Dr Rayner and mycorrhizas


In the 1920s English biologist Dr. M.C. Rayner found herself facing a problem: how to get trees to grow on the old heath at Wareham in Dorset. This was the "Egdon Heath" of Thomas Hardy's novel "Return of the Native", a land of dark spirit that loomed over everything and blighted everyone's lives.

Dr Rayner found that it certainly blighted trees -- they just wouldn't grow there. The soil seemed to be toxic to them. The forestation program laid down for the heath had ground to a halt.

Then she found that the tree seedlings would grow if you composted the soil first -- but it had to be compost, simply supplying plant nutrients in chemical form just didn't work. There was obviously some biological, rather than merely chemical, factor at play, and she finally tracked it down, to an obscure discovery of the previous century concerning soil fungi. This was the beginning of her famous work with mycorrhiza -- fungus-roots, the symbiotic relationship between plant roots and soil fungi without which most plants cannot thrive, while many cannot even survive without their fungal partners.

Meanwhile, working in India, Albert Howard, who developed the Indore composting system and subsequently founded the organic growing movement, was facing a different problem: he couldn't understand why a single application of compost often resulted in such vivid improvements in both crop yield and pest resistance, whereas the soil improvements resulting from humus application could only be expected to be slow and progressive. "The improvement following humus was the reverse of slow -- it was immediate and spectacular. Some other factor besides soil fertility appeared, therefore, to be at work." (See Humus and Disease Resistance -- Sir Albert Howard)

He sent sample roots to Rayner, and she discovered the answer: Howard's compost was establishing the mycorrhizal association where before it had been absent in the degraded, overworked plantation soils. The vital role of biological factors in plant growth, rather than the mere provision of chemical nutrients, thus became one of the major planks of the organic growing movement.

All subsequent work has served to underpin the fundamental importance of the vast masses of soil micro-organisms in plant nutrition and growth, and particularly that of the mycorrhiza-forming soil fungi.

"It is well known that mycorrhizae can benefit the growth and health of plants, but it is not widely known or appreciated just how critical and normal this association is to the well-being of plants, especially in disturbed ecosystems" (Dr. Robert G. Linderman, USDA-ARS, Horticultural Crops Research Laboratory).

What also is not very widely known is how chemical fertilizers and pesticides can damage or even destroy the essential soil fungi, as well as the rest of the vast web of soil microlife so vital to soil and crop health.

What is the mycorrhizal association? Simply put, in a healthy soil plant roots are invaded by a friendly soil fungus; the fungus actually feeds the plant, and in return the plant feeds the fungus the products of the green leaf which the fungus is unable to make for itself. It is a very ancient and widespread arrangement, long overlooked after its initial discovery mainly because the plant pathologists of the time, with their orientation towards disease, saw the fungal invasion as a pest attack.

Long out of print,
"Trees and Toadstools" by Dr. Rayner is an excellent introduction to the subject. With her husband and co-worker, Professor W. Neilson-Jones, she also wrote an account of the work with mycorrhizas at Wareham: "Problems in Tree Nutrition -- An account of researches concerned primarily with the mycorrhizal habit in relation to forestry and with some biological aspects of soil fertility" (Faber and Faber, 1944), also long out of print, though we hope eventually to add it to this library.

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