On April 12th, I planted four SIPs--shown at left in the pic above--with the same control group of greens--tatsoi, bok choy, chard, rapa--and fertilizer.
The variable was that each SIP had a different soilless mix. Three weeks later, the early results are in.
SIP #1 - 30% one yr old mix (coir/earthworm castings, peat) from my potato box experiment, 50% 3 yr old BAACTO (peat based) potting mix, 20% perlite.
SIP #2 - 70% Three year old BAACTO potting mix, 30% added perlite
SIP #3 - 40% Three year old BAACTO potting mix, 40% coir, 20% perlite.
SIP #4 - 70% coir, 30% perlite.
I bought the coir from Rolanka and reconstituted it with water. The wetted volume is what is referred to in the above formulas. According to the literature, it is a superior growing medium as well as an eco friendly substitute for peat. Which is why I want it to work.
After these initial tests, my sense is that, unfortunately, the coir doesn't perform as well as potting mix. A maximum of 40% coir seems to be a good bet. Of course this could change, it's still early.
We'll keep doing tests on other types of plants throughout our growing season.