Microbial activity was higher in the N300 and PS45 plots than the N0 plots in both years, but especially in 2011 when CO2 emissions increased by >60% and phosphatase activity by >40%. This is consistent with previous studies showing that the continuous addition of manure had a significant impact on basal respiration [22] and soil biological activity in general [51]. In contrast, Aira et al. [52] found that the application of PS reduced microbial biomass and microbial activity in the short term. It was found no significant difference between the two fertilizer treat- ments for these parameters, perhaps due to the heterogeneity of replicate soil samples (Table 6). Phosphatase activity can be repressed by a feedback mechanism induced by the reaction product phosphate, as shown when microbes are transferred from phosphate-free to phosphate-supplemented medium [53]. Chun- derova and Zubeta [54] showed that after 4 years of cropping, high phosphate concentrations at field testing sites inhibited microbial