Agriculture Reference
In-Depth Information
a third. Permanent escape was provided by the rather more tardy introduction, over the
17th to 19th centuries, of turnips and nitrogen-bearing legumes, such as clover and sain-
foin, into the farming rotation. These cultivated crops could feed considerably more anim-
als than could be pastured on a strip of fallow. The Norfolk four-course rotation (pioneered
by Coke), of wheat, turnips, barley and clover, never left the land idle and fed everything
not consumed by humans to livestock.
The combined effect of legumes and turnips was to reduce the fallow while in-
creasing the output of animal feed. Farmers were able to keep more livestock, and this
in turn increased the supply of animal manure. Animal products were the main fer-
tilizer used on arable land, so with more manure available soil fertility improved and
yields per acre rose.
6
This view, from J V Beckett in 1990, echoes that of the agricultural historian, Lord Ernle,
80 years previously :
The field cultivation of roots, clover and artificial grasses … enabled farmers to
carry more numerous, bigger and heavier stock; more stock gave more manure; more
manure raised larger crops; larger crops supported still larger flocks and herds.
7
This was the classic view which I once accepted, but now consider needs adjusting. Al-
though animals were key to the advances of the agricultural revolution, manure played a
smaller role than it occupies in the account propagated with such enthusiasm by Lord Ernle,
John Seymour and others. The extra nitrogen came from the growing of legume crops for
animals, but not necessarily via the digestive tracts of animals that ate them. This might
seem a nice distinction but it is crucial to the debate between organic livestock farmers and
organic stockless farmers that is the focus of much of this chapter.
Nitrogen is an essential nutrient for growing crops, and in many situations, as in medi-
tunately there is plenty of nitrogen in the atmosphere, and from there nature dispenses it
in regular and fairly generous doses into the soil. Some of it falls as rain, and some of it
is fixed in the soil by plants, algae, bacteria or by other mechanisms. A number of wild or
semi-wild ecosystems, notably grassland, accumulate and store it, much as they also store
carbon. A hectare of long established pasture, in England, typically holds about 7,275 kilos
of stored nitrogen.
When the descendants of Cain grub up grassland, that stored nitrogen becomes access-
ible to them for their crops. Initially there are high yields. However, nature is prudent as
well as generous, and she doesn't hand out her blessings all at once. Plants can only absorb
nitrogen when it is in a 'mineralized' or 'free' state, and in a recently ploughed up pasture
