Yield response of canola as a biofuel feedstock and soil quality changes under treated urban wastewater irrigation and soil amendment application

Abstract

Abstract Treated urban wastewater (TWW) is seen as a potential alternative for agricultural irrigation in arid west Texas region, due to scarcity of Freshwater (FW) supplies. However, TWW can potentially cause soil salinization and affect soil quality and crop productivity. Therefore, crops that are salt-tolerant and less water-intensive are needed to sustain agriculture in this region. Canola (Brassica napus L.) as an edible oilseed and biodiesel/biofuel crop, is salt-tolerant and relatively less water-intensive than crops that are traditional to this area. This two–year field study evaluated the performance of canola under TWW irrigation in terms of its seed yield potential and seed quality (oil content, oil yield and salt constituents), along with quantifying changes in soil salinity and sodicity. Experimental design included a randomized block split-plot with water quality (FW and TWW) as the main-plot and soil amendment (gypsum + sulfur and no-amendment) as the subplot factor. Results show that TWW application did not significantly affect canola seed yields in any of the two years. On average, seed yields were 1975 kg ha−1 across all treatments and years. Seed oil content, oil yield and mineral constituents were also not affected by TWW irrigation. Nevertheless, average seed oil content was 42 % and oil yield was 849 kg ha−1. Other than the effects on soil salinity and sodicity, Gypsum + Sulfur application did not influence canola seed productivity and quality. Changes in soil salinity and sodicity were more prominent under TWW irrigation but the levels were below the thresholds after two years. Gypsum + Sulfur application significantly reduced soil sodicity, especially in TWW irrigated soils. These results highlight that TWW can be successfully used to grow canola as a biofuel feedstock in this arid region while following appropriate soil management practices to alleviate sodicity hazard of TWW in the long-term.