Refreshing grow bag soil

[Cranraspberry]

How do you folks usually refresh container soil? I have a few 10 gallon grow bags I’ll be reusing, and the soil level in them has gone down quite a bit.

[FatBeeFarm]

I can explain what I do, but I'm also curious about what other people do too. I always appreciate good advice!

So my set up is probably atypical, but I generally use 84 growbags a year in a double row with drip irrigation set up. I have a fair number of raised beds to refresh as well. With that much to refresh I start by ordering 5 to 8 yards of compost delivered. That leaves me plenty for veggie gardening and also enough for my yard and my flower garden beds. Any I don't use is still good next year. I just order more truckloads as I need it.

To refresh a grow bag, I first empty it into my wheelbarrow, then add 4 or so shovelfuls of compost, plus 1/4 cup of blood meal, 1/4 cup of bone meal, 1/4 cup of slow release fertilizer, 1/4 to 1/2 cup of alfalfa meal, maybe a partial 1/16th cup or so of Azomite, and maybe some fresh vermiculite if it looks like it needs it (but I'm going to try rice hulls this coming year instead because of cost.) Then I mix it all together thoroughly with my shovel and refill the grow bag. I generally have excess soil left over which I'll add to my raised beds which have settled a bit over winter (I generally refresh grow bags in April). Rinse and repeat 83 times. It takes several days to do it and it's a real workout. Every year I think, "Why am I doing this? I'm getting too old for this and I should just do all raised beds." So then I make more raised beds in the fall. Then in January I go crazy and make garden plans which require all the new beds, the old beds, and also still require all the old grow bags, lol. Joining this site isn't helping my problem either.

My actual recipe for refreshing the grow bags has worked well for 6 years now though. I'm sure there are ways to improve it and/or make it most cost effective, and maybe less labor intensive, so I'm anxious to hear what other people have to add.

[Cranraspberry]

@FatBeeFarm 84 bags!!! That definitely does sound like a workout. I was actually thinking of something along those lines, except on a much smaller scale.

[Labradors]

For smaller scale, I have eight 3 gallon planters on my deck in which I grow Maglia Rosa and Taste Patio tomatoes. I empty each planter into my wheelbarrow, removing the old plant and roots. I make my own compost using my own aged chicken manure, so each planter gets 1/4 to 1/3rd of this compost added to it.
I started doing this because I couldn't buy new potting mix during Covid, and I've done it very successfully ever since .

[FatBeeFarm]

@FatBeeFarm 84 bags!!! That definitely does sound like a workout. I was actually thinking of something along those lines, except on a much smaller scale.

Have fun with it! I've found the 10 gallon grow bags work really, really well for pepper plants and determinate tomatoes. No yield hit at all. They do reasonably OK with Eggplants, maybe a tiny yield hit. With indeterminate tomatoes, they'll produce fine for me, but the yield may be quite a bit less than if they had access to more than 10 gallons of soil. I notice this especially with cherry tomatoes like Sungold which can grow monstrous given enough soil to work with.

[Cranraspberry]

@Labradors thank you! I wish we had access to trustworthy manure! I’m attempting to make some compost over the winter in a contractor bag, but if it works out it won’t be much unfortunately.

@FatBeeFarm small yield is actually good. Last year we had 10 plants in raised beds and 1 in a grow bag and were absolutely drowning in tomatoes. I swore I’d plant less this year, but couldn’t narrow down the varieties so settled on 8 in ground and 3 in bags, and I’m counting on the growbag production to be much smaller. I got very, very burnt out last season and trying not to do the same again this year.

[Cole_Robbie]

A handful of worm castings is effective and economical.

[bower]

I refresh my potting mix by adding 1/3 compost by volume, a bit of lime, crushed kelp, and some pelleted chicken manure. Then I add bone meal at planting time for tomatoes.
If you don't have and can't get compost, I would go with a fresh bag of your mix, in the same proportion 1/3 new to 2/3 old.
I bet all these recipes work great and it simply depends on what you've got. Tomatoes are heavy feeders so it's safe to assume they have used up what was there the year before. Digging some compost or ferts in early will also help to break down any small roots left in the soil. OTOH If the soil is compacted and the structure has broken down, you might need something fibrous to restore the ideal texture.

[Cranraspberry]

We have a nice local bagged leaf compost here called Leafgro that I really like, but I suspect it’s not nearly as good as the fresh stuff you make yourself. The community garden’s compost pile doesn’t really get hot enough, and people dump all sorts of stuff in there that you’re not supposed to (from invasive weeds to plastic), so it’s unfortunately not a great resource either.

In any case sounds like 1/3 fresh plus whatever amendments I have on hand is the way to go.