Turfgrass generally needs a lot of water to stay green and healthy during hot and dry periods. In cooler, wetter climates like the coastal Pacific Northwest, there is plenty of rain from October to June, but very little rain from July to September. Tall fescue can stay healthy with less frequent watering and minimal water replacement, so in more recent years it has become more commonly used in lawns, sports fields and pastures.
By understanding the optimal watering levels and schedules, Oregon growers can conserve water, reduce costs and maintain high-quality turfgrass.
Oregon’s grass seed industry produces 90% of the cool-season grass seed in the United States. To support growers, researchers in the College of Agricultural Sciences at Oregon State University aimed to see how different watering levels and schedules affect tall fescue's appearance and weed growth, so they conducted a field study on Thunderstruck tall fescue at the OSU Lewis-Brown Farm in Corvallis.
They tested different watering treatments from July 1 to September 15 in both 2021 and 2022. These included watering once a week or four times a week at two levels — 45% and 80% of the usual water replacement — and a control group with no watering.
The study, published in the International Turfgrass Society Research Journal, found that watering once a week or four times a week at 45% and 80% replacement rates kept the grass healthy. No watering was needed from September 15, 2021, to July 1, 2022, due to sufficient rainfall. The researchers found that watering tall fescue at the highest level (80%) gave the best grass color, while not watering at all resulted in the lowest color ratings.
However, the grass still looked good most of the year without any watering. In the first year, the grass stayed green until mid-August without watering, when the soil moisture dropped below 18%. In the second year, it stayed green until the end of August, when the soil moisture was below 9%. This suggests that monitoring soil moisture and watering only when it gets too low can help save water.
Not watering also led to fewer weeds like annual bluegrass and spotted spurge. The moderate temperatures, silty clay loam soil and adequate rainfall from October to June in Western Oregon help keep tall fescue healthy during the summer drought.
This research provides valuable insights for Oregon tall fescue growers. By understanding the optimal watering levels and schedules, growers can conserve water, reduce costs and maintain high-quality turfgrass.
The findings also highlight the benefits of less frequent watering in reducing weed populations, which can lead to lower herbicide use and more sustainable turf management practices. Overall, this research supports the efficient and environmentally friendly cultivation of tall fescue in Oregon.
The research team, all in the Department of Horticulture, included: Alec Kowalewski, professor and Grover Family Endowed Sustainable Urban Landscapes Specialist; Brian McDonald, senior faculty research assistant; research associates Ruying Wang and Charles Schmid; graduate student Emily Braithwaite; and Tim Stock, senior instructor and leader of the OSU School IPM Program.
Funding for the study was provided by the United States Department of Agriculture’s National Institute of Food and Agriculture.
