Carbon sequestration in soils of central Asia

Problems of frequent drought stress, low soil organic carbon (SOC) concentration, low aggregation, susceptibility to compaction, salinization and accelerated soil erosion in dry regions are accentuated by removal of crop residues, mechanical methods of seedbed preparation, summer clean fallowing and overgrazing, and excessive irrigation. The attendant soil degradation and desertification lead to depletion of SOC, decline in biomass production, eutrophication/pollution of waters and emission of greenhouse gases. Adoption of conservation agriculture, based on the use of crop residue mulch and no till farming, can conserve water, reduce soil erosion, improve soil structure, enhance SOC concentration, and reduce the rate of enrichment of atmospheric CO2. The rate of SOC sequestration with conversion to conservation agriculture, elimination of summer fallowing and growing forages/cover crops may be 100 to 200 kg ha(-1) y(-1) in coarse-textured soils of semiarid regions and 150 to 300 kg ha(-1) y(-1) in heavy-textured soils of the subhumid regions. The potential of soil C sequestration in central Asia is 10 to 22 Tg C y(-1) (16 8 Tg C y(-1)) for about 50 years, and it represents 20 per cent of the CO2 emissions by fossil fuel combustion. Copyright (C) 2004 John Wiley Sons, Ltd.