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 single field experiment was conducted at Marana, AZ in 1988 and 1999 to evaluate a scheduled (based upon stage of growth) versus a feedback approach (based upon growth parameters and crop conditions) to nitrogen (N) and mepiquat chloride (PixTM) applications on Upland cotton (Gossypium hirsutum L.). The parameters used in the feedback applications for both N and Pix included fruit retention (FR) levels and height to node ratios (HNRs) with respect to established baselines for irrigated cotton grown in the desert Southwest. Treatments consisted of all combinations of feedback and scheduled applications of both N and Pix. In 1998, the highest lint yields occurred in the treatment consisting of Pix feedback and N feedback (treatment two) management. However, there were no significant differences (P≤0.05) among any of the treatments with respect to yield. In 1999, significant light yield increases (P<0.05) were found in the treatments consisting of Pix feedback and N feedback (treatment two), Pix scheduled and N scheduled (treatment three), and Pix scheduled and N scheduled (treatment five) management approaches.

A series of experiments have been conducted from 1988 to 1999 at various locations across the cotton producing regions of Arizona to evaluate mepiquat chloride (MC) applications in terms of plant growth and yield. These experiments were designed to evaluate MC under three application regimes. These regimes included low rate multiple applications, late season applications, and a feedback vs. scheduled management of MC and nitrogen (N) applications. The objective of this summary (including a total of 31 site-years) is to determine which of these three application regimes offer the greatest opportunity for a positive lint yield response to MC. Stability analysis was conducted by regressing the treatment mean lint yield against the environmental mean for each application regime. Results from the stability analyses revealed that the most viable method of application is a feedback approach for both MC and fertilizer N. The most reliable technique associated with plant assessment in a feedback approach was the height to node ratio (HNR) to indicate vegetative tendencies for determining the appropriate rate and timing of MC applications.

Each year the University of Arizona conducts upland cotton variety tests to evaluate the performance of a diverse set of experimental lines and commercial varieties in Arizona. One such program is the Regional Variety Test (RVT). In 1999, we evaluated a total of 59 varieties at one or more locations in Arizona. These varieties were submitted to us for testing by 16 private seed companies and two public breeding programs. This report presents the results of the trials conducted at Maricopa, Marana, and Safford.

A study was conducted at the University of Arizona Maricopa Agricultural Center (MAC) to compare growth and development characteristics and determine differences in fruiting pattern and retention among two obsolete (Deltapine 16 and Acala 442) and three modern (Deltapine Acala 90, Deltapine 5415, and NuCotn 33b) Upland (G. hirsutum L.) cotton cultivars grown in an irrigated production system in Arizona. Results indicated that the majority of yield was produced at fruiting branches 10 through 18 at position one. Lint yield results indicated no significant differences among all cultivars tested, except for Acala 442, which was significantly lower than all others. Obsolete cultivars produced significantly higher amounts of lint on vegetative branches than modern varieties. Deltapine 16, followed by NuCotn 33b, had the highest harvest index and was the most efficient cultivar grown with respect to dry matter partitioning.

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.

Experimental strains containing the Bollgard II® gene construct have been developed in upland cotton through transformation of DP50B. We evaluated the field performance of two of these new strains at four locations in Arizona. Lint yields of these two lines compare favorably with the parent material used to develop the lines (DP50B), but are significantly lower than other conventional and transgenic varieties that are adapted to Arizona. Fiber quality was not compromised in the Bollgard II strains. In fact, one line, 15813, produced fiber that was of superior quality to DP50B. One of the lines (15985) was similar to DP50B for all traits measured in this test. These results show that the Bollgard II gene construct does not, in itself, compromise agronomic performance. Thus, it should be possible to successfully place Bollgard II into other varieties that are adapted to Arizona in order to produce an agronomically superior variety with the added benefit of the Bollgard II technology.

An experiment was conducted at the University of Arizona Maricopa Agricultural Center, Maricopa, Arizona in 1999 to compare and evaluate agronomic and economic differences between Ultra Narrow Row (UNR) and conventional cotton row spacing systems with respect to yield, fiber quality, earliness potential, plant growth and development, and production costs. Row spacing was 10 and 40 inches for the UNR and conventional systems, respectively. Two varieties were evaluated within each row spacing, Sure Grow 747 (SG 747) and Delta Pine 429RR (DP 429RR). Lygus populations were extremely high in the Maricopa, Arizona region in 1999 which resulted in poor fruit retention from early through mid-season. As a result of poor boll load through mid-season, the UNR plots were irrigated and grown later into the season than desired along with the conventional cotton in order to set and develop a later season boll load. The mean lint yield averaged across row spacing was significantly greater (P=0.05) in the UNR row spacing at 1334 lb/A than for the conventional row spacing at 1213 lb/A. SG 747 produced 1426 and 1337lb/A of lint in the UNR and conventional systems, respectively. DP 429RR produced 1242 and 1089 lb/A of lint in the UNR and conventional systems respectively. Fiber grades were all 21 or 31 in both UNR and conventional systems. Micronaire was 4.9 or less in both varieties within the UNR system. Micronaire was high at 5.3 in the conventionally produced SG 747 resulting in discount but was acceptable at 4.7 in the conventionally produced DP 429RR. Length and strength measurements met base standards in all cotton variety and row spacing combinations. Neither the conventional or the UNR cotton production systems were profitable due primarily to high chemical insect control costs and early season boll loss. However, UNR production costs were lower by $0.09 per pound than in the conventional system on a cash cost basis and $0.14 per pound lower when considering total costs including variable and ownership costs.

In two 1999 Arizona studies, a preplant incorporated (PPI) application of Prowl (2.4 pt/A) or Treflan (0.75 lb a.i./A) followed by a topical Roundup Ultra (1 qt/A) application at the 3 to 4 true leaf cotton growth stage provided good weed control. At the University of Arizona Maricopa Agricultural Center field that had low density weed populations, a postemergence topical Staple (1.8 oz/A) application also provided good weed control was more expensive. At the Buckeye, Arizona study site, a PPI application of Prowl at a reduced rate (1.2 pt/A) was as effective as the full rate (2.4 pt/A) but a preemergence application of Prowl (2.4 pt/A) was not as effective as either of the PPI Prowl rates or PPI Treflan (0.75 lb a.i./A). A postemergence topical Staple application (1.8 oz/A) following the Roundup Ultra application did not significantly improve weed control. After one field season of experimentation and observation in Arizona UNR cotton, experience suggests that in fields with low to moderate weed populations, a PPI Prowl or Treflan application followed by a postemergence topical Roundup Ultra application will provide acceptable weed control in most fields. However, the presence of nutsedge or other difficult to control weeds may require two postemergence topical Roundup Ultra application prior to the four leaf growth stage of cotton. More research is needed to further explore weed control options in Arizona UNR cotton production systems.