A blizzard blew in early yesterday morning, took the power out and froze the ground up hard. Now it is an icy white world with a few inches of snow. My hoophouse project is buried and I'm still awaiting the arrival of the pvc pipe so I'm hoping we don't get much more snow for a few days. The foundation is all set for these ribs and I want to get ready so all I need to do is wing up the plastic in the early spring. I have my potting soil curing ready for the seedling starts that will commence next month. I thought I'd share my recipe for those of you that are looking to make their own. I don't sterilize the soil, as I've never had big problems with damping off, given the right moisture, airflow and microbial balance. I don't want to kill the mycorrhizae and other beneficial microbes. So I like a good compost as the basis of the mix, to provide that community of organisms that keep things healthy. We had a problem with mold in the greenhouse once and solved the problem with a horsetail and chamomile spray. (mix 1/8 cup of dried horsetail, and 1/8 cup chamomile in 1 gallon of boiled water, let steep for a couple hours. strain.)
Here is the recipe for potting soil mix:
2 parts screened, mature (2/3 year old) compost
2 part peat
1/2 - 1 part soil
1 part vermiculite
I pile up these ingredients onto a large plywood sheet in my shed, mix with a shovel, make an indentation in the center and add water into this bowl. When absorbed I mix again and repeat until the soil balls up and crumbles without any water squeezing out. If it doesn't hold together adequately I'll adjust the materials (more compost) until I get it right.
I like a mix with some plasticity as I use a blockmaker rather than flats or plastic for most of my starts. They come in several sizes and the blocks fit into one another in an ingenious way so fine roots are not as disturbed as traditional transplanting. Johnny's Select Seeds carries them. The challenge is in achieving a plastic soil without it being too heavy. I do broadcast some seeds densly in flats and transplant later (parsley for e.g) to save on space under the lights.
For fertility I rely on my good compost and soil, and use kelp, fish bonemeal, foliar fish and have used bloodmeal in the past but have given this up.
I've started my seedling under florescent lights hanging from ropes on tiered shelves... . but I like the idea of this simple design and may set up this system. Its important that air circulation isn't compromised and that the room is warm to maximize quick growth. Once the early starts: onions and leeks are up, healthy and have a few inches of growth, I'll transfer them to the hoophouse to free up space for brassicas, parsley, basil, tomatoes, etc, under the lights. The hoophouse in march and april will keep the killing frost off of the hardier starts and provide warmth for growth when its sunny. I'll start lettuce right in the hoophose.