Assessment of Turfgrass Root Growth in Compacted Soils

Abstract

Soil compaction often prevents turfgrass roots from growing to deeper sources of water and nutrients. Root response of ten turfgrass species to a compacted subsurface layer was examined in a greenhouse experiment. Research objectives were to determine if a compacted subsurface soil layer reduces root penetration and shoot growth for each of ten turfgrass species and to determine the bulk density of a subsurface layer at which root growth is impaired for each of ten turfgrass species. Ten turfgrass species were grown for four to eight weeks in 13-cm diameter x 25-cm long columns filled with loamy sand soil material. Each column was divided into three sections. The top and bottom sections were packed to a bulk density of 1.6 Mg cm-3, and the middle (treatment) layer was packed to 1.6, 1.7, 1.8, 1.9, or 2.0 Mg m-3. Soil compaction reduced root growth for each of the ten turfgrass species; the effect of compaction on root and shoot growth varied among species. Root penetrability varied among species and bulk densities as determined by the amount of root dry mass recovered in the bottom of each column. Root biomass in the bottom layer decreased as bulk density of the middle layer increased, with the most significant reduction occurring between 1.7 and 1.8 Mg m-3 for Kentucky bluegrass, bentgrass, perennial ryegrass, tall fescue, St. Augustinegrass, and paspalum. A significant growth reduction occurred between 1.8 and 1.9 Mg m-3 for zoysiagrass, centipedegrass, bermduagrass, and buffalograss. Better turf growth can be expected if management practices are used which eliminate compacted subsurface layers or reduce soil compaction prior to turf establishment.