Nutrient extraction by Helianthus annuus L. irrigated with treated domestic sewage

The reuse of water derived from domestic wastewater is a practice that can be used to increase the efficiency of water resources management as an alternative in regions with water scarcity. However, domestic wastewater composition has, besides water, chemical elements that might cause toxic effects in plants. The objective of this work was to evaluate the nutrients content and accumulation in sunflowers (Helianthus annuus L.) irrigated with treated domestic sewage using uni- and multivariate approaches. The treatments consisted of two factors: four types of water [W1—sewage treated by upflow anaerobic sludge blanket (UASB) reactor type; W2—sewage treated by anaerobic digester and filtering; W3—sewage treated by anaerobic filtration; and W4—water supply]; and two irrigation depths [D1—equal to crop evapotranspiration (ETc) and D2—1.2 ETc]. Leaves, capitulum and achenes were collected to evaluate the concentrations of N, P, K, Ca, Mg and S at the end of the cycle (96 days). The data were submitted to canonical discriminant analysis and to analysis of variance. The multivariate approach resulted in the discrimination of two large groups in relation to nutrient content: one formed by plants irrigated with water from domestic sewage and another by plants irrigated only with supply water. The treated domestic sewage was able to provide nutrients to supply the recommended crop requirement. The most extracted nutrients by sunflowers were K > N > Ca > Mg = P > S when irrigated with domestic sewage, and K > N > Mg > Ca > P > S when irrigated with water.