Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 12/12/2002
Publication Date: 12/12/2002
Citation: Reeves, D.W. 2002. Carbon sequestration in soil management and plant rotation systems. Anais II Congresso de Soja - Mercosoja 2002, Perspecivas do Agronegocio da Soja, June 3-6, 2002, Fox do Iquacu - PR, Brazil. Ministerio da Agricultura, Pecuaria e Abastecimento, Republica Federativa do Brasil. p. 131-137. 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: Research from Brazil has shown that warm humid climates have great potential to increase soil C. We conducted a 4 yr study on a sandy coastal plain soil in east-central Alabama (USA) to compare economics and soil C storage from various cotton rotations under conservation and conventional tillage. An intensive system used sunn hemp (Crotalaria juncea L.) and ultra-narrow row (UNR, 19-cm) cotton in a rotation with wheat (Triticum aestivum L.) and corn (Zea mays L.). Standard systems used continuous cotton (both standard 100-cm rows and UNR) and a corn - cotton rotation. The UNR systems with conservation tillage had the highest net returns [$259 ha-1 yr-1 (continuous) and $240 ha-1 yr-1 (intensive)] while the conventional tillage continuous 100-cm system had the lowest returns ($89 ha-1 yr-1). Conservation tillage increased SOC concentration in the top 5-cm of soil 46% compared to conventional tillage. Cropping system affected SOC levels to the 10-cm depth and the corn-cotton rotation resulted in the lowest SOC levels of all systems. Results suggest that small grain cover crops and wheat for grain in the intensive system were the dominate factor in soil C changes. Our results suggest that the Brazilian model of cropping intensification, coupled with conservation tillage, is economically superior. More importantly, this model has the potential to rapidly increase soil C; improving soil quality and productivity in the long term and enhancing economic sustainability of producers.