Seeded Zoysiagrass Establishment in a Perennial Ryegrass Sward

Abstract

Many golf course superintendents in the transition zone of the USA are interested in converting their perennial ryegrass (Lolium perenne L.) fairways to warm‐season grasses to reduce irrigation and fungicide expenses. This research was conducted to identify strategies for converting perennial ryegrass swards maintained under golf course fairway conditions to seeded ‘Zenith’ zoysiagrass (Zoysia japonica Steudel). An experiment was initiated in 1999 (Study I) at the Rocky Ford Turfgrass Research Center at Manhattan, KS, to evaluate the influence of traffic, plant growth regulator (PGR), or glyphosate [N‐(phosphonomethyl) glycine] application to perennial ryegrass and perennial ryegrass scalping on zoysiagrass emergence and coverage. In 2000, a second experiment (Study II) was initiated to evaluate zoysiagrass coverage response after perennial ryegrass was treated with glyphosate or scalping, as in Study I, and a zoysiagrass strip‐seeding technique was also evaluated. Each study was evaluated for three consecutive years. Before seeding zoysiagrass at 42 kg pure live seed (PLS) ha−1 in mid June, plots in all treatments were aerified and verticut. Trafficking turf with a smooth power roller in Study I reduced turfgrass quality during the first year of establishment and reduced zoysiagrass seedling emergence 6 wk after seeding and coverage in each of three evaluation years. Plant growth regulators applied to perennial ryegrass before seeding in Study I did not enhance zoysiagrass seedling emergence or coverage. Perennial ryegrass treated with glyphosate or scalped during the first 6 wk after seeding exhibited greater zoysiagrass seedling emergence than PGR‐treated or untreated turf in Study I. Zoysiagrass coverage in glyphosate‐treated perennial ryegrass was 75 and 84% by October of the first year in Studies I and II, respectively. Scalping perennial ryegrass resulted in 75% (Study I) and 40% (Study II) zoysiagrass coverage by the end of the third season of establishment. Strip seeding zoysiagrass at 84 kg PLS ha−1 into 7.6‐cm wide glyphosate‐treated strips, spaced 33 cm apart, resulted in 73% coverage by the end of the third season of establishment in Study II. In general, the treatments that resulted in greatest perennial ryegrass suppression resulted in the largest percentage of zoysiagrass coverage 3 yr after seeding.