Fertilizing – Just Before Rain

Q: We received two similar questions that have been answered together.

We have a zoysia lawn on a sloping lot. We fertilized three days before we had four inches of rainfall in 48 hours. We suspect that most of the fertilizer is in the back yard of our neighbor. Do we need to fertilize again?

and

I managed to apply my winter pre emergent two days before Hurricane Ivan dumped his generous rainfall on my lawn. Was the application in vain?

A: Actually, there should be no worries in either situation. Turf fertilizers are designed to release their nutrients over several weeks: water flowing over the fertilizer granules only dissolves a little of the fertilizer at a time. If the granules themselves washed down the hill there would be a problem but I doubt that happened. They are so small that they are likely still nestled at the base of the grass plants.

Pre-emergent herbicide granules, on the other hand, are designed to dissolve rapidly and stay put. My bet is that the chemical dissolved into the ground during the first half-hour of rain and still remains there. I would not re-apply a pre-emergent.

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