“Houston, we have a problem.”
Take at look at the photo below. On the right are Painted Tongue seeds planted with the fancy organic potting soil and worm castings at a ratio of 3:1. On the left are the same seeds planted in the organic potting soil only. They didn't come up at all. Other seeds that did come up sat there, stunted, refusing to grow.
Now, common sense would have indicated that I do a soil test before I started planting, but I thought “Hey, this is fancy organic potting soil and it should make the plants grow really well.” Grrrrr….
So after the fact, I did have my kiddos run a soil test on the potting soil and on the worm castings. Here are the results.
Organic potting soil:
The pH is around 6.5 (slightly acidic), the phosphorus (P, blue) is “sufficient”, the potash (K, orange) is “adequate”, but the nitrogen (N, pink)is completely depleted – nada, zip, zilch! No wonder things wouldn't grow.
The pH is around 7 (neutral), the phosphorus (P, blue) is “sufficient”, the potash (K, orange) is “depleted”, and the nitrogen (N, pink) is off the charts – high surplus. So to get a full range of the basic nutrients in my potting soil, I should have probably mixed in some greensand with my worm castings and added both to the potting soil. Live and learn.
Next season I either mix my own potting soil from scratch, starting with garden soil, which will mean planning ahead since my garden is usually very frozen when I want to start seedlings, or at the very least I test my seed starting mix before I start planting seeds in it. Luckily I amended most of my seed flats with the worm castings, but still, it was pretty aggravating to spend extra money on what I thought was a better product, only to have to produce very poorly.
Update: Since this post was originally written, I've switched to FoxFarm Organic Potting soil and have much better results.
Right now I'm in the process of finishing spring planting in the garden (late, I know, but sometimes things don't go as planned). I've been harvesting herbs and greens of various sorts, and the things that have been planted thus far seem to be doing well. Temps have been a little up and down, but we keep getting rain at pretty regular intervals, and it hasn't been super cold (except right around Mother's Day – it snowed :-P). The dehydrator is full of chamomile and there are massive amounts of catnip hung in the basement to dry. I've been busting my butt trying to finish planting, so I hope you'll bear with me as my posting schedule is likely to be quite erratic.