A soil test would certainly be helpful, and they are inexpensive (stick with the field test, should be <$10). I would not try to plant clover without one, but you could do OK if you stuck with annual grasses (oats, winter rye, winter wheat). Oats and winter rye in a mix would be a great option to plant in late summer as you are planning. I would buy seed, fertilizer, and supplies from a local farm/garden supply store so you can ask questions and advice locally. Here are some places that do soil testing for Ontario soils http://www.omafra.gov.on.ca/english/...e/soillabs.htm

I have not heard of northern harvest products.