CONSERVATION ROTATIONS FOR COTTON PRODUCTION AND CARBON STORAGE

Authors: Reeves, Donald; DELANEY, D - AUBURN UNIVERSITY

Submitted to: Southern Conservation Tillage for Sustainable Agriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/24/2002
Publication Date: 6/24/2002
Citation: Reeves, D.W., Delaney, D.P. 2002. Conservation rotations for cotton production and carbon storage. In: E. Van Santen (ed.) Proceedings of the 25th Annual Southern Conservation Tillage for Sustainable Agriculture - Making Conservation Tillage Conventional: Building a Future on 25 Years of Research. Special Report no. 1, Alabama Agricultural Experiment Station and Auburn University, June 24-26, 2002, Auburn, Alabama. p. 344-348.

Interpretive Summary: Loss of soil carbon (organic matter) is a major cause of soil degradation in the Southeast. There is a need to develop cropping systems that are both profitable and that increase soil carbon. Adopting ideas from Brazil, we compared economics and soil carbon storage from various cotton rotations under conservation and conventional tillage in a field study in Alabama. An intensive system used a tropical legume (sunn hemp) and ultra-narrow row (UNR,7-inch) cotton in a rotation with wheat and corn. Standard systems used continuous cotton (both standard 40-inch rows and UNR) and a corn - cotton rotation. The UNR systems with conservation tillage had the highest net returns (from $97 to $105/acre per year) while the traditional system of conventional tillage-continuous cotton (40-inch rows) had the lowest returns ($36/acre per year). Conservation tillage increased soil carbon in the soil surface 46% compared to conventional tillage. Carbon storage was increased by systems that used wheat grown for grain or winter cereal cover crops. This information can be used by extension, NRCS, and private-sector consultants to promote the use of production systems that result in increased soil carbon; improving soil quality and productivity in the long term and enhancing economic sustainability of producers.

Technical Abstract: We conducted a 4-yr study on a Compass loamy sand (Plinthic Paleudult) to compare economics and soil organic carbon (SOC) storage of an intensive cropping system to standard cotton production systems in the Southeast. The system uses sunn hemp (Crotalaria juncea L.) and ultra-narrow row (UNR; 8-inch drill) cotton in a rotation with wheat (Triticum aestivum L.) and corn (Zea mays L.). The standard systems used continuous cotton (both standard 40-inch rows and ultra-narrow row) and a corn - cotton rotation with standard row widths. A cover crop mixture of black oat (Avena strigosa Schreb.)/rye (Secale cereale L.) was used in all systems preceding cotton and a white lupin (Lupinus albus L.)/crimson clover (Trifolium incarnatum L.) mix was used before corn in the corn-cotton and intensive system. All systems were tested under conservation and conventional tillage. At the end of the experiment, soil C was determined by dry combustion. The UNR systems with conservation tillage had the highest net returns [$105 A-1 yr-1 (continuous) and $97 A-1 yr-1 (intensive)] while the conventional tillage continuous 40-in system had the lowest returns ($36 A-1 yr-1). Conservation tillage increased SOC concentration in the top 2-in of soil 46% compared to conventional tillage. Cropping system affected SOC levels to the 4-in depth and the corn-cotton rotation resulted in the lowest SOC levels of all systems. For these drought-sensitive soils, UNR cotton production systems with conservation tillage and small grain cover or cash crops have the potential to rapidly increase soil organic matter; improving soil productivity and enhancing economic sustainability.