Two field experiments were conducted near Marana and Coolidge, AZ in 1999 to evaluate the effectiveness of a number of defoliation treatments on Upland (var. DP 33b and AP 6101) cotton. All treatments consisted of materials commercially available in Arizona. Results reinforce general recommendations regarding the use of low rates (relative to the label ranges) under warm weather conditions and increasing rates as temperatures cool. Defoliation treatments of Ginstar alone did a satisfactory job of defoliation and regrowth/topgrowth contol and were very similar to treatments including Prep or Integrate. Adding Prep or Integrate to Ginstar in this experiment did not improve defoliation or topgrowth control.

Weekly production advisories and weather updates are now available from the Internet. Nineteen location-specific advisories are developed each Monday morning and then transferred to the Main AZMET Internet Web Page located at URL address http://ag.arizona.edu/azmet. To retrieve advisories or updates from the Internet users must 1) log on to the Internet using the procedures required by your Internet service provider; 2) enter the URL for the Main AZMET Web Page; 3) move to the Cotton Advisory sub-page; and 4) select the advisory or update of interest. Advisories for the most recent week, this year to date, and all of 1999 are available at this Internet address.

A field study was conducted in 1999 at the University of Arizona Marana Agricultural Center (1,974 ft. elevation) to evaluate the effects of three planting dates on yield and crop development for eight Upland varieties. Soil temperature effects associated with date of planting and method of planting (dry or wet planting) were also evaluated in relation to soil temperature at the depth of seed placement. Planting dates ranged from 28 April to 20 May and 821-1157 heat units accumulated since Jan 1 (HU/Jan 1, 86/55o F thresholds). Lint yields generally declined with later dates of planting for all varieties. Soil temperatures associated with the dry planting method, which requires a water-up irrigation, experienced much wider diurnal variations, had slightly lower mean temperatures, and were more strongly coupled to ambient air conditions. Thus, dry planting methods impose more potential risk in terms of seedling stress. Overall, crop growth and development patterns or yield results were not significantly different between the planting methods. Either method can provide satisfactory results if managed appropriately.

Arizona Cooperative Extension generates and distributes weather-based Planting Date and Cotton Development Advisories for 19 cotton production areas (Aguila, Buckeye, Cochise Co., Coolidge, Eloy, Greenlee Co., Harquahala, Laveen, Litchfield Pk., Marana, Maricopa, Mohave Valley, Paloma, Parker, Pinal Co., Queen Creek, Roll, Safford and Yuma Valley). Planting Date Advisories are distributed from legal first planting date until the end of April and provide updates on heat-unit-based planting windows, recent and forecasted weather conditions, heat unit accumulations, variety selection, soil temperatures, recommended plant population, and early insect management and control. Cotton Development Advisories are distributed from early May through early September and provide updates on crop development, insects, weather and agronomy. The Cotton Advisory Program will continue in 2000, and growers may obtain from the AZMET Internet Web Page (http://ag.arizona.edu/azmet) or by mail/fax from local extension offices.

A series of boll measurements were taken at numerous locations in cotton producing areas across Arizona in 1999 in an attempt to continue to develop a yield prediction model with a project that began in 1993. Results from 1995 showed the strongest relationship between final open boll counts and yield compared to a number of other measurements. Based on these results, data collection on boll counts began in 1996 and has continued in 1997, 1998, and 1999. Boll counts were taken as the number of harvestable bolls per meter. All boll count measurements were made within one week of harvest. Number of bolls per unit area were then correlated to lint yield and an estimate for the number of bolls per area needed to produce a bale of lint was calculated. Estimates using all four years of data combined indicate that approximately 38 bolls per meter are needed to produce one bale of lint per acre.

An Integrated Cotton Management (ICM) Demonstration project was conducted on the Demonstration Farm at the Maricopa Agricultural Center in 1999 for the second year. In this project, all current guidelines and recommendations disseminated by the University of Arizona were integrated in a systems approach for cotton production. The Extension Specialists in agronomy, entomology, irrigation management, weed sciences, and plant pathology following the University recommendations made the management decisions. On a 52.7 acre field, 78% Bt and 22% non-Bt cotton was planted into moisture on April 9, 1999. Because of problems with cool temperatures and deep seeding, a stand of only 25,000 plants/acre was established. Weed control was achieved with one preplant application and two cultivations. The field was sprayed three times for lygus and two times for whitefly control. Approximately 38.6 acre-inches of irrigation water was applied. An average of 3005 lb/acre of seed cotton were harvested. After harvesting, a field budget was established. The variable costs per acre were $594.96 and the total cost was $957.96/acre. Average micronaire was 4.45, strength was 28.41 gm/Tex, length was 1.10 (1/100 in.) and grade color was 21. The price received for the cotton was 74.82¢/lb, including LPD and hail damage payments, just over 3¢/lb below the break-even price. An additional $139/acre in PFC payments was received but not calculated into the budget. This project demonstrates the utility and compatibility of current recommendations and the potential for integration of all disciplinary guidelines in one system.

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.

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.