Arizona has experienced a trend toward increasing fiber micronaire values in recent years resulting in substantial discounts on fiber value. There is some evidence to suggest that irrigation termination management can impact fiber micronaire. Field studies were conducted in 2000 and 2001 at the University of Arizona Maricopa Agricultural Center (MAC; 1,175 ft. elevation) and the Yuma Valley Agricultural Center (YVAC; 150 ft. elevation) to evaluate the effects of three dates of irrigation termination on the yield of several Upland cotton varieties. Three dates of irrigation termination (IT1, IT2, and IT3) were imposed based upon crop development. The earliest irrigation termination date, IT1 was made slightly ahead of an optimum date to provide sufficient soil-water such that bolls set at the end of the first fruiting cycle would not be water stressed and could be fully matured. Thus, the IT1 date was imposed to try to reduce overall micronaire. The second termination (IT2) date provided one additional irrigation over an optimal point for the first cycle fruit set and two irrigations beyond IT1. The final (IT3) date (later September) was staged so that soil moisture would be sufficient for the development of a full top-crop potential. Lint yield and micronaire results have consistently revealed significant differences among the IT treatments. The micronaire values were consistently less than 5.0 for the IT1 treatments. Micronaire and lint yield values increased with later IT dates.

Arizona has experienced a trend toward increasing fiber micronaire values in recent years resulting in substantial discounts on fiber value. There is some evidence to suggest management can influence fiber micronaire. Approximately 400 cases were identified in cotton production areas in Arizona ranging from the lower Colorado River Valley to near 2,000 ft. elevation with grower cooperators in the 2000 and 2001 seasons. Field records were developed for each field by use of the University of Arizona Cotton Monitoring System (UA-CMS) for points such as variety, planting date, fertility management, irrigation schedules, irrigation termination, defoliation, etc. Routine plant measurements were conducted to monitor crop growth and development and to identify fruiting patterns and retention through the season. As the crop approached cutout and the lower bolls began to open, open boll samples were then collected from the lowest four, first position bolls (theoretically the bolls with the highest micronaire potential on the plant) from 10 plants, ginned, and the fiber analyzed for micronaire (low 4). From that point forward, total boll counts per unit area and percent open boll measurements are being made on 14-day intervals until the crop is defoliated. Following defoliation, final plant maps were performed. Relationships among low 4 sample micronaire, irrigation termination (IT), defoliation, and final crop micronaire were analyzed. Results indicate strong relationships with final fiber micronaire for factors such as total heat units (HU) accumulated by the crop from planting to IT, variety, region of production (environment), and green boll load at cutout. Results showed that as total HU accumulated from planting to IT exceeded approximately 2950 HU, micronaire levels significantly increased.

Nine defoliation treatments based on standard and reduced rates of Ginstar and Chlorate plus two additives (compounds F and S) were applied to Pima and Upland cotton to compare the treatment effects on percent leaf drop and yields. All of the treatments were beneficial to leaf drop compared to the untreated check with the Ginstar treatments generally performing better than the Chlorate. Both of the additives enhanced the early defoliation effectiveness for the reduced rates of Chlorate and Ginstar over all other treatments, including the full rates of the Chlorate and Ginstar. Generally, this same enhanced effectiveness was seen of the additives plus reduced rates over the full rates of Chlorate and Ginstar throughout the defoliation process. This is the second year of the study.

Two replicated on-farm short staple variety trials were planted in 1999. Twenty-two varieties were evaluated on the Claridge farm in Solomon and fifteen varieties on the Colvin farm near Ft. Thomas. Several new varieties were planted in these studies, including 2 transgenic varieties: DP 5690RR, BXN 16; 4 Israeli inter-specific hybrids and six other varieties seen for the first time. DP 35B was the highest yielding variety in the Claridge trial with BXN 47 a close second. Both varieties yielded over 1300 pounds of lint per acre. PM 1440 was the highest yielding variety in the Colvin trial with SG 747 and DP 5690RR following closely behind. These varieties yielded between 700 and 800 pounds of lint per acre. Other agronomic data from the varieties and HVI values from the lint are also included in this report.

Upland cotton advanced strains and commercial check comparison varieties were evaluated in replicated field studies at four locations in 1999. The test sites include Yuma, AZ., Buckeye, AZ., Maricopa, AZ., and Safford, AZ.. Ten seed companies submitted a maximum of five advanced strains entries per location. Three commercial check varieties were used at each site for comparison purposes and included DP 5415, SG 125, and STV 474.

A preliminary investigation was made in Ultra-narrow row cotton production on the Safford Agricultural Center to see if there was any promise in that technology for cotton producers in the high deserts of Arizona. Increases in plant populations to near 100,000 plants per acre in single lines, double lines and quadruple lines per bed were the goals of the study. In-season plant mapping to evaluate differences in plant growth characteristics were done along with yield measurements to evaluate differences. Yield increases were not seen with increases in plant populations in single row plantings nor in multiple row plantings.

A single field study was established in 2001 at the Safford Agricultural Center to evaluate the effects of planting date and variety on crop growth and yield. Ten varieties were selected and planted on three separate planting dates in a split-plot randomized complete block design with four replications. Results from this experiment indicated significant differences due to planting date and variety. The interaction between planting date and variety was not significant. Yield trends were increasing with later planting dates which is thought to be a function of the inclement weather conditions surrounding particularly planting date one but also two. This experiment provides some interesting results with respect to seedling vigor, survivability, and ultimately yield for the different varieties tested.

A single field experiment was established in 2001 at the Safford Agricultural Center to evaluate the effects planting method and seeding rate have on plant population and yield of an Upland cotton cultivar Deltapine DP655BR. Two planting methods; planting into moisture (pre-irrigate) and dry plant/water-up, were main effects with three seeding rates of 10, 20, and 30 lbs./acre as sub-effects. These effects were evaluated with respect to stand establishment and yield. Analysis of variance showed no significant differences with respect to planting method for either plant population or yield, so data was combined across main effects. Significant differences were observed in plant population and yield as a function of seeding rate. A linear increase in yield with plant population was observed. These results are not consistent with previous research performed examining plant population effects on yield. This experiment will be conducted again in 2002 in an effort to validate results observed in 2001.

The Acala and Upland Variety trials typically grown in Cochise County were combined into one study in 1999 and were planted on the Glenn Schmidt farm, in Kansas Settlement. Twelve varieties were tested including three New Mexico Acalas and one Interspecific Hybrid from Israel. The highest yielding variety in the trial was FM 989 with a yield near 1200 pounds of lint. It was also the highest yielding variety in the Cochise County trial in 1998. PM 1560 BG came in a close second with the Israeli varity (Hazera 151-208) and the two New Mexico varieties (1517-95 and 1517-99) yielding over 1100 pounds of lint.

Four field tests were conducted at three Arizona locations in 1999 to evaluate the performance of transgenic cotton varieties in Arizona. We included a total of 34 varieties in one or more of these tests. Across locations and varieties, Bollgard (BG) and stacked BG and Roundup Ready (BGRR) varieties produced about 7 to 8% greater lint yields than the conventional varieties from which they were derived. Across all varieties and all tests, the average lint yield of the Roundup Ultra sprayed RR or BGRR treatments was 1569 lb./A, while the average yield of the unsprayed RR or BGRR treatments was 1580 lb./A. Roundup Ready (RR) varieties produced lint yields similar to the conventional varieties with a couple of exceptions. Roundup Ready varieties tended to be taller and more vigorous than the conventional parent. Transgenic varieties were often different from the conventional parent in one or more traits, such as fiber quality, lint percent, boll weight, or maturity, but the variation was not associated with a particular transgene.