I have no idea whether my soil is depleted by over-use of chemical fertiliser as the second occupant of this property, who lived here for sixty years or so, and was apparently an enthusiastic gardener, died in 1999. He might have been a keen composter, he might not. What I do know is that his successors imported a load of topsoil to create a new border, filled it with plants and then did nothing for six years. I have incorporated loads of well-rotted manure and will continue to do so, but that may not be enough, I don't know. Some of the plants suffered last summer but then it was very dry and they are all pretty young. Because I garden organically and we have a problem with foxes (so no blood/fish/bone), there is not much available to us in the way of fertilisers. An obvious alternative is seaweed meal (or calcified seaweed but I am concerned that it might raise my soil pH).

As for soil-testing, well, it is likely to cost more money to test my soil for trace elements - which would involve sending off a sample to a lab, as the kits you buy from the garden centre don't cover these - than buying a few bags of Rockdust or seaweed meal, and if the soil test told me that I needed to add trace elements, then I would still have the expense of buying the powdered rock.

If a soil test tells you to add something, I would strongly recommend you don't add some expensive product that won't even tell you what it contains. Do you even know if it is is alkaline or acid? Here's a quote for you: "it contains a natural balance of lime", how can they know what is a healthy balance of lime without knowing what your soil is like? Its not even truly organic (in the sense of being sustainable), its mined! Here's another quote for you: "SEER Rockdust is freshly crushed volcanic rock from Collace Quarry in Perthshire, Scotland." Please don't be taken in by their frequent mention of the word "organic", because they aren't. Basalt is allowed by the Soil Association only by written permission and with a special justification.

The one thing that rock dust will not supply, and I can guarantee this, is nitrogen. Much maligned by the trendy modern soil fetishists, it is still the single most important nutrient for plants. Your composted manure provides that plus a wide range of minerals and trace elements, in balanced quantities :)

If you really want to go ahead with some powdered rock, and some soils will certainly benefit from added basalt, check for a more local source. Quarried basalt dust is a waste product and is available for around thirty quid a ton delivered, or bagged for about a pound a kilo. The exact chemical makeup of basalt varies with location but expect any basalt to be a mix of calcium, sodium, magnesium, and iron silicates, relatively inert and, if anything, acidic although several remarks on the SEER pages imply that their dust is alkaline.

Chill, chill. Gardening's supposed to be a relaxing, pleasurable hobby. It doesn't matter if it's not perfect. You don't have to change the world one garden at a time, though every little bit helps, I guess. It would help the most if everyone just used home-made compost on their gardens and grew what was willing to grow in it. Which is usually most things.

On the other hand, if home-made compost has not ever been added back to our garden - and I have no reason to believe that it has - then it would not be surprising if the soil were depleted of nutrients.

And, if the restoration of nutrients reduces the amount of watering I have to do in summer - which has been the experience of the Thomsons - then that would save me a lot of time and trouble (and indeed expense - given that last year I had to buy and run an electric pump to empty the contents of my daughter's paddling pool over my borders to stop the plants from dying).

All in all, I think I will add some seaweed meal and see how I get on with that (plus home-made compost plus well-rotted horse manure).

Here we are talking about a very wide spectrum of minerals and trace elements, in a highly absorbable form.
One such that is known to be deficient in root-crops grown in Norfolk (where many of our carrots come from) is Selenium.

And it isn't just about what the plants want to take-up, its as much about the ability of the soil's micro-organisms to support plant and root growth. The Russians did a lot of research into root chemistry and biology this during the post-war years, not able to afford the massive quantities on NPK style fertilisers being used more & more in the West to retain crop-production.

I also don't think its the deplection of trace elements by use of chemical fertilisers as much as the depletion by repetitive growing of crops that take them out, many now residing deep in cemeteries or long since washed out to sea. It is known that Nitrogen sufficiency is extremely important of course, but far from the sole arbiter of healthy & fully nutritious crops... as evinced by the slow dawning that sufficient protein, carboyhdrate & fat were only a very crude guide to human nutrition.

PS I'd like to know where to get volcanic rock-dust at £30/ton delivered (without buying 30 tons!)

Read more:
1. Angus Rock Dust

Minerals – crushed basalt rock dust. We use crushed rock [which incidentally is a waste product at the quarry & would otherwise go to landfill] for incorporating into soils and growing media. This ‘organic’ basalt igneous rock which contains olivine, feldspar and augite is rich in natural plant nutrients (particularly, but not only potassium [K], magnesium [Mg], calcium [Ca], iron [Fe] and sodium [Na]). Although not traditionally recognised as a plant nutrient silicon [Si] is also present in generous levels. The availability of Silicon to plants has been proven to reduce the incidence of disease in crops. We have analysed our rock dust to ensure that levels of toxic heavy metals are extremely low and therefore 100% safe to use for ornamentals and food crops alike. We have looked at rock from many different quarries had them analysed and we use the best and most consistent product known to us.

