Tips From The Pros

SPORTS FIELD SOD – PART 3: PLASTIC GROWN SOD

For reference, please see Sports Field Sod, Part 1 and Part 2.

(In full disclosure, the author is a technical consultant for Green Valley Turf Co. in Littleton, CO. a company that carries a line of plastic grown bluegrass sods).

As revenue and event scheduling pressure increases at almost all categories of sports field management, sports field event repair sod is no longer a contingency in case the field doesn’t hold up. There are things being done on large stadium fields as well as municipal park fields these days where no grass in the world could hold up. Slowly but surely, large field events like concerts have crept into the playing seasons of various sports, no longer relegated to the “off-season” to allow for field repair. 2018 will see more in-season stadium shows than I can remember. For example, the fabled Wrigley Field in Chicago hosted 10 concerts last year and looks to build on that for 2018. It was barely 10 years ago the stadium concert tour business was as lean as it gets, with musicians struggling to get paid for their works in the new digital music age. There were maybe a handful of acts scheduling stadium tours and maybe only in a few hand-picked cities. Eventually, as I understand it, the music business realized live shows were the way to make money. It wasn’t long before it was realized the best money was the big stadium show, if you could sell it, and now many more acts are hitting the road this year playing the big houses in North America and worldwide.

Sponsorship has grown fast in sports. Sponsors negotiate goodies like use of the playing field for a private corporate picnic, small concert or team building.

Across the US the relatively new concept of amateur “travel teams” in youth sports has sprouted a new tournament industry at our local parks, a trend identified correctly I believe by Disney’s Wide World of Sports 20 years ago (Now ESPN Wide World of Sports).

Yes, it’s a good time to be in the sports venue business. But this only works, and the cash only keeps flowing, to the extent we can maintain acceptable playing surfaces for the teams and repair any damage in shorter and shorter repair windows. And as I have tried to drill into anyone who will listen, high performance sod plays a key role in making all this possible on natural grass playing fields. Post-event repair windows, once counted in weeks and even months not so long ago, are down to days – sometimes hours. In such a challenge, sports field managers must change their outlook and tactics. We are no long laying sod in many cases, we are installing playing surfaces! They need to be ready to play almost instantly. When a baseball park pulls its mound and sods the infield 15 or 20 times a summer to accommodate a soccer club, they are laying a playing surface, not sod. When a football stadium pulls out the grass and re-sods overnight for logo changes between games, they are laying a playing surface, not sod. When a venue with synthetic turf overlays the entire field with natural grass for a soccer game, they are laying a playing surface, not sod. Who gets adequate time to fully establish a partially or fully sodded playing surface these days? Nobody I know.

Sports field managers don’t care about concerts or other events on the field, it’s part of what they signed up for. They do care seriously about their limited capacity to repair a field to acceptable levels of play and appearance within today’s very tight windows. They are thinking about the team, and that next home game.

This is where plastic grown sod technology rides in to save the day I believe. Plastic grown sod (PGS, also known as Sod on Plastic - SOP) is not necessarily a new concept, and early research at Michigan State (also here and here) nearly 20 years ago showed some of the advantages to this establishment method. Yet the idea never really took off commercially from what I saw.

The bottom line is that in today’s rich stadium and sports venue economy, there is a need for a premium sod product that is ready to play immediately after installation. This new venue requirement for instant natural grass playing surface repair is the result of fundamental changes in the music and sports industries described; the demand for a premium sod solution is born.

The demand for high quality sod in new construction fields is seeing a similar growth in demand as the field-repair market from what I see, and it makes sense here as well. Think about it. We sweat the soil profile details, then we get vague with field sod specifications. For all the time and money spent on a new fields sub-components like soil, drainage, irrigation and the engineering needed to make it work, it amazes me how little attention we pay to the sod. It’s the one part of all of this that will become the playing surface, often very quickly. Inappropriate varieties of grass grown in sod farm soils that may create layers in the finished field soil profile are to be avoided at all costs in my world. And while there are exceptions, like a sand-cap design field where you actually engineer the soil layers and drainage, my experiences are that soil layers make life much more difficult for the one who actually flies this spaceship, the sports field manager. No, you don’t want similar soil in your sod, you want matching soil that has been engineered to work with your underlying rootzone. You want a clean sand sod, vigorous and without organics in the original soil from my perspective. Why start the organics accumulation war by giving the opponent a head start? That almost always means importing your soil to a sod farm or manufacturing it onsite. To me, this idea of imported sod soil works far better on plastic.

