Fate of nitrogen and phosphorus from source-separated human urine in a calcareous soil
Résumé
Human urine concentrates 88% of the nitrogen and 50% of the phosphorus excreted by humans, making it a potential alternative
crop fertilizer. However, knowledge gaps remain on the fate of nitrogen in situations favouring NH3 volatilization and on the
availability of P from urine in soils. This study aimed at identifying the fate of nitrogen and phosphorus supplied by human urine
from source separation toilets in a calcareous soil. To this end, a spinach crop was fertilized with 2 different doses of human urine and compared with a synthetic fertilizer treatment and an unfertilized control. The experiment was conducted in 4 soil tanks (50-cm depth) in greenhouse condi-
tions, according to a randomized block scheme. We monitored soil mineral nitrogen over time and simulated nitrogen volatiliza-
tion using Hydrus-1D and Visual Minteq softwares. We also monitored soil phosphorus pools, carbon, nitrogen and phosphorus
(CNP) in microbial biomass, soil pH and electrical conductivity. Only an excessive input of urine affected soil pH (decreasing it
by 0.2 units) and soil conductivity (increasing it by 183%). The phosphorus supplied was either taken up by the crop or remained
mostly in the available P pool, as demonstrated by a net increase of the resin and bicarbonate extractable P. Ammonium seemed
to be nitrified within about 10 days after application. However, both Visual Minteq and Hydrus models estimated that more than
50% of the nitrogen supplied was lost by ammonia volatilization. Overall, our results indicate that direct application of urine to a
calcareous soil provides available nutrients for plant growth, but that heavy losses of volatilized nitrogen are to be expected. Our
results also question whether long-term application could affect soil pH and salinity.
Domaines
Sciences de l'environnementOrigine | Fichiers éditeurs autorisés sur une archive ouverte |
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