Relationship between orchardgrass (Dactylis glomerata) dominance and the soil chemical characteristics of nonallophanic Andosol under cutting and cattle grazing

Soil acidity affects botanical compositions and pasture production, but the relationship between orchardgrass persistence and the soil nutrients in acidic soils with different management methods is understudied in production fields. Here, using exchangeable acidity (y₁) as an indicator of exchangeable aluminum (Al), we conducted a survey to investigate the relationship between orchardgrass dominance and the soil characteristics in sown pastures under different management practices. The botanical composition and soil chemical conditions were investigated in six orchardgrass–tall fescue mixed pastures (two cutting meadows and four cattle grazing pastures) from June 18 to July 17, 2018. Six- and three-line transects were fixed in each meadow or pasture, respectively, and five measurement locations were set along each transect at 10-m intervals. Each location had three square plots (20 × 20 cm) for the vegetation survey and three consecutive soil sampling plots (4-cm diameter) adjacent to the middle square plot. The dominant plant species in each plot was recorded, and soil samples were collected at 0- to 5-cm depth to measure y₁ and major soil nutrients. The y₁ ranged from 3.55 to 25.83 in the cutting meadows, which was wider than in the grazing pastures (1.85–16.29). In the cutting meadows, the dominance frequency of orchardgrass increased with the rise in y₁, whereas that of tall fescue decreased in cutting meadows. No significant relationship was found between dominance frequencies and y₁ in the grazing pastures. Although concentration of some soil nutrients varied with y₁, these nutrients were not related to the dominance frequencies of orchardgrass for either management strategy. These results suggest that orchardgrass declines are prevented at high exchangeable Al sites by the non-establishment of less Al-tolerant plant species under cutting conditions.