Olivine [(Mg, Fe)2SiO4], which is magnesium & iron rich, is unstable and therefore breaks down and releases its nutrients. Feldpsars, rich in calcium & silicon, breakdown into clay particles releasing calcium which is essential for cell structure within plants. The clay that is formed during the breakdown of feldspar helps nutrient buffering and improves cation exchange capacity [CEC] of the soil/growing media. Improved CEC enables more efficient use of essential nutrient by the plant. Augite [(Ca, Na)(Mg, Fe, Al)(Al, Si)2 O6] is rich in both magnesium, calcium and iron, another essential plant nutrient used in the production of chlorophyll [the green colour in leaves].
This rock dust when applied to the soil slowly breaks down with the action of weather and microbial activity and releases its nutrient to the soil thus making them available to the plants. It is also noticeable that worms and soil fauna appear to seek out this rock dust and are themselves more active when these minerals are present. This has a double benefit in that firstly the nutrients are released from the rock for the plants benefit, but also the soil/growing media becomes active with soil fauna offering even greater richness to the soil and improves plant health.

It is believed that the presence of Angus Rock Dust in the soil increases the rate of absorption of Carbon dioxide [CO2] from the atmosphere thus reducing the speed of climate change.

Apply Angus Rock Dust as soon as possible. The sooner it is applied, the sooner it begins to benefit your soil and plants. After the first application further annual applications in the autumn are recommended.

Soil based applications
For existing trees, shrubs, herbaceous borders, bulbs, fruit trees & bushes:
• 1st application now @ 2kg/m2 [8 tonne/acre or 20 tonne/ha.]
• Annual applications in autumn/winter @ 500g/m2 [2 tonne/acre or 5 tonne/ha.]
Best applied to soil surface and covered with organic mulch [VermiCompost], nature will take the rock dust and its goodness to the root zone.

For existing lawns & pasture, meadows etc:
• 1st application now @ 2kg/m2 [8 tonne/acre or 20 tonne/ha.]
• Annual applications in autumn/winter @ 500g/m2 [2 tonne/acre or 5 tonne/ha.]
Best applied to soil surface and top dressed with organic mulch [VermiCompost], nature will take the rock dust and its goodness to the root zone
(NB: Use with care on lawns as sand/grit particles may damage cylinder mowers)

For vegetable gardens [all crops]:
• 1st application now @ 3kg/m2 [12 tonne/acre or 30 tonne/ha.]
• Annual applications in autumn/winter @ 1kg/m2 [4 tonne/acre or 10 tonne/ha.]
Best applied to soil surface, but if you are digging then we suggest you double the rate of use and incorporate to a depth of up to 300mm.

Planting of trees, shrubs and root balled plants:
• Back fill with your natural soil and 5% Angus rock dust.

Planting of bulbs:
• Sprinkle 2kg/m2 [8 tonne/acre or 20 tonne/ha.] to the soil surface prior to planting

Preparation for laying of turf or sowing of grass seed for lawns, pasture etc:
• Sprinkle 2kg/m2 [8 tonne/acre or 20 tonne/ha.] to the soil and rake in to the surface.

Compost / Growing media applications
Always use Angus VermiCompost with Angus Rock Dust in non-soil based growing media [commonly, but not always accurately, referred to as compost].

For all crops/plants in all types/sizes of containers mix 5% Angus Rock Dust and 5% VermiCompost with the growing media.
Eg. If using 90 litres of growing media mix in 5kg of Angus Rock Dust and 5 litres of Angus VermiCompost.

Composting
Angus Rock Dust is an ideal addition to your compost heap. Sprinkle a dusting to each layer to encourage speedy activation of microbes and ready to use compost sooner.

For other applications please don’t hesitate to contact Angus Horticulture Ltd’s sales office on 01241 829049 or e-mail them sales@angus-horticulture.co.uk. We’ll be pleased to help. All products mentioned can be purchased in our online shop www.angus-horticulture.co.uk

According to documentation found on the Soil Associations website, ground basalt [Angus Rock Dust] may, with justification, be used in the production of organically grown crops.
Soil Association organic standards:january2009 4.8.9 : Revised "With justification, you may use stone meal, such as ground basalt."
Basalt Rock Dust has also been verified by Soil Association and certificated by Scottish Organic Producers Association [SOPA] and Organic Farmers & Growers [OF&G].

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