THE INFLUENCE OF SOIL ORGANIC MATTER AND MYCORRHIZA ON THE MINERAL CONTENT OF FOOD PLANTS

There is now very extensive research indicating the adverse effects on human health of low levels of minerals in food. The decline of minerals in British food has been monitored by M.A.F.F. since 1940. A review from this data has recently been carried out and published (1).

In vegetables only phosphorus has risen since 1940. Six other important elements have fallen, with copper falling as much as 76%. Similarly in fruit, phosphorus is 2% up and the others are down, with iron down 24%. Declines have also been recorded in milk, meat and cheese.

At Eastleigh, over the past 14 years, we have carried out extensive research to increase the plants mineral content by using Mycorrhizal-forming fungi. This group of beneficial root fungi occur naturally in association with 80% of land plants. Mycorrhiza is reduced or eliminated by soil disturbance and destroyed by chemical fertilizer. (2). The reason for such a dramatic loss of nutrition over the past sixty years may be due, in part, to the loss of this important soil micro-organism.

In two of our trials we investigated the mineral content effects of chemical fertilizer or Organic Matter. In the Organic Matter part of these trials we found considerable variation. See graph Below for mineral score.

In order to achieve a simple comparison of plant minerals,

Each mineral was averaged for all samples.

Then the appropriate mineral in each sample was taken as a percentage of the average.

Finally the percentage for each mineral in a sample was averaged to give a mineral score.

Before considering the Eastleigh data, what do other reports tell us? One of the first to add science to organic farming was E.B.Balfour in her book "The Living Soil". One set of data in this book compares the minerals in crops from 3 differently managed farms.

Aggregating 10 minerals in a variety of crops the mineral scores are:-

1. Mixed organic -103

2. Stockless organic -102

3. Mixed, using some chemical fertilizer 94.

The Eastleigh Data

The trial conducted on Eastleigh soil has a neutral to high pH. In this trial broad beans and carrots were grown with and without mycorrhiza and with 3 or 4 levels of mushroom compost. The results are given in the graph below.

These progressive increases in the mineral content of broad beans and onions seem to provide the possibility to go on for ever. There is, however, some unpublished data which indicate that in excess, organic matter can have the opposite effect.

Whilst the results above give encouragement that the Good Gardeners' Association is heading in the right direction there is much more work yet to be done. We hope that in the coming years we will be able to secure significant funding, based on successful trials as above, to carry out further research. Our ultimate goal will be to advise our members accordingly the best way forward for growing more nutritious food whilst at the same time strengthening the organic movement.

John Reeves
(GGA Council Member)

References

(1) Thomas David M.Sc., D.I.C. Mineral Depletion in Food Over the Period 1940-1991. The Nutrition Practitioner. Vol.3. July 2001 pp27-29

(2) Reeves J. Influence of Agriculture on Mineral Nutrition and Health. Eastleigh Research. Lydbrook, Glos.