I was told I can add up to 100 pounds per 100 s/f of ‘composted’ cow manure on top of my perennial flower bed in the Fall and again in the Spring. Is it true? That is about 4 to 6″ thick. Would this much compost manure suffocate the existing plants? Would the new growths grow through this layer?
Certified GKH Gardening Expert
That sounded like a lot to me, too, and I found varying recommendations in university extension publications, from 100 pounds per year (per 100 square feet) to 200 pounds per year (per 100 square feet). I believe that is if you are trying to supply most of your nitrogen needs from that application. With that much manure, you have to be careful about not getting too much phosphorous and potassium. Other sources said add a 2 to 3 inch layer around existing plants and work into soil or leave as mulch. That sounds much better than a 4 to 6 inch layer.
I would not add it both fall and spring. All the sources I read said one or the other (once per year).
You wouldn't cover any existing plants with it. You can use it as a mulch and put several inches alongside your plants.