Roots from a previous grow are not a good addition to any pot, (they can and will rot) so if you re-use the soil...be sure to remove as much of 'em as possible. Nothing uncomposted should ever go in your pots.

Ph drops are common with re-used soil, so additional buffering (garden lime or something similar) will likely be needed.

Flushing the soil you are about to re-use is a damn good idea, as it will loosten the salts and crap that have built-up over the last grow. Not a good idea to re-use soil without flushing well.

Farmers often rotate crops, plant companion crops, and use crop sequencing to replenish soils, and keep 'em bioactive.

Re-using soils will create a 'crusty' condition (calcium, lime, rust, etc...) rendering it unable to absorb water. A surfactant can be used to break water surface tention, allowing easier absorption in the soil. Dishsoap works well, but make sure it isn't anti-bacterial, or it will kill the bioactivity in the soil. (1/2 tsp:gallon of ph'd water) One application lasts a while.

If you are going to re-use soil...it's best to have a good grasp of cannabis growing and troubleshooting. It's nowhere near as good as fresh, for consistency and results. In the long run, you can save a few dollars, but it may cost shitloads in frustration, extra work and heartache.
Rusty Trichome Reviewed by Rusty Trichome on . Re-using Soil Re-using soil has its benefits: 1. Despite having to buy new soil, which in some cases is good. Due to the fact that you probally used some or part of the nutes in the soil - is a good thing for new plants and helpful for future plants, like; seedlings and sprouts. 2. Soil, is an anchor to your plants, if you re-use you have a less of a chance of causing nut burn from the start, as most feeds you buy will compensate for loss of nutes in soil (if your gonna be using nutes to beef up your Rating: 5