Application of Human Urine in Agriculture

Abstract

Although it is known that human urine contains valuable plants nutrients, too much urine application may cause an accumulation of several ions in soil. Among them, excess of Na inhibits plant growth, while excess of nitrogen can build up in plant tissues. Therefore, the objectives of this study was to (1) evaluate when and how often human urine should be applied in agriculture as fertilizer solution, (2) examine the effects of uncontrolled application of human urine dose in agriculture, (3) and examine the effects of continuous application of uncontrolled human urine application dose in agriculture through continuous cultivations. The results revealed that application of urine at one time before cultivation is not effective for plant growth due to high ions intensity in low saline soil and high nutrients leached from soil. Besides, continuous application of extra urine volumes in the range of 2–3 times (U-2Vo and U-3Vo) higher than plant requirement (U-Vo) had no adverse effect on plant growth and yields under three-time continuous cultivations, since treated soils were far to be saline (EC < 2mS/cm; SAR < 13), and more than 39% of the total Na applied in all urine treatments was removed by plant from soil. However, continuous application of double (U-2Vo) and triple (U-3Vo) volumes of urine caused accumulation of N in plant and soil and decreased plant K/Na ratio (substitution of K+ by Na+). While in the adequate urine volume (U-Vo), there was no accumulation of N in soil, no increased of N in plant tissues, but plant K/Na ratio decreased. So, these results suggested that adequate application of human urine based on plant N requirement and management of salts from urine is required even in the adequate urine volume application for its sustainable reuse in agriculture.