Spring and autumn animal treading effects on pre-grazing herbage mass and tiller density on two contrasting pasture types in Ireland

A perennial ryegrass (Lolium perenne L.)-dominated sward on a well-drained soil (Experiment 1) and a creeping bent (Agrostis stolonifera L.)-dominated sward on a poorly drained soil (Experiment 2) were subjected to four treading treatments: control (C, no damage), light damage (L), moderate damage (M) or severe damage (S) to quantify the effects on herbage dry-matter (DM) production and tiller density. In Experiment 1, treading damage was imposed in spring. In Experiment 2, one-third of the site was damaged in autumn, one-third in spring and one-third in both spring and autumn. Both sites were rotationally grazed after treading treatments. Pre-grazing herbage mass was measured eight times in Experiment 1 and seven times in Experiment 2 on each plot, and tiller density was assessed four times in each experiment. In Experiment 1, pre-grazing herbage mass was reduced by 30% in S plots at the first harvest after damage, but cumulative pre-grazing herbage DM production was not different between treatments (12.7 t DM ha(-1)). In Experiment 2, annual cumulative pre-grazing herbage mass was reduced by between 14 and 49%, depending on intensity of treading damage event and season when damage occurred. Tiller density was not affected by treatment in either experiment. A perennial ryegrass-dominated sward on a well-drained soil was resilient to heavy treading damage. A creeping bent-dominated sward on poorly drained soil requires a more careful grazing management approach to avoid major losses in cumulative pre-grazing herbage mass production during wet weather grazing events.