Geoscience Reference
In-Depth Information
AGRICULTURAL SOILS: A SIDEWAYS LOOK
Chapters 4
and
5
mentioned a range of soil pests including eelworms, slugs and many
insects, but what about the rest of the soil fauna? Does it make any beneficial contri-
bution to agriculture? The possible significance of earthworms and other invertebrates
was reviewed in the late 1950s and early 1960s but with rather uncertain conclusions.
The activities of worms - in draining and aerating the soil, in macerating dead veget-
able matter and rendering it more available to attack by microorganisms, and in helping
to create good crumb structure - were evidently what Sellar and Yeatman would have
called a 'Good Thing' in
1066 and All That.
It was another matter, however, to demon-
strate this quantitatively. Small scale experiments, in which earthworms were added to
pot-grown cereal plants, were inconclusive because, although there was some indica-
tion that worms improved yields, it often seemed that they were equally effective alive
or dead!
Though this approach has proved rather intractable, there has been a great deal
of productive research in Britain, especially at Rothamsted Experimental Station by
C.A.Edwards and others, and also in Europe and the USA, on the incidental effects of
agricultural practices upon the soil fauna. This chapter considers some of these effects
and the way the microflora deals with the array of pesticides that are applied to farm-
land soils. It then looks briefly at other problem areas of modern intensive agriculture,
and finally at organic farming as an alternative.
C
ULTIVATION
Realistic estimates of the numbers of soil organisms were just becoming available
around 1950 when E.W.Russell was revising the 8th edition of Sir E.J.Russell's
Soil
Conditions and Plant Growth.
Much effort had been spent in developing extraction
techniques for pests such as wireworms and eelworms, and was being extended to
groups such as micro-arthropods. It thus became clear just how impoverished the fauna
of arable soils was in comparison with permanent grassland. Ploughing causes a drastic
reduction in most groups of animals, an effect which is intensified if the soil is kept
in a fallow condition. Only those species persist that are capable of living in mineral
soil without a surface humus layer. They must also withstand the rigours of change:
the physical upheaval of ploughing, and the greater fluctuations in micro-climate that
