Nitrogen and sprigging rate effects on Latitude 36 bermudagrass establishment

Figure 1 Bermudagrass cover four weeks after planting on plots sprigged at 200 (A), 400 (B), 600 (C) and 800 (D) bushels per acre. In all the photos, the nitrogen rates are 0, 11, 22 and 44 lbs. nitrogen/acre/week from left to right, and the boundaries of individual nitrogen rate plots are indicted by orange dots on the soil. (Photos: Gregg Munshaw)

Bermudagrass (Cynodon sp.) is widely grown throughout the southern United States for recreational and aesthetic purposes. Bermudagrass provides a heat- and drought-tolerant turfgrass that exhibits vigorous growth and good wear tolerance. Bermudagrass also is popular on golf courses because of the speed at which it establishes and recuperates. Superintendents often need to establish turfgrass rapidly in order to keep tees, fairways and rough in play.

Establishing bermudagrass from sprigs on golf courses provides an economical propagation method compared to sodding. Although much research has focused on bermudagrass seeding rates for establishment, little information is available concerning optimum sprigging rates for bermudagrasses. A recommendation of a minimum rate of 100 bushels/acre reported excellent cover in three weeks. Others have recommended sprigging rates of 218 to 653 bushels/acre to reach full cover within 10 to 12 weeks after sprigging. For quicker establishment, sprigging rates up to 1,089 bushels/acre are recommended. The common logic is that higher sprigging rates result in faster establishment than lower rates.

Nitrogen effects on establishment

The effect of nitrogen on bermudagrass establishment from seed has been well documented, however, there appear to be large discrepancies in recommended nitrogen rates for establishing vegetative cultivars.

Recommended nitrogen rates from previous establishment studies on Tifway bermudagrass range from 44 lbs./acre per month to 271 lbs./acre per month. However, a study looking at establishment of Tifway and Latitude 36 bermudagrasses showed that high N rates (175 lbs./acre nitrogen per month) were beneficial only shortly after planting, and lower nitrogen rates were equally effective for establishment as the study progressed. Although discrepancies in nitrogen recommendations during bermudagrass establishment exist, most agree that at least some nitrogen is required to improve establishment.

Because little science-based information exists on newer cultivars regarding optimum sprigging and nitrogen rates during bermudagrass establishment, a study was conducted to examine these factors across four locations in the United States for the newer cultivar Latitude 36. The objective of this study was to characterize the effect of sprigging and nitrogen rates to bermudagrass establishment from sprigs in areas throughout the southern and transition zones of the United States.

Sites and data collected

The experiment was conducted in summer 2015 at university research facilities in Baton Rouge, La., Starkville, Miss., Stillwater, Okla., and Lexington, Ky. (USDA hardiness zones 9A, 8A, 7A, and 6B, respectively).

Table 1 Effect of nitrogen rate on turfgrass cover across all sprigging rates over a six-week observation period at four locations during summer of 2015. † Values followed by an uppercase letter within a row are not significantly different (P<0.05). ‡ Values followed by a lowercase letter within a column are not significantly different (P<0.05).

The soil at the Burden Center (Louisiana State University) was an Oliver silt loam (fine-silty, mixed, thermic, Typic Fragiudalf; pH: 7.3; 88 lbs./acre phosphorus (P); 473 lbs./acre potassium (K)). The soil at the R. R. Foil Research Center (Mississippi State University) was a Marietta fine sandy loam (fine-loamy, siliceous, Fluvaquentic Eutrochrept; pH: 5.7; 329 lbs./acre P; 341 lbs./acre K). The soil at the OSU Turfgrass Research Center (Oklahoma State University) was a Norge loam (fine-silty, mixed, active, thermic Udic Paleustolls; pH: 7.2; 144 lbs./acre P; 263 lbs./acre K). The site was modified in 2009 and USGA-specification sand was added and mixed to the top 8 inches of the soil profile. A soil sample was collected on July 15, 2015 and the soil texture was classified as a sandy loam according to the USDA soil textural triangle (USDA, 2016) and consisted of 72.5 percent sand, 13.8 percent silt, and 13.8 percent clay. The soil at the A.J. Powell, Jr. Turfgrass Research Center (University of Kentucky) was a Maury silt loam (fine, mixed, mesic, typic Paleudalf; pH: 5.2; 448 lbs./acre P; 318 lbs./acre K). Winstead Turf Farms, Arlington, Tenn. donated Latitude 36 bermudagrass sprigs for all locations.

Plots were established the second week of July at all locations with the exception of Louisiana, where the study was established the third week of July. Whole plots measured 12 feet by 10 feet. We applied granular fertilizer at planting at rates of 0, 11, 22 and 44 lbs./acre nitrogen with 13.0N-5.7P-10.8K, and then weekly at the same rates using urea (46N-0P-0K) until plots were established (approximately 90-percent groundcover measured by digital image analysis).

We hand-sprigged bermudagrass at rates of 200, 400, 600 and 800 U.S. bushels/acre to cover the spectrum between low, high and commonly recommended sprigging rates. We rolled plots following sprigging to increase sprig-to-soil contact and oxadiazon. We applied Ronstar G (Bayer Environmental Science) over the sprigs at a rate of 150 lbs./acre. We chose Latitude 36 for this study because it’s a new, yet highly used cultivar that exhibits excellent turf quality characteristics, as well as its suitability for all locations of this study.

