Root development of bermudagrass and tall fescue as affected by cutting interval and growth regulators

A study was conducted to characterize changes in bermudagrass (Cynodon dactylon L.] Pers.) and tall fescue (Festuca arundinacea Schreb.) root development over time and with depth, and to determine the effects of defoliation interval and chemical seedhead suppression on root and shoot growth. Field plots were established on a fine-silty, mixed mesic Typic Fragiudult soil in Fayetteville, AR, USA, and each plot contained three minirhizotrons (plexiglass observation tubes) to a depth of 40 cm. Images of roots in 10-cm depth increments were periodically videorecorded, and total root length (RL) and root length density (RLD) were measured with a computer-interfaced tracing probe. Treatments consisted of two cutting intervals, 3 and 6 weeks, and two plant growth regulator (PGR) treatments, an untreated control and either 300 g ha^-1 mefluidide on tall fescue in early spring of both years or 10 g ha^-1 each of metsulfuron methyl (MSM) and sulfometuron methyl (SMM) applied in late May of both post-establishment years. Data were analyzed separately for the establishment period (planting to the first date of PGR application) and the subsequent post-establishment period. Bermulagrass exhibited a two-stage root establishment pattern characterized first by minimal root development in conjunction with stolon proliferation and soil surface colonization, followed by accumulation of total RL over two subsequent forage production seasons. There was a net accumulation of root mass during the winter dormancy period of 1986–87. Total RL of tall fescue peaked one and a half years after planting. Cutting interval had no influence on RL and RLD. Application of a PGR did not affect RL but did alter RLD of both species. Application of mefluidide to tall fescue stimulated RLD 64 days after application, whereas bermudagrass RLD was retarded by MSM and SMM up to 50 days after application. Trends in root growth did not closely follow patterns of shoot growth. Published with the approval of the Director of the Arkansas Agricultural Experiment Station. Published with the approval of the Director of the Arkansas Agricultural Experiment Station.