The aim of this study was to evaluate the effects of different covers (oil, plastic film, perforated polystyrene float, peat and zeolites) oil slurry settling characteristics and ammonia emission during storage and following surface application in the field. Laboratory trials were carried out for 15 days using a pilot scale device. Samples of 5 kg slurry were used. At the end of the storage period, distributions of dry matter, pH, total ammoniacal nitrogen and total Kjeldahl nitrogen in slurry were characterized. In the field, ammonia volatilisation was measured for three days using a wind tunnel system. Oil and plastic film retained all ammoniacal nitrogen forms in the slurry, whereas the others reduced ammonia volatilisation by reducing the emitting surface or by adsorbing/ absorbing ammonia. Over the whole process studied (storage plus application) ammonia emissions were reduced by 40% by oil up to 65-71% by zeolites with different particle sizes.