Salt-induced land and water degradation in the Aral Sea basin: A challenge to sustainable agriculture in Central Asia
Expansion of irrigated agriculture in the Aral Sea Basin in the second half of the twentieth century led to the conversion of vast tracks of virgin land into productive agricultural systems resulting in significant increases in employment opportunities and income generation. The positive effects of the development of irrigated agriculture were replete with serious environmental implications. Excessive use of irrigation water coupled with inadequate drainage systems has caused large-scale land degradation and water quality deterioration in downstream parts of the basin, which is fed by two main rivers, the Amu-Darya and Syr-Darya. Recent estimates suggest that more than 50% of irrigated soils are salt-affected and/or waterlogged in Central Asia. Considering the availability of natural and human resources in the Aral Sea Basin as well as the recent research addressing soil and water management, there is cause for cautious optimism. Research-based interventions that have shown significant promise in addressing this impasse include: (1) rehabilitation of abandoned salt-affected lands through halophytic plant species; (2) introduction of 35-day-old early maturing rice varieties to withstand ambient soil and irrigation water salinity; (3) productivity enhancement of high-magnesium soils and water resources through calcium-based soil amendments; (4) use of certain tree species as biological pumps to lower elevated groundwater levels in waterlogged areas; (5) optimal use of fertilizers, particularly those supplying nitrogen, to mitigate the adverse effects of soil and irrigation water salinity; (6) mulching of furrows under saline conditions to reduce evaporation and salinity buildup in the root zone; and (7) establishment of multipurpose tree and shrub species for biomass and renewable energy production. Because of water withdrawals for agriculture from two main transboundary rivers in the Aral Sea Basin, there would be a need for policy level interventions conducive for enhancing interstate cooperation to transform salt-affected soil and saline water resources from an environmental and productivity constraint into an economic asset.