Phytoremediate Explosives - Plant Grass - for a Quick Solution

Mounting evidence shows native grasses could destroy explosives pollution
The Kansas City Star

Missouri researchers are investigating whether native grasses can clean up pollution caused by explosives at hundreds of locations across the country.

Besides the obvious reason, TNT is not good for you.

But grass, it turns out, might be dynamite for the problem.

TNT contaminates hundreds of sites in the US and Australia, from military firing ranges to old production dumps to waterways, and poses a threat to the human nervous system and to the liver and kidneys. It’s suspected to cause cancer. It can cause allergic reactions and attack the immune system, and it may lead to birth defects.

Left alone in the soil, TNT breaks down into an even more toxic substance.

If the problem is left in the dirt, maybe that’s where the solution can grow.

Three Missouri researchers have hit on an idea that could potentially scrub away the TNT danger:
Simply plant the right kind of grass.

The notion started with mounting evidence that native grasses could render harmless a common weed killer. That herbicide, atrazine, is the second most common herbicide used in agriculture in the U.S. and has been a stubborn pollutant in the nation’s waterways. Mounting evidence has shown that certain native grasses, and the microbes that thrive around their roots, convert the toxic leftovers from atrazine into harmless carbon dioxide.

Robert Lerch, John Yang and Chung-Ho Lin began talking about how chemically similar atrazine is to the explosives TNT and RDX. “If it worked for atrazine, we thought it might work for these things,” said Lin, a research professor for the University of Missouri Center for Agroforestry.

Should their idea succeed, it would offer a greener, cheaper and possibly quicker way to clean up more than 530 sites across the USA contaminated by the explosives.

Trinitrotoluene, or TNT, and cyclotrimethylene trinitramine, also called RDX, began creeping into U.S. soil and waterways decades ago, before the manufacturers of explosives came under stricter regulation.

The problem isn’t small. Of the 538 locations identified by the US Department of Defense with RDX or TNT contamination, 20 are Superfund sites — classified by the federal government as the country’s most dangerous abandoned toxic waste sites. Congress rejected a Pentagon proposal in 2005 to exempt the military from regulations for pollution from munitions.

“It’s a serious problem, and it’s widespread,” said Andrew Wetzler of the Natural Resources Defense Council. To clear a field tainted by those explosives — typically to haul away the dirt for incineration — can run from $100,000 to $1 million an acre.

The researchers in Columbia have doped soil samples with explosives and planted two species of grass.

In essence, the explosives practically disappear.

It’s unclear whether it’s the grasses — Eastern gamagrass and switchgrass [Panicum virgatum] seem to work best — do the work themselves, whether it’s two forms of bacteria that thrive in soils around grass roots that do the trick, or if something happens in how they work together.

But in a closet-size room basking in fluorescent lights, a solution to explosives pollution looks to be taking root.

The scientists added RDX and TNT to cup-size soil samples and planted the grasses. In just weeks, the toxic chemicals degraded harmlessly into carbon dioxide and water. “It’s a controlled situation to look at how these chemicals break down,” said Yang, the director of the Center of Environmental Sciences at Lincoln University.

The next step, perhaps still a year or two away, is to test the process outdoors.

The researchers are talking with the Army — the initial research has been covered by $110,000 in Defense Department grants — about trying the grasses on already contaminated sites.

Since the grasses are native and grow easily across the Midwest and the Southeast, they pose no threat of kudzu-like exotic species seen as their own environmental threat.

Initial tests show that the amount of RDX in soil is reduced by 50 percent in a matter of weeks, and TNT contamination drops by 95 percent. So, Lerch said, a year or two after planting, a field could be cleaned of the explosives contamination. And the cost might run less than $3,000 per acre.

“If this works, it will be great".

partially sourced ENN news
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Also interesting to note that switchgrass is also a promising third generation cellulosic source for ethanol production and is being researched extensively for that role as well.

Presumably the same process might be operating with a number of other grass species noted as being tolerant to atrazine. This could include a range of common tropical and warm temperate turf species that are tolerant to the herbicide.

Anyone in the Australian military out there that might want to fund a project here in Australia??

Is Your Couch or Zoysia Declining?

Summertime Blues: Couchgrass Decline (Part I)

While damage to couch is more prominent, especially in the USA - due to the sheer preponderance of the species on fine lawn areas - damage on zoysia, and other warm season turf species is probable, both there and elsewhere in the warmer regions of the world.

In many parts of the northern Australia and areas of South Africa couchgrass (Cynodon spp.) has suffered greatly this past summer, and symptoms may persist into autumn. Several reasons or causes have been given, but one prominent reason is – and I will use the U.S. term - bermudagrass decline. The first reported description of bermudagrass decline occurred in the southeastern United States (i.e. Florida).

Under hot humid and frequent rainfall, patches would develop on the turf and quickly coelesce forming larger non-descript areas of turf loss. The root systems turn black and die back is significant. Although, environmental factors like low light, and saturated soils no doubt contributed to the decline, the pathogen Gaeumannomyces graminis var. graminis was identified as the cause.

