Submitted to: Greenhouse Gas Emissions and Carbon Sequestration Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 6/14/2005
Publication Date: 8/1/2005
Citation: Sainju, U.M., Lenssen, A.W., Caesar, T., Waddell, J.T. 2005. Carbon sequestration in dryland soil and plant residue as affected by tillage and crop rotation. Third USDA Symposium on Greenhouse Gas Emissions and Carbon Sequestration in Agriculture and Forestry. p. 211. Interpretive Summary: Drylands in northern Great Plains have lost 30 to 50% of their original soil organic C (SOC) levels during the last 50 to 100 years due to continuous cultivation and summer fallowing. While cultivation is done to prepare seed beds for planting crops and controlling weeds, fallowing is done to increase soil water storage and production of succeeding crops. Intensive tillage increases the oxidation of SOC and fallowing increases its loss by reducing the amount of plant residue returned to the soil Increased soil moisture and temperature during fallowing can also accelerate mineralization of SOC Soil is vulnerable to wind erosion during fallow, which further increases its loss. Therefore, improved soil and crop management practices are needed that can conserve SOC, improve soil quality and productivity, and reduce soil erosion compared with the traditional wheat-fallow system.
Technical Abstract: Long-term use of conventional tillage and wheat (Triticum aestivum L.)-fallow systems in the Northern Great Plains have resulted in low soil organic C (SOC) levels. Management practices that increase C storage are needed to improve soil quality and sustainability of the farming system in this region. We examined the effects of two tillage practices [conventional till (CT) and no-till (NT)], five crop rotations [continuous spring wheat (CW), spring wheat-fallow (W-F), spring wheat-lentil (Lens culinaris Medic.) (W-L), spring wheat-spring wheat-fallow (W-W-F), and spring wheat-pea (Pisum sativum L.)-fallow (W-P-F)], and Conservation Reserve Program (CRP) planting on plant C input, SOC, and particulate organic C (POC). A field experiment was conducted in soil mapped as a mixture of Scobey clay loam (fine-loamy, mixed, Aridic Argiborolls) and Kevin clay loam (fine, montmorillonitic, Aridic Argiborolls) from 1998 to 2003 in Havre, MT. Total plant biomass returned to the soil from 1998 to 2003 was greater in CW (15.5 Mg ha-1) than in other rotations. Residue cover, amount, and C content in 2003 were 33 to 86% greater in NT than in CT and greater in CRP than in crop rotations. Residue amount (2.47 Mg ha-1) and C content (963 kg ha-1) were greater in NT with CW than in other treatments, except in CT with CRP and W-F and in NT with CRP and W-W-F. The SOC at 0- to 5-cm was 23% greater in NT (6.4 Mg ha-1) than in CT. The POC was not influenced by tillage and crop rotation, but POC/SOC ratio at 0- to 20-cm was greater in NT with W-L (369 g kg-1 SOC) than in CT with CW, W-F, and W-L. From 1998 to 2003, SOC at 0- to 20-cm decreased by 4% in CT but increased by 3% in NT. Carbon can be sequestered in dryland soils and plant residue using reduced tillage and increased cropping intensity, such as NT with CW, compared with traditional practice, such as CT with W-F system, thereby helping to improve soil quality and productivity and reduce soil erosion.