Applying phosphorus to a lawn

Asked April 25, 2019, 3:35 PM EDT

I have an established lawn with bare spots (specially around trees) and some weeds. My soil sample (late 2017) from University of Delaware says I have a pH of 5.4 and phosphorus index value of 12 - my soil is P deficient. (Last year, I spread lime to help the pH.) It recommends spreading triple superphosphate in the fall with seed planting, but I'd like to do it now around trees and bare areas. Is there any reason to wait other than fall being a better time to reseed? Also, my husband bought turf builder 30-0-4 to apply all over now. Should he exchange it for a more balanced fertilizer? Is it better to apply triple superphosphate separately?

Baltimore County Maryland

1 Response

Hi- the recommendation for when to fertilize was based on the fact that late summer/fall is the best time to re-seed. However, it is ok to apply the recommended lime and phosphate fertilizer now to benefit your trees. Rake the lime and fertilizer into the top 1-2 inches of soil to minimize off-site movement of nutrients. If this is a sloped area, please wait to spread the superphosphate until you are ready to re-seed.

The 30-0-4 can be used for your fall nitrogen applications to the lawn. Follow the UME recommendations:

Due to deep shade, tree roots, and thin soil, the bare areas may not grow turfgrass well regardless of your efforts.