Common hazardous ingredients
Ammonium nitrate, ammonium phosphate, ammonium sulfate, copper salts, lime, pesticides, potassium chloride.
Chemical or synthetic lawn and garden fertilizers tend to be water soluble and concentrated. As such they can be easily overused and therefore likely to end up in waterways after rain or watering.
Harmful if ingested. Single ingredient fertilizers such as ammonium nitrate are corrosive to the skin, eyes and mucous membranes. Both chemical and organic fertilizers can pollute surface and groundwater. Some fertilizers also contain toxic weed killers.
Follow label instructions carefully and use in moderation. Wear nitrile gloves. Do not apply fertilizer if a heavy rain is predicted. Use caution on slopes and lawn edges so fertilizer will not wash into lakes, streams or storm drains.
Use a slow-release fertilizer with at least 50 percent of the nitrogen in insoluble form. Calculate and apply carefully: no more than 1 pound of actual nitrogen per 1,000 square feet of area per application.
Fertilizers with weed killers (pesticides) commonly used on lawns do not target weeds effectively, often result in unnecessary application of pesticides and may cause damage or death to nearby trees and shrubs.
Keep leftover fertilizer tightly sealed in a clearly labeled plastic bag and store in a secure area away from children, pets and moisture.
Best: Use up or give away. If the fertilizer does not contain pesticides (does not say “weed” or “weed killer” in the name or on the label), dispose of the empty container or packaging in the garbage.
If the fertilizer contains pesticides and is not expired, banned or restricted (call your Oregon State University County Extension Office if you are uncertain) use up according to label instructions or give away. Empty pesticide containers made of plastic or glass or with plastic or foil liners should be triple-rinsed with water. Use rinse water as regular strength pesticide according to label directions. Wrap empty container in newspaper and dispose in the garbage.
Second best: Unwanted fertilizer that does not contain pesticides should be placed in a heavy-duty plastic bag and disposed of in the garbage. Those that contain pesticides should be taken to a hazardous waste facility or collection event.
Learn gardening tips that reduce or eliminate the need for fertilizers