Can heavy rain ruin recently applied fertilizer?
Written by
Nguyen Minh
Reviewed by
Prof. Martin Thorne, Ph.D.Intense rainfall causes lawn booster fertilizer to become an environmental danger. Lashing rains cause nutrients to wash into storm drains from surface-applied applications within 1 inch of rainfall in 24 hours (40-60%). During the last monsoon season, a client in Phoenix had a 20-5-10 application that washed into citrus groves, burning the roots ($1,200 crop damage).
Pre-Storm Checks
- Verify 48-hour weather forecasts
- Switch to polymer-coated granules if rain risk >30%
- Map drainage paths away from waterways
Post-Storm Actions
- Wait 3 dry days before reapplying
- Reduce nitrogen rates by 50%
- Test soil salinity before corrections
Regional patterns of rainfall dictate your fertility strategy. Florida's summer thunderstorms necessitate split applications, with half the dose before rainfall and the other half following rainfall. Arizona's monsoons? Schedule your feeds during the predicted dry periods between rains. I saved a Tucson golf course 18 percent on fertilizer costs by using weather modeling software to model when the rains would treat a large swath of the course.
Precision is paramount for restoring areas that have been washed out. It's a good idea to check the soil pH level and the nutrient residual on the site before making another application. A client in Denver had a lawn that was washed out. It tested for 12ppm nitrogen, so we made an application of 8-2-4 nitrogens (N), phosphorus (P), and potassium (K) fertilizers rather than full strength - which is a 20-5-10 (N-P-K). Three weeks later, the turf density matched areas without washout and without over-fertilizing the ecosystem.
Read the full article: When to Fertilize Lawn: By Region & Grass Type
