely applications resulted in slightly more vigorous plants than the bi-weekly treated watermelon plants. Cantaloupe vine growth, number of fruit set, yield weight, and fruit size were not different between Messenger treatments and were not enhanced compared to the untreated check.

Processing onions were treated with AuxiGro in spring 2001. Applications were applied at four and 7.5 weeks prior to harvest. A single application of 4 oz. product/acre at either four or 7.5 weeks prior to harvest increased yield by approximately 0.7 tons/acre. Two applications resulted in a 1.3 tons/acre yield increase. Differences noted were not statistically different, but the two application treatment provided an increased net return of approximately $95/acre.

Dry Seed+, a fertilizer/plant growth regulator, was applied to processing onions at planting in the fall of 1998 to evaluate the effect on yields. Yield data obtained June 1999 indicated no effect in this experiment, although this was dissimilar to other trial results. Salt content at the field was thought to have limited yields, and have stressed growing plants, which may have contributed to lack of yield differences noted. Further testing is necessary to further evaluate this product.

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