The Bluegrass Blog

Pass the Basalt!

Posted on January 29, 2018

Using rock minerals to improve carrot flavour and nutrition at Bluegrass Farm. 

“The ‘green revolution’ in Asia provided impressive steps forward with regards to food production, but in recent years the rate of increase has slowed down considerably… It is important to note that the external inputs for higher crop production, such as fertilizers, pesticides and herbicides, are reliant on non-renewable fossil fuels… Their energy-intensive production and shipment around the world is, in the long run, not sustainable.  In addition, many of the high external input practices in the green revolution have been environmentally not very sound, and are in fact far from ‘ green’.  We require practical, low-cost and result-orientated long-term strategies that address the needs of farmers and the need for better and long-term care of the land.”  Peter Van Straaten, 2006.

Peter Van Straaten (University of Guelph) is credited as being at the forefront of soil remineralization and agrogeology to improve soil and crop quality.  A review of rock minerals as fertilizers was written by Eliot Coleman in 1975. Coleman concludes that selecting the right rock mineral for a particular soil, applying it at the appropriate rate, and utilizing particles that are small as possible will lead to improvements of agricultural crops.  There are now organizations such as Remineralize the Earth working on education and knowledge transfer and companies like Rock Dust Local (Vermont) who specialize in the sale of a wide variety of rock dusts.

In 2017, we conducted a soil amendment research study on carrots at Bluegrass Farm. The goal of our study was to determine if different soil amendments could improve the flavour and nutrition of carrots. We applied three different kinds of rock minerals to the soil on different plots, and then harvested and tested the carrots for Brix levels. We also invited our winter CSA members to participate in a blind taste test by providing them with all three carrot types in bags labelled A, B, and C.

Our three soil amendments were Spanish River Carbonatite (SRC), Wollastonite, and basalt. All three are naturally occurring rock deposits. They are considered broad spectrum multi-nutrient rock fertilizers since they contain over fifty different elements at trace levels.  Table 1 provides a detailed breakdown of the available nutrients found in the three different rock minerals.

Table 1. Percent content of selected elements in our multi-nutrient rock minerals.

Spanish River Carbonatite (%) Wollastonite (%) Basalt (%)
Phosphorus 0.3 0.1
Potassium 0.78 0.1 2
Magnesium 1.3 6 3
Calcium 20 16.5 5
Iron 4 2.2 7
Silicon 27 25


To assess nutritional value, we measured the Brix levels of juice from carrots grown in each plot. Brix is a measure of the amount of light that is refracted (bent) while passing through a fluid. High brix readings in plant juices are often used as a surrogate for greater nutrient density, as Brix is a sum of the sucrose, fructose, vitamins, minerals, amino acids, proteins, hormones, and other solids.

Carrots from our control group (no rock minerals applied) had a Brix level of 9. “A” carrots (Spanish River Carbonatite) had 9.5. “B” carrots (Wollastonite) had 9. “C” carrots (Basalt) were the highest at 11.

Table 2 illustrates our CSA member votes on their favourite tasting carrot.  While the results were mixed, indicating that taste is a subjective quality, overall our CSA members identified “C” carrots as having the best tasting or sweetest flavour, followed closely by “A”. Of the three rock minerals, basalt contains the highest levels of micronutrients and trace elements. This may have resulted in higher Brix levels, and may be reflected in the carrot taste testing.

Table 2. Survey results from CSA members with ranking of A, B and C carrots. (Some participants only ranked their first choice).

1st 2nd 3rd
A (SRC) 7 6 3
B (Wollastonite) 3 5 7
C (Basalt) 8 3 4


The photo below shows a taste test completed by one of our CSA members and his one year old son, Jason and Jacob Garlough.  As Jason put it: “Length of carrots were equal at start of experiment so the deliciousness factor is inversely related to their ending length below.” It appears that C is the clear winner in this highly rigorous taste trial!

Another CSA member, Anita, shared this photo from her son David, who took the carrots to his Grade 2/3 class to share the taste test.  These are the class’ tasting notes for carrot ‘B’, but note that their top pick was also ‘C’.








Overall, we feel that there is a need for more holistic soil science, where we consider the role of micronutrients not just on plant yield, but on plant nutrition, soil microorganism activity and human health.  For too long, there has been too much emphasis on nitrogen, phosphorus and potassium for crop yield.  There is an urgent need to remineralize the land with micronutrients and trace elements that play critical roles in the agroecosystem.

We continue to lose quantity and quality of soils around the world through current agricultural practices.  As a result, studies have shown a reduction of elements and nutrients in our food by 14-37% (calcium, phosphorus, iron, potassium and vitamins) (Davis et al., 2004).  Our goal for organic agriculture is to produce nutrient dense foods in an ecological manner that will sustain and improve human health.

Rock minerals are cost effective, slow release, and readily available.  In contrast to conventional chemical fertilizers, rock minerals offer a low risk of groundwater contamination and are compliant with the organic production regime.  Our initial experiment has shown enough promise that it is worth further investigation of additional rock dusts on carrots and other vegetable crops at Bluegrass Farm.  (This experiment focused solely on carrots; other crops have different nutritional requirements and may benefit differently from various rock minerals.) Our research was limited due to financial constraints, however, a detailed nutrient analysis of our soil amended carrots would allow us to better understand what nutrients are moving from the soil to create better tasting and more nutritious carrots.


This research would not have occurred without support from Achillea Endeavours, Ottawa, Ontario.

Thanks to our CSA members for eating their veggies and conducting scientific trials at their dinner tables!


Coleman, Eliot.  1975.  The use of ground rock powders in agriculture: A survey of the literature on granites, feldspars, micas, and basalts.  Small Farm Research Association.  Harborside, Maine 04642

Davis, D.R. Epp, M.D., Riordan, H.D. 2004. Changes in USDA food composition data for 43 garden crops, 1950 to 1999. Journal of the American College of Nutrition. 23(6):669-82.

Van Straaten, Peter.  2006.  Farming with rocks and minerals: challenges and opportunities.  Annals of the Brazilian Academy of Sciences. 78(4): 731-747


By: Bradley Wright, B.Sc., M.E.S., Bluegrass Farm