Effects of treated wastewater irrigation on soil properties and lettuce yield

Domestic effluents may contain important nutrients for agricultural crop development, and reusing this effluent on irrigation can reduce the potable water demand, recycle nutrients, and decrease effluent discharges on water bodies. This study evaluated the changes on physical, chemical and microbiological characteristics of a Dusky Red Latosol, the yield and the quality of lettuce after cultivation with treated wastewater on irrigation. In a greenhouse, lettuces were irrigated using drinking water with conventional fertilization (T1) and treated wastewater with partial conventional fertilization (T2). After the lettuce harvest, the physical, chemical and microbiological properties of soil, the nutrients, and the microbiological quality of lettuce leaves were evaluated. Sodium adsorption ratio, magnesium, calcium, sodium, potassium, nitrate, chlorate, pH, electrical conductivity, total coliforms, Escherichia coli, chemical and biochemical oxygen demand were analyzed in irrigation water. The concentration of some soil nutrients (K, Ca, H, Al, and S) increased after irrigation with T2, and the presence of E. coli bacteria was not observed on lettuce leaves or in the soil. The T2 did not damage the physical properties of soil and increased its nutrients. Lettuce production (in terms of fresh weight) was higher in lettuce cultivated on T2 than that cultivated on T1. The treated wastewater quality was appropriate for lettuce drip irrigation.