DIVISION S-6—SOIL & WATER MANAGEMENT & CONSERVATION Conservation Tillage Systems for Cotton in the Tennessee Valley

ern Tennessee (Stevens et al., 1992; Bradley, 1993; Triplett et al., 1996), conservation tillage practiced on silty clay Yield reductions from no-tillage cotton (Gossypium hirsutum L.) soils in northern Alabama resulted in 8 to 15% yield jeopardized adoption of conservation systems in the Tennessee Valley region of north Alabama in the early 1990s. We conducted a study from reductions compared with conventional tillage (Brown 1995 to 1999 on a Decatur silt loam (fine, kaolinitic, thermic Rhodic et al., 1985; Burmester et al., 1993). Slow accumulation Paleudults) to develop a practical conservation tillage system with of growing degree day-units (base 15.5 C) in the spring competitive yields for the region. Treatments included a factorial and the potential for early fall freezes complicates mancombination of fall ridging (ridged and nonridged) and fall non-inveragement decisions in conservation tillage systems for sion deep tillage (none, in-row subsoiling, paratilling), along with the region (Norfleet et al., 1997). Consequently, many spring strip tillage and conventional tillage (fall chisel-spring disk). farmers were reluctant to adopt conservation tillage on All treatments, except conventional tillage, were established with a rye (Secale cereale L.) cover crop. Tillage systems were evaluated for a large scale, despite possible long term benefits of imsoil temperature, penetration resistance, a soil compaction index, soil proved soil quality. water, plant population, and seed cotton yield. Paratilling reduced Specific problems with conservation tillage must be soil compaction index 29 and 31% compared with conventional tillage overcome before widespread adoption of such systems and no-tillage, respectively. Subsoiling reduced the compaction index will occur in the region. Conservation tillage systems 12 and 15% compared with conventional tillage and no-tillage, respecthat produce large amounts of crop residue can modertively. Soil water content was decreased with the fall paratilled and ate soil temperature because residue acts as insulation subsoiled conservation tillage systems, compared with conventional (Lal, 1976; NeSmith et al., 1987). Planting cotton on tillage and no-tillage, suggesting increased rooting. Fall non-inversion deep tillage, either paratilling or in-row subsoiling with a narrowridges or removing residue from the soil surface may shanked subsoiler, resulted in the highest seed cotton yields; 16% alleviate soil temperature problems. Ridges have been greater than conventional tillage (2660 kg ha 1 ), and 10% greater found to provide better aeration and a warmer seedbed, than strict no-tillage (2810 kg ha 1 ) across a 4-yr duration. In this which allows for earlier planting and enhanced cotton region, non-inversion deep tillage under the row in fall, coupled with development (Boquet and Coco, 1993). Shinners et al. a rye cover crop to produce adequate residue for moisture conserva(1994) found that a residue free band (i.e., strip tillage) tion and erosion control, is a highly competitive and practical conservaincreased soil temperatures for corn (Zea mays L.) tion tillage system. growth in southern Wisconsin. An increase in soil compaction has also been impliS of the Tennessee River Valley in northern cated for poor cotton performance with conservation Alabama are inherently productive, but have pretillage in the region (Burmester et al., 1993). In-row dominantly been cropped to cotton since before the subsoiling at planting is frequently used to alleviate soil U.S. Civil War. Since cotton, a low residue crop, has compaction for cotton grown on sandy coastal plain been produced continuously for an extended period of soils (Vepraskas and Guthrie, 1992; Raper et al., 1994; time, soil degradation has occurred as a result of erosion Reeves and Mullins, 1995; Mullins et al., 1997). Howand loss of organic matter. ever, in a conservation tillage system, Touchton et al. Degradation of soil quality and increasing govern(1986) reported no cotton yield response to spring inmental regulations on the 50 to 60% of cropland classirow subsoiling in the Tennessee River Valley. Spring tillage in the silty clay soils of this region forms clods, fied as highly erodible land in the region resulted in leaving a rough seed bed that is frequently difficult to some farmers turning to conservation tillage systems in plant into, and which may suppress yields. The objective the early 1990s. The predominant system implemented of our research was to develop a conservation tillage was to plant without tillage directly into existing cotton system for cotton on Tennessee Valley soils that would stubble with no winter cover crop. Although equivalent manage soil compaction, maintain competitive yields, or greater yields have been reported for cotton grown and facilitate widespread adoption of conservation tillwith conservation tillage compared with conventional age in the region. tillage on loessial soils in northern Mississippi and westMATERIALS AND METHODS E.B. Schwab, D.W. Reeves, and R.L. Raper, USDA-ARS Soil Dynamics Research Unit, 411 S. Donahue Dr., Auburn, AL 36832; C.H. The study was initiated in November of 1994 at the TennesBurmester, Dep. of Agronomy and Soils, 202 Funchess Hall, Auburn see Valley Research and Extension Center of the Alabama University, Auburn, AL 36849. Joint contribution of the USDA-ARS Agriculture Experiment Station, in Belle Mina, AL. The soil and Auburn University Alabama Agric. Exp. Stn. Research supported in part by the Alabama Cotton Commission. Received 21 June 2001. *Corresponding author ([email protected]). Abbreviations: DAP, days after planting; RCB, randomized complete block design. Published in Soil Sci. Soc. Am. J. 66:569–577 (2002).