Horticulture

Fall Overseeding

“Heavy Repetitive Fall Overseeding To Improve Low-Input Sports Fields”

A Report To The New York State Turfgrass Association

Principle Investigator: David Chinery, Cornell Cooperative Extension of Rensselaer County, 61 State St., Troy, NY 12180

Cooperators: Dr. Frank Rossi, Cornell University, Ithaca, NY

Dennis Weatherwax, The Averill Park School District, Averill Park, NY

Jim Conroy, The City Of Troy, Troy, NY

Introduction: Overseeding, or distributing seed over an existing turfgrass area to increase density, is a traditional practice followed by many turfgrass managers. Unfortunately, success in overseeding is not easily accomplished. To improve the chances that a high rate of seed germination and establishment will occur, it is often recommended that some sort of cultivation is done before seeding. Types of cultivation include removing cores of soil (core cultivation), spiking, and vertical mowing. An aggressive overseeding program for a sports field might be to overseed four or five times per year, hoping each time for some limited success. Home lawns and commercial properties, which are not usually overseeded, might be overseeded once or twice per year in a “best case” scenario. With limitations on the use of pesticides increasing, overseeding might seem to be a better option than ever. However, turfgrass managers often report disappointing results with overseeding (1). This is especially true on low-input fields, or fields where fertilizer, irrigation, weed management, and other cultural activities are limited or nonexistent. The cultivation requirement attached to overseeding can be disruptive to the use of the turf area in question, as well as adding costs. Clearly, easier and more effective ways to overseed turfgrass areas are needed.

In August of 2003 a research project examining heavy, repetitive overseeding was conducted on a two sports fields in the Capital District. This study was designed to put into practice the ideas of Dr. Frank Rossi, Extension Turfgrass Specialist at Cornell University (2). Dr. Rossi has demonstrated that dramatic increases in turfgrass density were possible when high rates of perennial ryegrass (Lolium perenne) were overseeded weekly on a simulated sports field.

Objective: To demonstrate the practice of heavy, repetitive overseeding on two low-input Capital District sports fields using three seeding rates.

Procedures: Anyone who has visited practice soccer and football fields at high schools and parks would probably agree that many are examples of ugly, beat-up turf and weeds. Two fields were used in this study. The practice football field at Averill Park High School had compacted clay loam soil, a low pH (5.9), and was composed of bare spots, crabgrass, knotweed, plantain, dandelion, perennial ryegrass and Kentucky bluegrass. The second field was a multi-purpose soccer/football field in an inner city park, Prospect Park, in Troy. The soil was a loam with pH 7.5. The predominate species here were purslane, Kentucky bluegrass, perennial ryegrass, and goosegrass. See Table 1 for a description of the initial composition of each field.

Table 1. Initial composition (% of each component) on the two study fields

	Per. ryegrass/Ken. bluegrass	Bare	Purslane	Goosegrass	Crabgrass	Plantain	Knotweed	Dandelion
Averill Park High School	4.4	1.3	0	0	57.8	2.1	32.3	0.8
Prospect Park	17.5	38	27.9	15.2	<1	<1	<1	0

Four treatments were made: no seed (check plots), and overseeding at rates of 2, 6 and 10 pounds of seed per 1,000 square feet (M), with three replications made of each treatment at each site. Overseeding started on August 14 and continued weekly (except for the week of 9/18) until October 16, for a total of 10 applications in 11 weeks. Seed was distributed evenly across the plots using a Gandy drop spreader. There was no cultivation done on the sites (other than that done by the football/soccer players or other field users); the seed was simply spread on the plots. No irrigation was supplied, as rainfall was abundant. Traffic and wear on the Averill Park field was concentrated in the center, and as a consequence one set of plots received light traffic, one medium, and one heavy. All of the plots at the Prospect Park field seemed to received equal traffic.

Results : Results for Averill Park field are outlined in Table 2. Turfgrass density increased for all treatments, even for the check plots that did not receive overseeding. Small amounts of turfgrass already existed in these plots, and when competition from the weeds was removed after they died from frost and cooler temperatures, the density of the grasses increased. This same phenomenon is also partly responsible for the increase in density of the overseeded plots as well, except for the three treatments that started with no turfgrass, in which case the increase in density can be attributed to overseeding alone. “Net increase in turfgrass density” was calculated as the density estimated at Week 11 minus the initial density. It is an attempt to measure the density increase caused by overseeding and to remove the influence of a plot having some turfgrass at the beginning of the study. The largest net increase in turfgrass density was seen in the 6 lbs./M light traffic plot, where density increased from 0 % turfgrass at Week 0 to 100% at Week 11. The largest increase in net density for heavy traffic plots was also seen in the 6lbs./M plots, where density increased from 0 to 78.1%. Plots overseeded with 10 lbs./M had higher net increases in density at Week 5, but the 6 lbs./M plots had greater net increase in density by Week 11 of the study. For a visual comparison, see Photo 1.

