Effects of treated wastewater irrigation on element concentrations in soil and maize plants

Surface water resources are scarce, and groundwater is the main source of water in Oman. Water shortage has lead to overpumping and reservoir depletion, which has caused seawater intrusion in coastal areas and salinization of groundwater and soils. Treated wastewater maintains environmental quality while providing sustainable agriculture and preserving scarce water sources. The numbers of wastewater treatment plants in Oman have been increased enormously, with the produced water utilized in forage production. Field experiments were conducted during the 2006-7 season to determine the effect of water quality (thrice-treated wastewater and fresh water), water quantity (1.4 ETc, 1.0 Etc, and 0.6 ETc), and their interaction on the chemical composition of forage maize. Soil moisture distributions and salinity redistributions were monitored throughout the experiments. The results indicated that treated wastewater leached more salts down the profile than fresh water. Treated wastewater also reduced the sodium adsorption ratio (SAR) by 74%, whereas fresh water reduced it by 68%. Fresh water treatments were observed to have greater moisture content than the treated wastewater. This was attributed to the fact that treated wastewater contained dissolved organic matter that slightly improves the physical conditions of the soil, resulting in increased water penetrations, and contained greater amounts of nutrients, resulting in vigorous plants that abstracted more water. The results also indicated that plants irrigated with treated wastewater contained greater nitrogen concentrations at all levels of water quantities than those irrigated with fresh water. However, potassium, phosphorus, calcium, magnesium, iron, sulfur, boron, zinc, copper, and manganese uptakes of forage maize did not show any significant differences between fresh and treated wastewater.