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Some effects of organic growth-promoting substances (auximones) on the soil organisms concerned in the nitrogen cycle

1917; Royal Society; Volume: 89; Issue: 621 Linguagem: Inglês

10.1098/rspb.1917.0009

2053-9185

Florence Annie Mockeridge,

Peatlands and Wetlands Ecology

It is a well-established fact that the presence of a certain amount of humus in soil is essential to complete fertility, and it is equally well known that this organic matter, whether supplied in the form of stable or green manure, is far more effective when decomposed, or “rotted,” than when fresh. This has been attributed to the soluble humus formed during the rotting, but wherein lies the peculiar merit of this soluble humus has long been a debatable point, some considering that it serves primarily as a plant nutrient, while others claim that its most important effect is upon the bacterial flora of the soil. It is well known that raw peat, although rich in humus, is practically useless as a manure, on account of its acid and insoluble nature. This insoluble humus can be neutralised and rendered largely soluble by extraction with alkalies, and almost all experiments on the effect of soluble humus on bacteria have hitherto been carried out with such extracts. Too much reliance must not be placed on the results obtained with these chemically prepared substances, for they are not strictly comparable with the soluble humus produced in the soil by natural processes. However, Bottomley has shown that it is possible, by inoculating peat with certain aërobic soil bacteria, and keeping it under suitable conditions, to convert it into a partially soluble humus in a comparatively short time. A similar bacterial action is taking place more slowly in every rotting manure heap and in all soils, for the longer stable and farm manures are kept, the more water-soluble brown humus can be extracted from them. Bottomley’s bacterial treatment of the peat simply reproduces and hastens these natural processes, and the product of the treatment, which is known as “bacterised peat,” is practically the counterpart, in a more concentrated form, of rotting stable manure or of green manures which are undergoing decomposition in the soil. The soluble humus which can be extracted from it may be justly considered to approximate more closely to the natural product than any extracts obtained by chemical processes, and the effects of this soluble humus on soil bacteria accordingly reproduce more exactly the influence of the organic matter of soils upon the bacterial flora.