Fertilizers, herbicides, and insecticides have various ecological effects, toxicities, 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.
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.
PREPARATION AND HANDLING BMPs
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 and use the lowest rate that will effectively control the pest. Record the amount of pesticides, herbicides, and fertilizers used for future reference.
- 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.
- Triple rinse containers, and use rinse water as product. Dispose of unused pesticide as hazardous waste.
- 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.
- Do not mix or prepare pesticides for application near storm drains.
- Purchase only the amount of pesticide that you can reasonably use in a given time period (month or year depending on the product).
- Dispose of empty pesticide containers according to the instructions on the container label.
CHEMICAL APPLICATION BMPs
The following guidelines should be followed when applying chemicals:
- 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 calm, dry weather is in the forecast to prevent drift and wash off. 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.
- Use pesticides only if there is an actual pest problem (not on a regular preventative schedule).
- Do not apply pesticides, herbicides, or fertilizers during irrigation or within 48 hours of predicted rainfall with greater than 50% probability as predicted by the National Oceanic and Atmospheric Administration (NOAA).
- Limit or replace herbicide and pesticide use (e.g., conducting manual weed and insect removal).
- Only apply pesticides when wind speeds are low (less than 5 mph).
- Employ techniques to minimize off-target application (e.g. spray drift) of pesticides, including consideration of alternative application techniques.
- Fertilizers should be worked into the soil rather than dumped or broadcast onto the surface.
- Sweep pavement and sidewalk if fertilizer is spilled on these surfaces before applying irrigation water.
- Reduce mowing of grass to allow for greater pollutant removal.
- Keep grass clippings and leaves away from waterways and out of the street using mulching, composting, or landfilling.