## 3 Results
Values of total N and CWS were higher in soils amended with composted horse manure (0.39 \(\pm\) 0.01% and 636 \(\pm\) 46 mg C kg\({}^{-1}\) soil) and dried cow slurry (0.37 \(\pm\) 0.03% and 565 \(\pm\) 65 mg C kg\({}^{-1}\) soil) than in control unamended soils (0.28 \(\pm\) 0.02% and 317 \(\pm\) 28 mg C kg\({}^{-1}\) soil) (Table 3). Values of soil pH were slightly, not relevantly, higher in soils amended with composted horse manure, whereas a slight increase in electrical conductivity (EC) was observed in soils amended with dried cow slurry (1.7 \(\pm\) 0.1 dS m\({}^{-1}\)) with respect to control soils (1.4 \(\pm\) 0.1 dS m\({}^{-1}\); \(p<\) 0.06) (Table 3). The application of organic amendments, especially dried cow slurry, increased the values of most of the microbial parameters determined here. Microbial activity parameters (see below) were significantly higher in soils amended with dried cow slurry, followed by soils amended with composted horse manure and, finally, unamended controls (Figure 2; F = 16.1, \(p<0.002\)) (Table 4). According to the variation partitioning analysis, \"amendment\" application accounted for 64% of the explained variation, while \"bioaugmentation\" and \"plant\" growth explained only 1.3 and 2.2% of the variation, respectively. Significantly highest values of soil respiration (\(4\pm 0.3\) mg C kg\({}^{-1}\) soil) were, in general, obtained in soils amended with dried cow slurry (Table 4). Lowest values of soil respiration (\(1.57\pm 0.3\) mg C kg\({}^{-1}\) soil) were detected in unamended controls [planted pots showed significantly higher values (\(1.85\pm 0.07\) mg C kg\({}^{-1}\) soil) than unplanted pots (\(1.30\pm 0.01\) mg C kg\({}^{-1}\) soil)] (Table 4). Bioaugmentation led to lower values of soil respiration in planted pots amended with composted horse manure and dried cow slurry, compared to unamended controls. Regarding N\({}_{\text{PM}}\), values were higher (\(106\pm 24\) mg N-NH\({}_{4}\)\({}^{+}\) kg\({}^{-1}\) DW soil) in soils amended with dried cow slurry (lowest values--\(6\pm 3\) mg N-NH\({}_{4}\)\({}^{+}\) kg\({}^{-1}\) DW soil - were obtained in soils amended with composted horse manure. N\({}_{\text{PM}}\) values were higher in planted vs. unplanted soils (\(120\pm 13\) and \(90\pm 25\) mg N-NH\({}_{4}\)\({}^{+}\) kg\({}^{-1}\) DW soil, respectively). Bioaugmentation did not cause significant differences among treatments in regard to N\({}_{\text{PM}}\). Concerning soil enzyme activities, the \"amendment\" factor was significant for all soils, with highest values being detected in soils amended with dried cow slurry. The \"plant\" factor was significant for 6 enzyme activities (out of 9), with generally higher values observed in planted vs. unplanted pots. No clear effect of the \"bioaugmentation\" factor was observed for soil enzyme activities. Figure 2: Biplot of the redundancy analysis (RDA) performed on soil microbial activity parameters. URE: urease; SUL: arylsulphatase; DEH: dehydrogenase; LEU: L-Leu-aminopeptidase; GLU: \(\beta\)-glucosidase; GLM: \(\beta\)-glucosidase; ALA: L-Ala-aminophenidase; XYL: xylosidase; PHO: acid phosphatase; R: respiration; N\({}_{\text{PM}}\): potentially mineralizable N. Compost: amended with composted horse manure; Cow slurry: amended with dried cow slurry.