Effect of covers on swine slurry nitrogen conservation during storage in Mediterranean conditions

31 Pag., 5 Tabl., 2 Fig. The definitive version is available at: http://www.springerlink.com/content/1385-1314/Swine slurry (SS) is usually stored in open ponds in Mediterranean conditions before being applied to crop fields. During this storage nitrogen (N) is lost to the atmosphere mainly by ammonia volatilization diminishing the fertilizer value of the slurry and causing environmental problems. Permeable covers made from plant materials are low-cost alternatives to reduce these losses. This work evaluates the effectiveness of four composite permeable covers to conserve N during SS storage under semi-arid Mediterranean conditions. The covers, supported by a raschel mesh floating over the SS, were 3.5 and 7 cm thickness pine bark (PB3.5 and PB7), 8 cm thickness pruned wood (PW8), and 8 cm thickness cornstalk (CS8) and uncovered treatment (C). In the first four storage months, the pine bark and cornstalk covers conserved ammonium more effectively than the pruned wood and the control treatments (73–76% of the initial mass of SS ammonium conserved in the PB3.5, PB7 and CS8 treatments, against 51 and 39% in the PW8 and C treatments). In contrast, after 10 months of SS storage all treatments behaved similarly (conservation of ammonium below 20%) due to cover’s physical degradation. In general, the nutrient concentrations in SS and their ratios changed during storage and the C/N ratio at the end of the experiment was affected by the type of cover pointing to differential effects between covers. The pine bark and cornstalk covers were more effective than pruned wood to conserve N in SS stored for 4 months, a period that matches satisfactorily with the spring-summer months of typical SS storage in semi-arid Mediterranean conditions.This study was funded by the Research Agreement between Gobierno de Aragón, La Caixa and Grupo Jorge S. L.Peer reviewe