grubs in part of my lawns
I had grubs in part of my lawns. I have tried for two years to regrow grass. I have added new soil 4 times and have seeded over at least 8 times. Have watered it faithfully. I finally have sparse and spindly grass growth. Some of the problem has occurred under my fruit trees. Is it possible that the soil is too acidic under the trees due to fruit dropping? Can I spread some potash over problem areas?
I think it most likely that the problem is too much shade. You can of course have the soil analyzed for pH and various minerals. But fruit drop doesn't significantly change the pH, although it can contribute to disease and pests, so you shouldn't leave it on the ground anyway. If the grass under the trees wasn't compromised to begin with, you would have been less likely to have a grub problem. Have you considered a ground cover or shade garden; they can be very beautiful and much less work than trying to get grass to grow where it doesn't want to. Here are some ideas: https://www.gardeningknowhow.com/special/shade/ground-covers-for-shade.htm