NC State Extension Publications

Are Your Groundwater and Surface Water Protected from Your Lawn Care and Gardening Activities?

Most homeowners care for lawns, gardens, shrubs, and trees by applying plant nutrients and sometimes pesticides. Improper application and storage of these products may result in products moving through the soil into the groundwater or washing off into surface waters. Your well is usually near your house or in the yard where you have a lawn or garden. It is important to know how to maintain these areas while still protecting your water supply. Proper application of fertilizers and pesticides, safe storage practices, and correct watering are all part of the overall protection plan.

Surface waters need to be protected from lawn and garden activities that cause soil erosion. Land-distributing activities, uncovered soil surfaces, and the absence of water-retaining structures may cause soil to move into streams, lakes, and estuaries. Excess sediment in surface waters can kill important food sources for fish and cause the quality of the water to decline. It is important that you keep your soil on your property. You can do this by minimizing the amount of bare soil that is exposed to rain.

This publication leads you through an evaluation of your home and property to determine the pollution and health risks of your water supply protection practices. If there is a problem or a potential problem, this publication has information about how to solve the problems.                    

How Can We Help?

We have prepared this publication to help you focus on potential problems with your drinking water or other water resources that may be caused by improper lawn or garden care. Read this publication before you begin answering the questions. Then walk around your lawn, garden, and area where you store and load your pesticides and fertilizers.

Each of the following sections deals with different topics. Each topic has a question for you to answer. Your answers will help you to see where you have potential problems.

  • If you answer a question either a or b, you have a few problems with your lawn care and gardening activities.
  • If you answer a question either c or d, there may be a problem with the way you care for your lawn and garden.
  • If you answer a question either c or d, you will want to consider making changes in your lawn care and gardening activities in order to protect your drinking water.

If you would like further help in assessing the condition of your lawn care or gardening activities, please contact your local NC Cooperative Extension center and talk with your extension agent.

How Safe is Your Drinking Water?

If you drink water, it comes from a well or spring (groundwater sources) or a river or lake (surface water sources). Drinking water in North Carolina is generally safe, but it can become polluted if we are not careful. Many of the things we do at home can pollute our water and the environment. Poorly maintained or designed septic and animal waste systems can pollute surface and groundwater. Pesticides, fertilizers, fuels, and cleaning products can contaminate our water when they are not stored and handled properly.

It is nearly impossible to get pollutants out of water once they are there. Expensive treatments or new wells would be required to get safe drinking water again. Clearly, it is much more effective to keep pollutants out of water than to try to clean it up afterward.

People who have their own wells or springs for drinking water need to be especially aware of pollution sources because their water is not tested for contaminants as is city water. This is called wellhead protection and involves careful attention to the activities near your well to be sure the water remains safe. However, all people are responsible for protecting drinking water supplies, whether it is their own or their neighbors'.

Fertilizers

How do you store and handle your fertilizers?

Select the answer that best describes how you store and handle your fertilizer:

  1. No fertilizers are stored.
  2. Fertilizers are stored away from the well and all spills are promptly cleaned up.
  3. Fertilizers are stored near the well and spills are not cleaned up.
  4. Fertilizers are stored in the pump house of the well; OR do not know.

Fertilizers should be stored in a locked, dry cabinet away from your well. Keep fertilizers and pesticides on separate shelves. Load your fertilizer spreader on the driveway or other hard surface so you can easily sweep up any spills. Any fertilizer that spills should be swept up and applied to your lawn or garden at the right time and in the right amount. If you are using liquid fertilizer on your grass, add fertilizer to the spray tank while it is on the lawn. This way, if you spill fertilizer, it will be used by the plants and not run off into surface waters. Do not store fertilizers with combustibles, such as gasoline or kerosene, because of explosion hazards.

How do you fertilize your lawn or your garden?

Select the answer that best describes how you fertilize your lawn or garden:

  1. You test your soil and apply the recommended amount of fertilizer at the proper times.
  2. You use fertilizer at the rate recommended by NC Cooperative Extension and you apply the fertilizer at the correct time.
  3. You apply fertilizer at the recommended times but you have no idea how much you are putting out.
  4. You apply more fertilizer than recommended and apply it many times each year; OR do not know.

The chemical in fertilizers that can most easily pollute groundwater is a form of nitrogen called nitrate. Nitrate moves readily in soil and it can move through the soil into the groundwater. Drinking water that contains 10 milligrams of nitrate per liter of water exceeds the drinking water standards and should not be used, especially for infant formula.

