April 10, 2014 06:26

Revegetation After the Drought

The job of revegetating disturbed or barren areas is never easy. You’ve got to have the right equipment, the right techniques, the right seed, and, hopefully, the right conditions. When the conditions are less than ideal, that job is made harder by several orders of magnitude. And perhaps no erosion control job is more difficult than trying to coax plant material to grow under drought conditions.

Jim Koweek understands how hard this is. As owner and president of Arizona Revegetation and Monitoring Company in Elgin, Arizona, he’s been doing revegetation work for 30 years, mostly remediating construction scarring and improving rangeland in a desert climate. “I try to do things that’ll tip the odds in my favor. If we have a decent rainy spell in the summer, then I’m a genius. But if I work in an area that gets nothing all summer, then I’m a bum and a thief.”

Steve Nelson, president of Nelson Consulting, Inc., works out of Farmington, New Mexico, where dry conditions are also the norm. “We’re in a semi-arid high desert. One year we’re wet, the next year or next three years we’re not.” Nelson’s company mainly does linear projects along pipelines. “These may go 500 miles, crossing multiple territories of biosphere: high deserts, low deserts, mountains, wetlands. We have to be able to rehab all those types of areas. It’s even more difficult in a drought. The only areas that will have any residual soil moisture are the wetlands.”

Nelson says that the biggest problem with drought is wind erosion. “Because the soil isn’t sticking to the ground, it needs moisture to hold it there.”

But if you really want to understand drought, go to Texas, which still hasn’t recovered from the big one of 2012. “It’s sad how dry we are,” said Dennis Markwardt, maintenance field support section director for the Texas Department of Transportation. “I was in the Panhandle recently, and everywhere you walk, dust comes up from your feet. It’s so powder dry, no vegetation is living. The western part of the state is running out of water. We’ve got places that are in Stage 4, which means you can only use water to flush the toilet and drink, and that’s it. Revegetation is pretty much nonexistent until we get some precipitation.”

But Markwardt still has to do his job, which involves supervising the re-greening of Texas’ many miles of highways. “On a road construction job, we’ll go ahead and seed it, roll out the soil retention blankets, nail them down and wait for rain. There’s not a whole lot else we can do at that point, except a rain dance.”

When it’s dry, go native 

Natives need less water, period. Naturally, they’re a no-brainer for drought conditions.

“I’m real big on native grasses and wildflowers, not so much because I love them, but because they work,” says Koweek. “This isn’t the first time in the history of blue grama that it’s come across dry conditions, so it’s genetically programmed to deal with them.”

“One of the best erosion control and revegetation methods is to salvage your topsoil and really take good care of it, because that topsoil has a tremendous seed bank in it,” says Markwardt. “You already know those species will grow in that location.”

Doing revegetation work under dry conditions means “going with things that will work without extra help,” says Koweek. “We look for species that, according to anybody’s best guess, can lay out there in the ground dormant for ten to 15 years, if necessary, waiting for the right conditions to occur. Really, there’s no magic to it; that’s pretty much all you can do.”

Koweek likes to use a wide variety of seeds in his mixes, including some annuals. “Most of what you eventually want in your community of plants will be perennials, but annuals are a lot easier to work with. I always draw the comparison that seed is like money; it takes some to make some.”

Locals only

The source of the seed is as critical as the species, according to Len Ballek, associate scientist at Herrera Environmental Consultants’ Missoula, Montana office. “It’s really important to get as close to your project site as possible with seed sources, and to always ask the seed companies what their sources are.”

This is because native plants are extremely well adapted to the specific environments in which they find themselves, through the process of natural selection that has taken place over hundreds of years. A plant or seed from many miles away might be the same species, but not as well-suited to your location.

“Just because there’s ponderosa pine and western wheat-grass in both Montana and Arizona doesn’t mean that they’re the same thing,” says Ballek. “They’ll break bud at different times, and have different water usage. If I know I have a large project coming up in three to four years, then I’ll set up something with a seed company where they’ll produce seed for me to use specifically on the project.”

