FINDING ANSWERS

LAKE LEACHING

Q

Our apartment complex is close to the lake and I am concerned about nitrate leaching into the lake from our fertilizer applications. We've been applying fertilizer to the bluegrass three times per year. Am I causing a nitrate problem? — Bay Village, Ohio

A

There can never be too much consideration of pollution prevention in our industry. Paying attention to research and structuring our practices accordingly will help everyone. The tremendous amount of research out there that addresses nitrate leaching can be confusing if you try to take it all in. Some simple items to keep in mind: Consider your soil type — sandy soils hold less fertilizer, which leach and enter groundwater; conversely, fine clay soils can compact, allowing the fertilizer to run off. Various turf and ornamental species have different demands for nutrients. Bermudagrass is a heavier feeder than zoysiagrass. So it's vital to know your species and treat accordingly. Neighboring or on-site ponds and lakes shorten the distance leachate needs to travel before hitting the water. Most research indicates that nitrate leaching is not a problem on turf, in general. However, most studies were performed on newly established turf that has not been compacted through normal use and does not have excess thatch layers. Recent research at Michigan State University has shown that established turfgrass has a greater risk of leaching. At 1 pound nitrogen per 1,000 square feet, they found more than 10 percent fertilizer nitrogen in leachate. Depending on your operations, you may benefit from splitting your three applications into four applications. The lower the concentration, the more likely the turfgrass roots will pick it up and utilize it.

LATE-FALL FERTILIZATION

Q

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I keep hearing about late-fall fertilizers on bermudagrass to help keep the turf greener later in the season. Should I worry about setting the turf up for freeze damage from the late feeding? — Apex, N.C.

A

Nearly all horticulture and turfgrass recommendations warn against late-season fertilization, believed to delay onset of dormancy. However, there is ample research that shows the application of 1 pound of nitrogen per 1,000 square feet per month can keep bermudagrass greener later into the fall. A recent study by researchers at Virginia Polytechnic Institute should help you with your decision-making. They made late-fall nitrogen applications, as well as applications of seaweed extract and iron every three weeks during the fall of 2001 and 2002. They then harvested bermudagrass stolon samples and subjected them to freezing temperatures. As expected, the bermudagrass stayed green later, but the nitrogen-fertilized plots did not suffer from reduced cold tolerance. Seaweed extract and iron did not reduce cold tolerance, nor did they assist in green color retention with late-fall applications. Keep in mind that higher rates of nitrogen could increase thatch production and also promote nitrate leaching, so keep moderation in mind.

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