Reuse of ProMix BX in grow bags
 

I'm wondering what the collective Tomatoville knowledge and experience is about using ProMix multiple times in grow bags for growing tomatoes & peppers. It seems that the first year I got little disease and very productive tomato plants and the second year reusing the same batch of ProMix I got more disease and less productivity. Fertilization and watering being very similar from year to year. Now I know there are many factors (like weather) that could cause this situation but I am relatively new to growing in grow bags and ProMix (5 yrs) and wonder what you guys and gals have learned about reusing ProMix from year to year. I should say that I soak the empty grow bags in a diluted bleach solution at the start of every growing season in an attempt to sterilize the grow bags before re-filling them with the ProMix

Dan

This spring, because of Covid, I didn't feel like going to the store to buy Promix. I had kept my pots, still full of Promix in the shed over the winter as I had read that people re-use their mix and add some nutrients. Thank goodness I had done that! I emptied them (individually) into a wheelbarrow so that I could add 1/4 of my own composted chicken manure to each pot.

I'm happy to say that all my compact tomatoes grew very well in last year's Pro-mix with added composted chicken manure :). I would venture to say that they grew as well as they had the previous year when I grew them in new Pro-mix.

Linda

I use mine for 3 years (then it starts to break down into mud), but add about a fourth per volume of my own compost in all three years.



Then, the dreaded year, time to empty all 200 containers and start with fresh.

Some of my containers I am sure date back to 2016 and were used 5 seasons. They started as Promix BX and might have odds and ends of compost, potting soil, or garden soil mixed in over the years to top off the containers if the level sank. Each spring, I take a shovel and break up the mix. Sometimes, if a container seems firmly packed, I dump that entire pot or more than one pot into a Rubbermaid storage tote and break up all the clods and mix in some fertilizer, then shovel it back into the containers. I've never bleached or otherwise treated any "soil" for diseases and haven't had any problems with reusing the same mix. These are large containers 24" diameter and plastic. They sit outdoors all winter because they are heavy and bulky to store, and I just don't move then very far from their summer location because they're a lot of freight to haul.

I've had mine at some point for 7 years. It was a bit too much, after about 5 you could see the decline. When I changed it, towards the bottom you could find a sort of soft rock formations, some quite big, like a nut. I think it was calcium carbonate or phosphate (from reaction with the fertilizers) due to my extremely hard water, and that was what made the production go down (constant problems with micronutrients).

As for foliar diseases, it's really not the soil, but the humidity, sun, aeration that make the big difference.