I am currently using Basalt dust from a local quarry. I started last year with a dust that was reported to me to be 90% thru a #200 mesh screen. I added 1/3 lb /sq ft with my regular amendments of home made compost, dolomite lime and an organic seed meal fertilizer. This year I added another 1/3 lb / sq ft of a reported 50% thru a #200 mesh screen. So I'm up to 2/3 lb/sq ft. I'm proceeding with caution because I am in the continuing process of researching the use of using rock dust. My main interest is increasing the nutrient density and improving the taste of the food I grow. I do not use any chemicals in my gardening. My experience so far is that I believe that I am growing the best tasting vegetables I have ever grown. I routinely have other folks who I give produce to say that it is the best tasting produce they have ever had. Although I have no scientific proof that my yields are higher than before the rock dust, they continue to be excellent. My earthworm population continues to increase. I have run a controlled experiment with a small sample of 2 sets of tomatoes and believe the rock dust amended tomatoes were superior. However the sample size was too small to be conclusive. I'm very encouraged by the results so far. And by the way, I have picked up about 1800lbs from the quarry so far for free.
I started a thread on this forum called soil building for nutrient density which I will be updating shortly.
Glenn
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