Does rockdust really work? Do your vegetables grow bigger for using it?
These are a few things which need to be discussed about the use of this so called "miracle dust" which will transform your garden, although rock dust has been used as a growing medium over thousands of years. The first thing I needed to establish was whether it is another expensive scam, or will it work as well with your veg as the advertisers say it will.
Well I used 3 x 25 kilo bags of it on my plot last year (Autumn of 2015 ready for the Spring of 2016) but I sieved it instead of just spreading it all on the garden. It comes in 25 K bags and is not quite what I had been led to believe as it is not really "dust" so much as dust mixed with up to 6 mm gravel - about half and half really. After some thought I dug the remaining gravel in later on.
Did rockdust work for me?
Well not that I could see, although I have had a phenomenal crop of runner beans this year (2016), as nearly everyone else did, but our crop of onions has been dreadful - a huge disappointment.
However, I still firmly believe that rock dust will work and make your veg extra large and show quality too, BUT, and there is always a big BUT with things like this - you need so much more of it in your soil over time that it may well not be financially viable. A few bags of this stuff will make zero difference to your crop as far as I can determine.
An example of why it will work if you can lay enough down is shown anywhere in the world where there is a volcano. Iceland is a perfect example as are parts of Japan where there are countless active volcanoes which are constantly billowing this dust into the air daily. The result being that gardens and allotments in the surrounding areas produce fantastic sized crops every year, and they do not need to dig anything else into their soil/dust mix.
You know as much or more about volcanoes as I do so you will know that an active volcano will blow it's dust high into the air for it to drift on the wind until it lands on the the ground which it then makes more fertile over time. The ash you see in the photo is what contains all the trace elements to keep your garden going - if you can get it at a reasonable price.
The words "over time" also have to be taken into account because I believe that time is a crucial element in the equation. Ground near to an active volcano will have had rock dust dropped on it for thousands of years, and that is a timescale which is impossible for us to replicate, but if you plough enough of what is essentially a waste product for quarry owners into your garden I'm prepared to believe that you will get some seriously good results.
However, my opinion, for what it's worth is that it is not financially viable to use it. Personally I live roughly 15 miles from a quarry in Derbyshire which sells rockdust in 25 kilo bags for just over £4 each, and I think this is the cheapest you will find it anywhere and if you wish to contact them their number is:
Tel: +44 (0)1629 636500 (Derbyshire Aggregates)
Mentioning my name won't get you a discount I'm afraid as I have only visited them once so they won't know who the Hell I am.