Table 2: Average percent turfgrass for eight treatments over ten seedings at Averill Park High School

Treatment	Week 0	Week 5	Week 11	Net increase in turfgrass density
Check, light traffic	3.1	12.5	28.1	25.0
Check, heavy traffic	9.4	34.3	46.8	37.4
2 lbs./M, light traffic	12.5	71.9	96.9	84.4
2 lbs./M, heavy traffic	0	28.1	59.3	59.3
6 lbs./M, light traffic	0	62.5	100.0	100.0
6 lbs./M, heavy traffic	0	31.2	78.1	78.1
10 lbs./M, light traffic	15.6	81.3	96.9	81.3
10 lbs./M, heavy traffic	3.1	53.1	75.0	71.9

Photo 1: From left to right: 2 lb./M, 6 lb./M and 10 lb./M seeding rates in a heavily trafficked portion of the practice field at Averill Park High School

 

Very different results were obtained at Propect Park (Table 3). In the first few weeks of the study, perennial ryegrass seedlings were observed to be germinating in many of the plots. After Week 5, all of the plots, except the untreated checks, had a net increase in turfgrass density. The largest increase of 50.9% was seen in the 10 lbs./M plots. After the week 5 observations, however, the 2 lbs./M plots continued to show an increase in turfgrass density, while the 6 lbs./M and 10 lbs./M showed decreases. This was largely due to factors on the site. The middle of this field is very compacted and slightly depressed. Given the large amount of rainfall during the time period this study was conducted, this depressed area flooded repeatedly. Seed from treated plots was observed to have washed away and moved onto untreated strips between the plots. Seedlings may have also been uprooted or died from flooding. While a net increase in turfgrass density was still achieved for all seeded treatments, these confounding factors decreased the possible gains which could have been made. These results clearly indicate that the topography of the field will influence the success of overseeding.

Table 3: Average percent turfgrass for four treatments over ten seedings at Prospect Park

Treatment	Week 0	Week 5	Week 11	Net increase in turfgrass density
Check	12.5	6.2	13.6	1.0
2 lbs./M	9.4	20.8	30.2	20.8
6 lbs./M	15.6	43.8	23.9	8.3
10 lbs./M	12.5	63.4	33.3	20.8

Photo 2: The sports field at Prospect Park, with the worn, depressed area evident in the middle of the field

Conclusions: These results indicate that heavy, repetitive overseeding using perennial ryegrass can improve turfgrass density on low-input sports fields. Greater increases were seen in plots receiving light traffic versus heavy traffic, yet even in plots with heavy traffic, significant increases were still seen. The least successful situation seen in this study was on the Prospect Park field, where the uneven topography combined with heavy rainfall caused seed to wash out

of treated plots and seedlings to die. An even (or at least not severely rutted) field surface is therefore important to overseeding success. Overseeding at the 6 lbs./M rate gave the greatest increase in net density and is also a less expensive alternative to the 10 lbs./M rate.

Is heavy, repetitive overseeding a cost-feasible proposition for sports fields? An internet search shows that perennial ryegrass seed prices range from $1.40 per pound to $2.80 per pound; wholesale prices and bulk quantities can push the low end price to less than $1.00 per pound. Given a $1.00 to $2.80 price range, the cost for a 10 week overseeding program at a 6 lb./M rate would be $60.00 to $168.00 for one thousand square feet. If a school wanted to overseed the middle of a worn football field (approximately 18,000 square feet), the cost would be in the range of $1,080.00 to $3,024.00. While this may not be an insignificant cost to financially-troubled school districts, it seems far less expensive than most pesticide treatments, or a lawsuit brought about from a student athlete’s injuries suffered due to a poorly-maintained sports field. Since cultivation is not necessary with heavy, repetitive overseeding, further expenses are avoided, and fields can remain in play as the overseeding is taking place. The effect of providing high-phosphorous fertilizer with overseeding should be studied, since such starter-fertilizer can increase seeding success and is fairly affordable.

A project examining how this system performs in spring conditions on home lawns is planned for 2004. If you have any questions or experiences with overseeding to share, please email me at dhc3@cornell.edu or call (518) 272-4210.

Resources cited:

1. “High School Sports Fields: The Last Frontier Of Turfgrass Management,” Ed Leonard and David Chinery, New York State Turfgrass Association, 2003.
2. “Aggressive Sports Turf Overseeding,” Dr. Frank Rossi, in “Cornell Field Day ’03 Program Booklet,” Cornell University, 2003

Thanks to The New York State Turfgrass Association for providing funding for this study, to Dr. Frank Rossi of Cornell University for technical support, and to Dennis Weatherwax of the Averill Park School District and Jim Conroy from the City of Troy for research sites.

Addendum Fall 2004:

The picture below illustrates the plots approximately one year after the first seeding date (from left to right 2 lbs./M, 6 lbs./M, and 10 lbs./M). The light colored grass is crabgrass, while the darker stripes are perennial ryegrass. Density in the seeded plots is 90% perennial ryegrass or greater for all treatments.