The effect of treated urban wastewater on soil properties, plant tissue composition and biomass productivity in berseem clover and corn

The use of wastewater for crop irrigation is a common application in many countries worldwide, and a rapid developing practice has been in Greece during the last years. In this study, the effect of treated urban wastewater in combination with fertilization on the dry biomass of forage species was investigated. Furthermore, the wastewater effect on soil and plant tissues composition was evaluated, in order to find out the nutrient elements changes and the possibility of systematic use of urban wastewater for irrigation in agriculture. The experiments were conducted for two successive years in a field nearby the local wastewater treatment plant of the municipality of Drama, Eastern Macedonia, Greece, using two forage species: berseem clover (Trifolium alexandrinum var. alex) and corn (Zea mays L., cv. PR38 H67, 90 days). Two irrigation treatments, potable tap water (T) and wastewater (W), and two fertilization treatments, without fertilization (wF) and fertilization (F), were applied in each irrigation treatment. Water, wastewater, soil and plant samples were analyzed for the nutritive and toxic chemical elements content. The results showed that the treated urban wastewater was suitable for irrigation of corn and clover, as the accumulation of the nutritive and toxic elements in the soil and in the species biomass varied in low level and didn’t cause any nutrient deficit or toxicity in the plants. The concentration of measured inorganic elements in the soil and plant tissues irrigated with W depended on the crop species and fertilization level. Moreover, the average yield per year of clover and corn ranked as follows: WF>WwF>TF>TwF. Treated urban wastewater effectively increased the yield of cultivated forage crop species, probably due to the nutritive value of the wastewater, although the differences were not statistically significant. This study provides important information on the use of treated wastewaters, increasing the possible irrigation water resources for forage crops. However, further investigation with several wastewater sources is needed for a balanced nutrition of the forage crops and also the presence of pathogenic microorganisms in the plant biomass and the soil should be considered.