Ammonia emissions from liquid and solid manure as influenced by ration composition.

To study the potential of reducing ammonia (NH3) emissions from cattle manure storage, chamber experiments were performed with different types of manure obtained from dairy cows fed rations with varied crude protein (CP) content. In a first experiment, the effects of rations containing 50% concentrate and CP contents of 17.5, 15 and 12.5% were compared. In a second experiment, typical forage-dominated summer (primarily grass only, 23% CP) and winter rations (primarily hay, 11% CP) were studied. The three manure types investigated were (i) liquid manure containing total excreta, (ii) urine rich slurry and (iii) solid manure as they are produced on Swiss farms with traditional buildings. The CP content of the ration had a marked effect on total and urinary nitrogen (N) excretion as well as on average NH3 emission rates and total N losses during storage of all manure types. The relative effect on NH3 emissions and N losses was overproportional compared to the changes in CP content of the ration. It was concluded that these effects would not only be true for manure storage but for whole farming systems due to the direct influence on N fluxes.