INTRODUCTION

Miracles apparently still happen. A soilscientist who manages to keep disease sensitive riceplants healthy, without one trace of pesticide, just some trace-elements? That sounds like witchcraft. "No plantdisease without mineralshortage" seems to be the astonishing conclusion. Why do we spray for billions of pesticides?

An entomologist at Cornell University once explained very clearly how much cereals, vegetables and fruit is being lost because of fungi, insects, weeds, viruses and bacteria. The figures are impressive: 37% of the USA harvest is being eaten by insects in the field or otherwise disturbed in its growth. Worldwide the percentage is assumed to be 50% (!). And, this in spite of all human efforts to turn the tide, including all chemistry and plant breeding programmes. Why is it that diseases and plagues can upset agriculture so strongly, whereas in nature they rarely appear?

The conventional explanation is that plague organisms enjoy an agricultural field so much because farmers put large amounts of the same plants in one field together and thereby provide a great dish for plague organisms.

Yet this doesn't explain all the successtories from organic agriculture. Jan Bokhorst, a soil scientist from the Dutch Louis Bolk Institute in Driebergen remembers how he 15 years ago walked with a professor from the Agricultural University Wageningen (LUW) through some test fields where a comparison was made between organic-dynamic and 'conventional' crops. "The organic-dynamic absolutely were not troubled by the carrotfly, whereas the 'conventional' carrot was loaded with them, in spite of spraying.

The German gardenwriter Alwin Seiffert has the same experiences with the colorado beetle. In his book "Gardening without poison" he describes how the potatofield of his neighbour was eaten by this little bigmouth, whereas the insect was hardly present in his own field, even though there was no separation between their fields. How is that possible?

The late Brazilian professorA.M. Primavesi, a soils scientist, pointed in the sixties in the direction of the soil. For him, that's where the cause was. Just as the explosive increase of diseaseproblems in Brazil had everything to do with the strong decrease of soilfertility. "On virginal grounds farmers never have problems with diseases. That is a fact every Brazilian farmer can confirm". Diseases reflect a shortage in minerals, according to Primavesi. No disease without a shortage. And the analyses seem to confirm it. Riceplants that were sensitive to fungal disease appeared to have considerably less magnesium, kalium, mangaan and copper than healthy rice.

Lice

According to the French researcher Frances Chaboussou who investigated the relationship plantnutrition/plantdisease till his death in 1985, insects, fungi, viruses and bacteria only become a problem when they are being provided with a very good dish. That is, when there are many easy solvable substances in the plantjuice. Is this a shocking conclusion or does it only look like one? Why do agricultural universities and industries invest long, long researchtime in an effort to avoid a fungus to enter a plant through poison and genetic engineering when the problem is not outside but inside the plant? Yet, LUW headteacher soilscience and plantnutrition W. G. Keltjens is not really surprised. "When a crop is very sensitive for lice" he says "it indeed seems to be the conclusion that these plants are very attractive for the lice. You indeed will find that the plantjuice is full with sugars or dissolved amino-acids, that the plant normally would transform to proteins. For some reason the plant does not manage anymore to transform all the dissolved sustances into proteins". But what's the cause? Less light? Cold spring? Wrong nutrition?

Primarily wrong nutrition, says Primavesi. In the magazine Agrochemica he and his wife describe in 1972 the sensational effect of some extra mangaan and copper in the soil. The riceplants stayed healthy, even under the worst conditions possible: disease sensitive varieties, strong nitrogeninput and strong contamination of seeds, soil and irrigationwater.

Firework

New firework in this area in recent years comes from the American biofysicist Arden B. Andersen. Andersen believes nothing of the axioma that diseases and plagues are the evildoers. The problem lies with man, he says, not with the disease. Fighting off of diseases is nothing else than fighting off the messengers of evil, whereas evil itself can go on undisturbed, because it is not recognised as such.

To Andersen also there is no plantdisease thinkable without an accompanying deficiency in minerals. He even goes one step further by specifying these shortages for tenths of diseases. Appearance of the coloradobeetle, for example points to a shortage of calcium, phosphorus, vitamin C, copper and mangaan; lice indicate a shortage of calcium, phosphorus, iron and copper. "If a plant lacks nutrition during growth, this results in mineraldeficient vegetables", he says "in a lower sugarcontent, a lesser taste and in less resistance against disease".

Sensitivity for disease is always being reflected in a low mineralcontent and a low sugarcontent of vegetables and fruit, according to the American biofysicist. "You can measure it yourself" Andersen suggests his readers. "For a few hundred dollars you can buy a refractocounter. The same little device that the softdrink industry uses to measure the sugarcontent of juices and lemonades, and do the test. Take one or two drops of a healthy cropplant and one or two drops of a diseases plant and compare the sugarcontent (refractionvalues). Healthy plants always have a higher sugarcontent".

Different crops have different refractionvalues beyond which cereals, vegetables and fruit do not become diseased. Beans with arefractionvalue of 14% and more will not get diseased. For strawberries it's 16%. The mineraldeficient plants are always the ones that are being affected". Diseases and plagues clear up the mess. "Diseases and plagues are nothing else than a way of nature to make known that there is a mineraldeficiency. What modern agriculture is doing, is replacing this natural filtersystem by chemistry. Apparently without problems. A car also still works when the gasolinefilter and the airfilter are removed.

But it does not mean it can be done without repercussion". Roel Voortman is a landscape ecologist, who works for the Foundation Research Worldfoodsupply of the Free University in Amsterdam. "I also often wondered why there is so little attention for the value of trace elements. Recently I looked at it for a country like Nigeria. The past 15 years nothing else has been imported than artificial fertilisersubstances like nitrogen, fosfates and kalium. One year there was also import of sulfur. That's all, whereas there are so many indications that yields can react very sensitive to some extra trace elements. The same here in Holland. Years ago there was a copperproblem in the northeast. One would expect some more awareness on the issue but in all debates the only focus is on nitrogen, fosfates and kalium. No attention is being given to trace elements and also not to the humus.

Why? I guess the matter is too complex. The knowledge in Africa is lacking but in the donorcountries it is also lacking".

There is not so much literature about the relationship between trace-elements and plantdiseases. Voorman: "I actually have only one reference at hand". It is typically a problem that at LUW has fallen between the wall and the ship.

"My archives are amazingly empty on this issue" says Jan Bokhorst from the Louis Bolk Institute, "soilscientists traditionally do not look plantdiseases and plantdisease-experts do not look at the soil". For years everybody was focussing on production. There simply was nothing else than production, there was no room for another angle. In the case of an emergency, the grower always could get the chemicals from the barn.

Keltjens: "Now the climate is different. In the Netherlands, fertilisation has become extremly unbalanced through all the liqui manure. There is such an overdose of nitrogen that the balance is gone. We are all very busy to get rid of overfertilisation. Now it's all about balances, the plant needs to get what it needs, not more". A next step according to Keltjens could be a further refinement of fertilisation: the relationship with diseases and plagues, on the basis of thorough research. "I think the time is ripe for it. We are close to it. We want to tackle the excesses, reduce chemistry and artificial fertilisers. Than comes the question: what are the alternatives?