Originally bermudagrass decline was only associated with bermudagrass. However, patch diseases caused by the same fungus, G. graminis var graminis have now been reported on most of the warm season turfgrasses. To reflect the increasing number of turfgrasses that are infected, the name has been changed to be more encompassing by calling these root diseases of warm season turfgrasses, “Root Decline of Warm- Season Turfgrasses” (Smiley,et al. 2006).

In the United States, where kikuyugrass (Penisetum clandestinum) is limited to southern California, a patch disease similar to bermudagrass decline has been reported.

[As a side-note, and one based on my opinion with no data to back it up, I wonder if some of the problems this past summer on kikuyugrass may have been due to this pathogen or one closely associated with it? - Henk Smith, Syngenta.]

[ From Syngenta, 6 June 2007]

Watch this space..............more to come as the story unfolds further. This is of particular interest to tropical north Australia!

In the USA, this disease seems to occur most often on intensively managed 3- to 6-year-old turfs, with many of the ultra-dwarf varieties prone to infection. Excessive nitrogen fertilization, potash deficiency, sharp increases in soil pH, and thatch accumulation increase turf susceptibility to attack by the causal fungus. Low maintenance bermudagrass lawns usually have little trouble. The disease is found on all bermudagrasses but is most damaging on the newer hybrid varieties.

Exceptionally low mowing heights, poor drainage, thatch accumulation, and high soil organic matter content have been linked with the occurrence of bermudagrass decline on greens and tees.

The causal fungus of bermudagrass decline is Gaeumannomyces graminis var. graminis. Related fungi, Leptosphaeria korrae and Ophiosphaerella herpotricha, have been shown to be related to the problem in other parts of the United States.

The same organism, Gaeumannomyces, is the fungus associated with take-all patch in St. Augustinegrass.

Initial symptoms of bermudagrass decline include chlorotic patches of turf 20 - 60cm in diameter. The turf thins out and may eventually be completely killed in these patches. Chlorotic leaf blades may develop next to green shoots at the margins of the diseased area. Roots of diseased bermudagrass are brown and without feeder roots and root hairs. Signs of the fungus on the root surface appear as dark brown hypal runners. The disease occurs on weakened or damaged turf which indicates that management could be the key to control.

If disease occurs, try to identify the predisposing factors and correct them through proper management practices. On golf greens, cricket wickets or other very low cut areas, simply raising the mowing height is the most effective management practice to correct the problem. Some fungicides are effective for the control of bermuda decline caused by Gaeumannomyces graminis. Since infection is thought to occur primarily in autumn, with disease progression continuing into the winter months under cool moist conditions, autumn or end of wet season applications may be the best time for fungicides to be applied for preventative purposes. The efficacy in controlling the already established disease may be disappointing.

For more information and assessment please contact us .

Carpet grass control - Monument does work - maybe

Monument herbicide has been used - probably for the first time in the NT - as a control option for sedges, carpet grass and annual grasses - on the main oval of a private school, and it has been very successful, so far.

Conditions for spraying were excellent, about 48 hours after mowing, with good soil moisture, and about 48 hours between spraying and first rain. The Monument was followed up by a DSMA spray in about 12 days. After three weeks carpet grass control was over 85%, although some was suppressed rather than killed outright. What remained was a few plants in formerly large patches, suitable for spot spraying or sprayed with a overall spray of further DSMA in a few weeks. Almost all sedges, annual grasses and many other perennial grasses including Chrysopogon acidulatus have been mostly eliminated. A follow up is often used, but may not be needed.

Because of the regular emergence of Mullumbimby couch, almost all year round, periodic use of DSMA will be needed to continue to reduce infestations to a lowered level, and so this will also continue to provide a good option to further reduce the carpet grass "spots" remaining, and any remnant grasses. Hopefully this will be able to be discontinued by the early dry season.

So........Monument may be a good option. Trials locally [ see photo - 8DAT showing the damage to narrow leaf carpet grass, the yellowish patch] have been impressive as a single pass option for weedy grasses in couch, as well as sedges. Locally, it is true that sedges tend to emerge most months of the year on irrigated areas, although peaking in the wet season. Get those wet season weeds, and big improvements can be made to reduce sedge levels, as there is much less emergence after April.

While not a perfect solution, using Monument has made a fantastic improvement to carpet grass in couch on this oval!

UPDATE - 24 February 2012

Carpet grass is Axonopus compressus or broad leaved carpet grass; narrow leaf carpet grass is Axonopus affinis just to ensure readers understand the issue.

Many curators / superintendents in north Australia still use glyphosate as a solution; metsulfuron may also be useful, especially on couch which is very tolerant of higher rates. It is a REAL issue in the wet tropical regions and especially broad leaved carpet grass thrives in wet soil / higher rain conditions, so better controlled irrigation management at a lower but adequate level can be part of the holistic management needed to get it under contol.

Is carpet grass a weed in your lawn?

Often carpet grass is used as a turf - it is well suited to shaded areas, for example. But more commonly, it appears as a weed in high quality turf areas where removal can be difficult.

Nominally, MSMA and DSMA are used for many grasses as post emergence herbicides. But with carpet grass, it seems as if there is relatively little effect, as it quickly regrows from rhizomes. It is worse in the warmer regions as carpet grass can grow quite quickly, even after spraying.

What is your experience? Is there a reasonable solution that can provide cost effective control of both narrow and broad leaved carpet grass?

Comments welcome.