Potting Mix & Paradoxes

The other day, I made my first potting mix. There’s a certain irony to potting mixes. Normal soil is made up almost entirely of clay, sand, and silt. Yet those ingredients are absent in most potting mix recipes. The popular mix ingredients are perlite, vermiculite, peat moss and compost. Up until now, we have been planting in straight compost with fair results. But I'd like to try the conventional wisdom. For this first mix, I went with something close to a standard recipe: 2 parts peat, 1 part perlite, 2.5 parts compost, and a bit of sand. I was fairly amazed at how much water the peat moss held! Each "part" of the mix was measured out using a 5 gallon bucket, so there was quite a bit of mix there, but the compost was already soaked and I had sprayed down the perlite before adding it (to keep it from throwing up so much dust). Still, to wet down the peat (again, to keep it from throwing up dust) I added gallon after gallon until it was all wet. I would guess that those 10 gallons of peat soaked up 5 gallons of water! I see what growers like it, germinating seeds and seedlings really don't like drying out! Still, peat moss is a non-renewable resource from Canada, and there’s something odd about growing "local food" with soil from that far away. As I said, I wanted to test it this once, but I hope I can find a substitute in the future. For our next mix I'd like to create something close to what the books describe as "perfect soil": a perfectly balanced loam of clay, silt, sand, and compost. I hope such a mix works near enough as well as the conventional mix we've just created, as it would be more sustainable.

It's almost odd putting so much thought and effort into potting mixes. And we put even more effort into the soil that our garden and grass will grow in. Most people probably think this makes sense because they think of soil as plant food. Once upon a time, everyone thought it was. But it's not. No plant has ever digested a speck of clay, or silt, or sand (or peat moss). Plants are made of air. The carbon of carbon dioxide is the raw material for their stems, leafs, and flowers. A process of conversion fired by sunlight and lubricated by water. So why do they even need soil? A question often asked rhetorically by the fathers of chemical agriculture.  But, you CAN see the soil change over time if plants are repeatedly grown and harvested. The soil changes from a rich black or brown to a light tan. From light and fluffy to hard and condensed. Plants, as a matter of fact, do eat from the soil. But the soil is their plate, not the food. They absorb the  minerals and chemicals that are available to them. And they are quite particular. You can't just put nitrogen into the ground. The nitrogen has to be in a certain chemical form. And it's the flora and fauna of the soil that puts the necessary amendments into the necessary form to grow healthy plants. These amendments are more catalyst than food, and the plant needs just a tiny amount of them. But they are absolutely necessary for growth. And so we obsess over soil. Healthy soil = healthy plants. Coincidentally, these same soil-living flora and fauna are also what keeps soil soft and friable, water-absorbing and root-friendly. Nature designs well.