Weeds and Railroads

Plant scientist keeps crossings free of dangerous vegetation

Railroads must constantly work to keep their crossings at road intersections safe. A plant scientist at the University of Missouri is helping them control weeds so drivers can better see oncoming trains and avoid collisions.

Reid Smeda, professor of plant sciences at the College of Agriculture, Food and Natural Resources, has been working with railroad transportation companies and their affiliates for more than a decade to devise strategies to combat vision-obstructing weeds. He is one of only a handful of plant scientists devoted to this area of public safety.

And the stakes are high. From 2011 to June of this year there were 7,273 collisions between highway vehicles and trains at 209,308 public and private crossings, according to the U.S. Department of Transportation. From June 2013 to June 2014 the number of accidents has increased more than 10 percent over the same period from 2012 to 2013.

The majority of these accidents — 3,349 cases — involved automobiles. About 250 people each year die in these accidents with around a thousand being injured.

Reid Smeda.Reid Smeda.

Weeds Love Crossings

Railroad crossings pose unique challenges for weed scientists who usually focus on increasing crop yields. In many ways, railway crossings are the most ideal place for weeds to grow, Smeda said.

Seeds from all over the country can be deposited there from trains that pass through. Crossings also receive maximum sunlight as trees have been cleared up to 300 feet from the road and up to 50 feet from the center of the track. Fertilizer transported by trains can be dropped from passing railcars, inadvertently providing nutrients to the weeds. As crossings lack a canopy of crops that occur in fields, weeds have no other plants to compete with.

The combination of stones and soil around the tracks is an ideal place for airborne weed seeds to find a protected place to sprout and grow, too. The gap between these stones poses challenges holding herbicides in place.

Railroads can’t indiscriminately spray herbicides as many tracks are adjacent to cropping areas and sensitive vegetation in people’s yards. Applicators also must be cautious about spraying into ditches adjacent to the elevated tracks as water can pool here and some herbicides could seep into the groundwater and cause contamination.

SONY DSCThere are also geographic challenges to controlling weeds along railways. Smeda said weed species can vary from mile to mile along a track. Also, weed species in the dry and hot southwest differ from those growing in the wetter and cooler northeast. A product that works well in Florida may not be effective in Idaho.

Though a big and unique problem, there aren’t many specific herbicides on the market for rail applications. Such products cost tens or hundreds of millions of dollars to develop. The railroads and weed scientists use products designed for the agricultural industry — the largest herbicide user — that are adapted for use at crossings.

Driver visibility isn’t the only reason for keeping railroad weeds under control. Weeds must be kept low so approaching trains can see each other, too. If dried weeds are too close to the tracks, sparks from the steel wheels can start fires, and flammable products transported by trains can ignite. A clear path adjacent to the tracks is also needed for workers to safely perform duties such as track maintenance and operating track switches.

A Unique Art of Weed Science

Much of Smeda’s recent research involves creating strategies for controlling herbicide-resistant weeds.

As in agriculture, some weeds are herbicide-resistant, such as kochia, Russian thistle and horseweed. “Water hemp, for instance, was not an issue until just a few years ago,” Smeda said. “Today, the species is becoming more resistant in farming due to herbicide overuse, which means seeds from these weeds are now an encroaching problem along right-of-ways.”

Another emerging weed Smeda is investigating is teasel, which can grow up to eight feet tall. Teasel is considered an invasive species in the United States and is known to form a monoculture, capable of crowding out all native plant species.

Teasel is a concern because it has few natural enemies, which allows it to rapidly proliferate. The teasel population has exploded in the last 30 years, particularly along railroad right-of-ways and highways where mowing equipment aids seed dispersal.

SONY DSCIn response to evolving herbicide resistance, Smeda is recommending that railroads move away from spraying the same herbicides year after year. Current best management practices include changing the chemistry every third year, which will slow the selection of resistant weeds.

Another strategy is using three-, four- and five-way herbicide mixes to eradicate hardy weeds instead of single or two-way mixes that’ve been common for years, Smeda said.

Smeda is also exploring different timing strategies in herbicide application and mowing. It’s a complex strategy involving the plants reproductive cycle and growth characteristics. The goal is to kill the weeds in as few applications as possible — once a year would be ideal. It is common in some areas to spray up to three times or more.

A promising strategy is to stop seed production. Recently Smeda has looked at improving the timing of pre- and post-emergent herbicide application to fool the weeds into producing seeds when weather conditions won’t allow them to germinate.

Reid Smeda and Carey Page, a post-doctoral student working with Smeda.Reid Smeda and Carey Page, a post-doctoral student working with Smeda.

Real Weeds, Simulated Crossing

Given that weeds at crossings are a national problem, Smeda travels the country looking for new issues, dropping into places where conventional methods no longer seem to work. Much of his research stretches from Michigan to Oklahoma where the weeds are most prevalent and tough.

In partnership with railroad companies, Smeda has established a test plot in the middle of the working Neff Rail Yard, northeast of downtown Kansas City. Another site is in northeast Kansas at the 18th Street Rail Yard. This site is unique as the soil was once well fertilized by cattle being shipped to the Kansas City Stockyards, and is an ideal site for grass weeds such as sprangletop. To access the dangerous rail yards, Smeda must undergo annual training and certification in railroad safety.

At these sites, Smeda monitors plant growth in this unique environment and watches the results of his intervention tests.

SONY DSCThese real-site plots are supplemented on several simulated crossings that Smeda has created to duplicate the soil and stone conditions unique to crossings. One location is at CAFNR’s Bradford Research Center, east of Columbia. Here, Smeda has constructed a small simulated railroad crossing that serves as a controlled environment for his tests. He can watch weeds through their lifecycle and compare the results of different weed-killing and mowing strategies over a long time. The project is currently looking for a donor to help expand the simulation and establish real tracks on it to create an even better simulation.

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