The best way to prevent the movement of nitrate into the groundwater is to apply no more nitrogen than the grass, garden plants, shrubs, or trees can use during the time that the plants are growing. Sweep up any fertilizer that ends up on your driveway or sidewalks, or in your curbs. Reapply this fertilizer to your planted areas. This will allow the fertilizer to grow plants instead of washing off into nearby streams and lakes.

For maintaining established lawns, NC Cooperative Extension recommends the following fertilizer rates and schedule.


Turf Monthly application ratea Total lb/nitrogen 1,000 sq ft/yr
J F M A M J J Ab S O N D
Bahiagrass 12 12 1
Bermudagrass 1 1 1 1 4.0
Centipedegrassc 12 12
Fescue, tall 12 to 1 1 1 2.5 to 3
Kentucky bluegrass 12 to 1 1 1 2.5 to 3
Kentucky bluegrass / fine fescue 12 to 1 1 1 2.5 to 3
Kentucky bluegrass / tall fescue 12 to 1 1 1 2.5 to 3
Kentucky bluegrass / tall fescue / fine fescue 12 to 1 1 1 2.5 to 3
Kentucky bluegrass / perennial ryegrass 12 to 1 1 1 2.5 to 3
St. Augustinegrass 12 12 1 12 2.5
Zoysiagrass 12 12 12 1.5
a Dates suggested are for the central piedmont. For the west, dates may be 1 to 2 weeks later in the spring and earlier in the fall; for the east, 1 to 2 weeks earlier in the spring and later in the fall.
b In the absence of soil test recommendations, apply about 1 lb of potassium per 1,000 square feet using 1.6 pounds of muriate potash (0-0-60) 5 pounds of potassium-magnesium sulfate (0-0-22), or 2 pounds of potassium sulfate (0-0-50) to bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass.
c Centipedegrass should be fertilized very lightly after establishment. An additional fertilization in August may enhance centipedegrass performance in coastal locations. Avoid using any phosphorus on centipedegrass after establishment.

Your garden should need no more than 3 to 4 pounds of nitrogen per thousand square feet during the entire growing season. If split into at least two or three applications, the fertilizer will steadily feed the plants without seeping into groundwater.

Rate of Nitrogen Application

To determine the amount of fertilizer needed, follow the directions on the fertilizer label, or follow the procedure described below.

  • To apply 1 pound of nitrogen per 1,000 square feet, divide the first number on the fertilizer bag into 100. For example, a 16-4-8 fertilizer should be applied at a rate of 6.25 pounds per 1,000 square feet (100/16 = 6.25).
  • To apply 12 pound of nitrogen per 1,000 square feet, divide the first number on the bag into 50. For example, a 10-10-10 fertilizer should be applied at a rate of 5 pounds per 1,000 square feet (50/10 = 5).

Pesticides

How do you store your pesticides?

Select the answer that best describes how you store pesticides:

  1. Pesticides are stored in original containers, clearly marked. There are no holes, tears, or weak seams in the containers.
  2. Pesticides are stored in original containers that are old and have labels that are hard to read or partially missing.
  3. Pesticides are stored in containers that are old and patched. Metal containers show signs of rusting.
  4. Pesticides are stored in containers that have holes or tears that allow pesticides to leak. There are no labels on the containers; OR do not know.

The fewer pesticides you buy, the fewer you will have to store. Typical lawn and garden pesticides consist of weed killers or herbicides, insecticides, and fungicides. Purchase only the amount and kind of pesticide that you need. Pesticides should always be stored in sound, properly labeled, original containers. Sound containers are your first defense against a spill or leak.

Like fertilizers, pesticides should be stored in a locked, dry cabinet away from your well. Keep fertilizers and pesticides on separate shelves. Store dry products above liquids to prevent wetting from spills. Dry formulated pesticide spills should be swept up and applied to your lawn or garden at the appropriate rates. Liquid pesticide spills should be soaked up using absorbent materials (soil, sawdust, cat litter). Place all material in a sealed container and recycle at a hazardous household waste recycling center.

Pesticide storage areas must be kept free from combustible materials (such as petroleum products) or operations that present a fire hazard (such as welding). Burning pesticides or even empty containers can create extremely toxic fumes.

Where do you handle your pesticides?

