Abstract

Segregating human urine from wastewater may significantly contribute to diminish the nitrogen and phosphorous problem, considered to be one of the major planetary limits already exceeded. Application of urine diluted in water in agriculture contributes to both sides of the problem. On one hand, it allows reduction of nutrient discharges into receiving bodies, on the other, it reduces the need for reactive nitrogen and its energy demand. Advantages of application of urine inbermudagrass and macronutrients accumulation are shown in the previous paper. This paper presents the results of the evaluation of accumulation of micronutrients (B, Fe, Mn, Cu and Zn) in soil and in leaves of bermudagrass irrigated with different dilutions of human urine in water. The experiment was conducted in a greenhouse in a completely randomized design with six treatments consistingof six urine doses (0 - control, 5, 10, 15, 20 and 25 ml of urine per liter of water), with four replicates. As for concentrations in the leaves, there was a significant difference between treatments for all nutrients, with the largest accumulations, of B, Fe and Mn, 120 days after planting, observed in the 10 mL L^-1 human urine dilution in water. There were significant differences among treatments in the soil layer 0-20 cm, for Fe, Mn and pH, concentrations as well as the levels of B and Mn in the soil layer 20-40 cm, and for B, Mn and pH between the layers analysed, in treatments 15, 20 and 25 ml L^-1. Dilutions between 10 and 20 ml L^-1 induced a greater accumulation of micronutrients in the plant tissue. The use of urine diluted in water provided adequate levels of micronutrients in the leaves in most of treatments, and it did not cause metal accumulation in the soil above the recommended levels for the bermudagrass cultivation.

Key words: Cynodon dactylon, nutrient recycling, water reuse.