1. Excavate the top 4-6 ins layer of dirt and fill back up with new topsoil of good quality.4 a: a+ ]% o; J$ u7 W
2. Reduce the use of chemical fertilizer and use organic one instead.
6 C* m2 G$ G8 M2 dI should tell a bobcat is required if you wanna do the whole front/back yard OR just spot-excavation (dig a bigger and deeper than normal hole, dump the old dirt and back fill w/ good topsoil when you want to plant a new tree) if you gonna do the job yourself.