Determination of the volatilization of ammonia from surface-applied cattle slurry by the micrometeorological mass balance method

Abstract

Agronomic experiments have shown that nitrogen applied in organic manures gives variable responses in grass growth (van Dijk & Sturm, 1983; Smith, Unwin & Williams, 1985). In a series of field trials in southern England, the average apparent recovery in herbage of the nitrogen from cow slurry was only 13% (Unwin, Pain & Whinham, 1986). The volatilization of ammonia from spread slurry is one possible mechanism for the nitrogen inefficiency (Freney, Simpson & Denmead, 1983; Ryden, 1984). Direct measurements of ammonia loss from land surfaces can be made by micrometeorological methods (Denmead, 1983) and, using the micrometeorological mass balance technique, high rates of ammonia loss were recorded after the land spreading of liquid dairy cattle manure in Canada (Beauchamp, Kidd & Thurtell, 1982). The micrometeorological mass balance method has been used in England to measure ammonia loss from a grazed sward (Ryden & McNeill, 1984). This paper presents the results of an experiment where the same method was used to measure the ammonia loss after land-spreading cattle slurry in Northern Ireland.