“It’s easy to take a species from one area and plant it someplace else,” adds Ballek. “It may live there for 20 years. But 20 years in the life of a native plant community is nothing. The plants that grow on that site have developed great resistance to insects, disease, or severe climatic events like extreme drought, because they lived through them.”

Ballek relates a story from early in his career, when he worked at a native-plant nursery. It illustrates his point perfectly. “A mine in Colorado wanted chokecherry and serviceberry seedlings for their reclamation plan. So we took seedlings from our inventory, from a Montana seed source, and went down and planted them. While we were there, I saw chokecherry and serviceberry already growing at the site that were full of fruit, so we collected a bunch of seed. The next year, we grew plants from that seed.”

“One early June, four years into this, we got a call from the mine’s project manager. He said, ‘We had a ten-degree night, and I think it froze all our plants.’ I figured that the first ones we put there would be all right, since they’d been in the ground a long time. But they were just fried—no leaves or anything. However, the plantings we did later, from seed collected onsite, had survived. They’d had their leaves frozen off, but at their bases, you could see where they were resprouting.”

Get rough with that soil

Seedbed preparation is critical. Whether you call it soil loosening, chiseling, roughening, or pockmarking, this step is essential, and never more so than during a drought. “You have to make sure that the soil surface is as rough as possible,” says Nelson. “It can’t look like your front yard. You want it rough so that the wind doesn’t blow the seed away.”

The idea here is to catch that moisture, the dew or rainfall, when it finally comes. “Even in a drought, you’re going to get moisture at some point,” says Koweek.

To rough up the soil, Koweek uses a tractor with a box scraper attached. “If I can’t get that, I’ll get a road grader with rippers on it.” Nelson uses a backhoe, trackhoe or dozer. “Most dozer operators aren’t skilled enough, so it’s easier to do with the back side of a bucket truck.”

“It’s no magic science,” adds Nelson. “You just shove the dirt around. I’m not talking about digging holes here; it’s more like sticking your hand in the soft earth and moving it back and forth, creating two- to six-inch pockets. Then, moisture and natural seed from off right-of-way can build up in those little indentations.”

Roughening’s even more important on slopes. “Most seed needs to be moist for about eight to 14 days,” says Koweek. “But almost no hard south- or west-facing slope is going to stay moist for that period of time, so it’s best if you can get it ripped or furrowed a little bit, three to four inches.”

But sometimes, the people you’re working for may not want to take the time for proper preparation. Koweek has run into this. “Some developers just want to get seed on the ground so they can meet their requirement, and that’s it; they really don’t care whether it comes up or not.”

“One of the things that always upsets me,” says Markwardt, “is that on some of our highway slopes, you can pour a cup of water at the top and catch the whole cup again at the bottom.” This happens because highway engineers and road construction people are used to compacting down roadways. “So, a lot of times when they’re done building a road, the right-of-way is packed down so hard that you can’t ever get grass established. They need to go in there and chisel it, making sure that the top four to six inches of soil is loose.”

Nelson believes in soil roughening so strongly that he even prefers it over hydroseeding, even though his company does that, too. “I get almost as good a response out of just roughing up the natural terrain,” he says. “Most desert areas will reseed themselves naturally. Granted, there are areas where you’ve got to hydroseed, because of the steepness of the terrain, or the type of material that you’re trying to get vegetation to grow on.”

Stage a cover-up

Once you’ve got the seed on the ground, you need to protect it. That’s never more critical than when you’re working under drought conditions.

Rock can be a star here. “It’s a great mulch material,” says Nelson. “It’ll hold the soil, and help hold in moisture. You wouldn’t think that rock would do that, but it does.”

He likes using broken tallus rock, the kind that’s found along railway crossings. “Not three-inch-diameter gravel—I’m talking rock that’s six to ten inches across, spread over the right-of-way. The water will run off the tallus rock and settle underneath, where your seed is.

The wind isn’t going to blow that rock away. Hopefully, you can find it right there on-site.”

You can also use rolled erosion control blankets (RECBs), wattles or erosion control fabric over the seed. “I’m big on straw wattles,” says Koweek. Ballek likes ECBs made of coconut straw and coir, depending upon the steepness of the slopes and the budget. His installation method, however, is quite different.

