Supplementary nitrogen (N) side-dressing via the irrigation system is needed in organic cropping. The aim here was to improve N-extraction efficiency, by testing five extraction protocols with guano, layer and broiler manures. The manure-N released by the different methods and manures was mainly in the form of ammonia and ranged from 50% to 85% with no differences among extraction methods. Volatilised ammonia from the extract solution was trapped. At the end of the extraction period, the pH of the extract solution was raised and the rest of the volatilised ammonia was trapped. In the case of guano, about 89% of the manure-N that was mineralised to the extract solution volatilised (after a pH increase), whereas in the layer and broiler manures, 59% and 54% were volatilised, respectively. Extraction of ammonia, its volatilisation and entrapment could provide a significantly more efficient N source than using the extract solution as currently recommended. (c) 2007 Elsevier Ltd. All rights reserved.