The Influence of aeration of sawdust litter in fattening pig units on the relative gaseous emission of NH3, N2O, N-2 and on N-budget.

This study aims at testing experimentally the effect of aeration of litter in intensive pig units on nitrogen budget and the nature of nitrogen gaseou s emissions. Rearing animals on deep litter provides treatment of these man ures at an early stage by composting and aeration of litter could offer a m ethod of controlling the compost temperature and water content. Two aeratio n systems for the litter (upflow and downflow) were checked against a contr ol system without aeration, over a period of 65 days corresponding to two s hortened fattening periods (25-60 kg). Detailed nitrogen balances were obta ined, and uncertainties estimated, from which the N-2 fraction was evaluate d by difference. Rearing animals on sawdust litter enables the removal of n itrogen from the compost as N-2 with efficiencies of 44, 53 and 74 +/- 13 % , respectively, of total nitrogen excreted for each of the three systems: u pflow aeration, downflow aeration and control. The smaller efficiencies of aerated systems with respect to the control are due to the supply of oxygen by aeration, Nitrogen accumulated in the litter is mainly under organic fo rm, and amounts to 19, 27 and 6 +/- 1.5 %, respecively, of the nitrogen con tent of the manure for the three systems. Nitrates only accumulate in the a erated systems (3-7 %), Irrespective of the system, about 30 % of the total nitrogen in the manure was removed as gases NH3 and N2O. The NH3/N2O ratio is 1.3 for the control and downflow aeration as opposed to 1.7 for upflow aeration. (C) Inra/Elsevier, Paris.