Granite as a source of micronutrients

John Lonsdale
Tue, 08 Nov 2005 20:36:02 PST
Quickly Googling 'granite micronutrients' revealed the following:

Granite meal (Also called granite dust) 
Ground granite. 3-5% potassium, 67% silica (sand), and micronutrients. Slow
release. One application can last 10 years. Improves soil structure.
Broadcast 10 lbs. per 100 sq. ft. on soils low in potassium, 5 lbs. on soils
with moderate potassium, and 2.5 lbs. on soils with adequate potassium. Rake
into the soil surface. 

Granite Meal 0-4-0 Micronutrients Very slow release of phosphorus. Will
build up reserves in the soil.

granite meal (high in K, plus micronutrients);

Crushed Granite 0 0 5 Contains 67% silicas and 19 trace minerals. Slow
release over a long period of time.

Micronutrients:  A low level of boron (B) should be corrected with about 5
to 10 lb borax per acre (2-4 ounces/1,000 sq ft) - no more, as some crops
are sensitive to too much B.  For other micronutrients, moderately low
levels can be amended with good compost, seaweed meal or rock powders such
as granite dust (check label for micronutrient content).  

Remember these are micronutrients we are talking about.  You don't have to
see big chunks dissolving to achieve physiologically relevant concentrations
of micronutrients.  Of course all of the above and more are subject to the
usual physical parameters that will modify availability.


John T Lonsdale PhD
407 Edgewood Drive,
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