Comparison of Interseeded Legumes and Small Grains for Cover Crop Establishment in Cotton J. Wayne Keeling,* Arthur G. Matches, C. Philip Brown, and T. Peter Karnezos ABSTRACT Wind erosion of soil is a potential problem in unprotected cotton (Gos- sypium hirsutum L.) fields on the Southern High Plains of Texas during winter and early spring. Our objective was to determine which winter annual forage legumes and small grains may be successfully established by fall Intel-seeding into standing cotton. Thirteen plantings were made over 6 yr at three locations. Both cotton and the interseeded forages were grown under rainfed conditions. The forages were winter wheat (Triticum aestivum L. emend. Thell.), rye (Secale cereale L.), Austrian winter pea [Pisum sativum subsp. pisum van arvense (L.) Poir.], hairy vetch (Vicia villosa Roth), subterranean clover (Trifolium subterraneum L.; 5 cultivars), rose clover (Trif. hirtum All.; 3 cultivars), crimson clover (Trif. incarnation L.; 2 cultivars), red clover (Trif. pratense L.), berseem clover (Trif. alexandrinum L.), and barrel medic (Medicago truncatula Gaertn.; 2 cultivars). Successful stands of wheat, rye, winter pea, and hairy vetch were obtained in 69% of the plantings, but in only 53% for the other forages. Establishment of the small-seeded legumes (clovers and medics), which must be planted at a shallow depth, seemed to be governed by the timing of effective rainfall events after seeding. Estab- lishment of the larger-seeded wheat, rye, winter pea, and vetch was less dependent on timely rainfall after planting. Of these winter annu- als, wheat and rye were the most dependable in producing a soil cover. T HE SOUTHERN HIGH PLAINS of Texas is a major cot- ton producing region, with annual planting of between 1.04 to 1.32 million ha in the 25 counties surrounding Lub- bock. Interest in conservation tillage production systems has increased because of the potential for reducing pro- duction costs and increasing profitability as well as sat- isfying the conservation compliance provision of the U.S. J.W. Keeling, Texas A&M Agric. Exp. Stn., Rt. 3, Box 219, Lubbock, TX 79401; A.G. Matches and C.P. Brown, Texas Tech Univ., Dep. of Plant and Soil Sciences, Box 42134, Lubbock, TX 74909; T.P. Karnezos, Altech, Nicholasville, KY 40356. Received 28 Mar. 1995. *Corresponding author. Published in Agron. J. 88:219-222 (1996). Food Security Act of 1985 (Harman et al., 1989). Con- servation tillage systems with terminated wheat (killed by herbicide prior to cotton planting) as a cover crop increased cotton yields and profitability on the Texas Southern High Plains (Segarra et al., 1991; Keeling et al., 1989). Because cotton produces very little crop residue, cotton fields are highly erodible during late winter and spring. Cover crops provide an effective alternative for protecting soil from erosion. Legumes might be superior to small grains as cover crops on the High Plains of Texas, because of their N 2 -fixation capabilities (Kramer and Davis, 1949). Fall-seeded legume cover crops have shown significant N contributions to sub- sequent crop production, as well as providing soil protec- tion during winter months (Blevins et al., 1990; Holder- baum et al., 1990; Power et al., 1991; Touchton et al., 1984; Wagger, 1989; Stevensetal., 1992). Growth during the fall provides cover to protect soils during late winter and spring, which are typically periods with low rainfall and high winds. Our objective was to determine whether annual legumes and small grains can be successfully es- tablished when fall-seeded into standing cotton. MATERIALS AND METHODS Nonirrigated cotton (Paymaster HS26) was grown with a pre- plant application of trifluralin [2,6-dinitro-A^,A^-dipropyl-4-(tri- fluoromethyl)benzenamine] at rates of 0.56 to 0.67 kg ha~' for control of annual weeds. Plots were cultivated as needed to con- trol weeds. The canopy was never completely closed between rows for any experiment. Cotton lint was usually harvested in November. Just prior to boll opening, the forage cover crops were planted as three rows spaced 25 cm apart between cotton rows spaced 102 cm apart. Plots were 1.8 m long. A late-season cultivation was performed to prepare the soil prior to forage Abbreviations: DM, dry matter. Published March, 1996