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Oddly enough, another chemical that efficiently suppresses the growth of weeds is found in common corn. It's a dipeptide, a set of two amino acids found in the germ of the corn seed that acts as a natural herbicide, preventing seeds from developing root systems.
Dr. Nick Christians of Iowa State University was studying soil pathogens when he accidently stumbled upon this perfect herbicide - one that's effective, cheap, natural and non-toxic. A decade after his discovery - and after scores of experiments demonstrating its destructiveness to 30 common weeds, including crabgrass - corn gluten was registered last year as an herbicide in California.
Corn gluten, an inexpensive byproduct of the extraction of corn syrup from the seed, is currently the only form of the corn herbicide available. Sold in pellet form, corn gluten has the additional advantage of biodegrading into a natural nitrogen fertilizer. Dr. Christians is in the early stages of developing a liquid form of the corn herbicide by mixing an extract of the dipeptides with vegetable oils that can easily be sprayed on soil surfaces to stop seed germination.
Meanwhile, application of corn gluten pellets at a rate of 10-20 pounds per 1,000 square feet has been proven to provide significant control of both grasses and broadleaf weeds. Depending on market conditions, corn gluten can be a cost-effective alternative to synthetic herbicides in many applications. It is especially useful for landscape weed control, where it kills the seeds of unwanted vegetation while providing nutrients to desirable plants.
One of corn gluten's best attributes is that it's not a poison to people. The U.S. Environmental Protection Agency concludes that its residues are non-toxic since "corn gluten occurs naturally in food and the environment," and notes that "corn has been used as a food and feed as long as corn has been known to and used by humankind, with no reported adverse effects."
Corn gluten is a cost effective alternative to synthetic herbicides especially when the many expenses related to herbicide application - such as the high cost of equipment maintenance and the potential of damage to health and environmental by harsh chemicals - are compared to corn gluten's low impact.
The potential for adverse environmental impacts is low; corn gluten does not pollute air or leave poisonous residues. It is not expected to be a significant impact to water quality because - unlike that of water-polluting chemical nitrogen fertilizers currently used - its breakdown to nitrogen is much more slow and gradual.
Corn gluten's effectiveness depends on its timely application, preferably early in the growing season. Mulching equipment designed for large landscaping projects can spread it quickly and efficiently on roadsides, a big plus for maintenance crews that don't want to spend any more time in traffic than necessary.
Probably the most attractive feature from an applicator's viewpoint is that special care doesn't need to be taken to avoid school bus stops, wildlife refuges, neighborhood paths and other sensitive areas because corn gluten won't hurt anyone.
Hot Air From the North
A botanist's recollection of how his mother used to kill weeds was the inspiration for the latest alternative to herbicides: plain, old-fashioned steam.
David Polster, hired by Canadian Pacific (CP) to study how to rid train tracks of unwanted vegetation, recalled how his mother would pour boiling water into sidewalk cracks to kill weeds and he then took it from there.
CP Rail patched together a colossal, eight-car set-up of used water tanks and ancient boilers to create a prototype steam machine that looks something like a mobile rocket launcher. A brief shot of steam heats plant cell membranes to the bursting point, causing the plant to wilt and die.
Four years of tests proved steam's incredible herbicidal efficacy against woody nuisance species. Polster demonstrated, for example, that steam could kill broom, one of the most invasive and hard to control plants in California, with just one pass.
Other results were just as impressive. Herbicide sensitive legumes returned where only tough weeds had grown when chemicals were used. Perennials that can re-sprout from underground roots were controlled with multiple steaming and now only require one or two passes per year.
Using Canada's steam machine for roadside weed control proved problematic since the equipment is bulky and uses a vast amount of water. The obstacles seemed insurmountable until a California agricultural inventor needed to make a machine to remove leaves from grape vines for the wine giant Gallo Vineyards.
Seeking to lower its cost of $140 an acre, Gallo called in Claude Brown of Lodi. He reconfigured a dry steam machine - the same type used for cleaning - with a centrifuge that removes excess water from the steam before discharging it. What is released is vapor that is as hot but not as wet as steam, using far less water. Three years and a phenomenal savings of $134 per acre later, Gallo is happy.
Along the way, someone noticed that Brown's machine also kills weeds when aimed in the right direction. Caltrans maintenance managers on the North Coast began looking at steam to fill the niche once occupied by chemical herbicides. The potential for financial savings is enormous for weeds also, especially considering the wear and tear on equipment from using potent chemicals.
But Caltrans, the mighty $6 billion a year agency, has expended a paltry $8,500 to alter and test the machine, once again slowing progress to a snail's pace. Will the potential of steam wind up as bureaucratic hot air? It may be up to the public to steamroller official inertia.
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