Carelessly applied fertillizer Image adapted from WI DNR, Lawn and Garden Fertilizers
Fertilizers, herbicides, and insecticides have various ecological effects, toxicity, and chemical fate and transport based on the product’s chemical components. Depending on the chemicals’ characteristics, they can have unintended harmful effects on terrestrial and aquatic plants and animals, and can end up in our soil, water, and air. Nitrates from fertilizers can migrate through the soil profile and contaminate ground water supplies beyond safe drinking water levels.
Phosphorus from fertilizers contributes to eutrophication of surface water bodies that depletes oxygen levels and can lead to fish kills.
This fact sheet provides guidance on program development for minimizing fertilizer and pesticide application.
Benefits and pollution reduction
Practicing proper fertilizer, herbicide, and pesticide application reduces the risk of these materials being transported by stormwater to downstream water bodies. Minimizing chemical use by employing best management practices (BMPs) for both application and material handling helps to eliminate a significant cause of stormwater pollution. Some BMPs have the potential to reduce costs associated with grounds keeping and maintenance, while improving the aesthetics and vegetative health of grounds where they’re implemented.
Program development and implementation
Programs designed to manage and minimize chemical application typically include a combination of the elements identified below. The BMPs and chemical alternatives discussed can provide the content for training programs and public education materials.
Integrated pest management
Integrated pest management (IPM) is a pest control system that employs mechanical, biological, cultural, and/or chemical mechanisms as determined by a thorough evaluation of the conditions rather than addressing every condition with chemicals.
The following are IPM strategies:
- Cultural control – selected timing and location of plantings to avoid pests
- Host resistance – planting vegetation that is resistant to pests
- Mechanical control – weeding; setting insect traps
- Biological control – stocking beetles to attack purple loosestrife; protecting naturally-occurring insect predators, parasites, and pathogens
- Chemical control – using the least toxic pesticides available wherever possible
IPM strategies are employed only when pest populations reach an unacceptable economic or aesthetic threshold.
Chemical preparation and handling best management practices
The following guidelines should be followed when preparing and handling chemicals:
- Select the least toxic products available to minimize waste and applicator exposure
- Use products only as directed, reading and following all labels
- Inspect, maintain, and calibrate equipment used for mixing and application
- Prepare only as much herbicide/pesticide as is needed
- Be prepared with cleanup materials to cleanup spills immediately; use dry cleanup methods (e.g. squeegee and dust pan) rather than hosing down the spill site
- Close containers tightly after each use, even if planning to reopen them soon
- Store chemicals safely in a ventilated, well lit area that is away from drinking water wells or any other permanent or intermittent water bodies
- Dispose of rinse water properly and recycle containers properly. For pesticides, triple rinsing or pressure rinsing with reuse of rinse water for future pesticide applications is recommended by the University of Minnesota. Proper rinsing of pesticide containers is also a requirement of Minnesota State and federal law.
- Monitor all fertilizer/pesticide application quantities and sites in order to provide guidance for future treatments
- Keep products in their original containers and mark the date of purchase on each container. Use older materials first.
Chemical application best management practices
The following guidelines should be followed when preparing and handling chemicals:
- Employ IPM
- Consider having the soil tested before applying fertilizer in order to determine what nutrients must be added
- Avoid application over impervious surfaces; sweep granular fertilizer back onto the grass to prevent it from washing into the storm sewer system
- Apply when sufficient calm, dry weather is in the forecast to prevent drift and washoff. Lawn fertilization programs should begin in fall, not in spring; this will prevent shallow root growth. Tree and shrub fertilization programs should occur in late fall or early spring when the plants are dormant.
- Do not apply to bare or eroding soil
- Do not apply near water systems such as streams and lakes unless the product is specifically designed for use in shoreline or aquatic environments
- Do not apply near wells
- Do not over fertilize. Too much nitrogen will cause plants to grow shallow roots creating a less hardy landscape (e.g. especially bad for athletic fields and parks) that requires more watering. Healthy trees and shrubs do not require annual fertilizing.
- Consider causes such as poor soils, insects, disease, or current weather patterns before applying fertilizer as a remedy for poor growth
- Organic fertilizer - Most organic fertilizers release nutrients more slowly and contain lower concentrations of nutrients. The slow-release function provides the lower concentration of nutrients over a longer period of time which is good for sandy soils where fast-release fertilizers can leach nutrients into the ground water. Fast-release fertilizers are more effective for heavy clay or compacted soils. Organic fertilizers have the additional benefit of recycling waste that would otherwise contribute to landfills and/or pollution.
- Grass clippings - Mulching mowers create fine grass clippings that will break down and add nitrogen and organic matter to the soil. Leave grass clippings on the lawn over the season to provide the equivalent of one regular fertilizer application that will not cause thatch.
- Aerate' - Aerating a compacted lawn punches holes in the soil to allow air, water, and nutrients to reach the roots. Leave the small plugs of thatch and soil on your lawn and they will quickly decompose. The best time to aerate is in the early fall.
- Compost - Apply a thin layer of compost (1/4” or less) to provide nutrients and additional water retention properties to combat dry periods. High-quality compost is available in nurseries by the bag or in bulk, or you can make your own. The best time to apply compost to lawn is in the spring using a wheelbarrow, shovel and lawn rake. A 1/4” layer requires about one cubic yard of compost per 1,500 to 2,000 square feet of lawn area.
- Soybean fertilizer - Michigan State University began using soybeans as turf fertilizer in 2000. Their studies suggest that soybeans perform equal to or better than chemical fertilizers. Ground soybeans provide a slow-release of nutrients to the lawn and are harmless to people, pets, and other plant material. In addition, soybeans are phosphorus-free. Because they are organic, each application improves the growing media, and they will not burn the grass.
Public education brochures
Develop public education brochures to encourage residents to limit chemical use by educating them about the human health risks and natural resource impacts associated with improper application. Typically tri-folded, double-sided informational sheets can be mass-mailed to educate residents. If ordinances or fines are associated with improper chemical application, these would also be included in this education piece.
Chemical application ordinance
Introduce a law enforced by the MS4 whereby individuals or entities responsible for chemical application receive a fine for chemical application that varies from product labeling. Other city-developed regulations might include required soil testing before fertilizer application.
Fertilizer and pesticide applicator licensing
The Minnesota Department of Agriculture (MDA) requires all persons who apply fertilizer or pesticide for hire (regardless of whether the product is custom blended, bagged, bulk, etc.) to obtain a fertilizer or pesticide applicator license, respectively from the MDA. A license is required for any application, including applications to lawns, plants (including trees and shrubs), and interior landscapes. Annual attendance at applicator recertification workshops is required.
If monitoring application rates at project sites in order to provide guidance for future application rates and methods (an effective chemical application BMP), it is important to maintain good records and use staff time to visit application sites.
A soil sample and nutrient test costs less than 💲25 per sample and is easily the best value for fertilizer minimization. Soybean and organic fertilizers can be up to three times the cost of standard chemical fertilizer. Reduced labor costs associated with fewer applications in larger amounts can help to offset this cost. However, alternative practices employed in place of fertilizers (see Fertilizer Alternatives above) can easily be less expensive than chemical application. Similarly, practicing IPM can reduce herbicide and pesticide application costs.