Interesting there are three forms of nutrients currently obtained directly from rocks. Magnesium and Calcium are supplied by ground dolomite ( sometimes sold as dolomitic limestone) Calcium from ground limestone. Phoshate from ground phosphate bearing rock ( sometimes sold as green sand). Ground basalt can also supply quantities of Magnesium and some Calcium. depending on the rocks composition other elements like iron, zinc, sulfur may be available is smaller quanties. None of them are complete within themselves, which is why commercial fertilizers are processed and mixed. The basic premise is sound, nutients do need to be replaced, or soil amended if it never had the nutrients to begin with. Potassium is also mined, primarily in Canada, New Mexico, Utah. It is an ore left from the evaporation of receding seas. Processing is needed because in its natural state it is mixed with sodium chloride ( table salt). Withe exception of nitrogen which is today made mostly from Natural gas. (use to be the fossilized Chilean bat guano) most of todays commercial fertilizers are processed from rocks or ores.

Ground or powdered rock consists of various minerals, depending on the source of the rock, and is useful as a fertilizer. There is nothing new about that. The first two articles hype that simple fact.

I buy 40 lb. bags of rock phosphate, green sand, limestone and gypsum from my local garden store at a very reasonable price. I bring it home in my car. I would not like to pay for shipping rock from Scotland. Feathers maybe, but not rock.

Rock powders are not very soluble. Their minerals dissolve slowly over a long period of time. Rock phosphate is rich in phosphorus. Green sand has lots of potassium. Limestone contributes calcium as does gypsum. Dolomitic limestone has both calcium and magnesium. Since all of these are unrefined rock, they contain a variety of other minerals in lesser amounts.

Soluble fertilizers are useful for giving a quick boost of minerals when necessary. Granulated or powdered rock improves some soils, especially the less fertile ones such as my sandy soil, which is made up mostly of inert grains of silica. There's nothing exotic or magical about it and it doesn't need to be expensive. Rock is the most abundant substance on earth. :)

Jim

Ha! Looks like Farmerdilla and I were posting at the same time. It think our posts are basically in agreement.

Jim

Let me add two inorganic things that one could use, following a soil test.

The first is wood ash, which is approximately 50% Ca, and contains several to few percent of Mg, K and P. Basically, when you burn wood all the N goes up the chimney, and roughly half the P goes too. Everything else stays in the residue.
Percentages will vary because no burn is equal (that is, variable amounts of carbon are left, skewing the percentages by weight). But basically, if you have wood ash, you will have to add N and some P. Every other micronutrient (manganese, copper, zinc, iron) is in there.

The other thing which I do not see used as fertilizer, but should, is iron slag, the residual from turning iron ore into iron metal. It looks and feels like concrete grit. Obviously one needs to make sure the foundry is not smelting, say, lead as well. iron slag is also mostly Calcium (about 50%), and also rich in micronutrients, though not as much as wood ash, specifically not as rich in K. But It is very cheap and very slow release too, so a good solution if you have specific mineral needs at your site.

The link is a complete load of crap.

In the first 10 seconds of reading it states obvious crap. A couple who transformed the infertile soil of their Perthshire croft by adding rock dust to it have developed the process into an export business

This is the first warning shot, people are making money from their information/product. 'It's been said that we need to eat five apples to get the same nutrients we used to get from one apple 40 years ago. But when we had one of our carrots analysed and compared with a shop-bought one, it had 10 times as many nutrients.'

This is an often repeated, but completely baseless claim. Today's produce is not nutritionally deficient. This is one of those ignorant ideas that says since modern ag uses synthetics instead of just organics the resulting produce is somehow less nutritious. Complete bunk. Produce is like a human fetus. It takes what it needs and if it kill the mother/land doing so it doesn't care. Today's produce according to every scientific test I have seen is comparable to that produced 50 years ago. Cameron Thomson said using rock dust mimics the earth's glacial cycles. 'Modern soils are relatively barren and artificial fertilisers are needed, but rock dust accelerates that natural weathering process,' he said.

This claim is true, but deceptive. Any means of providing adequate crop nutrients capable of sustaining the plant to fruiting will produce edible fruit of good nutritional quality.

I've used a product called Glacial Rock Dust, which as you would expect is ground up rock dust left in the wake of glacial activity. I used it hoping it would provide a broad spectrum of minerals, and it was much cheaper than my other choice which was Kelp Meal. I can't say that it has been working or not, simply not enough time and experience. But I've decided that Kelp meal isn't so much more expensive when you consider how much more rock dust is required and how much more Kelp Meal is in one pound.

My gardens go back 65 plus years. After this experience, and a heck of a lot of reading, I would suggest that we add far too much "stuff" to our dirt. P and K in the soil are used very slowly and a little goes a very long way and the surplus is usually washed out into the environment where it is not needed, leading to a lot of bad results. Nitrogen is the only one of the big three that needs regular, substantial replacing in the typical vegetable garden. Trace elements are just that: present in small traces and maintaining them does not require outlandish, expensive efforts. Check with the local branch of your state university, get a soil test, and save yourself some time and money, and end up with better vegetables as well.

Pretty good post by sconticut. That's the way it is. For everything except N, fertilize once during the lifetime of the garden. I do add wood ash every year but it is more of a pH matter (my soil, unamended, has a pH of 5.5).

What you have to add to the soil surely does depend on where you are. In high-rain areas like the PNW, calcium and magnesium leach thru the soil quite rapidly and need replacement. In addition, the soils here tend to get acidic so the addition of various limes is recommended for growing vegetables. However, our soils are quite naturally rich in potassium which never needs to be supplemented. In fact, I worry more about too much potassium than too little.

It all boils down to the fact that, after many decades of agricultural research, plant nutrition is well understood. There is nothing mysterious about the chemical make up of rocks and the appropriate uses of various kinds of rock dust. Any claims made for a particular rock dust, if they are made on the basis of some supposedly magical, mysterious, mystical or miraculous properties, are hokum.

Jim

Soil tests are cheap and readily available almost everywhere. Here in NC they're free...well, our tax dollars pay for it.

Indiscriminately adding something to your soil can do some bad things. More often than not the "bad thing" is totally wasting your money.

Woodash is not organic?

Technically yes, It is composed of all inorganic compounds. as are the rocks and ores discussed here. "Organic" gardening is a new use of the word, basicly meaning natural, but again a fine line to walk. Wood ash is approved for use by "Organic" gardeners but the processed components are not.