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Title: MODELING SOIL CARBON SEQUESTRATION IN AGRICULTURAL LANDS OF MALI

Author
item Doraiswamy, Paul
item McCarty, Gregory
item Hunt Jr, Earle
item YOST, R - UNIV OF HAWAII
item DOUMBIA, M - MALI INST. D'ECONOMIE
item Franzluebbers, Alan

Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2005
Publication Date: 11/30/2006
Citation: Doraiswamy, P.C., McCarty, G.W., Hunt Jr, E.R., Yost, R.S., Doumbia, M., Franzluebbers, A.J. 2006. Modeling soil carbon sequestration in agricultural lands of Mali. Agricultural Systems. doi:10.1016/j.agsy.2005.09.011.

Interpretive Summary: In the drought-prone Sudan-Sahelian zone of West Africa, agricultural operations are based on relatively low-output systems, which maintain production at subsitence levels. It is getting more difficult to sustain the required food suply for its people, because of land degradation from soil erosion and nutient mining. The resulting low soil fertility, combined with the variable rainfall and low water holding capacity, limit the area's production of maize, sorghum and millet. The primary soil relation constraints to production are water deficit and phsphorus and nitrogen dificiency. The Onjectives of this study are to characterize the potential for increasing levels of soil carbon for improving soil quality and carbon sequestration. Based on land-use classification, climate varibles, soil texture, in-situ soil carbon concentrations and crop growth characteristics, the EPIC-Century model was used to project the amounts of soil carbon sequestered for the region. Under continuous conventional cultivation with minimal fertilization and no residue management, the soil top layer was continously lost due to erosion, losing between 1.1 to 1/7 Mg C/ha over 25 years. The combination of modeling with land use classification was used to caluclate that between 54 kg C ha -1 year -1 may be sequestered for the study area with ridge tillage, increased application of fertilizers, and residue management. This is about one-third the rate used for large-scale estimates of carbon sequestration potential in West Africa.

Technical Abstract: Agriculture in sub-Saharan Africa is a low-input low-output system for subsitence. Some of these areas are becoming less able to feed the people, because of land degradation and erosion. The aims of this study are to characterize the potential for increasing levels of soil carbon for improving soil quality and carbon sequestration. A combination of high- and low- resolution imagery were used to develop landuse classification for an area of 64 km 2 near Omarobougou, Mali. Field sizes were generally small (10-50ha), and the primary cultivation systems are conventional tillage and ridge tillage, where tillage is performed by a combination of hand tools and animal-drawn plows. Based on land-use classifcation, climate variables, soil texture, in-situ soil carbon concentration, and crop growth characteristics, the EPIC-Century model was used to project the amounts of soil carbon sequestered for the region. Under the usual management practices in Mali, mean crop yield reported (1985-2000) for maize is 1/53 mg/ha, cotton is 1/2 Mg/ha, millet is 0.95 Mg/ha, and for sorghum is 0.95 Mg/ha. Year-to-year variations can be attributed to primarily rainfal and the amount of fertilizer applied. Under continuous conventional cultivation with minimal fertilization and no residue management, the soil top layer was continuously lost due to erosion, losing between 1/1 to 1/7 Mg C/ha over 25 years. The model projection suggest that soil erosion is controlled and that soil carbon sequestration is enhanced with a ridge tilage system, because of increased water infiltration, which increases crop production. The combination of modeling with the land use classification was used with ridge tillage, increased application of fertilizer, and residue management. This is about one-third the rate used for large-scale estimates of carbon sequestration potential in West Africa.