Select the answer that best describes how you mix pesticides:

  1. The mixing area is located as far as possible from your well and on an impermeable surface that will contain spills. You only mix the proper amount of pesticides.
  2. The mixing area is located as far as possible from your well and on an impermeable surface that will contain spills. You mix more pesticide than you can use.
  3. The mixing area is located near your well but on impermeable surface that will contain spills.
  4. The mixing area is located near your well. Spills soak into the ground; OR do not know.

Just as it is important to keep your storage area away from your well, it is also important to keep your mixing site as far away from your well as possible. Spilled pesticides can move through the soil into the groundwater and pollute your drinking water supply. The farther your mixing and loading site is located from your well, the greater the protection to your drinking water supply. If possible, mix your pesticides on an impermeable surface, such as concrete, which will contain a pesticide spill.

It is also important to mix only the amount of pesticide that you will use. First, measure how many square feet are in the area to be treated, such as your lawn or garden. Then read the label on the pesticide container and follow the instructions. These are often given in terms of amount of pesticide to use per thousand square feet. By properly measuring and calculating, you should have little or no spray mix left in your spray tank when done.

How do you use pesticides?

Select the answer that best describes how you use pesticides:

  1. You rarely use pesticides, but when you do, you use the correct pesticide at the proper amount and you do no apply the pesticide near the well.
  2. You occasionally use pesticides, but when you do, you use the correct pesticide at the proper amount and you do not apply the pesticide near the well.
  3. You frequently use pesticides. You apply more than you need, but you never apply pesticides near your well.
  4. You frequently use pesticides. You apply more than you need. Pesticide applications are made close to the well; OR do not know.

Homeowners frequently use pesticides to kill or control weeds (herbicides), insects (insecticides), and fungi (fungicides) that attack their lawn or garden plants. Some of these pesticides can move through the soil and into the groundwater.

Guidelines for the safe use of pesticides are provided below:

  • Accept a low level of weed, insect, and plant disease infestation.
  • Use pesticides only when absolutely necessary.
  • Identify pests correctly. Use the proper pesticides.
  • Read and follow the directions printed on the container labels.
  • Calibrate your spreader and sprayer to keep from applying too much pesticide.
  • Do not spray or apply pesticides near your well.
  • Do no spray or apply pesticides near your walkway and driveway.

How do you dispose of your pesticides?

Select the answer that best describes how you dispose of pesticides:

  1. You recycle all pesticides at a household hazardous waste disposal center. You never have any pesticide mix left in your sprayer.
  2. You recycle all pesticides at a household hazardous waste disposal center. You occasionally have a small amount of pesticide mix left in your sprayer.
  3. You bury or dump unused pesticides on your own property.
  4. You dump unused pesticides near your well; OR do not know.

Improper disposal of pesticide containers can lead to groundwater contamination because the chemical residue can leak into the ground. If you are using liquid pesticides, rinse the bottle three times. Be sure to pour the rinsings into your sprayer, not the drain. Discard empty and rinsed pesticide containers in the trash.

If you have properly measured the pesticide, you should have little or no spray left in your tank. The little that is left can be safely sprayed over the area that you treated.

Unused pesticides in their original containers can be recycled at hazardous waste collection centers or at pesticide container recycling programs offered by the county Cooperative Extension center. For more information on recycling lawn and garden pesticides, contact the NC Department of Environment and Natural Resources, Division of Waste Management at 877-623-6748.

Water

How do you water your plants?

Select the answer that best describes how you water your plants:

  1. You never water your lawn or garden.
  2. You only water when your plants need moisture and you always use the correct amount of water.
  3. You only water when your plants need moisture but you don't measure how much you apply.
  4. You water on a set schedule regardless of whether your grass or garden needs it; OR do not know.

Over-watering your plants can cause excess water to move through the soil. This water can carry pesticides or nitrates that can pollute your groundwater. The best way to avoid over-watering is simply to measure how much you are adding. You can measure water by placing shallow containers around your lawn or garden to collect the water from the sprinklers. Apply enough water to moisten the soil 4-6 inches deep for healthy root growth. This usually requires you to apply 12 inch of water on coarse, sandy soils and 1 inch on heavier clay soils.

What type of plants do you grow?

Select the answer that best describes the type of plants that you grow:

  1. You have only drought-tolerant plants.
  2. You have mostly drought-tolerant plants and some medium-drought-tolerant plants.
  3. You have mostly medium-drought-tolerant plants and some high-water-need plants.
  4. You have mostly high-water-need plants and a few medium-drought-tolerant plants; OR do not know.

