Buffers and runoff

Buffer zones of 3-inch-tall grass protect streams, lakes and ponds from pesticide and nutrient pollution when allowed to grow between turf and water bodies. You can reduce losses of pesticides and nutrients to runoff by ensuring chemicals aren't applied to saturated soil. Use pesticides that are less conducive to runoff such as those with low water solubility and high adsorption coefficients.

Reducing pesticide and
nutrient runoff using buffers

Taller grass in the rough can reduce the amounts of pesticides and nutrients
that run off into lakes, streams and ponds.

James H. Baird, Ph.D.

Many things can happen to a pesticide or nutrient following application to golf course turf. Ideally, most or all of the chemical will be taken up by the turfgrass plant or target pest.

Of course, chemicals also can be carried away from the golf course in runoff water. Because lakes, ponds and streams often border golf course fairways, the potential for pollution from runoff has been a subject of increasing environmental concern.

According to our research at Oklahoma State University, buffer strips of turfgrass can reduce runoff losses of pesticides and nutrients from turf. Our work also suggests some specifications for such buffer strips.

A portable rainfall simulator was used to apply precipitation in the runoff experiments.

Fate
It's important to recognize, however, that pesticide and nutrient “fates” are not limited to uptake and runoff.

On or in the soil, the pesticide or nutrient may undergo chemical degradation by microbes, sunlight or other chemical means. These types of chemical reactions don't necessarily “degrade” the product. Sometimes such reactions actually produce the active ingredient required by the turf.

In addition, a chemical may be volatilized from a solid or liquid to a gas and then lost to the atmosphere.

Many chemicals become adsorbed by soil mineral and organic matter. Lack of adsorption can result in leaching, which is common with negatively charged ions (such as nitrates) and in sandy soils.

Runoff
Overland flow of chemicals may occur when the precipitation rate exceeds the infiltration rate. Several factors affect surface loss of pesticides and nutrients:

Time between chemical application and precipitation event causing runoff

Amount and duration of precipitation event

Previous soil moisture

Slope

Amount and method of chemical application

Timing of chemical application in regard to plant uptake

Chemical properties

Rate of field degradation or transformation

Soil properties

Vegetation type or density (1,3)

Research
Our primary research objective was to evaluate and develop management strategies to reduce surface runoff of pesticides and nutrients from golf courses and other turf areas. Our strategies revolved around the use of buffers -- untreated vegetation zones between a treated area and surface water.

The star of our research team was a portable rainfall simulator. The simulator was equipped with 10 booms with staggered nozzles that rotated like a carousel to apply heavy, uniform precipitation over a 50-foot-diameter area containing four plots. The simulator could be transported among our eight simulation sites.

Former OSU turf student Brian White, now second assistant superintendent at Pleasant Valley CC in Little Rock, Ark., collects runoff samples and data during a simulated rainfall event.

Experimental design
The experiments took place on a 3-acre, sloped field of bermudagrass (Cynodon dactylon) located at the Oklahoma State University Agronomy Farm in Stillwater, Okla. The soil was a silt loam, and the average slope of the plots was 6 percent. Plot borders were made from plastic hoses filled with sand. A sand and bentonite clay mix prevented runoff from flowing underneath the hose borders. Endplates and collection troughs channeled runoff water toward the collection pits.

Each plot was 6 feet wide by 16 feet long and was mowed at 0.5 inch to represent a golf course fairway. The buffer area was considered to represent a golf course rough between the treated "fairway" and a runoff collection point (surface water).

The buffers were mowed at 0.5 inch to represent no rough and 1.5 inches to represent a standard mowing height for bermudagrass rough in Oklahoma. A deep, solid-tine aerator provided the aerification treatment, which occurred on the buffer area only.

1995 experiments
Fertilizer and insecticide were applied to the plots, which were then irrigated with 5 mm (0.2 inches) of water in 6 minutes using the simulator. The herbicides were then applied after the wetted turf had dried. Simulated rainfall was applied within 24 hours of application of pesticides and nutrients to simulate a worst-case scenario. Rainfall intensity was 64 mm per hour (2.5 inches per hour), and rainfall simulation events lasted 75 minutes.

Start of surface runoff was recorded when a continuous trickle of water was first observed at the collection pit. Samples were collected at preset times after the start of runoff for individual plots using a nominal sampling schedule. Most plots were sampled 10 times during the simulated rainfall period.

1995 results
Soil moisture before simulated rainfall in July was low. From the plot with no buffer, pesticide loss to surface runoff was 3 percent of applied amounts and nutrient loss to surface runoff was 2 percent.

In August, 165 mm (6.5 inches) of natural rainfall fell seven days before simulated rainfall and loss to surface runoff increased to 15 percent of pesticide applied and 10 percent of nutrients applied. Again, the greatest surface runoff losses occurred from the treatment containing no buffer.

