I remember vividly seeing on television the literally earth-shattering images of the Mount St. Helens volcano erupting in the United States in 1980. This gigantic explosion caused the collapse of a large portion of the mountain together with the ejection of millions of tons of volcanic dust which settled over eleven US states. In the immediate vicinity a wasteland was created with the land buried in a massively destructive deep layer of ash, however in further outlying agricultural areas, some remarkable effects were reported from a lighter deposit of the rock dust. Farmers noted a huge increase in yields — even to the extent that abandoned and unproductive orchards suddenly started producing viable crops again.
What had happened as a result of the eruption was nothing short of a natural ‘re-mineralisation’ of the land. For thousands of years peoples have settled on the slopes of volcanoes (sometime with disastrous results, as in Pompeii) due to the exceptionally fertile and productive soil, rich with minerals and trace elements. Glaciers are another natural method by which soil was created and made fertile. During the last ice age the crushing action of ice on volcanic rocks ground away the strata to produce many deep rich soils, that still feed human populations today, 10,000 years later.
For those of us who grow substantial amounts of our own food, keeping the soil replete with macro and micro-nutrients (or trace elements) is an important way of making sure that we also ‘mineralise’ ourselves for health and well-being. A tiny but very significant percentage of vegetable and fruit crops is made up of minerals, but most modern fertilisers replace just the basic NPK (Nitrogen, Phosphorus and Potassium), neglecting the vital trace elements, such as magnesium. The taking of crops from the land without efficient replacement of these nutrients, together with natural leaching from the action of weather, means that many soils are now nutrient deficient, which in turn implies that the whole food chain is similarly depleted.
Recently I discovered that rock dust can now be obtained that does the job of a ‘mini Mt. St. Helens eruption’ when spread on the soil — it puts back the mineral goodness that plants and ourselves need to thrive.
In the spring I top-dressed a bed for my maincrop Kestrel potatoes using about a handful per sq.m of rock dust, raked in prior to planting. I did see a very noticeable increase in plant health and vigour — the tops appeared ‘super green’ and lush, but the yield from one root, at well over 2 kgs, I thought was definitely impressive. Next spring will see me ‘dusting’ the kitchen garden once again!