We think of the word "chemical" in a negative way, unless we work in the industry. Yet even without a periodic table or large fertilizer makers, our preindustrial ancestors knew that soil needs certain things to be productive. Where they got them is another post, but here, for a start today, we need: nitrogen (from compost, green manures, animal manure, or fertilizer), potassium (from lime or ash, usually), and rock phosphate (a mineral).
It's easy to confuse the last two. I found a site providing the basic explanations, as well as where they come from. I think we'll be hearing more about phosphates soon; the trade war between the US and China may endanger supplies of this important additive for fertilizer. The US has some domestic production; all comes from mining.
I would love to find a sustainable, locally available substitute for rock phosphate. It's the missing ingredient in sustainable gardening. Luckily, I have chicken manure handy. When composted, it's a viable substitute, and there are others. These won't work on many large farms, but they provide a godsend for gardeners. Good compost seems able to provide all of the "big three," if it's the right mix of green materials (food scraps) and brown materials (fallen oak leaves, say).
Some plants, like nightshades (peppers and tomatoes in my garden) need a boost of rock phosphate annually. I provide it with a product called green sand, which is just what it looks like. As a mined rock, it's not sustainable. Yet a little seems to go a long way, so my current bag is only the second I've bought in 12 years.
We avoid other bagged commercial fertilizers on our farm; any left from my in-laws got spread broadly and thinly, to be rid of them. They are junk food, in many cases. Our goal is to build good soil longterm, using rotation and amendment and minimal tillage whenever possible.
So as we get ready for Spring gardens, what are you doing to get the soil ready?
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