Foliar applications of zinc as a chelate or sulphate with ammonium sulphate to plots of cotton resulted in beet armyworm infestations with leaf damage that was 2.3 to 3.1 times greater than that in control plots.

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Three upland cotton varielies--Stoneville 506, Deltapine 20, and Deltapine 77--were planted on 4 dates in 1988 at the Maricopa Agricultural Center and observed for flowering boll opening and lint yield. Results from the 1988 studies and those from similar tests in 1985-1987 are being used to determine the relationship of accumulated heat units to the timing of key stages in crop development.

Cotton lint yields in the variety trials in Graham county were higher than the 1987 yields by close to 200 pounds per acre. Two varieties, BR 110 and NK KNX 111 (now KC 311) yielded more than DP 90 at the Thatcher site, the highest yield being 1,569 pounds of lint per acre. In Eden, DP 90 was the highest yielding variety with 1,237 pounds of lint per acre. The New Mexico acalas didn't yield as much lint per acre as the top yielding varieties, but with 1988's premium, produced substantial income per acre. In Thatcher the highest yielding acala produced $861 per acre compared with BR 110's $910, whereas in Eden the highest yielding acala produced $736 per acre against DP 90's $717.

Nine acala varieties were grown in the Cochise area of Cochise county. An experimental New Mexico variety B510 was the top yielder in the test, producing 1,287 pounds of lint per acre. The top variety in 1987, 1517-77BR, was next to the bottom in the 1988 test, probably due to low plant population. Variety characteristics such as plant height, wilt susceptibility, relative maturity and lint turnout are quantified in the study along with final plant populations and lint quality. Information on cotton variety strip trials implemented in the county is also given.

Two short staple variety trials and 1 long staple variety trial were harvested in Greenlee county in 1988. In the short staple trial comparing the new and experimental New Mexico acalas with 2 other lower quality varieties, Genhains new GC 260 was the top yielding variety with 1,087 pounds of lint per acre, but it came in fifth when comparing dollar value per acre because of the premium structure for the New Mexico acalas. Two new experimental acalas, 2745 and B510, produced the highest income per acre. The short staple trial, which tested longer - season varieties, had problems with low micronaire values. The newly released 1517-88 variety produced the top yield and produced the most income per acre. Two of the experimental long staple varieties topped the yield of S-6 and 3 of the 7 varieties tested yielded over 650 pounds of lint per acre.

Seven upland cotton varieties and pima S-6 were demonstrated in Mohave Valley in Mohave County in 1988. The elevation there is 500 feet. Of the 7 upland varieties, 2 were new and had not previously been tried in the area; 1 had been tried for the first time last year. Pima S-6 was a new introduction to the Valley. Trial results indicated that the new introduction Tifcot 56 led the trial, yielding 901 lbs. of lint per acre. It was followed by DPL 90 at 886, DPL 50 at 884, DPL 77 at 819, BR 110 at 76$ DES 119 at 755, and Delcott 344 at 664. The first attempt at pima S-6 yielded 447 pounds of lint per acre. Its plot in 1988 was basically new ground that had not had a crop on it for the past 5 years.

When cotton is irrigated at long intervals, the root systems become less effective at absorbing water during heavy fruiting, even when the soil is moist. That ineffectiveness, if not counteracted by frequent watering can exaggerate water stress responses during fruiting and promote early cutout. Deltapine 90 cotton was grown at the Maricopa Agricultural Center in 1988 and watered either by daily drip irrigation or by level -basin flooding. In the flood-irrigated plots, various schedules for applying water during fruiting were compared with minimal differences in total water applied. The check treatment (9 postplant irrigations) yielded approximately 2 bales of lint per acre. Small supplemental irrigations on 13 July and 22 July, splitting the normal irrigation cycles, increased yield 45% for only 6% more applied water. Daily drip irrigation in the trials increased yield 63% above the check on 1% more applied water over the season. The results show that flood- irrigated yields can approach drip-irrigated yields without excessive water use, if the irrigation cycle is shortened during fruiting.

Three methods were used to schedule irrigations on replicated plots at the Maricopa Ag Center using DPL 90 cotton. The three methods were: a soil water balance model based on historic consumptive use curves, a soil water balance model based on the Modified Penman Equation and daily weather (AZMET), and infrared thermometry using the C.W.S.I. A potassium-bromide conservative tracer was applied at selected sites in the plots to evaluate leaching characteristics. The irrigation scheduling test was duplicated at the Safford Experiment Station and is presented in another report. Results from the 1988 data indicate that there was no significant difference in yield between the 3 methods. There was a significant difference in water applied; the historic consumptive-use curves was the lowest and the Penman equation method was the highest.

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