How Long Does Fertilizer Take to Work in the Grass?

Fertilizer provides nutrients that grass needs to grow, especially nitrogen, which grass uses to form chemicals necessary for photosynthesis. Quick-release nitrogen fertilizers work within days, but these fertilizers have other disadvantages. Slow-release nitrogen fertilizers take several weeks to improve the quality of your grass, but their effects also last longer.

Quick-release or soluble fertilizers provide available nitrogen to grass. Quick-release fertilizers usually improve your grass within a week or less, according to the Purdue Turfgrass Science Program. In good growing conditions, grass absorbs nitrogen into its grass blades 15 to 24 hours after application, according to the Midwest Sod Council. Quick-release fertilizer costs less than slow-release fertilizer, but it's also much more likely to burn your grass, especially if you apply it improperly. In addition, the effects of quick-release fertilizer won't last as long as slow-release fertilizers.

Slow-release fertilizer, also called controlled-release or insoluble fertilizer, is gradually broken down into available nitrogen by microorganisms. Slow-release nitrogen takes three to 10 weeks to improve your lawn. It's more expensive than quick-release forms of nitrogen fertilizer, but it's also less likely to harm your grass and provides longer-lasting effects. Slow-release fertilizer is ideal for summer fertilizing because it provides a long, gradual feed.

Many fertilizers offer a combination of quick-release and slow-release nitrogen. These fertilizers provide quick results without as much risk as quick-release formulations, but also provide a lasting feed. Read the back of the fertilizer label to determine which types of nitrogen are in your fertilizer; quick-release nitrogen may also be called soluble, while slow-release nitrogen may be called slowly available or water-insoluble. Combination fertilizers work well for fall applications.

Avoid overfertilizing your lawn, which increases the risk of turf diseases and insect problems. Read the fertilizer label carefully before using fertilizer. Getting your soil tested before applying fertilizer to your lawn helps you determine which nutrients your lawn needs. Along with nitrogen, lawn fertilizers commonly provide phosphorus and potassium; different formulations of fertilizer contain different proportions of these nutrients. Grasscycling, or leaving grass clippings on the grass after mowing, also reduces your need for fertilizing.