Denitrification from an irrigated soil fertilized with pig slurry under Mediterranean conditions

Under a Mediterranean climate, denitrification losses were quantified for 2 years on a sandy loam soil with an irrigated maize crop. The effect of pig slurry application at two different rates (165 and 495 kg N ha(-1), respectively, for PS1 and PS3) was compared with that of urea (U) applied at 165 kg N ha(-1) and with a control treatment (P0) without fertilizer. After application, the denitrification rate (DR) increased in PS1 and PS3 respect to P0 and decreased to the levels of the control treatment after 5 days. In July and August (the irrigation period) the DR increased considerably in all treatments with maximum values for the PS3 treatment (0.134 g N m(-2) day(-1) in the first year and 0.147 g N m(-2) day(-1) in the second year). The differences in DRs between each treatment could be explained by the pattern of water filled pore space, NO3- concentration of the soil solution and the soil temperature during the maize growing season. In the first year denitrification losses in the 0-10 cm layer were 1.90, 2.49, 2.87 and 4.00 g N m(-2) for P0, U, PS1 and PS3, respectively, while in the second year the losses were 1.21, 2.28, 2.47 and 3.42 g N m(-2). Finally, a simple predictive model (SOILN) was evaluated and found to give acceptable results.