ASABE Technical Library - Abstract

Abstract. Treated sewage effluent that usually contains more nutrients than conventional water is an alternative source of irrigation and nutrients for many countries where the scarcity of freshwater is a significant challenge. In order to quantify the effectiveness of nitrogen in the secondary treated sewage effluent (STSE) to plant growth, a pot experiment of maize under drip irrigation was conducted under a rain shelter. Two water sources of STSE and groundwater (GW) and four nitrogen levels of 0, 70, 140, and 210 kg ha^-1 (referred to as N0, N1, N2, N3, respectively) were tested using a completely randomized design with four replications. The ¹⁵N labeled urea with abundance of 10.19% was chosen as the nitrogen fertilizer. Isotope tracer method and fertilizer equivalence approach were adopted to assess the effectiveness of nitrogen contained in the STSE. For both STSE and GW, plant height, leaf area index, biomass, nitrogen uptake, nitrogen residual, nitrogen loss, and yield of maize tended to increase with an increasing nitrogen rate. The percentage utilization of fertilizer nitrogen showed a decreasing trend with an increasing nitrogen rate, while the percentage loss of fertilizer nitrogen increased with the rate. With an increasing nitrogen rate, maize irrigated with STSE absorbed more nitrogen derived from fertilizer, but less nitrogen derived from STSE. For the nitrogen levels tested, the yield of maize peaked at the N2 rate for both STSE and GW irrigation, and the yield for STSE irrigation was 3 to 20% greater than that for GW irrigation. The results obtained by the fertilizer equivalence approach indicated that the STSE contributed 69 to 55 kg ha^-1 of nitrogen when the nitrogen rates increased from 0 to 210 kg ha^-1.