Treated urban wastewater irrigation effects on bioenergy sorghum biomass, quality, and soil salinity in an arid environment

Land degradation due to elevated salinity and sodicity is a serious problem affecting many irrigated regions of the world. Salinity coupled with freshwater scarcity has forced many farmers in arid regions to abandon agricultural lands. This study evaluated irrigation potential of marginal quality treated urban wastewater to produce bioenergy sorghum on saline soils collected from an abandoned degraded salt affected lands in Texas and New Mexico under greenhouse conditions. Study results indicated that the energy sorghum biomass production and quality under wastewater irrigation were comparable to that irrigated with freshwater on nonsaline soils. Soil salinity especially in the subsurface increased over time under wastewater irrigation compared to that under freshwater irrigation. Soil sodicity (measured by sodium adsorption ratios) increased over time in all water-soil treatment combinations. Sodicity values were higher in treatments that received wastewater irrigation with no addition of calcium to counter sodium. Although sodicity exceeded the threshold value, no impairment in soil permeability was observed. Study results indicated a great potential for marginal quality water irrigation to improve degraded saline land productivity. Further field studies are required to confirm our greenhouse study results and the potential of bioenergy crops especially on saline soils and to highlight treated wastewater as a potential irrigation source.