CHEMICAL HOTLINE: Life after methyl bromide

University of Virginia uses alternative to methyl bromide for successful field renovation.

When Thomas Jefferson designed and founded the University of Virginia in 1819, a football stadium was not among the many architectural components of the campus. That's understandable, considering that football hadn't been invented yet. But football has become an American institution as surely as the Declaration of Independence penned by Jefferson. So it seems fitting that the University of Virginia (UVA) features a first-class football stadium to complement Jefferson's designs.

The university recently decided it was time to upgrade the football turf. The Cavaliers' football field, located within Scott Stadium, had consisted of Vamont bermudagrass turf for several years. Vamont was originally selected for its cold tolerance and toughness, but the Cavs decided it was time for an upgrade when newer bermudagrasses came onto the market that offered equal or better tolerances with improved aesthetics.

Tifsport bermudagrass was the choice. The challenge was to replace the Vamont with Tifsport. UVA selected Carolina Green Corp., a sports field contractor based in Indian Trail, N.C., for the task.

Because the old and new turfgrasses differed significantly in texture, color and density, it was imperative to completely eliminate the Vamont. Carolina Green's Chad Price explains that with such a high-profile stadium, concern existed that any breakthroughs of surviving Vamont could create patches that would be highly visible to fans in the stadium as well as television cameras placed high in the stadium. So it was clear from the start that a reliable method of eliminating the Vamont was a necessary part of the renovation.

With the impending loss of methyl bromide, fumigation options are becoming limited. One of the only remaining soil fumigants is BASF's Basamid. After exploring various options, Carolina Green decided Basamid was the way to go. Working with BASF technicians, Price and his colleagues set to work.

Mixing it up

According to Price, the renovation was divided into four basic steps, not including sodding. “First, we stripped the existing turf with a sod cutter to about 1.25 inches.” This is a bit deeper than you'd typically cut sod, but still not deep enough to remove the entire organic layer (or all of the Vamont rhizomes).

The next step was tilling. Using a reverse-tine, tractor-mounted tiller, Carolina Green mixed the soil down to about 8 inches. “That blended the remaining organic matter into the sand to produce a uniform profile,” says Price. The team had to be careful not to till any lower because the field was originally installed as a USGA-type, sand-based PAT system. Drainage lines, as well as irrigation piping, would be vulnerable to damage from tilling any deeper.

After tilling, it was time to level the field with a laser leveler. In other circumstances, this would've taken the process to the point where it was ready for sodding. However, with live Vamont rhizomes remaining in the soil, this was the time to fumigate. So the crew rough-leveled the field, and then it was time to apply the Basamid.

Spreading it out

The application of the Basamid, a fine-textured granular material, took place in a step-wise process using a drop spreader. According to Price, “We put out about 40 percent of the product, and then tilled it in to 6 or 7 inches. Then we came back again and applied another 40 percent. We tilled that in to about 4 inches. Finally, we spread the last 20 percent on top.” The result was a layering of material that increased in concentration with the highest amounts at the top of the soil profile.

Basamid is a granular product, so to become active, it requires irrigation. But you need to be accurate with the irrigation. “You have to irrigate, but you don't want to wash it through the profile. So you really have to watch how much you apply,” says Price.

The granules dissolve to a liquid within 24 to 48 hours, and then to a gas thereafter. The gas is the form that actually is active on the weeds. That's why the irrigation is necessary for the product to be effective.

Unlike methyl bromide, Basamid requires no tarping. But the vapors must remain in the soil to be effective. The way this occurs with Basamid is by the formation of a crust on the soil surface. The crust must remain moist to work, so irrigating after the initial application of water is important.

According to Price, after the initial watering-in, they “would lightly irrigate periodically through the day as the soil dried out. We had to do this for about 7 days. After a while, we got a feel for how often we had to irrigate, and we could set the irrigation controllers to do this. But it definitely took some monitoring.”

A distinct odor accompanies Basamid, and this was an important part of the monitoring. “It has a rotten egg odor,” says Price. “If you pick up a hint of the smell, it's a sign that it's time to irrigate again to seal up the surface. As soon as you do, the smell dissipates.”

After 7 days, the chemical had done its job and it was time for it to air out. Price accomplished this simply by ceasing the irrigations. After 3 days, the field was tilled once more, just to be sure the gas had dissipated.

The process was somewhat involved, but Price had some assistance. BASF technicians assisted him on-site. “It was a new product to us, so we really appreciated their help.”

The lettuce test

At this point, the ground was ready to be sodded. However, just to be sure, Price used a “lettuce test” to see if all gases had dissipated. Soil samples were taken from different places on the field, and then lettuce seeds were germinated in it. If active levels of Basamid were still present, the seeds would not germinate. Otherwise, the lettuce would begin to grow in around 24 hours. It did.

A final leveling with the laser leveler put the field in condition for sodding, which took place in late spring of this year. The timing was right not only for good growth of the new bermudagrass sod, but also for optimum temperatures for Basamid activity.

During sod installation, Price and his crew observed dead Vamont rhizomes and could see that the Basamid had worked. The sod went down as planned. “It looks great,” boasts Price. The turf will be maintained by field manager Jimmy Rogers and ready for play this fall.

Of course, we can only speculate what Jefferson would think of all this. But surely he'd be pleased that his beloved school continues to exercise the kind of pride Jefferson himself took in the hallowed grounds at UVA.

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