Geoscience Reference
In-Depth Information
soils of very poor lands (dunes, forests). The mixture of stable litter,
earth and excrements was then spread on cultivated fields. These fields
saw their fertility enhance while their level was gradually raised by
several decimetres, at times a metre or more. The technique would
have been used regularly between the thirteenth and nineteenth
centuries (Langohr 2001) but its origin should be much older (Blume
and Leinweber 2004).
In some soils, the shallow perched water table can rise to the surface in
winter and destroy the sown seed. To counter this risk, the fields were
often cultivated by the ridge-and-furrow technique between 1650 and
1950. This gave the land parcels the appearance of a corrugated iron
sheet. In other words, part of the area was sacrificed to reclaim the land
and better expose the remaining area (Fig. 2.24a).
Ridge-and-furrow fields
Soil
Soil
a: Furrow
Water table
b: Ridge
Fig. 2.24
Execution of furrows and ridges.
In The Netherlands, the water table is everywhere close to the surface.
The fields have sometimes been ridged in one single run (Fig. 2.24b). The
difference in height between the centre and the edge of the parcel could
be as much as 3 m and the quantity of earth moved, several thousand m
3
ha
-1
. The technique appeared around the fifteenth or sixteenth century.
But in the twentieth century these land shapes that impede movement
of machines have mostly been flattened.
Before the gradual introduction of fertilizers in agriculture, yields
could hardly be improved. The only way of increasing production was
to augment the cultivated area. In uneven lands, farmers sought to
cultivate the slopes by making terraces to establish different types of
operations, in particular orchards and vineyards. In the framework of
non-mechanized agriculture, the microscopic size of the parcels thus
created was not a great handicap (Legros and Argeles 1997). Also, there
was no other choice for survival.
In some regions of the world, farmers continue to cultivate the lands
on terraces for reasons known earlier in Europe (applies to southwestern
Terracing and levelling
