Using Stone Dust?

[AlittleSalt]

Autumn is here now, so I've been thinking of ways to amend the soil in our main garden and the other beds (Raised and not raised beds). Being that I am a retired/disabled 7th generation Stone Mason, I have a tile saw and a much larger brick saw with a diamond blade. I am wondering about using stone dust to add to the soil?

The stone types I have huge piles of are:

Limestone (Both cut stone and natural)
Sandstone that are from the property we live on
River Rock from the Brazos and smaller rivers nearby
Chalk Rock
Various assorted varieties of ledge stone and sedimentary types

I'm wondering if you guys might know about using stone dust as a way of adding trace elements/minerals/etc. ? Any info shared would be great.

[salix]

I have often wondered the same thing - I have always used a bit of the glacial rock dust with my fall amendments. My neighbour is a stone carver, and now I get pails of "exotic" stone/rock dust. So far it hasn't caused any problems, the garden improves every year. I wonder if the limestone and chalk rock would cause any pH problems if used in excess.

[drew51]

I try to add different minerals also. Once in, they stay for years, so no need to add more. I try and add something different every year. Azomite, rock phosphate, green sand etc.
My soil is already basic, so adding limestone is not needed. If added I would counter with adding peat to any added compost, or add sulfur and/or iron (iron-tone) too.

[mensplace]

Not by any means a geologist, but had been told many years ago that it totally depends upon the type of rock dust being considered. Apparently some of the harder rocks would take a long, long time before their various mineral components would weather and break down enough to be rendered usable for any plant use other than providing any benefit other than drainage and loosening of the soil. Even the softer ones have to be almost like a powder and even those may take a year or so.

[drew51]

Most rock from saws is a powder, and commercial products are too. Yeah about every 5 years I test my soil to see if I need to make any adjustments. For me long term is exactly what I'm looking for. I have to use sulfur for my blueberries and understand it takes 6 months to a year to work. I prep new beds a year in advance of adding new plants. I waited 30 years for a cactus to flower, so a year or two is no big deal.
Even compost takes a year to break down, part of gardening.

[mensplace]

My early quest took me to local quarries where they had tons of granite and marble dust. It was there that their representatives told me that I was free to get all I wanted, but that it takes hundreds if years for anything but the very finest powder to be usable by plants. As I said, I'm no geologist, but also know that many scientists question the cost versus benefit of some of the rock dust being marketed as miracle blends. Obviously, that is not to say that it includes all rock dusts or all situations. There are many soils and applications that would benefit from the right mineral formulations, while others are more suited for things like drainage.

[Redbaron]

It depends. I know "depends" is a lame answer. But in this case it is the truth. Nearly every soil on the planet has every nutrient needed for healthy plant growth, almost without exception. However, the nutrients may not be bioavailable. Or as soon as becoming bioavailable, may leach away quickly.

You need both a healthy free living bacteria and other soil microbe population and a large amount of fully decomposed and stable humus in the soil to insure that #1 the microbes can turn the non-available minerals into bioavailable minerals, #2 you have plenty of humus to adsorb the released minerals. What defines a healthy population and what defines the required % of humus varies according to the soil parent material. Adding parent material that releases minerals relatively quickly and easily (rock dust, rock phosphate, green sand, etc......) does mean that a generally lower bioactivity is required to meet the plants needs. So on the one hand it can help. On the other hand if the bioactivity of the soil is high enough, adding these things will show no improvement at all. And in cases where the bioactivity is very low, and/or the leaching rate very high, even adding these things won't be enough.

So there are 2 ways to attack the problem. Mineral supplements like rock dust and fertilisers, or feeding and maintaining a healthy soil food web. Or maybe a bit of both.

