Mowing height and fertility regime effects on tall fescue turf in the Pacific Northwest

Authors: WANG, RUYING - Oregon State University; HAMILTON, ZACHARY - Oregon State University; Mattox, Clint; MCDONALD, BRIAN - Oregon State University; SCHMID, CHARLES - Oregon State University; KOWALEWSKI, ALEC - Oregon State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2024
Publication Date: 8/16/2024
Citation: Wang, R., Hamilton, Z.J., Mattox, C.M., Mcdonald, B.W., Schmid, C.J., Kowalewski, A.R. 2024. Mowing height and fertility regime effects on tall fescue turf in the Pacific Northwest. HortScience. https://doi.org/10.21273/HORTSCI17871-24.
DOI: https://doi.org/10.21273/HORTSCI17871-24

Interpretive Summary: Tall fescue is valued for drought and heat tolerance in many regions of the United States. In the western cool-humid portion of the Pacific Northwest, tall fescue can be challenging to manage because of unacceptable winter quality caused by thinning and diseases that can lead to poor long-term performance. To assess if winter mowing height and fertility inputs may mitigate turfgrass thinning, a field trial was initiated in the autumn of 2020 in Corvallis, OR. Mowing heights of 5.1 and 7.6 cm were assessed alongside four seasonal fertility timings and three annual nitrogen rates (98, 196, and 294 kg N ha-1 yr-1). Turfgrass quality was assessed using percent green cover from light box images and plant health was assessed using normalized difference vegetative index (NDVI). Findings from this study suggest that autumn fertilization provides a benefit to tall fescue green cover in the winter months. Regarding fertility rate, 294 kg N ha-1 yr-1 produced higher green turf cover and higher NDVI, compared to 98 or 196 kg N ha-1 yr-1. Mowing height data suggest that tall fescue could be mowed lower at 5.1 cm during cool, humid winter months and higher at 7.6 cm in other seasons for better overall turfgrass growth and less winter disease and thinning. Our research provided practical cultural practices for managing tall fescue in the Pacific Northwest or similar climates.

Technical Abstract: The western portion of the Pacific Northwest is known for being dry in the summer and cool, humid in the other months. Tall fescue is valued for its drought and heat tolerance making it a desirable choice in regions where water is scarce and often restricted by legislation during periods of drought in the summer. However, cool, and humid climates make it challenging to manage tall fescue in the winter, because unacceptable quality is often observed due to low-temperature diseases and thinning in turf. A field trial was initiated in the autumn of 2020 in Corvallis, OR to assess the effects of mowing height as well as fertility timing and rate on tall fescue turf. Two mowing heights of 5.1 and 7.6 cm, four seasonal fertility timings, and three levels of annual N rates of 98, 196, and 294 kg ha-1·yr-1 were evaluated using a 2 × 4 × 3 factorial experiment in a strip-plot design. Quantitative data of percent green cover and normalized difference vegetative index (NDVI) suggest that autumn fertilization is needed for cool, humid areas where tall fescue is actively growing in the winter months. The annual fertilization rate of 294 kg N ha-1·yr-1 produced higher green turf cover and NDVI, compared to 98 or 196 kg N ha-1 yr-1. Furthermore, divergent effects of mowing heights were observed during winter compared to other months, suggesting that tall fescue could be mowed lower at 5.1 cm during cool, humid winter months and higher at 7.6 cm in other seasons for better overall turfgrass growth and less winter disease and thinning. Our research provided practical cultural practices for managing tall fescue in the Pacific Northwest or similar climates.