38. Integrating Agroforestry and Pastures for Soil Salinity Management in Dryland Ecosystems in Aral Sea Basin

Salt-affected lands in the Central Asian region demonstrate the most characteristic features of natural continental terrestrial salinization, sodication, and alkalinization. Low organic matter (<1.0%), high salt contents, and poor water-holding capacity render these soils unproductive. The predominant salinity type is sulfate-chloride. The Na⁺ and \( {\rm{SO}}_{4}^{2-}\)are dominant ions. Total nitrogen and phosphorus ranged between 0.7–5.5 mg kg⁻¹ and 10.0–18.26 mg kg⁻¹, respectively. Available potassium is low or moderate. Vegetation richness, botanic species diversity, and plant biomass were well integrated with soil moisture and soil salinity. A linear regression equation between apparent soil electrical conductivity (EM38) and quantitative Na⁺ accumulation for 0–75 cm (r ²  =  0.88) soil profiles allowed us to identify the proportional contribution and interactive effects of each plant community (calculated for C₃/C₄ species abundance) at fine desert landscape scale. Foliar δ¹³C (carbon discrimination ) indexes as an indicator of long-term water-use efficiency in plants in a restored forest – pastures ecosystem showed that δ¹³C of C₃ species increased with a decrease in soil water availability, suggesting that water-use efficiency increased with decreasing soil moisture and salinity. The C₄ species’ occurrences were observed to be absent and/or scarce within relatively lower soil moisture microhabitats, whereas they occurred and/or even had a high abundance within relatively higher soil moisture microhabitats and salinity, suggesting limited moisture available was a key factor of limiting C₄ distribution in arid region. The suitable coexistence of C3/C4 into an integrated agroforestry – farming system comprising 12–15% of tree cover, 58% of alfalfa, and 27–30% of annual forage crops provides satisfactory drainage – control of these salt affected marginal lands preventing salts accumulation at the root zone area. Trees/shrub plantations were deeply planting (sticks tap into the water table) through seedlings transplanting in early spring or late autumn seasons. A limited irrigation with low-quality water has been applied during the initial stage of growth before sole reliance on available drainage water (EC 4.5–12.3 dS m⁻¹) resource becomes possible. The most promising plants including stands of native rangeland halophytes grown alone, or mixed with various traditional salt-tolerant trees, and fodder crops are addressed in this chapter.