PBA, soil + PBa; PBV, soil + PB (ventilated incubation); PBS, soil + PB (sealed incubation); CKV, soil only (ventilated incubation); and CKS, soil only (sealed incubation).
Each value is the mean of three replicates with the standard deviation and values marked with the same letters in each column are not significantly different (P > 0.05).