Effects of treated urban wastewater irrigation on bioenergy sorghum and soil quality

Authors: CHAGANTI, VIJAYASATYA - Texas Agrilife Research; GANJEGUNTE, GIRISHA - Texas Agrilife Research; NIU, GENHUA - Texas Agrilife Research; ULERY, APRIL - New Mexico State University; FLYNN, ROBERT - New Mexico State University; ENCISO, JUAN - Texas Agrilife Research; MEKI, MANYOWA - Texas Agrilife Research; Kiniry, James

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2019
Publication Date: 2/20/2020
Citation: Chaganti, V.N., Ganjegunte, G., Niu, G., Ulery, A., Flynn, R., Enciso, J.M., Meki, M.N., Kiniry, J.R. 2020. Effects of treated urban wastewater irrigation on bioenergy sorghum and soil quality. Agricultural Water Management. 228:105894. https://doi.org/10.1016/j.agwat.2019.105894.
DOI: https://doi.org/10.1016/j.agwat.2019.105894

Interpretive Summary: Prolonged drought in west Texas has caused freshwater scarcities in the Rio Grande basin, forcing growers to abandon agricultural lands. Marginal quality treated urban wastewater could be used to augment the limited available irrigation water. However, higher salinity in wastewater could damage crops and decrease soil quality. Therefore, developing information on crops that are less water-intensive and salt-tolerant is important to sustain agriculture in this region. Drought tolerant and salt tolerant sorghum could provide revenue due to increasing demand for its lignocellulosic biomass in biofuel industry. Our objectives were to (i) evaluate the irrigation potential of treated urban wastewater in biomass sorghum production and (ii) quantify changes in soil quality including soil salinity. We irrigated with different water types (fresh and wastewater) soil treatments (gypsum + sulfur). Sorghum biomass yields were not significantly different between fresh and wastewaters in any year. Differences in biomass quality were observed over time as an indirect consequence of increased soil salinity after wastewater irrigation. Soil quality changes were apparent with salinity, increasing over time with irrigation. This effect was pronounced under wastewater irrigation. Application of gypsum and sulfur significantly reduced soil salinity in wastewater irrigated plots. Thus treated wastewater can be successfully used to grow biomass sorghum in arid regions. However, appropriate soil management practices are needed to counter the effects of high sodium in wastewater. These results have important implications in diversifying cropping pattern in this region while also help extend freshwater supplies through increased reuse of treated urban wastewater.

Technical Abstract: Prolonged drought in arid west Texas has resulted in freshwater scarcities in the Rio Grande basin, forcing growers to abandon agricultural lands. Augmenting freshwater scarcities with marginal quality treated urban wastewater could be an alternative strategy. However, higher salinity in wastewater could be detrimental to crops and soil quality. Therefore, developing information on crops that are less water-intensive and salt-tolerant is important to sustain agriculture in this region. Sorghum is both drought and salt-tolerant and could potentially provide revenue due to increasing demand for its lignocellulosic biomass in biofuel industry. The objectives of this field study were to (i) evaluate the irrigation potential of treated urban wastewater in biomass sorghum production and (ii) quantify changes in soil quality including soil salinity and sodicity. A split-plot experimental design was used with water type (fresh and wastewater) as the main-plot and soil amendments (non-amended and gypsum + sulfur) as the subplot factors. Results show that sorghum biomass yields were not significantly different between fresh and wastewaters in any of the years. Differences in biomass quality were observed overtime but as an indirect consequence of increased soil salinity and/or sodicity after wastewater irrigation. Soil quality changes were apparent with salinity and sodicity increasing over time with irrigation, but this effect was pronounced under wastewater irrigation. Application of gypsum and sulfur was able to significantly reduce soil sodicity, especially in wastewater irrigated plots. The results from this study highlight that treated wastewater can be successfully used to grow biomass sorghum in arid regions. However, appropriate soil management practices should be in place to counter the effects of high sodium in wastewater. These results have important implications in diversifying cropping pattern in this region while also help extend freshwater supplies through increased reuse of treated urban wastewater.