Granite dust is more powdery and would contain some trace minerals in an unknown analysis. This could add soil minerals. The finer the dust the quicker it becomes available.

Sand, unless very fine powder dust would not add much nutrients, but can improve drainage and looseness in soil if enough is added, Sand is mostly silicon and if powder adds stalk strength if uptaken in the plant.

For example, limestone rocks are rich in calcium. Granite rocks are rich in potassium, etc. Seaweeds of course are the king of micronutrient fertilizers and soil amendments. There can be up to 70+ trace elements in seaweed. In locations where seaweed is not readily available; rock powders is one answer to the problem.

Research continues to reveal that insoluble tiny particles like rock powder minerals, can be easily digested or absorbed via microbial activity, over time, into the anatomy of growing plants, thriving in the presence of rich organic compost, and other forms of powerful biostimulants like aerobic compost teas.

Obviously a heavy clay soil is very difficult to initially dig, whereas a sandy loam is much easier. Heavy clay soils can be improved considerably by adding a lot of sawdust and mason's sand. DO NOT use beach or river sand! Mason's sand, being crushed granite, has sharp edges and actually loosens the soil.

Al

Think of stirring BBs into pudding. Will a handful of BBs in a quart of pudding make it drain better or increase aeration? NO You can't start with something like peat/compost/coir ... and increase the drainage or aeration by adding a small fraction of granite or any other large particles.

There is SOME benefit in adding these particles, though. They take up space then, that water an no longer occupy because they have no internal porosity. Essentially, when adding particles like perlite and granite to water retentive soils, all you're doing is reducing the amount of water the soil is capable of holding. The up side is that in decreasing water retention, air returns to the soil more rapidly. The down side is the PWT height remains the same ...... unless these large particles (usually in combination with other large particles, like pine bark) are a SIGNIFICANT fraction of the soil 60-100%.

You can learn a lot more about container soils by joining any one of dozens of conversations (or starting a new thread) on the Container Gardening Forum.

Al

Al

According to things I have read lately lack of B causes a lot of problems, more than the land grants typically indicate. The land grants also pay strangely little attention to sulphur, maybe because sulfates are used a lot in conventional ag and/or because sulfur in the air pollution was heavy until 15-20 years ago. Even now in southern Ontario enough sulphur is in the air that it doesn't need to be added to ag soils, but many places now have too little.

So yes, epsom salt can be very helpful.

Al

Kimm, think about this: the building up of soil with OM has various limitations. I have been practicing explicitly just that for a dozen years at various sites. The OM itself can be and actually will be lacking certain minerals depending on the soils it is grown in. If one's general area is lacking macro and micro nutrients, and one's inputs are mostly made up of OM from the area, how are deficiencies going to not occur? For example, around here, as with most leachable soils, B is very low to non-existant. How am I going to build up B without adding imported borax? I think a lot of my problems with insects might be due to this and other deficiencies that are difficult to impossible to correct with my own compost or local OM. Manganese is another, the soils are very low. Where is it going to come from?

Maybe the bio-accumulators can do it, but so far that hasn't worked extremely well for me. Sandy soils especially are probably going to need to be artificially mineralized on occassion.

BTW - I agree with what you said about the limitations involved with depending entirely on OM as a cure-all for everything. OM is important to soil health, but it doesn't guarantee that there will/can not be deficiencies. Too much OM can also be a limiting factor.

Al

Al