Overall, we concluded:

Buffers were effective in reducing pesticide and nutrient runoff, due in part to dilution.

In most instances, the buffer mowing heights in the 1995 study (0.5 vs. 1.5 inches) and aerification did not significantly affect pesticide and nutrient runoff.

Surface runoff losses of pesticides and nutrients increased when the soil was saturated at the time of application.

Greater runoff losses occurred from the herbicides and urea fertilizer, which have higher water solubilities and lower adsorption compared with the insecticide and S-coated urea fertilizer.

1996 experiments
The following year we set out to test whether a taller buffer mowing height would affect pesticide and nutrient runoff. In one experiment, we compared buffer mowing heights of 0.5, 1.5 and 3 inches. All buffers were 16 feet in length. In a separate experiment, we continued to evaluate the effect of buffer length on runoff. This time we evaluated buffer lengths of 0, 4, 8 and 16 feet. All buffers were mowed at 1.5 inches.

In July 1996, 19 mm (0.75 inches) of natural rainfall occurred within 5 days of simulated rainfall. In contrast, 56 mm (2.2 inches) of natural rainfall occurred within 5 days of simulated rainfall in August 1996. As in 1995, greater pesticide and nutrient loss to surface runoff occurred when the soil was more saturated at the time of application.

Buffer height experiment
The 3-inch buffer height created an obstacle to overland flow, delayed the onset of surface runoff and reduced the total amount of surface runoff water. In most instances, the tallest buffer height also reduced pesticide and nutrient loss to surface runoff.

Buffer length results
Once again, results from the 1996 buffer length experiment showed the effectiveness of using buffers to reduce pesticide and nutrient runoff. However, few significant differences were observed among the 4-, 8- or 16-foot buffer treatments.

When we analyzed individual samples from the no-buffer and 16-foot buffer treatments, we found the buffer not only reduced the concentration of pesticides and nutrients in the runoff, it also delayed the runoff of the chemicals.

Surface water pools at the junction between the 0.5-inch treated "fairway" area and the 3-inch-tall grass in the "rough," or buffer.

Conclusions
Overall, our results support other recent environmental research that has shown turfgrass to be an effective filter of applied chemicals. Less than 2 percent of the applied pesticides and nutrients were recovered in surface runoff water when buffers were used and when applications were made during unsaturated soil conditions. Furthermore, nominal runoff losses occurred as a result of a simulated worst-case scenario when 3.1 inches of simulated rainfall fell within 24 hours of application.

Based upon the findings of our research, the following "best management practices" are recommended to reduce surface runoff losses of pesticides and nutrients from turf:

Incorporate buffers between surface water and areas receiving pesticides and fertilizer.

Buffers should be made as wide as possible, or according to regulations that govern the site. The effective width of a buffer is dependent upon slope, size of watershed, resource functional value and other factors. Additional research using large runoff plots is needed to determine effective buffer widths for turf situations.

Maintain buffers at mowing heights of 3 inches or higher. Additional research is necessary to evaluate the effectiveness of taller vegetation for reducing runoff.

Avoid application of pesticides and fertilizer after heavy rain or irrigation.

Use pesticides that possess chemical properties that are less conducive to runoff (such as low water solubility and high adsorption coefficients).

Acknowledgments
This article reports research supported by a grant from the USGA in Far Hills, N.J. The author is grateful to the other members of the Oklahoma State University turfgrass runoff team: Nick Basta, Ph.D., and Gordon Johnson, Ph.D., department of plant and soil sciences; Ray Huhnke, Ph.D., Dan Storm, Ph.D., and Mike Smolen, Ph.D., department of biosystems and agricultural engineering; and Mark Payton, Ph.D., department of statistics. Special thanks to Steve Wilcoxen, superintendent at Karsten Creek GC, for use of a deep-tine aerator.

References

1. Balogh, J.C., and J.L. Anderson. 1992. Environmental impacts of turfgrass pesticides. p. 221-253. In: J.C. Balogh and W.J. Walker (eds.), Golf course management and construction: Environmental issues. Lewis Publishers, Chelsea, Mich.
2. Cole, J.T., J.H. Baird, N.T. Basta, R.L. Huhnke, D.E. Storm, G.V. Johnson, M.E. Payton, M.D. Smolen, D.L. Martin and J.C. Cole. 1997. Influence of buffers on pesticide and nutrient runoff from bermudagrass turf. Journal of Environmental Quality 26:1589-1598.
3. Walker, W.J., and B. Branham. 1992. Environmental impacts of turfgrass fertilization. p. 105-219. In: J.C. Balogh and W.J. Walker (eds.), Golf course management and construction: Environmental issues. Lewis Publishers, Chelsea, Mich.

James H. Baird, Ph.D., is assistant professor of turfgrass physiology at Michigan State University in East Lansing.