What about reusing last year's soil outdoors? My holes are still kinda full. lol. Can I just add some fresh soil to it and mix it up? Or do I need to just get rid of it, and get new bags? I got most of the roots out after harvest, when I was just messin around. Just wondering if it's possible? Would save me a lot of $ if it is.
When properly done your soil can be improved each year. Under the surface there is beneficial microbial relationships being formed that will actually allow better nute uptake on your plants. You should not even re spade your holes so that you don't disturb these connections. Instead you might add some nitrogen via manure, etc., blending it into the top six inches of your hole. Do this in fall after harvest, let it sit till planting time after covering with some mulch. When plant is flowering you can then add a bit of organic P and P.
My soil gets amended every three grows, using a common soilless mix found in the organic section and improved by me, haha, and to be honest, the third crop is usually the best. Soil/soiless mix, whatever you want to call it, gets better with age. EWC is the entire key anyway and I'm just semi-organic.
The soil media holds the plant / roots. The plant in a container can only consume what is already there or it is given by the grower. If it still has something in it that the plant likes and it can periodically be added to with more plant goodies, the plant has a chance to thrive.
If the soil has excess salts, bad bugs etc. or other contaminants that deter growth or kill micro beasties, it should be discarded.
If you don't believe me, ask the worms, they will know.