Duke Survey gives interesting insight into fertilizer use

Jul. 20, 2013 @ 11:19 AM

Both the Falls and Jordan lake watershed rules call for the reduction of non-point source pollution, which comes from a variety of human activities, such as home lawn fertilizer use.

So how does the behavior of homeowners when applying fertilizer effect water quality? A recent survey provides some clues.

During March and April, a Duke Graduate student mailed a Durham Fertilizer Behavior Survey, to 1,000 randomly selected single-family homes. Approximately 40 percent of landowners participated. The survey asked homeowners questions about fertilization practices and their lawn care behavior and attitudes.

Of the 60 questions asked, it is the responses to six that provide an insight to the challenges Durham faces to reduce non-point sources of nutrients. When asked if they have ever had a soil test on their lawns; 79 percent said never and 21 percent had a test completed in the past three years. When asked, “do you ever apply fertilizer before a rain,”  85 percent said yes and 15 percent said never. Only 62 percent sweep up spilled fertilizer on impervious surfaces, with 38 percent stating no.  When asked, “do you apply fertilizer near a stream,” 90 percent said no and 10 percent yes, which is great news! Surprisingly, 79 percent did not know what the numbers on a bag of fertilizer indicate (amount of nitrogen-phosphorous-potassium). The survey had a sample problem on calculating how much nitrogen to use in a 1,000-square-foot-lawn and 91 percent of the respondents answered the question incorrectly.

Plants can only use so much nitrogen or phosphorous, and applying extra can become a problem. Phosphorus is one of the major causes of blue-green algae in water bodies in the United States. Studies have shown that increases in nitrate loss are often due to soil texture, over-application of fertilizer, poor infiltration, turf grass age and the seasons. The survey responses suggest that nutrient loss and misapplication of fertilizer by homeowners could be contributing to excess nutrients making their way to Jordan and Falls lakes.

Other states have addressed the problem through local legislation. Ten states have passed regulations pertaining to non-farm fertilizer. In these states, laws restrict homeowners’ use of fertilizers containing phosphorus, recommend not leaving grass clippings or spilled fertilizer on impervious surfaces and not applying before a rain storm or on frozen ground. They set buffer requirements for non-farm fertilizer use, ranging from 15-20 feet away from surface waters. Four states require 20 percent slow release of nitrogen in their fertilizers. Commercial fertilizer applicators have to complete a training and certification program and pay an annual fee around $100. Other states require commercial applicators to fill out an application form with a fee, and violators face a civil penalty ranging from $100 to $500.

Durham is tasked to reduce further nutrients from entering Falls and Jordan lakes. Proper lawn fertilization education is needed, and one such program is the Voluntary Nutrient Reduction Program (VNRP). Led by the Durham Soil and Water Conservation District, the VNRP encourages following best management practices when applying fertilizer to their lawns or gardens and reduce fertilizer use by up to 40 percent. More about the VNRP can be learned at http://dconc.gov . With future population growth, Durham County leaders may need to look at adopting some policies passed in other states and expand its education and outreach programs, to meet a greater need.

Kim Yewchuk is a senior from the State University of New York, College of Agriculture & Technology, and Bachelor Degree Internship Program from Cobleskill, New York, serving as an intern with the Durham Soil & Water Conservation District.

The Durham Soil and Water Conservation District is part of Durham County Government. Their mission is to conserve, enhance and promote the natural resources of Durham County by providing technical assistance, environmental education information and economic incentives to County citizens and by exhibiting a diversified program to meet its changing needs. To learn more please visit http://dconc.gov