What is Plastic Grown Sod (PGS)?

Simply put, plastic grown sod is just as it sounds. Sod. Grown on top of an impermeable plastic barrier lain over and existing soil. It may be a simple concept, but in execution it is anything but simple. Getting to a finished product, a bullet-proof roll of playing surface, is basically rocket-turf. Just think about how many agronomic principles you are defying by putting an impermeable layer in your soil, and you begin to get the idea. The margins on maintenance at the farm are thin. Just figuring out how to produce it will be a challenge if you are not experienced, but the good news is that it turns back to a very simple solution for the field manager in need of virtually instant field repair these days.

How are PGS fields constructed?

It’s important, I think, to touch on the two general methods used to produce PGS. You either construct your profile and seed or sprig the grass, or you thinly cut some existing sod, transport it to and install it on top of plastic, then topdress to the desired harvest thickness. While I have seen both methods work, I believe that establishing plastic grown sod at your farm by seed and sprig may enjoy some important benefits. It seems to me that the cut-and-topdress method would require 2 acres at the farm to produce every acre of final product and wouldn’t that have to add costs? The seed or sprig method gives you more first-generation genetics that can be more easily documented. For cool season grasses at a sod farm (predominately bluegrasses), different varieties may regrow differently and the genetics on the second field harvest may be different in successive cuts. It may be a different story on warm season sods like bermudagrasses, but it does seem to me the closer you can stay to the earliest certified generations, the more confidence I would have in getting the variety(s) of grass I have specified. Whatever method used, we should all agree that you want to document as very best you can that you are getting the varieties of grasses you have specified in your final plastic grown sod product.

I would want to see my nursery sod cut as thin as possible and washed. You could probably save establishment time by cutting a thicker nursery harvest, minimizing how much topdressing would be required to get to specified thickness, but you want to make sure you don’t create layers of differing soils in the final product and ultimately in your field. You know I don’t like layers in a field’s soil profile.

Another concern of mine is the rate at which the nursery sod is topdressed up to achieve the specified thickness after transplanting to plastic. You can probably get most healthy grasses to grow up and through an inch or even more of sand topdressing per year from what I’ve seen, but I’m not convinced you can achieve the surface stability required of the finished product. I could be wrong of course, the idea has not been scientifically tested to my knowledge.

To me, it may be easier for the turfgrass producer to cut, transplant to plastic and topdress. Believe me, it’s not nearly as tricky as establishing from seed or sprigs, but the benefits of the more challenging seed/sprig method go to the field manager and venue in my book.

Again, there are readily available examples of plastic grown sod products, cool and warm season, successfully produced and used in construction and repair projects using a sod-and-topdress method. The benefits described above to the seed/sprig method are just my theories and surely others disagree. So I’ll will let the Turfgrass Producers worry about how to manufacture the product and focus on the many benefits to the field managers, the venues and the end users in including plastic grown sod in their field management programs when appropriate.

Turf Tips 101: The Costs and Benefits of Sod on Plastic.

Costs.

A properly produced plastic grown sports field sod brings many key benefits to the field manager. It is a premium product that I hesitate to even call sod, when properly constructed, and premium products cost more to produce. They also solve problems that the cheaper versions struggle with. From my experiences the added costs are minimal, especially in light of the significant non-sporting event revenue generated at most stadiums these days, events that caused the damage that created the need for a premium, instant repair product. The forward-looking researchers 20 years ago had the right idea at the wrong time the way I see it. But with the new stadium economies, PGS is a value-added solution and a mission critical product for any venue interested in high field use revenue production and meeting its obligation to very quickly return the playing surface to acceptable conditions. To me, any added costs should be proportionally borne by all the field user groups who make quick-use field repair a necessity.

Benefits.

High stability immediately after installation.

