Our organisation has just completed a study looking at mineral levels of
four vegetables (silver beet, capsicums, beans and tomatoes) to see
whether soil manipulation could improve the nutritional characteristics
of these vegetables. Equivalent vegetables from a supermarket were also
analysed.
The hypothesis was based on the observation that consumers purchase
fruit and vegetables from supermarkets and stores on the assumption that
they are providing them with sound nutrition. They do not necessarily
know the variety or where or how they are grown. Our belief is that
despite its often glossy wonderful appearance food today is not
delivering the range of nutrient elements that it should. The taste is
often very average.
We all know that many factors in the production process can affect the
ultimate nutrition of the crop, ie fertility management, variety, stage
of ripening, post harvest chemical treatment, storage, etc
We concentrated on the production end of the supply chain.
The soil that the trial vegetables were grown on is a degraded volcanic
soil pH of 4.5 low in nutrient elements such as calcium, magnesium,
potassium and trace elements. It is in fact in the last stages of the
weathering cycle with aluminium and iron oxides and hydoxides evident in
the mineral fraction (X-ray diffraction was used to analyse the mineral
components). Analysis indicates that the cation exchange minerals are
scarce (supported by a low CEC in the soil analysis) and humus is low,
meaning that storage of plant nutrients for ready access for plant roots
is also low.
This soil was revitalised with rock dust(basalt) and specific
prescription mineral fertiliser containing calcium, magnesium,
potassium, phosphorus and trace elements, a zeolite mineral added to
increase the exchange capacity and good quality compost added to
increase the biological activity of the soil and to aid in mobilisation
of nutrients from the minerals added.
It should be emphasised that this was not a replicated plot experiment
and the results are only an indication and not a direct comparative
study. The trial is however sufficient to illustrate that replenishing a
depleted soil with the correct minerals will result in mineral rich
foods. A lot more work needs to be done in this area and to expand the
nutrient elements to include more mineral elements, proteins, amino
acids, phytochemicals, etc. When we examined the analytical results from
the vegetables grown on the revitalised soils and the supermarket items
mineral levels were often ten times higher on the revitalised soil.
Australian soils as many people would know are very old and fragile
requiring careful treatment. Our results indicate that perhaps
conventional management supplying only a limited number of nutrients
through synthetic fertilisers and not replenishing organic matter may
not be providing the nutrition that Australian consumers believe to be
the case. I believe it was Wm Albrecht that said production levels
continued well after quality diminished. Perhaps we are seeing this in
Australia at the present time?
We hope this limited study will stimulate further research.
Results are below:
beans tomatoes capsicum silver beet
calcium S 40 6.7 4.7 6
O 480 67 84 1600
potassium S 260 200 150 450
O 1900 300 1600 2600
magnesium S 26 10 11 69
O 240 89 700 1700
sodium S <1 2.4 <1 180
O <10 26 20 1800
iron S .6 <.5 <.5 1.4
O <5 <5 <5 9.4
zinc S .38 .19 .13 .57
O 3.4 1.2 2.5 130
mg/kg
S-supermarket produce
O-organic/revitalised soil
I hope this table reproduces so readers can follow the results.
Chris Alenson
Technica Adviser
Organic Advisory Service
Organic Retailears & Growers Association of Australia
email oas@alphalink.com.au
I hope this table reproduces so readers can follow the esults.
Chris Alenson
Technica Adviser
Organic Advisory Service
Organic Retailears & Growers Association of Australia
email oas@alphalink.com.au
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