Agricultural management intensity a stronger driver of soil nutrients and enzymatic activities than regional-scale geographic factors in Irish grasslands.

Understanding the comparative influence of agricultural management intensity and regional-scale geographic factors on the level of soil nutrients and microbial activities in Irish grasslands is a key research gap. To address this, a regional-scale survey was undertaken, spanning two Irish regions (‘Region’), one favourable to agricultural productivity (South-East) and one less-favourable (West). From each region, soil samples were taken from three different grassland management intensities (‘Manage’, n=12); intensive, low-input grassland and extensively-grazed pasture, a total of 72 sites. Statistical differences were tested via nested ANOVA. Potassium (K), sulfur (S) and phosphorus (P), essential macronutrients for plant growth, responded significantly to ‘Manage’ (all p < 0.01), but not to ‘Region’ (p > 0.05). There was a significant effect of ‘Manage’ on K, S and P in the favourable region, with this effect also seen for K and S in the less-favourable region (all p < 0.05). These effects were driven by higher values in intensive grasslands. A significant effect of ‘Manage’ was also seen on the activity of four carbon-cycling enzymes; β-glucosidase, chitinase, cellobiohydrolase, and β-xylosidase (all p < 0.05), with no significant effect of ‘Region’ observed (p > 0.05). The enzymes β-glucosidase and β-xylosidase were significantly influenced by ‘Manage’ in both the favourable and less-favourable regions, with higher activity levels seen in intensive grasslands compared to extensively-grazed pasture in each instance (all p < 0.05). These results highlight the stronger influence that agricultural management intensity has on soil nutrients and microbial activities in Irish grasslands compared to regional-scale geographic factors.