Firstly let me say that Basalt rock dust is not a fertiliser. It is not a fertiliser because it lacks the qualifying levels of Nitrogen, Potassium and Phosphorous.
Typical composition table of rock dust
|
Element |
Unit |
|
calcium |
%w/w |
6.44 |
iron |
%w/w |
10.5 |
magnesium |
%w/w |
6.54 |
sulfur |
%w/w |
0.21 |
potassium |
%w/w |
1.25 |
phosphorus |
mg/kg |
3030 |
cobalt |
mg/kg |
35 |
copper |
mg/kg |
43 |
manganese |
mg/kg |
790 |
molybdenum |
mg/kg |
<5 |
zinc |
mg/kg |
92 |
silicon |
%w/w |
21.6 |
Benefits of using Basalt rock dust
Boosts organic soil fertility
Can create bigger, healthier crops, with better flavour and a longer shelf life
When you purchase Basalt rock dust it will be a dark grey to black colour which (when added to soil) rapidly weathers to brown or rust-red due to oxidation of its iron-rich minerals.
However, basaltic rocks exhibit a wide range of shading due to regional geochemical processes, so when crushed the resulting dust may well be another colour entirely - possibly a light tan, but it has the same make up as dark Basalt.
We hear and read lots about the importance of organic farming methods to replenish the soil with nutrients which are lost over time, and adding compost to garden soil, for example, can replenish some of these nutrients.
That is all well and good and is a recognised thing to do but these days the re-mineralisation of the soil, which until recently had not been seriously considered, is becoming known as a necessary step to reintroduce vital minerals and trace elements into our soil