DDD Conference

Dr. Shmuel Assouline

Irrigation with Treated Wastewater: Effects on the Hydro-Ecological Functioning of the Root Zone

Volcani Institute, Agricultural Research Organization, Israel

The challenge of meeting the projected doubling of global demand for food by 2050 is monumental. It is further exacerbated by the limited prospects for land expansion and rapidly dwindling water resources. A promising strategy for increasing crop yields per unit land requires the expansion of irrigated agriculture and the harnessing of water sources previously considered ‘‘marginal’’ (saline, treated effluent, and desalinated water). Such an expansion, however, must carefully consider potential risks on soil hydro-ecological functioning. It seems that long-term use of treated wastewater (WW) for irrigation of orchards planted on heavy soils causes yield reduction and crop damages. In terms of water quality, WW are characterized by higher concentrations of sodium and dissolved organic content that affect both soil exchangeable sodium percentage and soil wettability. The long-term use of WW for irrigation of clayey soils causes significant changes in the soil hydraulic properties that might affect the water and air regime in the root zone. These might affect the chemical and biological conditions in the root zone, affecting plant nutrition, root development and microbial activity. Mixing of water qualities can reduce this negative impact. Adapting the appropriate irrigation to the soil and water qualities can mitigate it. Therefore, the primary challenges to the sustainability of agroecosystems when marginal water sources are allocated to irrigation lies with the hazards of saline and sodic conditions, and the unintended consequences on soil hydro-ecological functioning. Multidisciplinary approaches that combine new scientific knowhow with legislative, economic, and societal tools are required to ensure safe and sustainable use of water resources of different qualities. New scientific knowhow integrating key biophysical processes with ecological interactions at appropriate spatial and temporal scales should be developed.

 

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