Table 2 Effect of sprigging rate on turfgrass cover across all nitrogen rates over a six-week period at four locations during summer of 2015. † Values followed by an uppercase letter within a row are not significantly different (P<0.05). ‡ Values followed by a lowercase letter within a column are not significantly different (P<0.05).

We took photos weekly with a light box and digitally analyzed them with SigmaScan Pro (Systat Software, Inc.) and objectively measured plot cover. We mowed plots twice a week with a rotary mower set at 2 inches and returned clippings. We irrigated as needed to prevent wilt. We applied no pesticides during the experimental period.

Statistical analysis

The experimental design was a split-plot with four replications nested at each location. We recorded the dependent variable bermudagrass coverage weekly.

Rather than looking for differences across locations, we selected statistical design to find general trends in bermudagrass establishment requirements across the southern region of the United States during suitable environmental conditions for establishing bermudagrass. We performed statistical analysis of bermudagrass coverage data using the mixed procedure in SAS (version 9.4, SAS Institute), with weekly bermudagrass coverage analyzed over time using repeated measures analysis. Means for the dependent variable bermudagrass coverage was separated according to Fisher’s least significant difference (LSD) (P≤0.05) when the fixed effects of sprig rate, N rate or weeks after planting were significant (P≤0.05).

Nitrogen influence on establishment rate

In general, as weekly nitrogen rate increased from 0 to 44 lbs./acre, bermudagrass coverage increased concurrently over the establishment period (Table 1). Interestingly, all nitrogen rates resulted in approximately 90-percent coverage within four weeks after planting (Figure 1), indicating the aggressiveness of Latitude 36 compared to Tifsport and Tifway bermudagrasses, which typically take five to seven weeks to achieve full coverage.

Although nitrogen rate was statistically significant at almost every observation date, differences were slight (i.e. <4 percent difference in plot cover between high and low nitrogen rates at four weeks after planting) and likely not relevant for superintendents. In similar work examining the effect of nitrogen and sprigging rates, other researchers have reported that increasing nitrogen rates up to 33 lbs./acre/week improved establishment of TifEagle bermudagrass.

In the current study, the results align with nitrogen rates of 44 lbs. nitrogen/acre/month rather than 271 lbs. nitrogen/acre/month when evaluating bermudagrass establishment by sprigs. Because all but the lowest nitrogen rate (0 lbs. nitrogen/acre/week) reached ≥90 percent coverage within four weeks after planting, the use of additional nitrogen may not be warranted, especially if mitigation of potential offsite nitrogen pollution is a concern.

Reduction in nitrogen rates from 44 to 11 or 22 lbs./acre/week is supported from an economical and environmental standpoint, but also when considering that unfertilized plots exhibited improvements in coverage at each observation date, with ≥90 percent coverage five weeks after planting, the benefits of high nitrogen rates are questionable.

Sprig rate affects establishment rate

The more important factor to accelerate bermudagrass establishment appears to be sprig rate (Table 2). The effect of sprig rate on turfgrass cover showed that increasing rates not only resulted in higher initial coverages but maintained higher coverages until all sprig rates resulted in full coverage six weeks after planting (Figure 1).

For example, sprigs planted at the lowest rate of 200 bushels/acre had 19.9-percent cover one week after planting and achieved >90-percent cover five weeks after planting, compared to the highest sprig rate of 800 bushels/acre, which had 41.8-percent coverage one week after planting and 95.4-percent cover within four weeks after planting.

However, as is the case with nitrogen, excessive sprigging rates do not necessarily provide proportional benefits. For example, sprigging rates of 400 and 600 bushels/acre resulted in coverages of 91.3 percent and 94.1 percent, respectively, at four weeks after planting, compared to the highest sprig rate of 800 bushels/acre at 95.4-percent cover. The influence of sprig rate on bermudagrass establishment may be more pronounced for slower-growing bermudagrass cultivars.

Superintendents commonly are under pressure to establish turfgrass surfaces as quickly as possible. Decreasing the duration of establishment not only shortens the period turfed areas cannot be used but can potentially reduce offsite sediment loading and P losses.

So, if the goal is to accelerate bermudagrass coverage on finely textured soils, we recommend a sprig rate of 400 to 600 bushels/acre and applying 11 to 22 lbs. nitrogen/acre/week until established. However, increasing sprigging rate at more than 600 bushels/acre results only in slight increases in cover during the establishment period and does not reduce time to full cover.

As long as temperatures are suitable for bermudagrass growth and superintendents use finer-textured soils, results should be similar to those found in this study, regardless of location.

Gregg C. Munshaw, Ph.D., and Kenneth Cropper, Ph.D., are at the University of Kentucky, Jeffery S. Beasley, Ph.D., is at Louisiana State University, Christian Baldwin, Ph.D., is at Scotts Miracle-Gro Co., H. Wayne Philley and Barry R. Stewart, Ph.D., are at Mississippi State University, Justin Q. Moss, Ph.D., is at Oklahoma State University and Chrissie A. Segars, Ph.D., is at the University of Tennessee-Martin. You may reach Gregg Munshaw at gcmunshaw@uky.edu for more information.

Acknowledgements

The authors thank David Blouin, Ph.D., Louisiana State University, for assistance with experimental design and statistical analysis.

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