240 Agricultural Revolutions and Change
1949a, pp134–135), though in the county as a whole the proportion was only 9
per cent. By 1801 much of this county had been enclosed and converted to pasture
(Turner, 1981, p296). The balance in other places was quite different: in Bedford-
shire 21 per cent of the arable in 32 open-field parishes was under peas and beans,
and 29 per cent in 45 Northamptonshire parishes (Turner, 1989, p52).
While pulses are less efficient at fixing atmospheric nitrogen than are small
seeded legumes such as clover, trefoil or sainfoin, they would have made at least as
important a contribution to the amount of nitrogen in the system thereby helping
to ensure the overall sustainability of the arable (Shiel, 1991, p76). The standard
model of the nitrogen cycle suggests that grain crops can experience an increase in
yields of 15 kilograms for every one kilogram of nitrogen supplied, but this rela-
tionship does not expand infinitely. Instead it is driven by Liebig’s ‘Law of the
Minimum’ in which the initial nitrogen deficiency is rectified by the fixing of
nitrogen from appropriate crops in a more or less linear relationship of 1:15 until
such time that a limit is achieved. Beyond this limit further application of nitrogen
does not result in further yield improvements. Thus the integral base fertility of the
soil was maintained but constantly we need to remind ourselves that this was not
scientifically understood. Instead it was a sustainability cycle borne of generations
of experience and experimentation. So what might appear as cutting edge innova-
tion in crop mixes was more likely to have evolved through trial and error. For
example, oats were occasionally planted in the pease field (Marshall, 1790, p225),
but if they were this took place in late spring, and in common with the use of
barley in the corn field, they provided a safety net if bad weather had previously
prevented farmers from sowing pulses. This safety net ensured sustenance for the
animals. The pease or pulse course might occupy as much as 50 per cent of the
arable land that was not in fallow, and its principal purpose was to supply fodder
for the livestock.
The final course in the rotation was the fallow, which was a restorative period,
without the demands of a sown crop. It also acted as a cleaning period, providing
an opportunity to remove weeds from the field. Once the pease crop was harvested
the field was thrown open for livestock to feed on the stubble, on remnant grasses,
weeds and the grass leys. Depasturing also took place on the passageways that
afforded access into and across the fields. These were strips of lands known as
baulks and headlands. They were integral to the fields and their functions. So also,
paradoxically, were weeds. If they were allowed to proliferate at certain times this
was not always a sign of backwardness in field management. Arthur Young, the
noted agricultural writer and traveller of the late 18th and early 19th centuries
observed, ‘you cannot clear weeds until first you let them germinate’ (Young, 1771,
p291). Therefore the fallow field was not normally ploughed in the autumn.
Instead the weed seeds were allowed to germinate, thus providing feed for the
sheep that were grazed on the fallow. The first ploughing was left until late in the
spring (Marshall, 1790, p225; Loudon, 1831, p802; Fox, 1981, pp94–95). A sec-
ond ploughing was typically made in midsummer, when any weeds which were
going to seed were ploughed in before they produced seed heads. A final ploughing