Q.Our Older Orange Tree Died From An Oozing Fungal Disease On The Lower Trunk. We’ve Cut The Tree Down. Before Planting A New Tree,
how to prep the soil? We’ve read that the oozing fungus is most likely in the soil, a consequence of over-watering or lack of drainage. We don’t want to make the same mistake with a new tree. We cut the tree down on Dec. 1. We plan to plant a new tree, probably a lemon tree, in the spring. How do we prep the soil for the new tree? Do we just let it lay fallow? Water it? Remove a lot of the soil and add potting soil? Add compost? Thank you.

Certified GKH Gardening Expert
I wonder if your tree had cytospora canker? It causes an orange or amber oozing, but is caused by an airborne fungus that gains entry though wounds. Completely removing the tree was the best solution to prevent fungal spores from gaining entry into other trees. Since you aren't sure exactly what the tree died of, it wouldn't hurt to remove some of the soil like you suggested and replace it with topsoil mixed with compost. If you aren't in a hurry to plant you can alternately sterilize the soil by solarization. Cover the area with clear plastic and weigh the edges down with bricks. It's best done in the hottest part of summer and leave the plastic on for about 8 weeks.
https://www.gardeningknowhow.com/plant-problems/disease/weeping-amber-in-trees.htm