[drew51]

A good example for using rock dust, or say azomite. Here in Michigan we are very low in selenium. Horses have come up lame due to deficiencies. They were fed on local food. So no matter how many bacteria, if activity is low or high, if you don't have it, you don't have it.
Also IMHO you would have to work hard to keep bacteria low, the soil is so full, and they can reproduce fast (some bacteria produce 1 million generations in 24 hours). And this you can consider a professional opinion since I used to be paid to grow bacteria. If you removed all matter on earth except that of bacteria, you would still see outlines of everything on earth. Buildings, plants, people, etc.
We have more bacteria in us than actual human cells. Not just a few more, 10 times more.

As far as the many statements I have seen about chemical fertilizers killing bacteria, well this is sort of a spin on the truth. If I add sulfuric acid to my plant water for blueberries, the bacteria that convert sulfur to sulfuric acid do decrease. They have nothing to eat! But as soon as I add sulfur the population explodes. Same thing with NPK too. To claim it is harmful to use chemical fertilizers is spinning of the truth. Yes it does decrease populations, but it's easy enough to increase them, just feed them. No doubt using chemical fertilizers exclusively will have a negative effect on the soil, and will deplete soil of nutrients. But using them in con★★★★★★★★ with organics most certainly will not deplete the soil.

[drew51]

I'm no geologist either but I would not give much weight to opinions on bacterial metabolism from geologists. Well he would know some, but best do your own research!
I thought this was an informative article
http://onlinelibrary.wiley.com/doi/1...tb00494.x/full

This one is good too
http://mic.sgmjournals.org/content/156/3/609.full

[creister]

Based on where you live, your soil is alkaline. I would not add limestone, chalk, or any other alkaline rock. Check out dirtdoctor.com.

[Cole_Robbie]

Relating to bacteria, I've seen greenhouse and farm equipment sold to inject chlorine into the irrigation water. Is the idea in that situation that the bad bacteria must drastically outnumber the good? I would have thought the chlorine would be bad for plants.

And back to the thread topic, I think guano deserves a mention along with rock dust. The mined deposits are petrified and sometimes hundreds of years old. They break down slowly in soil, similar at least to rock dust.

I've used greensand and bat guano before. I want to try being organic next year, which will entail adding rock phosphate and probably azomite as well.

[moray-eel-bite]

Originally Posted by drew51

Also IMHO you would have to work hard to keep bacteria low, the soil is so full, and they can reproduce fast (some bacteria produce 1 million generations in 24 hours). And this you can consider a professional opinion since I used to be paid to grow bacteria.

This is not true. If you meant millions of individuals then that is possible, but the fastest generation time of any bacteria I'm aware of is about 10 minutes. 24hrs*60minutes/10minutes/generation = 144 generations... which is very fast for bacteria. The average is closer to 60 minutes or so and can be thousands of minutes.

[AlittleSalt]

Originally Posted by creister

Based on where you live, your soil is alkaline. I would not add limestone, chalk, or any other alkaline rock. Check out dirtdoctor.com.

Yes, Alkaline. In our main garden, we use a meter that shows it to be at 6.8 PH. However, there are areas outside the garden with no soil amendments that I have tested at 5.5 PH

I'm going to send in a soil sample to Texas A&M to have it correctly tested this Fall.

Looks like I've got a lot of reading to do. Thanks for all the replies everyone.

[moray-eel-bite]

Originally Posted by AlittleSalt

Yes, Alkaline. In our main garden, we use a meter that shows it to be at 6.8 PH. However, there are areas outside the garden with no soil amendments that I have tested at 5.5 PH

I'm going to send in a soil sample to Texas A&M to have it correctly tested this Fall.

Looks like I've got a lot of reading to do. Thanks for all the replies everyone.

6.8 and 5.5 are actually slightly acidic, not alkaline. The 5.5 areas could use adjustment for most veggies but a Texas a&m test is where I'd start before monkeying.

[AlittleSalt]

Originally Posted by moray-eel-bite

6.8 and 5.5 are actually slightly acidic, not alkaline. The 5.5 areas could use adjustment for most veggies but a Texas a&m test is where I'd start before monkeying.

You are right. I meant acidic.

Having to take meds for pain stinks.