Fróðskaparrit - 01.01.1991, Side 143

FAROESE SPADE-CULTIVATION . .
147
Fig. 4. Rossleypur. The bottom swings open like a door. Drawn at Gásadalur in 1986 by R. Guttesen.
The worst obstacles seem to be:
- the growing season is very short.
- average max. temperatures during period
of ripening are very low.
- the soils are very wet, hence acid and of
low fertility.
- the tendency for excessive leaching of
plant nutrients is high because of high
precipitation.
- the harvesting period is often too wet for
natural drying of the crop.
- there is a risk of wind-erosion in the bare
fields.
Generally, reinavelta with its sloping teigar
eases most of the problems mentioned. It is
a main remedy to improving the drainage,
done essentially by locally increasing the gra-
dient of the cultivated surface, shortening
the slopes and providing an erosion-resistant
system of drainage channels. As a result, the
soil temperature is raised, microbiological
decomposition augmented, and the soil qua-
lities ameliorated. As the velting also buries
the grass vegetation through the inversion of
the turves, turning up the underlying black
soil face up, the surface albedo is lowered,
and soil temperature increased due to radia-
tion. Measurements show that this increase
can be in the order of 1-2 degrees Celsius
(L.E. Hansen 1987), adding the equivalent
of about one month to the growing season.
Part of the increase of temperature may stem
from released heat from the biological