Plastic grown sod is not harvested with a sod-cutter and underground reciprocating blade. Rather, it is simply peeled off the plastic and rolled. This has several benefits, especially in terms of quick playability after install, in my opinion. PGS will develop a tight root-mass in the shallow rootzone encapsulated by the plastic barrier. Plastic grown sod is never root-pruned by a harvester blade. To me, this has to significantly reduce transplant shock and drought stress after the sod is installed. From my experiences I can say PGS also holds together much, much better during all the physical beatings of harvest, roll, handling, truck transport, off-handling at the stadium and install. The tight root-mass is very tough relative to the traditionally cut sods in performance testing I have done on bluegrass sods. There is less stretching of the sod as it is rolled out at installation by my measurements. I’ve seen that it doesn’t leave soil on top after you roll it out because of the encapsulated root mass. For my money, the greatest benefits to using a plastic grown sod are seen after installation at the stadium in terms of time to acceptable surface stability, or footing if you will, consistency and smoothness of finish grade (important for ball-roll). Here’s video of me testing for surface stability with a shear vane tester on PGS bluegrass sod at Green Valley Turf Co. Here’s one where we test tensile strength on “The Rack”.

Tight post-installation seams.

The sidewalls of plastic grown sod are incredibly crisp and vertical. The result is almost invisible seams after installation, saving a lot of time in post-installation seam mitigation and making a better, more consistent playing surface more quickly as far as I’m concerned.

Use the soil you want and need.

On high-performance engineered sand soil fields (“sand based”), you can import and use clean, washed and expertly engineered and manufactured sand that exactly matches the rootzone sand in the field to be repaired. This helps eliminate layers in the final sod-over-soil profile which can create drainage and air-filled porosity issues on your field. In turn the grass vigor and health decline, and down we go. No, to me it’s best to eliminate layers from the top down.

Virtually eliminate Poa annua.

Plastic grown sod on engineered, washed sands can produce a product clean of Poa annua from what I have seen, even any potential soil-banked P. annua or other weed seeds. To me this is a huge benefit. On seeded or sprigged plots, you bring in clean, washed sand and certified seed for each batch. Clean.

Better post-installation rooting.

It was once thought by some that a plastic grown sod was somehow “rootbound” and would not root in very well after installed. This never made sense to me. I always figured that any limitations to rooting noticed after installing traditionally harvested, thick-cut sod had to do with the stress of root-pruning at harvest and soil profile layers created by soil-types and/or thatch levels. I believe that since plastic grown sod comes with all its roots intact, there is a much greater “starch bank” to use for the fuel needed in rooting – in the form of carbohydrates stored primarily in the roots. A simple post-installation experiment I did at Green Valley Turf CO. supported this hypothesis in both spring and hot summer installation runs.

Cut large specialty pieces of repair sod.

In harvesting plastic grown sod, you are not limited by the capacity and length of a cutting blade. The largest traditional cuts I have seen are 48-inches. Anything wider than that may over-stress the blade cause warping and bowing or even breakage. Since plastic grown sod is peeled and not cut, you don’t have any length and width limits to your roll beyond what you can practically handle and transport.

Create sod from non-sod-forming grasses.

Due to the tight, woven root-mass in PGS compared to traditionally cut sods, growing your sod on plastic better allows you to produce sods using species of grasses with bunch type growth habits. I’ve seen these sods available traditionally cut using netting, it just works much better on plastic, from what I’ve seen. Examples might be Perennial Ryegrass or Tall Fescue.

Resources of the Month:

Carolina Green’s website for GameOn Grass. Here’s a YouTube time-lapse video of a quick change at Keenan Stadium at the University of North Carolina, changing-out and painting entire playing surface in 18 hours.

Green Valley Turf Company’s HD Sports 2.0 Lay&Play. Here’s 3 YouTube videos from Green Valley Turf describing their plastic grown sports field sod product. What is HD Sports 2.0 Lay and Play?HD Sports 2.0 Lacrosse in Parking Lot, and HD Sports 2.0 Instant Golf Tee.

Note: There may be other turfgrass producers carrying a formal sod-on-plastic product or products, but I don’t know of any. If you do, please email me (turf444@gmail.com) the info and I will include links in future editions of Tips from the Pros.

End Quote: “Any problem can be solved with a little ingenuity.” - MacGyver