Is my diy potting mix adequate ? How long after mixing can I plant?

Asked January 22, 2019, 5:31 PM EST

I'm planning on mixing my own soilless media for my outdoor vegetable container garden this year following the recipe below. While I intend to save a few dollars , I also hope to have a better draining/more oxygen rich mix for my larger pots, control over fertilizer and amounts, etc. Is there anything about my recipe that "pops out" as inadequate for optimal plant health? Also, how long before I can plant after the media has been mixed? Thank you! 2.4yrds peat 2yrds pumice 1/2yrd garden compost 1/2yrd worm castings 10lbs Fish Bone Meal 3-16-0 15lbs Langbeinite 0-0-22 22lbs Azomite 48lbs Oystershell Flour (for ph adjustment)

Benton County Oregon soil and fertility issues

1 Response

Wow! that's some recipe!

1. It will surely hold water (peat) and drain well (pumice).
2. NPK appears to be covered by castings, fish meal, langbeinite.

Items of concern:
1. Compost is such a heterogeneous thing - is this your compost? I'd conduct some kind of test for weed seed. I'd fill and water a couple of pots, hold them in a warm sunny place, and see whether any weeds germinate. Are you sure it has no fungal diseases?
2. pH adjustments - how was the weight of oystershell flour determined? This material will raise the pH, which may be a good thing, given the volume of peat moss in the mix.

pH controls the molecular form of plant nutrients, and how soluble they are. Plants can only take up dissolved nutrients, and only one form of each of the essential nutrients. The exception is N, of which plants take up 2 forms. I think the only way to really know what the pH of this mix is, is to have a test done. You could use a meter, but you'd have to find a protocol for potting mixes or compost, rather than soil.

These publications may have some value for you: