Carbon Sequestration in Dryland Agriculture
Drylands cover about 4886 million hectares (Mha) in ice-free land areas of the world. Of this, 2124 Mha is in semi-arid regions, 2180 Mha in arid regions, and 581 Mha in extremely arid regions. Predominant soils of dryland areas include 307 Mha of Alfisols, 1657 Mha of Aridisols, 1915 Mha of Entisols, 547 Mha of Mollisols, 188 Mha of Vertisols, and 290 Mha of miscellaneous soils. Most soils in dryland regions are young, characterized by less weathering, and dominated by physical weathering processes. In general, soils have low soil organic carbon (SOC) concentration ranging from 0.05 to 0.5% in the surface horizon. However, dryland soils have high concentrations of soil inorganic carbon (SIC) especially in the calcic/petrocalcic horizon which also has high concentrations of secondary/pedogenic carbonates. The strategy to improving SOC and SIC pools in these soils involves improving water and nutrient-use efficiencies by decreasing losses and improving biomass production. Land use/farming practices to achieve these goals include conservation tillage, mulch farming, including cover crops in the rotation cycle, mixed farming/cropping, agroforestry, ley farming, and adoption of integrated nutrient and pest management practices. There are also options for management of grazing lands and forest lands such as controlled grazing, planting improved species, fire management etc. Conversion to recommended land use and management practices can bring about a modest increase in SOC pool, and in SIC pool through formation of secondary carbonates. Enhancing SOC pool is more challenging in dryland soils than in humid temperate climates. Principal limitations to SOC sequestration are low precipitation, high temperatures, low clay content in soil, and low biomass productivity due to harsh climate, drought prone soils of low inherent fertility, and often resource-poor farmers.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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