Effects of treated municipal wastewater irrigation on soil properties, switchgrass biomass production and quality under arid climate

•Alamo, a lowland ecotype cultivar was able to tolerate high levels of salinity.•Six years average switchgrass biomass production ranged from 267 to 335g per column for different treatments evaluated in the study.•Biomass qualities of under treated urban wastewater and freshwater irrigation did not differ significantly.•Soil Salinity increased over time in all treatments but sodicity in rootzone remained under threshold when adequate calcium was available.•High SAR under wastewater did not decrease soil permeability because of high electrolyte concentration. Ongoing severe drought and increased demand for freshwater by municipal and industrial sectors have reduced the freshwater availability for agriculture in the far west Texas region. The region has enormous potential for developing alternative water sources for a bioenergy crop that requires less water and can grow on saline soils. In addition to improving farm income, this can help in producing 137 billion liters of bio-based transportation fuels goal set by the U.S. Congress by the year 2022. This study evaluated switchgrass (Panicum virgatum L.) performance under treated urban wastewater irrigation on salt affected soils amended with gypsum and polymer using soil columns prepared from a salt affected land over six years under greenhouse conditions that mimicked the climatic conditions of the study region. Results indicated that switchgrass produced appreciable biomass even under highly saline and sodic conditions. Qualities of biomass under treated urban wastewater were comparable to that produced under freshwater irrigation. Expectedly, soil salinity increased with time at a greater rate under wastewater irrigation than freshwater. Soil SAR values were below threshold when adequate Ca was available to counter sodicity. In addition irrigation with treated wastewater improved nitrogen and potassium status in the root zone. This can reduce of cost of fertilization and increase farm profitability.