Cotton Yield and Fiber Quality from Irrigated Tillage Systems in the Tennessee Valley

Cotton (Gossypium hirsutum L.) yield and quality responses to irrigation have not been described for conservation management systems that growers are rapidly adopting. We conducted a field experiment from 2001–2003 in the Tennessee Valley near Belle Mina, AL on a Decatur silt loam (fine, kaolinitic, thermic Rhodic Paleudults) to examine how irrigation regimes and tillage systems affect ginning percentage, lint yield, and fiber quality (length, micronaire, strength, and fiber length uniformity). Treatments were arranged with a splitplot structure in a randomized complete block design with three replications.Main plots were a factorial combination of conventional tillage (CT) with and without a fall paratill operation and no surface tillage (NST) following a rye (Secale cereale L.) cover crop with and without a fall paratill operation. Subplots were irrigation regimes (0, 2.7, 5.4, and 8.1mmd). Ginning percentage increased 2% followingCT in 1 of 3 yr (2002) while irrigation improved ginning percentage in 2 of 3 yr (2002 and 2003). The NST systems increased lint yields 13% in 2003 compared with CT systems while irrigation increased yields 46 and 32% over nonirrigated yields in 2002 and 2003, respectively. Fiber properties were affected by tillage systems, primarily in 2002. Irrigation regimes affected length, micronaire, and fiber length uniformity in 2002 and 2003. Fall paratilling had no effect on any measured variable, except for an inconsistent difference between tillage systems for fiber length uniformity. An irrigated conservation system, utilizing a cover crop, can improve cotton yields and positively influence fiber characteristics in the Tennessee Valley. WATER CAN BE A MAJOR limiting factor for cotton producers during the growing season due to sporadic summer rainfall patterns. Intermittent rainfall has prompted growers to utilize irrigation, if available, to supplement cotton water requirements during periods of short-term drought. Previous research has documented increased cotton yields and net returns with LEPA (lowenergy precision application) and sprinkler-irrigated cotton compared with nonirrigated cotton in the Texas High Plains and theDelta region ofMississippi (Bronson et al., 2001; Pringle and Martin, 2003). In the southeastern USA, annual rainfall normally exceeds evapotranspiration but is frequently distributed poorly, especially during the cotton growing season (Camp et al., 1999). Producers of agronomic crops, such as cotton, produced in coarse-textured soils of the southeastern Coastal Plain utilize overhead sprinkler systems for their irrigation requirements. Other irrigation alternatives, such as subsurface drip irrigation have been investigated to reduce water usage and deep tillage requirements of compacted soils (Camp et al., 1997, 1999). The researchers theorized that by keeping the soil moist, soil strength would be reduced, enabling roots to penetrate the compacted layer. That would diminish the need for a deep tillage operation, which is complicated by the presence of subsurface drip tape. Other concerns related to efficient water use have prompted some regulatory agencies to offer growers monetary alternatives to restrict irrigation in an effort to maintain water resources (Balkcom et al., 2004). A conservation system that utilizes a high-residue cover crop with noninversion deep tillage, to alleviate soil compaction, can also increase infiltration of rainfall and/or overhead irrigation, which may reduce water requirements, thereby protecting water resources. The elimination of compacted layers with noninversion tillage enables roots to explore a larger soil volume to obtain nutrients and moisture while surface soil disturbance is minimized to maintain crop residue on the soil surface (Busscher et al., 1988; Schwab et al., 2002). Previous studies conducted on coarse-textured Coastal Plain soils, prone to soil compaction, have documented yield responses for various crops to some form of deep tillage (Reeves and Touchton, 1986; Reeves and Mullins, 1995; Touchton et al., 1986). Finer-textured soils located in the Tennessee Valley, degraded from erosion attributed to long-term conventional farming practices and cotton monocropping, also responded to some form of fall in-row deep tillage (Raper et al., 2000a, 2000b; Schwab et al., 2002). However, a cover crop with no deep tillage produced yields similar to deep tillage on these fine-textured soils (Raper et al., 2000a, 2000b). Touchton et al. (1986) reported reduced cotton yields and no response to spring in-row subsoiling compared with CT and no-tillage across 2 yr. These studies all utilized a cover crop combined with deep tillage to accentuate the benefits of conservation tillage. Integrating irrigation and a conservation system that utilizes a cover crop has not been examined on a finer-textured soil of the Tennessee Valley. Therefore, our objective was to compare ginning percentages, lint yields, and fiber quality (length, micronaire, strength, and fiber length uniformity) across different irrigation levels in conventional and conservation tillage systems, with and without fall paratilling. MATERIALS AND METHODS The experimental site was established on a Decatur silt loam at the Tennessee Valley Research and Extension Center K.S. Balkcom, USDA-ARS, Natl. Soil Dynamics Lab., 411 S. Donahue Dr., Auburn, AL 36832; D.W. Reeves, USDA-ARS, J. Phil Campbell Sr.–Nat. Resour. Conserv. Cent., 1420 Experiment Stn. Rd., Watkinsville, GA 30677; J.N. Shaw, 202 Funchess Hall, Dep. of Agron. and Soils, Auburn Univ., Auburn, AL 36844; C.H. Burmester, Tennessee Valley Res. and Exp. Stn., P.O. Box 159, Belle Mina, AL 35615; and L.M. Curtis (retired), Dep. of Agric. Eng., Auburn, AL 36844. Received 26 July 2005. *Corresponding author ([email protected]). Published in Agron. J. 98:596–602 (2006).