Center Update: Fraise Mowing Turfgrass Surfaces
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Fraise Mowing Bermudagrass Surfaces: Effects and Recovery
PI: Grady Miller; Student: Ray McCauley
Fraise mowing (fraze/fraise mowing) is a cultural practice that was devised in the Netherlands during the mid-1990s and is similar to vertical mowing. While vertical mowing partially impacts the surface (≤30%), fraise mowing’s impact is absolute- encompassing 100% of the surface with potentially reaching up to 2-inch depths in a single pass. This makes fraise mowing an appealing thatch management tool especially with bermudagrasses. Thatch removal is the primary benefit of fraise mowing, but other demonstrated benefits of fraise mowing include Poa annua control an overseeding removal (McCauley et al., 2019; Hansen and Christians, 2015; Baker et al., 2005). These benefits come at price, though. Fraise mowing disrupts turf quality until bermudagrass regenerates from remnant rhizomes and stolons. This duration of this disruption depends on fraise mowing depth, and recovery times can range from 3 to ≥6 weeks for 0.25 inch and 1-inch depths, respectively (Shelton et al., 2016). Despite nearly 25 years of use, there has been limited research on fraise mowing. To satisfy this void, we conducted multiple field studies over the past four years that monitored fraise mowing’s impact on soil physical properties, its ability to remove shallow compaction, and practices to expedite bermudagrass’ recovery after fraise mowing.
A number of independent field studies have been conducted since 2016 to evaluate a number of soil and plant responses to fraise mowing. One field study was conducted from mid-June through mid-August each year in 2016-2019 that assessed the effects of three fraise mowing depths on soil physical properties. Thatch depth, infiltration rate, soil surface hardness, soil shear strength, and soil water retention were monitored in two soils (loam and sand) at 14-d intervals starting immediately after fraise mowing. Following some initial tests, a hollow-tine aerification treatment was included with the three fraise mowing depths (0.25, 0.5, 1.0 inches) in 2017 and 2018 with the objective of evaluating the effects of both cultural practices on soil physical properties and bermudagrass recovery. Compaction from routine traffic in turfgrass systems is usually confined to the surface 3-inches of the soil profile. These depths overlap with the functional depths of fraise mowers. Two field studies were initiated to evaluate fraise mowing’s potential for relieving shallow soil compaction. Study I was conducted on four athletic fields in Chapel Hill, NC. Simulated traffic was applied with a traffic simulator at the equivalent of 0, 20, 40, or 60 American football games before fraise mowing at 0.8-inch depth. Two field studies were conducted in the summers of 2017 and 2018 to test sand topdressing and nitrogen fertility’s ability to hasten bermudagrass’ recovery. Both studies were fraise mowed in mid-June to 0.25 inches depth. Starting 7 days after fraise mowing (DAF), fertility plots received water soluble nitrogen (WSN) at rate of 0.25, 0.5, 0.75, or 1.0 lb. 1,000 ft-2 per week for four consecutive weeks from granular ammonium sulfate or one application water insoluble nitrogen (WIN) at 2.0 lbs. 1,000 ft-2 from granular polymer-coated urea. In the topdressing study, all plots received one independent sand application at 0, 7, or 14 days after fraise mowing to a depth of 0 (control), 0.13 (shallow), 0.25 (medium), or 0.5 inches (heavy).
Results and Discussion
Thatch content decreased ≤64% after fraise mowing at 1-inch in both soils. Soil surface hardness increased with deeper fraise mowing depths, and differences were more pronounced in the loam (≤49 gravities) compared to the sand (≤ 15 gravities). Shear strength in the sand decreased with 0.5 and 1.0-inch fraise mowing depths and the removal of more reinforcing roots and stolons. In the loam, the 1-inch fraise mowing depth had the highest shear strength (96 Nm) because it engaged the cohesive, underlying soil. Infiltration rate decreased with deeper fraise mowing depths, and the Ksat of the 1-inch depth was 6.8 in hr-1 slower than the control. Deeper fraise mowing depths removed more shallow organic matter, and soil water retention decreased 16 to 22% with 0.5 and 1.0-inch fraise mowing depths, respectively, compared to the control. These results indicate that fraise mowing did (positively and negatively) alter the soil physical properties in both soils and that deeper fraise mowing depths had a greater effect.
In the combination fraise mowing and aerification study, all fraise mowing treatments had unacceptable turf quality after treatment. However, combining fraise mowing with aerification did not delay bermudagrass recovery. Thatch content decreased with deeper fraise mowing depths but was unaffected by hollow-tine aerification. Immediately after treatment, Ksat was highest in the untreated control (36.5 in hr-1) and decreased with deeper fraise mowing depths. Aerification increased Ksat by 14 in hr-1, decreased surface hardness by ≤12 gravities, and lowered shallow shear strength by ≤16 Nm throughout the study. When practiced concurrently, fraise mowing and hollow-tine aerification were complimentary and positively affected the soil physical properties in both soils.
In two sampled sand-based fields, soil surface hardness and soil resistance decreased after fraise mowing. One sand-based field’s Ksat increased by 1 in hr-1 after fraise mowing. These improvements in soil physical properties indicate fraise mowing’s potential to relieve shallow soil compaction. Follow-up studies we conducted founds similar results.
In the recovery and topdressing studies, water soluble nitrogen treatments ≥0.5 lb. 1,000ft-2 had acceptable turf quality and cover in 21 DAF. All fertilized treatments had acceptable turf quality by 28 DAF. Withholding nitrogen delayed bermudagrass recovery beyond 28 DAF. Control, shallow, and medium topdressing treatments had acceptable turf quality and cover in 28 DAF, regardless of sand application date. All topdressing depths applied immediately after fraise mowing had acceptable turf quality by 28 DAF. When applied 7 or 14 DAF, the heavy rate delayed bermudagrass recovery by ≥7 days compared to all other treatments. Sand topdressing did not accelerate bermudagrass recovery following fraise mowing. Therefore, nitrogen fertilization at ≥0.5 lb. 1,000 ft-2 was the most effective practice at hastening bermudagrass recovery following fraise mowing.
Fraise mowing is a very disruptive cultural practice, and bermudagrass requires ≥3 weeks to recover from it. Results from our studies provide turf managers with concrete steps to shorten this downtime with nitrogen fertilization while informing them of fraise mowing’s effects on soil physical properties. The successful pairing of aerification with fraise mowing was also demonstrated, as well as fraise mowing’s potential to remove shallow soil compaction. These results will remove some of the apprehension of this practice and may lead to its expanded use.
Baker, S.W., A.G. Owen, and A.R. Woollacott. 2005. Physical and chemical control of Poa annua on professional football pitches. J. Turfgrass Sports Surf. Sci. 81:47-61.
Hansen, K., and N. Christians. 2015. Establishing Kentucky bluegrass after fraze mowing: time to recovery after fraze mowing can be affected by seeding rates and the use of turf covers. Golf Course Manage. 83(7):88-93.
McCauley, R.K., Pinnix, G.D. and G.L. Miller. 2019. Fraise mowing as a spring transition aid. Crop, Forage & Turfgrass Manage. 5: 1-5 190025.
Shelton, C., J. Booth, and D. McCall. 2016. Impact of fraze mowing on spring dead spot severity and recovery. VA Turfgrass J. 12-13.