This article offers practical advice on in-row weeding techniques and tooling setups.

The efficacy of Roundupm herbicide for the control of common Arizona weeds in Roundup Ready® cotton was evaluated in field studies conducted at the Maricopa Agricultural Center in 1995. Promising results were obtained with 1 lb a.i./A (1 quart/A) over-the-top band applications of Roundup when cotton had 1 to 2 true leaves followed by a second, "sloppy", post-directed application ofRoundup at 1 lb a.i./A when cotton had 4 to 5 true leaves. Excellent control of small Palmer Amaranth, Wright Groundcherry, and annual morningglory seedlings was obtained with each 1 lb a.i./A Roundup application in the broadleaf weed study. The two sequential 1 lb a.i./A Roundup applications kept plots free of broadleaf weeds until layby. In the nutsedge weed control study, it was found that nutsedge plants treated with a single 1 lb a. i./A application of Roundup were stunted and exhibited leaf chlorosis, but efficacy was marginal with weed control ratings of only 40 to 50 percent. Nutsedge control ratings for an application of norflurazon (i.e., Zorial) alone or combined with Roundup applied at the 1 to 2 true leaf stage of cotton were 63 and 75 percent, respectively. Two sequential applications of Roundup at 1 lb a.i./A, both with or without norflurazon, resulted in about 90 percent nutsedge control. Roundup Ready cotton exhibited good tolerance to two sequential early season 1 lb a.i./A Roundup applications, as made in these studies, with no apparent seed cotton or lint yield reductions.

Although the cost for water is one of the largest expenditures in a grower's budget, many growers still over -irrigate their fields to assure that there will be no yield losses. Although these over -irrigations usually do not cause any negative effect to the crop, they can cause the loss of available nitrogen to the plant and the potential of nitrate contamination of groundwater resources. To assess what impact over-irrigation may have on yield and the potential for groundwater contamination, a drainage lysimeter study was initiated at the Maricopa Agricultural Center, Maricopa Arizona. Drainage lysimeters are large steel boxes with the tops open. In this study, three lysimeters were installed. The lysimeters were 80" wide (two row widths), five feet long, and six feet deep. They were placed 18 inches below the soil surface and filled with soil as to best represent the soil in its natural condition. On April 10, cotton was dry planted and watered up. Throughout the season, water samples were taken from the lysimeters and from suction lysimeters placed in the field. Nitrogen applications were made according to field conditions and weekly petiole sampling. Irrigations were made according to field conditions and using the AZSCHED irrigation scheduling program. Treatment one was irrigated according to the schedule and amount recommended by AZSCHED. In treatment two, the timing was the same as treatment one, but the amount applied was 0.25 times more. Treatment three was also irrigated at the same time but with 0.5 times more water. Yield samples were taken at the end of the season and showed no significant differences between treatments, with yields averaging about 1100 lbs /acre of lint. The drainage amounts ranged from 4" in treatment three to 1.5 inches in treatment one. The corresponding nitrate -N losses were 33 lbs/acre for treatment three and 20 lbs/acre for treatment one. Monitoring will continue over the winter to assess the impact of winter rainfall.

Lint yield response to three irrigation treatments based on allowable soil moisture depletion regimes of 50, 75, and 100% depletion of available soil moisture was tested on both a determinate (D&PL 5415) and an indeterminate (D&PL 5816) upland cotton. Arizona Meteorological Weather Networks' (AZMET) potential evapotranspiration (ETo) estimates in combination with cotton crop coefficients were used in a summation manner until targeted depletion thresholds were reached which then triggered the desired irrigation event. The experiment consisted of three irrigation treatments with each main irrigation treatment containing both the determinate and indeterminate variety selection resulting in a randomized complete block split plot design. Actual irrigation volume delivered was 46, 42, and 32 acre inches /acre in 1994 and 52, 48, and 36 acre inches /acre in 1995 for the wet, medium, and dry treatment respectively. Lint yields were significantly reduced in 1994 when available soil moisture depletion exceeded 75% in the determinate variety with no significant yield differences in the indeterminate variety in 1994 across all irrigation treatment regimes. In 1995, lint yields were down across all treatments and varieties with the only statistically significant reduction in lint yield (relative to all 1995 yields) occurring in the dry indeterminate block

Eighteen long staple varieties were tested in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. The highest yielding variety in 1995 was OA 312 (Conquistador) with a yield of 937 pounds of lint per acre. It was followed by OA 304 the high yielding variety from the year before and three other Olvey varieties and Phytogen 57. The average yield from this trial was nearly 100 pounds per acre higher than the previous trial Yield and other agronomic data as well as fiber quality data are contained in this paper.

Twenty one Upland cotton advanced strains varieties which are not commercially available were evaluated in replicated field studies in 1995 on two farm sites in Queen Creek, Arizona and Buckeye, Arizona representing seven seed companies. Twenty four advanced strains representing eight seed companies were evaluated on a commercial site in Gila Bend, Arizona. Participating seed companies submitted three advanced strain entries, plus a commercially available check of their choice at each site. The Gila Bend site represented strains of a more indeterminate nature for a full season production approach, while the sites at Buckeye and Queen Creek consisted of more determinate entry characteristics to represent a reduced season production approach. The highest lint yields were obtained from Germains 9230 (1756 lb./a), Delta and Pine Land Co. 5517 (1116 lb./a), and Delta and Pine Land Co. 9057 (1578 lb./a) at Queen Creek, Buckeye, and Gila Bend respectively.

Sixteen short staple advanced strains/varieties were grown in a replicated field on the Safford Agricultural Center in 1995. These included entries from ChemBred, Delta Pine, Sure-Grow, Olvey and Associates, McDaniels, NMSU and Australia. The Australian materials produced quite well with three of the entries placing in the top four with respect to lint yield. The highest yielding cultivar being an Australian entry, A83203-183, with a yield of 1508.5 pounds of lint per acre. In addition to yield data, this report includes many agronomic parameters including seedling vigor index, height to node ratio, and boll size. HVI analyses are also included in the report.

Variety trials were grown at two locations and with two different sets of short staple varieties. One trial on the Robbs farm, north of Kansas Settlement, tested eight acalas varieties from New Mexico and California. The other trial on the Curry farm, southwest of Kansas Settlement and north of Sunsites, tested twelve upland varieties as part of the statewide testing program. The latter trial was grown under drip irrigation.

Forty one short staple varieties were grown in a replicated field trial on the Safford Agricultural Center. DP 5690 was the highest yielding variety with a yield of 1302 pounds of lint per acre with DP 90 in second place but with 100 pounds of lint less per acre. Seedcotton yields were essentially identical to 1994.

Eleven field experiments were conducted in many of the cotton growing areas of Arizona in 1995 for the purpose of evaluating Upland cotton varieties in terms of adaptability and performance. Seven commercial cottonseed companies participated in the program. Two varieties were submitted from each company at each location. Experiments were conducted on grower - cooperator fields in each case. Locations used in the program spanned the range of conditions common to cotton producing areas of the state from about 150 ft. to 4, 000 ft. elevation. Results indicated a broad range of adaptability and competitiveness on the part of each of the participating companies and their representative varieties. The 1995 season offered some extremes in terms of weather conditions, with very cold spring temperatures, followed by very hot conditions in July and August. Variety performance under these extremes offers an opportunity for review and comparison with regard to adaptability. Each of the companies offers a compliment of varieties that can serve to match various production strategies commonly employed in the state as well as showing a strong capacity to be regionally adaptive.