1. Excavate the top 4-6 ins layer of dirt and fill back up with new topsoil of good quality.9 ]/ w4 W9 s- U1 M6 R# Z
2. Reduce the use of chemical fertilizer and use organic one instead.
$ t0 n* O& _' A3 pI 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.