Environmental Engineering Reference
In-Depth Information
Improved record keeping makes it much easier to trace the rising yields during
the eighteenth and nineteenth centuries. Better implements (allowing timely comple-
tion of critical i eld tasks), a progressive reduction of fallow, increased manuring,
regular crop rotations, and the diffusion of new cultivars were the key ingredients
of the process. As expected, yields began to rise i rst in some of the most densely
populated regions, including the Low Countries, England, and Japan. Farmers in
densely settled Flanders were as much as two centuries ahead of their German or
French neighbors in reclaiming the region's wetlands, gradually abandoning exten-
sive fallowing, adopting several standard crop rotations, and applying increasing
amounts of organic fertilizers.
In the eighteenth century, Flanders' organic recycling (manure, night soil, oil
cakes, and wood ash) averaged 10 t/ha (Slicher van Bath 1963), and some i elds
received every year as much 30 t/ha. By 1800 less than 10% of arable land on Dutch
farms was fallowed, and there was a close integration of cropping with livestock
production (Baars 1973). In England, rotations that included legume cover crops—
such as the four-year succession of wheat, turnips, barley, and clover—had doubled
or even tripled the rate of symbiotic nitrogen i xation (Campbell and Overton 1993),
and Chorley (1981) considered their regular adoption to be as signii cant for the
society as the contemporaneous diffusion of steam power.
English wheat yields began a steady, slow increase already after 1600, but a real
surge in productivity came only between 1820 and 1860, a result of extensive land
drainage, regular crop rotations, and higher rates of manuring: by 1850 many coun-
ties had harvests of 2 t/ha (Stanhill 1976). Dutch wheat yields doubled during the
nineteenth century to 2 t/ha. But neither in the Netherlands nor in England could
these yield increases satisfy the combined effect of population growth and a rising
demand for better diets, and both countries saw a substantial expansion of their
cultivated area: in the already highly intensively cultivated Netherlands it grew by
a quarter between 1750 and 1900, and in the UK the increase was nearly threefold
(HYDE 2011). The same forces acted in Japan, where the average rice yield sur-
passed 1 t/ha already during the early seventeenth century, 100 years later it was
about 1.5 t/ha, during the i rst full decade of the Meiji era (1870) it reached 2 t/ha,
and in 1900 the average yield of husked rice was about 2.25 t/ha, or 25% higher
if expressed as unmilled paddy rice (Miyamoto 2004; Bassino 2006).
Even when compared with the best mid-nineteen-century performance, modern
plant breeding eventually tripled the Japanese rice yields and more than quadrupled
the Dutch rate. Its most important goal has been to boost HI, that is, to increase
