I’ve been building my own organic soil mixes for years. For a long time I used a super basic recipe of peat moss, perlite, humus and dolomite lime, and the majority of nutrients for my plants would come from brewed guano teas. About a year ago I decided to bulk up my mix, and “super-charge” it with some different amendments. I didn’t do much research before I started, and the stuff I added ended up spiking my pH way up, locking out phosphorous and creating a huge deficiency along the way (the higher the pH raises above 6.5, the more the phosphorous becomes unavailable to the plant). I started gathering some knowledge on the different things I added to mix and found that one of the new ingredients, Azomite, has a natural pH of 8.0! The Azomite, along with the dolomite lime I added to the peat moss, made for a very alkaline soil environment.
So, I think I figured out the problem, but just to be sure, let’s do an experiment and try to fix it. Four days ago I made a new 5 gallon batch soil. This mix of ingredients is pretty similar to what I’ve been using, and this is what’s in it…
- Pro-Mix BX – 3 gallons (60%)
- Mushroom compost – 1 gallon (20%)
- Ancient Forest humus – 1 gallon (20%)
- Dr. Earth All Purpose mix – 1/2 cup
- Organicare Bloom – 1/2 cup
- Primal Harvest high ‘P’ bat guano – 1/2 cup
- Azomite – 5 Tbls
- Azos – 5 Tbls
- Mycos – 5 Tbls
4/4/2012 – After everything was mixed together, I moistened it with a mild solution of Neptunes hydrolyzed fish fertilizer. I used a Bluelab soil pH meter and the initial pH read 6.1, which is a little low for soil but still right in the area of where I wanted it to be. Then I let it sit partially covered for two days to compost.
4/6/2012 – I checked the pH of the mix after two days of composting, and found that it had spiked from 6.1 all the way up to 7.0. This is actually what I expected to happen to the pH, but I didn’t think it would rise that fast. I moistened the mix again using Foxfarm Big Bloom (which is a super organic guano and castings tea that’s rich in microbial life), and let it sit partially covered again.
4/8/2012 – Two more days passed, and I used the Bluelab to check the pH again and found it rose again from 7.0 to 7.3. To lower the pH, I added another gallon of peat moss, a half gallon of Ancient Forest, and a quarter cup of Dr. Earths All Purpose. I checked the pH again and it was down to 6.7.
That’s where it’s at right now. This mix will sit and compost for at least two weeks before I use it to pot any plants. Hopefully in that time the pH will get down around 6.3 to 6.5. I’ll post updates frequently, so check back in to follow along with the results.
Stop by our store, Garden Doctor, for more information on organic soils and amendments. We’re the best indoor garden supply store serving the Grand Rapids area. We carry the top hydroponic systems, nutrient brands, grow lights, fans and filters, and everything else needed to maintain an amazing indoor garden.
2974 28th Street SW
Grandville, MI 49418