“Using marginal quality water for an energy crop in arid regions: Effect of salinity and boron distribution patterns”

Marginal-quality water, such as recycled wastewater (RWW), is now commonly used for irrigation in regions with limited freshwater resources. However, the practice can pose a threat to soil conservation due to the high soluble salts content present in such water resources. Long-term sustainability of use therefore requires a sound understanding of the soil salinity distribution and appropriate selection of both crop and irrigation system. Jatropha curcas L. (JCL) has been proposed as an ideal candidate for biofuel production in arid and semi-arid regions under RWW irrigation, particularly on account of its high salt tolerance. The present study evaluates the evolution and distribution of soil salt and boron (B) as a potential constraint on the sustainability of a “JCL-RWW” farming system on the island of Fuerteventura (Canary Islands-Spain) during five years of cultivation under surface drip irrigation (SDI) and sub-surface drip irrigation (SSDI). The results indicate that, under high evaporative demand conditions, SSDI does not appear to offer any advantage over SDI in terms of soil salt distribution. The results indicate that irrigation with RWW has increased boron concentrations by a factor of 7 (soil Typic Torrifluvents; TT) and 5 (soil Typic Haplocambids; TH), respectively, in relation to the control soils. Irrigation with RWW has also led to a rise in soil salinity reached values of 59 and 81 dS m −1 for soil TT and TH, respectively. For soil TT and TH SAR, reached values of 56 and 80 (meq L−1)0.5, respectively as a result of irrigation with RWW. Although salinity does not seem to be a factor limiting crop production, irrigation with RWW can accelerate natural soil salinization processes in regions where desertification is of particular concern.