Agriculture Reference
In-Depth Information
A subsistence economy can make up its small shortfall in phosphorus relatively easily,
for example by feeding animals on outlying land which is not being cultivated and has a
small natural income of phosphorus. The advantage of dovecotes, whose birds foraged far
and wide, becomes clear once one understands the phosphorus cycle. But an agricultural
economy which exports has to locate substantial sources of nutrients to replenish its phos-
phorus. In his comparison of various agricultural systems, Newman concludes that Egypt
has always been able to do this thanks to the silt deposited by the flooding of the Nile. But
the records of a manor farm in Cuxham, Oxfordshire, show that even in the 14th century far
more phosphorus was being exported off the farm than was delivered onto it, and though it
had relatively high yields for the period, the farm was drawing upon its capital, its store of
phosphorus in the soil.
Liebig realized that with the simultaneous development of industrial capitalism and flush
toilets, land was being depleted of its phosphorus much faster than before, and some-
how the process needed to be reversed. As is so often the case, the Government ignored
the sound but unwelcome advice of its hired consultant, and opted to build two massive
pipelines to flush the sewage into the Thames estuary rather than recycle it. Liebig respon-
ded by starting work on developing artificial fertilizers, which he concluded appeared to be
the only way of replacing the nutrients that were so wantonly wasted.
But while the government refused to set an example in London, other municipalities and
individuals set about taking advantage of the resource. Graham Harvey describes one of the
earliest of these schemes, at Craigentinny Meadows on the sandy land between Edinburgh
and the sea:
Sewage was collected in ponds and allowed to settle for a short time before being passed
down a wide open drain known as the Foul Burn with an outfall in the Forth estuary. Farm-
ers with land alongside the burn drew off agreed amounts of the slurry to irrigate their
grasslands. Most of the fertilized grass was cut for hay and fed to dairy cows housed in
sheds in the nearby towns of Leith, Musselburgh and Portobello as well as Edinburgh itself.
Old grassland produced about 40 tons an acre [100 tonnes per hectare] on the contents of
Scottish water closets, ryegrass pastures as much as 60 tons (150 tonnes per ha).
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150 tonnes per hectare, equivalent to over 25 tonnes of hay, is a phenomenal yield, even
by today's standard. The Edinburgh system was engineered to run down a dedicated chan-
nel, the Foul Burn, but other schemes simply took advantage of nutrients that were being
poured into the rivers. The Duke of Portland constructed 400 acres of water meadows along
the banks of the river Maun, into which the growing settlement of Mansfield obligingly
dumped all its sewage. The irrigated meadows were described by one observer as 'the pride
