If we're talking about the red plastic protein tubs I use you should at least amend the soil. Either dump all the old soil onto a tarp and add new compost and organic matter, plus enough sand or pea gravel to assist with drainage. Or just use the old soil for layering in your compost pile and use fresh mix.
If you have problems with disease or pest dumping the soil on a hard flat surface, spreading it thin, and giving it a week of sunlight to kill some of the bad microorganisms will help. This is a good idea anyway because it helps to prevent sour pockets developing in the contained soil.
I think 4 inches is a pretty generous reservoir. I go with a little over one and still worry about steamimg the roots in hotter weather although depending on climate that may not be an issue for you.
|