Making mud pies was a favorite pastime when I was young. Maybe you, too, remember patting the damp earth into your favorite toy dishes. It was a fun experience to share with my girls last weekend when we started making a big mud pie.
I found information online about preparing one's own potting soil, which included doing your own pasteurizing in a home oven. It sounded a little strange, but we thought we'd give it a try. The girls watched anxiously to see how many earthworms would pop out when I started turning the compost pile.
I dug out what appeared to be the richest soil and humus. Then it needed sifting. Since we hadn't yet found time to make a large screen, a large metal grilling tray with holes worked fine. Once we were relatively sure that our sifted dirt was devoid of rocks, roots and earthworms, it was time to haul our bucket inside.
I used a glass casserole baking dish, which seemed like it would clean up easily. The next step is not a how-to from me, but rather an explanation of how it worked for us. This is a moderately difficult project, and not one I would necessarily recommend that everyone try. I was supposed to heat up the oven, then stick an oven-proof meat thermometer through foil, into my covered dish of damp soil. The next few minutes are critical, because the soil must reach a maximum temperature for a certain amount of time, but never be too hot (toxic) or too cool (not pasteurized) while inside the oven. The goal is to kill any bacteria or seeds in the soil that might interfere with the delicate seed-starting process later on. My thermometer was either too old or not really oven-proof, because it quit working right before I was supposed to take my first reading. I had to guess my way through the baking process that had already begun, estimating based on the oven temperature and length of time my pan was inside it. I would caution you to not guess your way through this step like I did.
For instructions, I would suggest checking out this brief story from Oregon State University, this guide from Penn State, or going to Mother Earth News and typing in "potting soil" for the more detailed article by Barbara Pleasant.
I moved ahead with the process of putting the contents of our pasteurized mud pie into a mix with some store-bought, organic potting soil and extra sphagnum moss. I was trying to save money by stretching the more expensive bagged potting soil with the moss and the homemade mud pie. After the thermometer incident and an evening of earthy scent wafting through the kitchen, I'm not sure if I'll try this again.
Tomorrow: From mud pie to seed starting