posted 11 years ago
I'd suggest taking a second look at rock dust. During the Great Depression, we lost most of our topsoil, and it keeps getting degraded. That topsoil had glacial rock dust from the last ice age already in it, but even with that richness in the soil that's been lost, depending on your location, there's wide swaths of mineral deficiencies in the soil.
Part of my family is from the Great Lakes region, which used to be called the goiter belt. My great grandmother died tragically young from a goiter caused by iodine deficiency, in a way that had negative implications for three generations of my family. There's an entire region of soils with insufficient iodine in them. In the south, there's another band of soil that's deficient in selenium. A hundred years ago, White Muscle Disease was an issue- perfectly healthy children would drop over dead, and horses would as well. Not enough selenium in the soils for proper muscle development.
With the advent or railroads bringing in out-of-season (and out-of-region) produce in the 1890's and the development of the non-local, big agra foods, as well as aggressive supplementation of certain types of foods (Iodized salt, vitamin D enhanced milk), these problems just aren't a problem anymore.
However, if you're trying to grow most of YOUR food on YOUR land... if the underlying rock beneath your feet lacks these minerals, so will your plants, and so will you. It takes very little, really, to get more minerals in your soil, and it makes an enormous difference to the health of your soil, from the microbes to the trees.
I get some of mine from a place that makes granite countertops. They have a water jet system (you don't want the dust if they have an aluminum saw, you'll get too much aluminum in your soil), and they just throw out the dust. I bring them baked goods, they save the dust for me in a bucket. It's fantastic stuff, I've used it to bring nearly dead fruit trees back to life.
Rock dust and other mineral fertilizers really are one of the most sustainable ways of improving soil, even for large-scale farms. You don't have to apply that much, that often, and if you practice good cultivation techniques and don't let all your topsoil run off into the ocean, but mulch/compost/use permanent crops, you'll end up with fantastically healthy soils forever. I did some calculations on the soils at my old place, and if I recall correctly, I would need to apply rock dust every year for 5 years, then once every 5 years for another 3-4 times, then once a decade from then on to completely fix my soils.
Given that my house was on old farmland that was gutted during the dust bowl (local records suggest somewhere between 4-8 feet of topsoil lost), I figure it's just putting BACK most of what the soil lost in the first place. I just make sure that I get my minerals from places far enough away from the underlying rock of my location that it'll fix the micro nutrient deficiencies I probably have (selenium being the big one, probably vanadium too).
I am a super research nerd. Any advise given is worth precisely what you paid for it. Your mileage may vary, proceed at your own risk, I could be full of poo and completely wrong, feel free to ignore me completely.