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

摘要

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.