Conservation Tillage and Cover Crop Influences on Cotton Production on a Southeastern U.S. Coastal Plain Soil

Understanding cover crop and tillage system interactions within specific environments can help maximize productivity and economic returns of cotton (Gossypium hirsutum L.) produced on sandy coastal plain soils of the southeastern USA. A strip-plot design with three replications was used to evaluate the cover crops Austrian winter pea [Pisum sativum L. ssp. arvense (L.)], balansa clover (Trifolium michelianum Savi), crimson clover (Trifolium incarnatum L.), hairy vetch (Vicia villosa Roth subsp. villosa), oil seed radish (Raphanus sativus L.), black oat (Avena strigosa Schreb.), and rye (Secale cereale L.) and tillage (strip and none) influences on cotton grown on a Bonifay fine sand (loamy, siliceous, subactive, thermic Grossarenic Plinthic Paleudults) nearWaynesboro,GA from 1999 to 2003. Drought influenced production 3 of 4 yr. Cover crop biomass was greatest from rye, intermediate from black oat, oilseed radish, hairy vetch, and Austrian winter pea. Hairy vetch and Austrian winter pea contained more than 80 kg N ha while other cover crops averaged ,40 kg N ha. Cotton yields following black oat and rye had returns above variable costs ha $461 and $406, respectively. Strip-tillage increased yields by 192 kg ha and annual returns by $112 ha over no-tillage, most likely due to improved available water. Combining strip-tillage with black oat was the best combination for maximizing profit. Using black oat with strip-tillage could increase cotton profit by $50 to $75 ha compared to systems using rye on the 1.45 million ha of cotton where conservation systems have been adopted. CONSERVATION TILLAGE SYSTEMS offer significant environmental and economic advantages for growing cotton in the southeastern USA (Bruce et al., 1995). Adoption of conservation tillage systems for cotton in the Southeast has grown to nearly 50% on the 2.9 million ha planted in 2004 (CTIC, 2005). Implementation of the Conservation Security Program in the USDA 2002 Farm Bill should provide a stimulus for increased adoption of conservation tillage systems because payments increase as producersmeet higher standards of conservation and environmental management. Achieving greater levels of conservation and environmental management requires regionally specific information about how cropping system components interact so that producers can select the best combination of practices for their farming conditions (Schomberg et al., 2003). The southeastern U.S. Coastal Plain is humid subtropical with an average rainfall of about 1100 mm yr. Many Coastal Plain soils are sandy with low waterholding capacities and often have compacted subsurface layers that further limit water availability for crop growth. Deep tillage or in-row subsoiling is generally recommended to increase the volume of soil that plant roots explore for water and nutrients (Vepraskas and Guthrie, 1992; Raper et al., 1994; Reeves and Mullins, 1995; Mullins et al., 1997; Zou et al., 2001; Rosolem et al., 2002) thereby increasing yield potential (Threadgill, 1982; Busscher et al., 1995; Frederick et al., 1998; Busscher et al., 2000). Many producers in the Coastal Plain use “strip-tillage” which includes coulters, rolling baskets, and in-row subsoiling with a 20to 50-cm shank to disrupt compacted layers when first converting to conservation tillage (Busscher et al., 1995; Busscher and Bauer, 2003). Although this systemdisturbs a 15to 30-cm wide zone, the undisturbed interrow surface area remains covered by residues which help reduce erosion and evaporative water loss (Kaspar et al., 1990). The tilled zone allows operation of conventional planters and fertilizer applicators and promotes faster warming of soil (Kaspar et al., 1990) in the spring which can increase germination rates. Improved water use efficiency in strip-tilled soil can increase cotton production up to 35% compared to that in conventional tilled soil (Lascano et al., 1994). Responses to deep tillage in these soils can be variable because of inherent differences in crop growth, soil type, and tillage tools (Bodhinayake et al., 1998; Rosolem et al., 2002; Busscher and Bauer, 2003). Cropping practices may also have an influence on response to deep tillage. Raper et al. (2000) found no benefit to strip-tillage in spring compared with strict no-tillage on soils of the Tennessee River Valley in northern Alabama when a rye cover crop was used. Cover crops appear to reduce compaction or recompaction by minimizing traffic effects or by disrupting compaction during periods when the water content is favorable for plant growth (Ess et al., 1998; Raper et al., 2000; Rosolem et al., 2002). Maximizing conservation system productivity in the southeastern USA requires additional biomass inputs provided by cover crops because they are essential for improving and maintaining soil biological, chemical, and physical properties (Langdale et al., 1990). Winter cereals are effective cover crops in the region because they establish rapidly, provide good winter ground cover and produce consistent amounts of biomass. Legume cover H.H. Schomberg, D.M. Endale, and D.S. Fisher, USDA-ARS, J. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA; R.G. McDaniel, Univ. of Georgia, Coop. Ext. Service, Waynesboro, GA; E. Mallard, Monsanto Co., Waynesboro, GA; and M.L. Cabrera, Univ. of Georgia, Crop and Soil Sciences Dep., Athens, GA. The mention of trade or manufacturer names is made for information only and does not imply an endorsement, recommendation, or exclusion by USDA-Agricultural Research Service. Received 13 Dec. 2005. *Corresponding author ([email protected]). Published in Agron. J. 98:1247–1256 (2006).