One of the best ways to protect your groundwater is to use plants that are drought-tolerant and that are adapted to your area. Drought-tolerant or low-water-use plants can continue to survive once they are established, even during times of little rainfall. Because you do not have to water these plants, there is less chance that nitrate and pesticides will be carried with the water through the soil and into the groundwater. Some low-water-use plants for North Carolina are crape myrtle, elaeagnus, Eastern red cedar, Chinese and Japanese hollies, glossy abelia, and juniper.

If low-water-use plants are not practical, then try to use medium-water-use plants, such as azaleas. Water these plants only when they begin to show drought stress. Some plants will wilt when they are drought-stressed, while other plants will show marginal leaf burn.

Soil

Sediment in our streams and lakes can start as erosion from your property. Lawn and gardening activities such as establishing lawns, tilling gardens, or leaving areas without a cover crop can result in erosion. To prevent soil from moving off your property and into water resources, keep your soil covered with plants or mulch.

How do you plant your lawn?

Select the answer that best describes how you plant your lawn:

  1. You have an established lawn, with few to no bare spots and you never till your lawn.
  2. You occasionally reestablish your lawn or you are planting a new lawn and you always plant your lawn at the right time using straw mulch.
  3. You have an established lawn with many bare spots.
  4. When you plant a new lawn or reestablish your old lawn, you plant at the wrong time and you do not use straw mulch; OR do not know.

The best way to prevent bare areas that are easily erodible is to design your landscape to minimize steep slopes and areas that do not drain well. When you are establishing a lawn, minimize the exposure of bare soil by using straw to cover any ground that will be bare for more than 30 days before planting. Reapply the straw after planting. Be sure to plant at the best time for the type of grass you are using. Warm-season grasses (bermuda, zoysia, centipede, bahia and St. Augustine) should be planted in the late spring or early summer. Cool-season grasses (fescue, bluegrass, and ryegrass) should be planted in the fall. Water lightly to prevent water and soil from running off the surface.

What do you do with bare spots or tilled garden areas?

Select the answer that best describes what you do with bare spots or tilled garden areas:

  1. You have no bare soil surfaces in your landscaping.
  2. You have some bare soil surfaces in your landscaping, but the exposed soil areas are minimal and covered with mulch, or if the exposed surface area is a garden, you use buffers around the garden or mulch the entire garden.
  3. Some of your landscaping area is bare and you do not use any kind of mulch to cover the exposed soil, or if the exposed surface area is a garden, you do not use mulch in or buffers around the garden.
  4. Much of your landscaping area is bare but you do not use any kind of mulch to cover the exposed soil, or if the exposed surface area is a garden, you do not use mulch in or buffers around the garden; OR do not know.

Areas under large trees are easily laid bare when there are foot paths, children playing, or animals confined under the trees. This is because most plants that can withstand heavy traffic will not grow in the heavy shade under trees. To avoid having exposed soil under large trees, you can either mulch or grow shade-tolerant ground covers or shrubs. Then try to steer the heavy traffic away from the area by creating paths or locating play equipment elsewhere. If you must use the space under a tree, use a mulch or a porous patio (pavers, flagstones, etc.) to both protect the roots and prevent soil erosion.

The same solution should be used for shrubs; use a mulch around your shrubs or flower beds to protect the soil from erosion.

Maintain a "buffer" of mulched perennial landscaping around your garden to keep runoff from moving out of the garden and into the surface waters.

Acknowledgments

Concept adapted for North Carolina from materials produced by the National Home*A*Syst Program, University of Wisconsin (author Karen Filchak, University of Connecticut Cooperative Extension).

North Carolina's modification of Farm*A*Syst and Home*A*Syst is coordinated by Deanna L. Osmond, North Carolina State University. Technical editing was provided by Judith A. Gale.

This project has been funded through the United States Department of Agriculture Water Quality Initiative Funds.

This publication is a revision of an earlier version. The authors would like to thank A. Bruneau & A. Russell for their earlier contributions.

Authors:

Department Extension Leader (Nutrient Mgt and Water Quality)
Crop and Soil Sciences
Undergraduate Teaching Coordinator
Crop and Soil Sciences
Extension Specialist (Erosion & Sediment Control & Water Quality)
Crop and Soil Sciences

Publication date: July 19, 2015
AG-439-82

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