The Influence of Region, Drainage and Management on Soil Physicochemical Properties, Microbial Community, and Enzymatic Activities in Irish Agricultural Grasslands

This study investigated the comparative influence of regional difference in agronomic potential (‘Region'), natural drainage (‘Drainage’) and grassland management intensity (‘Manage’) on soil physicochemical variables, microbial community structure and soil enzymatic activity across 37 Irish grassland sites. Of the soil physicochemical variables measured, nested ANOVA models revealed that soil dry matter, total Carbon and Nitrogen, M3-Magnesium and M3-Calcium were significantly influenced by ‘Region’ (p < 0.05), while soil pH and soil organic Carbon were significantly influenced by both ‘Region’ and ‘Manage’, though the former had the stronger influence. No measured variable was significantly influenced by ‘Drainage’. A nested PERMANOVA model revealed that each of the three factors exerted a significant influence on soil microbial community structure (p < 0.05), with the community centroid distance (Euclidian) also revealing that there was a comparative influence between the three factors (distance range = 0.066 – 0.079). The factor ‘Drainage’ did have a stronger influence on the abundance of the fatty acid biomarker for the arbuscular mycorrizal fungi (effect size = 20.54%) than ‘Region’ (effect size = 10.05%), while ‘Manage’ did not display a significant effect. In contrast to soil microbial community structure, individual soil enzymatic activities mostly either did not significantly respond to any factor, or significantly responded to ‘Region’ (p < 0.05, i.e., β-N-acetyl-glucosaminidase and arylsulfatase). The study highlights the value of considering localized environmental drivers in studies relating to soil health at the national level, to support effective, context-specific management strategies for soil health.