planted annually, primarily in monoculture systems (TASS, 2002). Furthermore, about 5.5 million stocker Agriculture in the Texas High Plains depends heavily on irrigation cattle (about 25% of U.S. total; TASS, 2002; USDA with water withdrawn from the Ogallala aquifer at nonsustainable rates. Our hypothesis was that integrating crop and livestock systems Natl. Agric. Stat. Serv., 2003) are shipped into the High would reduce irrigation water use, maintain profitability, and diversify profitability, and impact on water use of (i) a cotton mono-Texas Tech Univ., Lubbock, TX 79409-2122; R. Kellison, Silver Creek culture system managed by best management practices Farm, Lockney, TX 79241; E. Segarra, Dep. of Agric. and Appl. Econ., Texas Tech Univ., Lubbock, TX 79409; T. Wheeler, Texas A&M for the area and (ii) an integrated cotton-forage-livestock Agric. Exp. Stn., Lubbock, TX 79403; P. Dotray, Dep. of Plant and system. This long-term project continues, but results of Soil Sci., Texas Tech Univ., Lubbock, TX 79409-2122 and Texas Coopthe first 5 yr are presented here. erative Extension, Lubbock, TX 79403; J.C. Conkwright, High Plains Underground Water Conservation District No. 1, Lubbock, TX 79411-2499; and V. Acosta-Martinez, USDA-ARS, Lubbock, TX 79415.

Field experiments conducted in 1991, 1992, and 1993 evaluated Palmer amaranth and devil's-claw control and cotton injury with pyrithiobac applied PPI, PRE, or POST. Pyrithiobac at 36 or 71 g ae/ha applied PPI, PRE, or POST did not injure cotton. Pyrithiobac at 140 g/ha applied PPI or PRE injured cotton 9 to 11% 6 wk after treatment. Cotton recovered and no injury was observed 12 wk after treatment. Pyrithiobac applied PPI and PRE at 71 g/ha controlled Palmer amaranth at least 97% 6 wk after treatment. Palmer amaranth control with pyrithiobac applied POST was more variable and influenced by environmental conditions. Palmer amaranth control with 71 g/ha of pyrithiobac exceeded that with 36 g/ha. Devil's-claw control with pyrithiobac was better with POST applications than PPI or PRE applications. Pyrithiobac applied POST at 140 g/ha controlled devil's-claw 83–97%. These studies indicate that pyrithiobac can effectively control Palmer amaranth and devil's-claw in cotton on the Texas Southern High Plains when applied at appropriate rates and timings.

The anticipated release of EnlistTM cotton, corn, and soybean cultivars likely will increase the use of 2,4-D, raising concerns over potential injury to susceptible cotton. An experiment was conducted at 12 locations over 2013 and 2014 to determine the impact of 2,4-D at rates simulating drift (2 g ae ha−1) and tank contamination (40 g ae ha−1) on cotton during six different growth stages. Growth stages at application included four leaf (4-lf), nine leaf (9-lf), first bloom (FB), FB + 2 wk, FB + 4 wk, and FB + 6 wk. Locations were grouped according to percent yield loss compared to the nontreated check (NTC), with group I having the least yield loss and group III having the most. Epinasty from 2,4-D was more pronounced with applications during vegetative growth stages. Importantly, yield loss did not correlate with visual symptomology, but more closely followed effects on boll number. The contamination rate at 9-lf, FB, or FB + 2 wk had the greatest effect across locations, reducing the number of bolls per plant when compared to the NTC, with no effect when applied at FB + 4 wk or later. A reduction of boll number was not detectable with the drift rate except in group III when applied at the FB stage. Yield was influenced by 2,4-D rate and stage of cotton growth. Over all locations, loss in yield of greater than 20% occurred at 5 of 12 locations when the drift rate was applied between 4-lf and FB + 2 wk (highest impact at FB). For the contamination rate, yield loss was observed at all 12 locations; averaged over these locations yield loss ranged from 7 to 66% across all growth stages. Results suggest the greatest yield impact from 2,4-D occurs between 9-lf and FB + 2 wk, and the level of impact is influenced by 2,4-D rate, crop growth stage, and environmental conditions.

Field experiments from 1997 to 1999 examined cotton cv. ‘Coker 312’ that was genetically transformed to tolerate glufosinate. None of the glufosinate treatments caused visible injury to the glufosinate-tolerant cotton, but treatments were lethal to nontransformed or nonexpressing cotton. No glufosinate treatment adversely affected plant height at maturity, total number of nodes, bolls per plant, or boll positions. Glufosinate applications of 0.6 kg ha−1 made at eight stages of growth, ranging from cotyledon stage to 50% open boll, did not adversely affect yield or fiber quality as measured by micronaire or fiber length and strength. Sequential glufosinate applications up to four stages of growth from the zero- to one-leaf stage to the 14- to 15-leaf stage or individual glufosinate applications at 3.3 kg ha−1 made at the two- to three-leaf stage of growth also did not adversely affect yield or fiber quality. Overall yields in these studies were low relative to normal Texas Southern High Plains cotton yield because these studies were conducted using a Coker 312 parental line, which is generally a poor performer in this region. This research indicated that the transformation events for glufosinate tolerance in cotton were successful and the glufosinate-tolerance gene was expressed throughout the growing season. Transformation and field testing of other cotton varieties are needed to improve varietal performance on the Texas Southern High Plains.