Abstract

Volatilisation of nitrogen from biosolids applied to land reduces the amount of nitrogen available for plant uptake and contamination of groundwater. This study determined rates of volatilisation of ammonium-nitrogen from biosolids after surface-application in a mature pine forest. Biosolids from the Bromley Waste Water Treatment Plant in Christchurch, New Zealand, were applied at 2 rates under controlled conditions to exclude leaching and plant uptake. Volatilisation was calculated using a mass balance approach.

Despite climatic conditions apparently not suited to volatilisation, 44–55% of the ammonium-nitrogen applied in biosolids was volatilised. The majority of the losses occurred within about 1 day of application, and 95% of the losses occurred within 5 days. The losses represent about 12% of the total nitrogen applied, or about one-third of the 'plant-available' nitrogen. As volatilised nitrogen is not available for plant uptake or leaching to groundwater, volatile losses of nitrogen applied in biosolids need to be considered when calculating rates of biosolids application to protect groundwater while providing nutritional benefit.