It's a warm spring day in Central Florida. A group of young men suited up for football practice are sprawled out on the bright green turf of the football field. But they're not resting after their workout. They're picking something up off the turf and putting it in their mouths. What is it? It's the rock salt the maintenance crew has spread onto the field to kill weeds.
Using salt to kill weeds on paspalum
By Stacie Zinn, president of Environmental Turf
It’s a warm spring day in Central Florida. A group of young men suited up for football practice are sprawled out on the bright green turf of the football field. But they’re not resting after their workout. They’re picking something up off the turf and putting it in their mouths. What is it? It’s the rock salt the maintenance crew has spread onto the field to kill weeds and the kids are eating it.
Chuck Pula, Parks & Recreation Director for the City of Winter Springs, FL, always laughs when he tells this story. Just goes to show how weird teenagers can be, eating anything they find on the ground. But even weirder, that the rock salt was there in the first place. Or is it?
Pula is among a growing number of parks and rec directors and sports field managers, along with their golf course colleagues, who have grassed their fields and facilities with Seashore Paspalum grass, which is highly salt tolerant, rather than using herbicides to kill weeds. Many professionals are now using salt to zap broadleaf weeds, crabgrass and goosegrass, and even to knock back, (but not kill), common bermuda.
Seashore Paspalum, (Paspalum vaginatum), originated on sand dunes, hence its tolerance to high salt levels. A warm-season turfgrass, it generally can be used anywhere one might consider using bermudagrass. It requires as little as half the water of a bermudagrass, and may be irrigated with a wide range of water quality, from potable to effluent, even seawater under proper management. Certain cultivars, especially Aloha Seashore Paspalum, developed by the University of Florida, exhibit speedy grow-in rates making it very appealing for sports turf managers looking for a grass that will heal quickly from sports-related wear.
Several parks under Pula’s direction feature fields of each of the three varieties mentioned. He said his team has used a granular salt, applied with a spreader, to control weeds.
During the cooler months, Pula said he has overseeded his fields with ryegrass to retain winter color. He said surprisingly the salt was a valuable tool to aid in the spring transition out of overseeding.
“It was incredible how fast it took the rye out of it,” Pula said.
In Charlotte County, on Florida’s southwest coast, Mike Reber is sports field foreman on more than a dozen football, soccer, baseball and softball fields grassed with Aloha, SeaDwarf or SeaIsle-1 Seashore Paspalum.
Reber said rather than applying the salt dry as they do in Winter Springs, he makes a slurry of water and salt and applies it to his paspalum through a 25-gallon sprayer that he attaches to the back of one of his Gator vehicles. Though Reber has tried the salt in nearly every form, from granulated to rock salt to table salt, he said he finds the finer the grains of salt the better. His recipe of one cup of salt per gallon of water, he said, works well on broadleaf weeds and crabgrass, though it is important to keep the mix agitated so that the salt doesn’t settle to the bottom of the sprayer.
Both bought the salt they used for their facilities at the local hardware store.
Though it’s difficult to get actual figures on how many sports turf managers are using salt to kill weeds on Seashore Paspalum sports fields, on the east coast of Florida, Erik Thor, technical sales representative for The Kilpatrick Company/Howard Fertilizer says he’s seen a marked increase in the number of his golf course superintendent customers who now buy salt to kill weeds on their courses. Five years ago, he sold about one ton of Morton’s Fine Solar Salt to his customers with Seashore Paspalum grassed golf courses. In 2008, he sold about 25 times that amount.
Morton’s Fine Solar Salt comes in 50-pound bags, wrapped 56 bags to a palette. Thor said if applied through a spreader, 200 pounds of salt will treat about an acre, at a cost of about $420 to $430 per ton.
To treat crabgrass and goosegrass, Thor recommends creating a salt solution in a 5-gallon bucket, mixing until the amount of salt reaches the point where it will no longer dissolve. Pour the contents of the bucket into a sprayer and make three applications of the salt mix, 5 days apart.
Though salt is not the only solution for treating weeds on paspalum, Thor said he feels there is a place for it, “especially if you’re going environmentally friendly.”
Here are several cultivars used on sports fields, commonly available as sod or sprigs:
Aloha is a joint release from the University of Florida and the University of Hawaii. It is a semi-dwarf, marketed by Environmental Turf and its network of licensed growers. In university tests, Aloha was shown to have a faster grow-in rate than other varieties tested, and also shows some resistance to the sod webworm and green bug aphid.
SeaDwarf is the only dwarf cultivar of Seashore Paspalum and features a finer texture than other paspalum varieties. It can be mowed below 1/10 of an inch.
SeaIsle-1, a semi-dwarf variety, was developed by the University of Georgia; their tests show good wear tolerance.