Stubble Height Management Changes the Productivity of Perennial Ryegrass and Tall Fescue Pastures

Abstract

Pasture‐based dairy operators usually aim to optimize defoliation intensity to maximize forage production and nutritive value. The objective was to determine forage accumulation, nutritive value, and tiller density of tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] and perennial ryegrass (L. perenne L.) when repeatedly mowed to a stubble height of 2.5, 5, 7.5, 10, 12.5, or 15 cm. In a 2‐yr study conducted near Columbia, MO, plots were mown to their respective stubble height whenever they grew to a “trigger” height of 20 to 22 plate meter units (approximately 4000 kg ha−1 dry matter [DM] to soil surface). In Year 1, tall fescue mowed to 2.5 cm accumulated 14,440 kg ha−1 which was the most of any treatment. In Year 2, forage accumulation for tall fescue mowed to 2.5, 5, or 7.5 cm did not differ, but was approximately 15% more than perennial ryegrass mowed to the same heights. For both species, forage harvested at stubble heights ≥10 cm had greater nutritive value than at heights of ≤7.5 cm. Perennial ryegrass had 60% fewer tillers for stubble heights ≤7.5 cm compared to heights ≥10 cm. Tall fescue showed no difference in tiller density for any stubble height. Milk production ha−1, predicted via MILK2006, was greater for stubble heights ≤7.5 cm, primarily due to greater forage accumulation. This study showed that tall fescue is better suited than perennial ryegrass for pasture‐based dairies in the Midwest because of its greater forage yield, estimated milk production, and stand (tiller) density.