“All the manuals talk about digging a ditch along the top of the slope, keying the erosion control fabric into the ditch, and then rolling it down the hill. But slopes are never completely uniform. Water can form a pipe under there, in those air pockets, and wash the fabric out.” So Ballek does it backwards. He keys the fabric in from the bottom of the slope, and rolls it up the hill. (He always helps out the crews, “Otherwise, they’ll hate me,” he says.) “It’s hard work, but the fabric fits down tight, against all the little holes.”

Ballek also believes in a different approach to hydroseeding when it’s dry. “I’ve heard people say, ‘You can hydroseed, but if you have really severe drought conditions, it’ll never make it. But where I’ve seen it fail is when they just mix the seed with mulch. So when I write specs, I require a two-pass method. The first pass, you spray the seed and just a trace of mulch, maybe only 100 pounds per acre. You want the seed to go directly on the surface of the soil. The second pass is all mulch, sprayed on top, as a protective layer.”

Direct soil contact is vital for the seed to take. If the seed is suspended in the mulch layer, it’ll germinate there. Normally, that’s okay; but in a drought, the new seedlings will dry out and die before they can stick their roots in the ground.

Timing is also important. “I try not to put seed on the ground more than six months before it could potentially come up,” says Koweek.

Less is more?

“I try to compensate for the seed I’m going to lose,” says Koweek. “When I first started doing this, I went to an erosion control event to try to learn everything in one day. One expert said that you can lose as much as 98 percent of your seed between the wind, rodents, insects and birds. We try to figure that into our seed mix, and seed much more heavily than the ground can actually carry, to make up for that.”

Not surprisingly, Ballek has a completely opposite view. “I hear this all the time, especially from landscape architects, and the statement is: ‘Seed is really cheap. If you want to make sure you’re going to get a good crop, put a lot of seed down.’ But there’s no way all that seed can take. They’ll use up all the available moisture, and you’ll have failure. What I’ve seen be successful in eastern Montana and even a lot of drier areas, is to hold the number of seeds per square foot back.” Ballek’s magic number for drought areas: a mere 24 seeds per square foot.

Damping down client expectations

“The hardest thing I find in dealing with drought is not the conditions,” says Koweek. “It’s that when the client signs the check, they think they’re buying grass and wildflowers, and fast!” “They can have unrealistic expectations. I’ll have to explain that working in an arid condition, there isn’t always moisture,” Koweek says. “So that’s a tough one. People just don’t have patience, especially if they came from someplace where you can eat a peach, throw the seed on the ground, and six months later, have a peach tree.”

“I’ve also run into problems on industrial or government projects, when the natural cycle conflicts with the business cycle,” continues Koweek. During one job at a military base, “some inspectors came in from Virginia, which has a completely different climate than Arizona. They said, ‘We want 70 percent coverage in four weeks.’” “We told them, ‘These are warm season grasses; they won’t even germinate until the ground temperature hits 80°.’ They said, ‘We don’t care; we still want 70 percent coverage in four weeks.’ That’s the military for you.” Funny thing about nature; it simply refuses to follow orders.

Ballek has other frustrations. “I work with a bunch of engineers. They seem to think, when it comes to revegetation, you just put some stuff out there and try it, and if it fails, say, ‘Well, it works most of the time.’ They don’t build bridges that way, and say, ‘Most of the time, the cars get across okay.’ You need to figure out why it didn’t work.”

“It takes a certain mindset to stake your entire business reputation on moisture in an arid land,” says Koweek, someone who does just that.

Hopefully, you won’t face drought conditions on a daily basis. However, should you ever face a revegetation project under “dust bowl” conditions in the future, we hope the experience and advice of professionals like these will be helpful.

Also in Soil Erosion News

In many ways, we are fortunate that, in our chosen profession, we are able to help people when certain disasters occur: the tornadoes in Missouri, Oklahoma, Louisiana and Georgia, the flooding in Louisiana, the snows in the northeastern part of the country, the rain in California, and the snow in Colorado....

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