Growing Mixture (Soil)

I found that “Mel’s Mix” ¹ of equal parts by volume of vermiculite, peat moss, and a wide variety of composts, was far too “hot” to use. When I took a sample to the county Ag Center for soil testing, it was off the charts in soluble salts (a measure of soil fertility). Their testing registers a maximum of 1800 parts per million, and my samples (I took several) all came back at 1800 ppm. Anything over 500 is considered “excessive” and they hand-wrote “Toxic levels” on one of the earlier samples.

The Soluble Salts scale is as follows:
0 – 50 = poor
51 – 100 = fair
101 – 300 = good
301 – 500 = excellent
Above 500 = excessive

I am currently working on bringing the level down some more. The latest soil sample had a reading of 500 ppm. While it might be OK for well-established plants, I’m afraid that it is still too hot for tender young seedlings. Here is the mix that gave me 500 ppm:
1 bale of peat moss, decompressed (7 cubic feet)
2 bags of vermiculite, less 0.8 bushel (7 cubic feet)
0.25 cubic feet yard and kitchen compost
1.375 cubic feet of commercial compost (mushroom, chicken, cow composts well mixed)

We will be adding more Fafard 3B potting soil to dilute it down some more. The amount has not yet been determined.