Degraded land within the irrigated areas of the Aral Sea Basin is characterized by high soil salinity, shallow saline groundwater (GW), low irrigation water availability and thus is often unsuitable for crop cultivation. Afforestation is one option for mitigating such degraded land but to be successful it requires the selection of appropriate tree species and irrigation techniques for tree establishment. In a two factorial split-plot experiment the survival, dry matter production, root growth, and biomass partitioning of Elaeagnus angustifolia L., Ulmus pumila L., and Populus euphratica Oliv. were compared under three irrigation regimes for two consecutive years. During the third year, the response of the plantations to the cessation of irrigation was evaluated. A "deficit" and "full" water treatment, respectively amounting to 80 and 160 mm year-1 was applied via drip irrigation. Traditional furrow irrigation supplied at the deficit rate, served as the control. Mixed linear model analysis showed significantly enhanced growth of P. euphratica under drip irrigation exceeding 7-14 times that under the control. Drip irrigation was not advantageous for the other species which effectively used the shallow (0.9-2.0 m deep) GW with a salinity ranging between 1.2 and 4.8 dS m-1. After cessation of irrigation, all species at the deficit-irrigated plots retained or increased their growth rates. In contrast, formerly full-irrigated P. euphratica slowed down by about 50%, indicating that deficit watering created better pre-conditions for coping with the termination of irrigation. E. angustifolia produced about 30 t ha-1 year-1 of above-ground biomass more than twice that of the other species, thus showing in the short-run its high potential on marginal land. U. pumila showed stable, albeit moderate growth rates and could be mixed with the short-living, fast-growing E. angustifolia plantations to optimize the yields. Low initial survival (57%) of P. euphratica was compensated for by its strong regeneration and drastically increasing growth rates. Initially high root-zone salinity exceeding 30 dS m-1, stabilized over time within the medium range even in the absence of irrigation. The application of costly drip irrigation for plantation establishment appears unnecessary in the Aral Sea region Khorezm where a shallow, slightly-to-moderately saline GW table prevails throughout the growing season.
Bibliographical noteFunding Information:
The German Ministry for Education and Research (BMBF; project number 0339970A), the Ministry for Schools, Science and Research of the State of Northrhine-Westfalia financially supported this study. Additional funds from DAAD (German Academic Exchange Service) are gratefully acknowledged. The research was conducted at the premises of the Urgench State University in Khorezm within the framework of ZEF/UNESCO landscape restructuring project. We are grateful for the valuable comments from two anonymous reviewers on the earlier version of the manuscript.
- Biomass production
- Drip irrigation
- Elaeagnus angustifolia
- Furrow irrigation
- Populus euphratica
- Root/shoot ratio
- Set-aside cropland
- Ulmus pumila
ASJC Scopus subject areas
- Nature and Landscape Conservation
- Management, Monitoring, Policy and Law