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Low quality Stoneville 825 seed produced reduced stands and, in most cases, reduced lint yields when planted at 3 dates and 3 planting dates at 3 locations in Arizona. Reduced lint yields were explained by reduced stands. Highest lint yield was obtained from the second plantings, 24 and 21 April at Marana and Safford, respectively.

The effect of various concentrations of calcium nitrate and calcium chloride on the primary root (radicle) growth of cotton seed at a suboptimal temperature was evaluated 14 days after imbibition onset under laboratory conditions. Both forms of calcium at concentrations up to 10 mM enhanced cotton seed radicle growth at 15 C.

The effect of calcium sulfate on cotton seed radicle growth at a low temperature was evaluated under laboratory conditions. Direct imbibition of solutions of calcium sulfate was stimulatory to radicle growth at 15 C at concentrations up to 10 mM. Anomalous stimulation of radicle growth at 15 C occurred when seed rolls moistened with water were placed adjacent to dilute open solutions of calcium and magnesium sulfate inside sealed chambers. The stimulation appeared due to an indirect influence of sulfate by an unknown mechanism.

In a preliminary, unreplicated test, cotton was planted in 40 inch and 27 inch rows on April 10 and again on May 1. Narrow rows outyielded 40 inch rows at both planting dates. The yield difference between the row spacing treatments was greatest in the May 1 planting. Both row spacings had higher yields when planted on the later date, as did both the DPL 90 and ST506 varieties used in the test.

The use of nitrification inhibitors delays the conversion of ammonium fertilizers to the nitrate form and has the potential to increase nitrogen use efficiency in irrigated agriculture. Two field experiments were conducted at the Maricopa Agricultural Center in 1986 to evaluate the effect of two nitrification inhibitors (N-Serve and an experimental compound, ACP) on the growth, yield, nitrogen uptake, and fertilizer use efficiency obtained by growing cotton using buried-drip and furrow irrigation. ¹⁵N labeled ammonium sulfate was applied with and without nitrification inhibitors at the beginning of the season. Whole plant samples were taken at the end of the season to determine N uptake efficiency. No significant differences in growth, lint yield or N uptake efficiency were detected due to the application of either inhibitor. The conditions where nitrification inhibitors might improve nitrogen use efficiency in furrow irrigated cotton production are discussed.

Purple nutsedge Cyperus rotundus is an important weed in cotton (Gossypium spp.) production in Arizona. It is estimated that 15% of the crop acreage is infested. The technology available for selective control of purple nutsedge is not adequate and the infestation level of this weed is increasing. In 1986, the thiocarbamate herbicides, vernolate (Surpass), EPTC (Eptam, Genep) and butylate (Swan +, Genate plus) were evaluated as preplant and postemergence incorporated applications for selective control of purple nutsedge in cotton. There were 25 different trials conducted in Arizona cotton fields. Butylate was more selective to seedling cotton than EPTC and vernolate but all were capable of unacceptable cotton injury. Where preplant irrigations require every furrow irrigation, this concentrated the thiocarbamates in the seed row and resulted in less selectivity. Preplant treatments controlled purple nutsedge for 1 or 2 postemergence irrigations. Postemergence applications were most effective following preplant treatments but were not consistent in controlling nutsedge season -long. This research indicates that purple nutsedge lowered yields only when the cotton was stunted in growth by severe early season infestations. Wherever cotton established dominance over the weeds, yields were not affected. Preplant applications of butylate, if carefully adjusted for the growing conditions, can provide early season control of purple nutsedge.

Research was conducted at Maricopa, AZ with EPTC (S -ethyl dipropyl carbamothioate) and butylate (S-ethyl bis(2-methylpropyl)carbamothioate) in 1986 to identify factors that influence the activity of these two thiocarbamates on cotton (Gossypium hirsutum). Butylate and eptc were applied alone and in combination with other cotton herbicides as either a preplant incorporated or preharrow treatment. The greatest injury to cotton and poorest weed control resulted when butylate or EPTC was applied alone on flat ground and incorporated to a depth of 2 inches or 4 to 6 inches. Adequate weed control and minimal injury to cotton was observed when these two thiocarbamates were applied pre-harrow.

Field research was conducted at Yuma and Goodyear, AZ on fallowed ground to measure the response of purple nutsedge to butylate and EPTC (Goodyear only). At Yuma, the greatest reduction in the number of live tubers resulted when two years of fallow were combined with annual summer application of 3.3 lb/A of butylate. At Goodyear, butylate and EPTC were more effective at controlling purple nutsedge when applied in early July vs early September. Also, one timely application of EPTC or butylate made in July was more successful in reducing the number of live tubers than two applications (July, Sept). September herbicide treatments were not as effective with an irrigation compared to without.

A breeding program aimed at increasing the ability of long and short staple cotton strains to emerge in saline soils under cool springtime soil conditions has now completed the second cycle of selection. Cycle II emergence results show evidence of progress.