Journal of Agricultural Science, Cambridge (1995), 125, 245-252. © 1995 Cambridge University Press 245 Ammonia volatilization following surface-applied pig and cattle slurry in France J.-F.MOAL 1 , J.MARTINEZ 1 *, F. GUIZIOU 1 AND C.-M. COSTE 2 1 CEMAGREF, Division Production et Economie Agricoles, 17 avenue de Cucille, 35044 Rennes, France 2 Centre de Phytopharmacie, Universite de Perpignan, 52 avenue de Villeneuve, 66860 Perpignan, France (Revised MS received 26 September 1994) SUMMARY Field experiments were carried out in Brittany (Western France) in 1993 to measure ammonia losses from surface-applied pig and cattle slurry. Experiments were conducted on grass, stubble (wheat and maize) and arable land using a wind tunnel system. Ammonia losses were followed during periods ranging from 20 to 96 h after slurry application. Rates of slurry applied varied from 40 to 200 m 3 /ha. In two experiments, losses from cattle slurry were respectively 75 and 54% of the ammoniacal nitrogen applied in the slurry. Ammonia emissions from pig slurry applied at a rate of 40 m 3 /ha, during spring and summer experiments, were higher on grass (45-63 % of the total ammoniacal nitrogen applied) than on wheat stubble (37-45%). On average, 75% of the total loss in all experiments occurred within the first 15 h after spreading. Significant correlations were found between ammonia losses (kg N/ha) and mean soil temperature and slurry dry matter content (%) using simple linear regressions and stepwise procedures. The time of application was also found to influence the magnitude of ammonia loss: 83 % of the total loss occurred within 6 h when the slurry was applied at midday compared with 42 % when it was applied in the evening. INTRODUCTION Intensification of livestock production has resulted in increases in ammonia emissions in several European countries (van der Molen et al. 1989; Jarvis & Pain 1990; Bless et al. 1991; Dobbelaere 1992; Sommer 1992). In France, 52% of pig production, 44% of poultry production and 21 % of dairy production is located in Brittany (Lamperiere 1993) and animal excreta are mainly collected as slurry (70-80%) and spread on the land. Annually, this material is estimated to contain 2 x 10 5 tonnes of elemental nitro- gen (N), with 57, 25 and 13% of the total nitrogen excreted being derived from cattle, pig and poultry production respectively (Abrassart et al. 1993). Ac- cording to Buijsman et al. (1987), ammonia volatil- ization from manures and slurries represents the most important source of atmospheric ammonia in Europe (80%). Ammonia emissions not only represent a loss of fertilizer value but are also a source of air pollution. Emissions occur from livestock houses (Oosthoek et al. 1991), slurry storage (De Bode 1991; Sommer 1992), landspreading of slurry and during the grazing period (Ryden 1986; Lockyer & Whitehead 1990; * To whom correspondence should be addressed. Whitehead & Raistrick 1993). Jarvis & Pain (1990) indicated that, in the UK, an average of 36% of agricultural ammonia emissions comes from slurry landspreading. In France, however, there is a lack of information on nitrogen losses and especially on ammonia losses from agricultural systems. The aims of this paper are (i) to present initial measurements of ammonia volatilization from surface-applied pig and cattle slurries in several agricultural situations (e.g. grass, stubble) in Brittany and (ii) to describe how these emissions are related to environmental factors and the physico-chemical characteristics of the slurries applied. MATERIALS AND METHODS Experimental treatments Eighteen separate experiments were carried out from February to November 1993 (Table 1). Each ex- periment included three replicates of each treatment except for Expts 1, 2, 3, 13 and 17 (no replicates). Slurries were applied at different rates varying from 40 to 200m 3 /ha. Experiments were conducted on arable land, grassland and stubble at seven sites throughout Brittany (Table 2).