Geoscience Reference
In-Depth Information
AGRICULTURAL SOILS: PRODUCTIVITY AND
MANAGEMENT
The King of Brobdingnag gave it for his opinion, that whoever could make two ears of
corn or two blades of grass to grow upon a spot of ground where only one grew be-
fore, would deserve better of mankind, and do more essential service than the whole
race of politicians put together.
J.D.Swift (1726) -
Gullivers Travels
The history of agricultural productivity in this country has been an unrivalled success
story during the past 40 years. The increased scientific understanding of soil conditions
and crop growth has underpinned a wide range of technological developments - new
crop varieties, new machinery, better drainage, artificial fertilizers and pesticides -
which have together led to crop yields unimagined in the early decades of this century.
Consider wheat yields in England, for example. We can look back over seven cen-
turies of records, and see how average yields have gradually risen from 4.3 cwt an acre
(0.54 tonnes per hectare) around AD 1200 to about 20 cwt an acre (2.5 t/ha) in 1950,
a nearly five-fold increase. Since then, however, within a single farming generation,
wheat yields have almost trebled again. In 1982 they stood at 50 cwt an acre while
1984 produced a record harvest at nearly 3 tons an acre (7.3 t/ha). The good conditions
for root development, the uniform rain distribution and favourable day/night temper-
atures could scarcely have been more atuned to the growth of wheat if they had been
computer-controlled. As one Cambridgeshire newspaper put it, “This almost ideal pat-
tern certainly made a major contribution to the Latenbury Farming Company's heavy
yields of generally high quality grain, averaging around… 70 cwt per acre for winter
wheat”.
The weather in 1984 was exceptional in allowing this expression of crop potential
- a near optimum uptake of nutrients from the soil with little let or hindrance from
pests and diseases. Such average yields have yet to be exceeded, and it is not clear
at present whether there is sufficient genetic potential for yields to rise much further.
Nevertheless, even this level of production far exceeds what G.W.Cooke thought pos-
sible in 1969 when he addressed this question in a symposium on
The Optimum Popu-
lation for Britain:
“The 'target' assumed in this paper is that of growing enough food
