I am curious to know if I should do a soil test to understand the level of nutrients that my vegetable garden contains and the possibility that I may not be replenishing the nutrients used by my plants each year. What type of cost am I looking at? I do not necessarily have a problem with the soil just yet but I do notice that yield has been somewhat down over the last 2 years even though I have been adding bags of cow manure. I am not adding any chemical fertilizer and I do not till over the dead plants. It started off 7 years ago as grass on a clay type soil bed, but over the years of tilling and adding top soil, manure, wood chips at one point, it has become much better. I stopped using the city of Toronto compost because I heard that they use the dead leaves and those leaves give off bad chemicals, not sure if there is truth to that?
By and large, in addition to adding nutrients to the soil, application of manure and other animal byproducts (bone meal and blood meal, for example) add organic matter to the soil, which improves soil texture, nutrient retention and release, and supports beneficial microorganisms. However, it is possible to overdo it.
You don’t tell us the size of your vegetable plot but do say that you are adding “bags” of cow manure. It is possible that this has led to an excess of phosphorus in the soil. Excessive soil phosphorus reduces the plant’s ability to take up required micronutrients, particularly iron and zinc, even when soil tests show there are adequate amounts of those nutrients in the soil.
Therefore, you are right in thinking it’s time to have your soil tested. A reliable facility for testing is the University of Guelph. They supply a variety of services on their web site, which is here.
Note that many organizations are not in full operation currently due to the COVID 19 crisis, so it would be a good idea to call the lab before taking and packing up your samples.
With respect to using Toronto’s compost, note that actually, fallen leaves are an ideal component of both large-scale and backyard composting. For a comprehensive guide on making your own compost, see our Gardening Guide on the subject here.