Category Archives: Irrigation

For the Love of the Game

Photo courtesy Deanna Dougan

By Molly Doyle

A little more than two decades ago, a love of turf and playing golf made Deanna Dougan’s decision to become a superintendent an easy one. During that time, she has helped design and create the additional nine holes at River Valley Golf and Country Club in St. Mary’s, Ont., and even had llamas as caddies on the course. She loves her job so much that she quit her own lawn care business to get back to maintaining the greens, where she also tries to get in a round or two of golf every week on her own course so she can ensure the members are playing in the best condition possible. The 48-year-old Dougan sat down with Canadian Groundskeeper to serve notice she has no immediate plans to retire, and River Valley will be her home away from home for years to come.

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Decreasing contamination of runoff: What the literature suggests

A healthy stand of turfgrass is not only of esthetic and recreational benefit, but can absorb rainwater and prevent runoff that contributes to erosion and carries pollutants such as dissolved nutrients. Photo © Ken Pavely

By Christopher Murray, PhD

Research consistently shows the volume of runoff decreases when turf is fertilized. Second, most studies show the concentration of nutrients in the runoff is more or less proportional to the amount of fertilizer added.

When considering the total amount of nutrients, though, the effect on runoff volume wins out over concentration: fertilizing decreases the total amount of nutrients in runoff, in most cases, compared with lawns where fertilization is eliminated. While the concentration of nutrients in the runoff may be higher when runoff occurs (and there are many studies showing that even nutrient concentration can be equal or lower with fertilization), because runoff occurs less frequently, the overall effect is often to reduce the amount of nutrients leaving the lawn.

Total nutrient loss is not the only item of concern when considering water quality. It is important to note even clean water can be a pollutant, as it carries with it the potential for erosion downstream and can overload stormwater systems, which can sometimes spill into sewer systems and cause hazardous overflows. Very little attention is paid to the benefit turfgrass provides simply because of its ability to decrease the strain on stormwater management systems.

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Decreasing contamination of runoff: Experimental considerations

Within 15 minutes of collecting a sample, a colourimeter can determine the phosphorous content of the water, though the total volume of runoff at that concentration is much more time-consuming to determine. Shown here are various water samples mixed with reagent that causes a colour change proportional to the amount of phosphorous in the sample. Photo courtesy Kayla Snyder

By Christopher Murray, PhD

An ideal study would be one where stands of various turfgrasses were monitored over long periods, some with fertilizer applied and some without, and with data collected regarding the amount of pollutants in runoff. This is easier written than done, of course, and many obstacles stand in the way of obtaining these ideal results.

First, a study that is perfectly realistic and controlled is difficult to achieve, and often one of these goals is sacrificed in favour of the other. Second, there is a logistical obstacle associated with measuring a wide variety of experiments probing different conditions, especially when long-term measurements are concerned. For example, to grow two different types of turf under three different fertilization regimes and two different watering regimes amounts to 12 individual tests that need to be monitored; the costs of researchers and automatic samplers can escalate very quickly as more variables are added to the experimental design.

Considering no studies are completely controlled, totally realistic, and performed with unlimited resources, one must make conclusions based on existing studies carefully—some experimental shortcomings are more likely to influence one’s interpretation than others. When considering the benefit to water quality associated with turfgrass, it is clear measuring the amount of runoff is at least as important as measuring the concentration of pollution in that runoff. However, the former is much more difficult to characterize than the latter.

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Decreasing contamination of runoff: The positive impacts of turfgrass

A stand of turfgrass maintained through application of fertilizer (a) will generally be healthier than one where fertilizer is restricted (b). Runoff carrying sediment and dissolved pollutants is more effectively absorbed and is given more time to infiltrate when the turf is healthier, though storms large enough to cause runoff may carry away excess fertilizer. In contrast, an unfertilized stand of turf will allow for higher volumes of runoff less likely to carry nutrients such as phosphorous and nitrogen. Image courtesy Chris Murray

By Christopher Murray, PhD

What role might turfgrass play in protecting water quality? Those who have ever noticed hydroseeding operations at a new development may already know turfgrass is a recognized means of stabilizing soil and preventing it from being carried away in runoff—a strategy for improving quality. Once the turfgrass is established, it continues to assist in management of both runoff quality and—increasingly, as the turf grows—quantity. As shoot density rises and the plant growth contributes to the soil’s permeability, the turf softens the impact of rainfall and restores some of the absorptive capability of the landscape. As the turfgrass grows, its ability to hold water and reduce the volume of runoff rises.

With this positive impact in mind, it is clear turfgrass maintenance is more than a purely cosmetic practice and it is worth looking closely at the risks and benefits associated with the use of fertilizer. Where there is less runoff, there may be less pollution; although it is counterintuitive, a stand of turfgrass made healthier through fertilization may allow less runoff to escape, reducing the nutrients carried into rivers and lakes. On the other hand, adding fertilizer must increase the amount of nutrients available to be carried away by runoff, so one would expect the concentration of pollution to grow, even though the volume might decrease.

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Decreasing contamination of runoff: Runoff and stormwater management

Vegetative groundcover such as turfgrass (a) has a much greater absorptive capability than less-permeable groundcover like asphalt (b), and can ‘soften’ the impact of storms by slowly releasing runoff and allowing more to infiltrate down into the ground. Impervious areas, in contrast, concentrate rainfall into fast-moving, high-volume flows that have greater ability to carry pollutants and cause erosion. Such runoff is often directed into storm drains, which may be directly connected to rivers, lakes, and streams. Image courtesy Chris Murray

By Christopher Murray, PhD

The issue is not that it rains, but rather what is put in the path of that rain. In areas with healthy terrestrial ecosystems, when rainwater falls it is absorbed by the soil and the organisms that live in and on it. Some of this water is used in the biological processes of the ecosystem, but most eventually makes its way out as groundwater or runoff. This takes time, and passage through these abiotic and biotic systems slows down the water, filtering it and ‘softening’ its impact. Where humans have developed the land and introduced paving, roofing, and otherwise waterproof large spaces, a runoff problem has been created. Rainfall is concentrated into fast-moving, high-volume torrents immediately carried to the stormwater management system. Little is absorbed in the process, and this water not only has the ability to carry more pollution (faster flows can carry larger debris farther), but it is also a powerful force for erosion—especially where new development is taking place and soil is bare.

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