why use rockdust in agriculture?

[piet b]

http://www.remineralize.org has the details ... well, some of them.

[John H]

The reference you give is pretty straight foward. They recommend dust from glacial rock which would be a mix of many different types of rocks (or minerals). Next choice is mixing seashore and/or river rock dust. In short any mix of rock types would give you a good mix of minerals to the soil. These minerals are the building blocks of soil. I think their best suggestion is adding the rock dust to the compost pile. My personal feelings are that the rock would be a reasonable addition to the soil, but I would doubt the value to the soil would justify the cost of the rock dust unless you were talking about soil for the vegetable garden or flower beds. The main type of rock dust used on a large farming system is the dust of limestone used to correct the pH of the soil.

[perthjamesagro]

many many reasons, First to adjust the soil PH(acidity) in the case of lime materials.
Also many types of roocks have been used in the past to add the macro and micro nutrients needed for plant growth like P,K, Ca, Mg, S, Mn,Fe, Cu. These are still used by some farmers now.
Also rock dust could be used to amend soild qualities like pore space and erosion factors

[Bill S]

it is the same principle as volcanic ash used in farm lands

[zipper]

Rock Dust adds minerals to the soil that crops need to grow better and stronger.

[donfletcheryh]

Let us be careful to observe that using rock dust is not universally appropriate. For example, our soil is a thin smear of lacustrian soil over glacial till. In our case the extensive mixture of rock fragments from a wide area brought here by glaciers makes rock dust a moot point.

In an area that gets soil laden flood water, rock dust is unlikely to accomplish anything.
If the available rodk dust is mostly limestone, and your soil pH is high, based on limestone, you would avoid that particular rock dust.

In many places, use of a deep-tillage cultivator can bring up all the rock dust you want. In my own land, it also brings up a lot of rock fragments too.