There are quite a few ways to tell that soil has gone bad, including those mentioned above. Look out for signs like soil dryness and poor moisture retention in particular. When soil goes bad, it tends to lose its structure and starts to crumble. Sometimes, wetting the soil will help to refresh it, but poor soil often looks cracked. It may also take on a dull, gray-brown color, rather than being rich and dark. If it is pale, this indicates that most of the nutrients have gone out of it and it won’t feed your plants properly. Finally, check for signs of mold or mildew in the soil. These indicate that it has gone off too.