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 treatments 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