by André Voisin
CONCLUSIONS
Lessons learnt from grass tetany, a metabolic disease caused by the soil
The pathology of the soil creates the pathology of the animal
Grass tetany has been, and still is, the cause of enormous losses in the herds of many countries. This heavy toll paid by agriculture to this "disease of civilization" of the grazing animal has perhaps not been in vain. Grass tetany has strikingly revealed the serious, very serious, consequences of incorrect application of fertilizers, whether mineral or organic. It is an excellent example of metabolic disease caused by the imbalances created in the soil by the methods of cultivation applied. It has taught us a lesson whose consequences are incalculable for veterinary as well as for human medicine, namely:
Ill-advised fertilizer ratios, mineral or organic, produce a pathological
condition in the soil. The pathology of the soil creates the pathology of
the animal.Enormous influence of fertilizers on the health of the grazing animal
Grass tetany has revealed in no uncertain manner the enormous influence exerted by the fertilizer applied to the soil on the grazing animal, the "biochemical photograph" of soil and herbage. It demonstrates, in effect, how mineral imbalances in the soil give rise to mineral imbalances in the composition of the herbage that may result in serious, if not fatal, disturbances in the metabolism of the grazing animal. By judicious fertilizer application it is possible to get herbage containing (in the dry matter) 2% potassium, 0-70% sodium and 0-25% magnesium: herbage that will produce a healthy animal with a normal metabolism.
But if, as the result of ill-advised fertilizer dressings, the herbage
(see Tables 4 and 11) contains 4-5 % potassium, 0-10% sodium and
0-15% magnesium, the metabolism of the animal consuming that herbage is
upset, tetany convulsions make their appearance and death may result.
Fortunately, at the same time as it reveals the possible dangers of
erroneous fertilizer application, grass tetany helps us to discover some
of the
rules 1
that must be applied to avoid these dangerous fertilizer effects.Two contrary and incorrect opinions
Grass tetany enables us also to decide between two groups representing completely opposite opinions:
| 1. | Some 2 fertilizer manufacturing firms have tried to deny at all costs that mineral fertilizers can have an injurious influence on health. An over-simple argument, with no accurate scientific data, as basis, has long been that: "Mineral fertilizers are not dangerous to human health because they do not harm animal health." Unfortunately, grass tetany demonstrates that mineral fertilizers, if wrongly applied, can be fatal to the animal. |
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| 2. | On the other hand there is another body of opinion, grouped together under the name "organic school", that declares that the application of mineral fertilizers (which this school chooses to describe as "artificial fertilizers") must be prohibited because of the dangers they present to health and that only organic fertilizers must be allowed.3 But grass tetany has shown (see Table 11) in particular that the imbalances created in the composition of herbage by liquid manure, an organic fertilizer, can be very much more marked than the imbalances caused by artificial, chemical fertilizer. In actual fact "artificial" fertilizers have to be called in to rectify the faults of the so-called "natural" fertilizer. |
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There can be no question of prohibiting mineral fertilizer
These lessons taught by grass tetany are all the more important as it is impossible to over-emphasize that there can be no question of turning back and suppressing mineral fertilizers-one of the most important and remarkable advances achieved by man.4 Such action would not only entail a considerable fall in the standard of living: it might even mean famine. It would be the action of a lunatic. But a folly at least as serious is to deny that mineral fertilizer, if wrongly applied, can be dangerous to health.
The great positive lesson of grass tetany is that well-applied mineral
fertilizers allow the output per acre of grass, milk and meat to be
increased, without harming in any way the health of the animal.
There is no cause, therefore, to give up the use of mineral fertilizers,
on condition that they are suitably applied. Unfortunately, this is not
always so at present. The first condition of judicious fertilizer
application is that we study not only the influence of the fertilizer on
the yield of the plant, as happened almost exclusively hitherto; in future
we must study above all the influence of the fertilizer on the biological
quality of the plant.Soil and fertilizer make the animal
The old farming proverb "The soil makes the animal" will henceforth have to read: "Soil and fertilizer make the animal!"
If tetany could succeed in convincing those who have forgotten it of the
truth of this statement, we would be able to conclude with confidence. If,
at first sight, grass tetany appears to present some alarming results, in
the long run it offers a positive and encouraging lesson applicable both
to human and to animal health.
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Regarding the new laws of scientific fertilizer application, see the
author's paper: "Do sensibly used mineral fertilizers harm human health?"
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Fortunately, not all; and it is a pleasure to acknowledge that some
manufacturers with enlightened attitudes have tried to remedy the faults
of their products. Mention can be made, among others, of the manufacturers
of a nitrogenous fertilizer containing copper, or of the producers of
potassium fertilizers recommending the use of their products containing
magnesium and/or sodium. *
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There is naturally no question of denying that organic fertilizers,
especially farmyard manure and compost, play a fundamental part in
maintaining soil fertility. *
- Regarding the good or bad effects of the use of mineral fertilizers on the evolution of our civilization, see the author's study The health of Men today remains bound to the health of the soil. *