Agriculture Reference
In-Depth Information
drive
counterrotating rod
Fig. 7.12
Rod-weeder (From Gist
2002
, altered)
sucking water to the surface. Therefore, weeds must be completely kept off the fi eld,
either by a site-specifi c application of herbicides or by cultivation. But capillaries of
soils as well can suck water to the surface. This applies particularly to non-disrupted,
continuous capillaries. Hence a bare, undisturbed, settled soil evaporates more
water than the same fi eld with a shallow, cultivated top layer (Wuest and Schillinger
2011
). The problem is that this top layer can promote erosion. So this top layer
either needs a special protection against erosion, or the disruption of the soils capil-
laries must occur below the surface with targeted precision. Technical solutions for
both alternatives are available.
The classical instrument for shallow cultivation with at least some inherent pro-
tection against erosion is the
rod-weeder
(Fig.
7.12
). Its main tool is a horizontal
square rod with vertical cross-sectional side lengths of about 25 mm. This rod is
oriented perpendicular to the direction of travel and is rotated against the direction
of travel. Its depth of operation is between 5 and 10 cm. This implement creates
stratifi cation or fractionation within its operating depth. Due to the rotations of the
rod against the direction of travel, coarse clods, weeds and residues mainly pass by
overhead. Small soil particles instead are not carried upwards and therefore squeezed
downwards. The result comes close to the ideal stratifi cation and fractionation as
pointed out in Fig.
7.11
. This implement up to now mainly is used for dry-land
farming in Northwestern areas of Canada and the USA. Its prospects in other parts
of the world as a means of preventing surface crusting and erosion in combination
with modern sowing techniques deserve attention.
When it comes to the disruption of the soil capillaries with targeted precision in
order to prevent evaporation, farmers in dry-land areas refer to a process of “
setting a
moisture line
” in the fi eld. The rod-weeder does this quite well because of its rather
shallow operation. And in addition it accumulates weeds, straw and clods on or near
the surface to assist in erosion control. However, it does not leave “anchored crop resi-
dues” as well as “anchored killed weeds” on the fi eld. The residues and weeds just are
lifted and mainly deposited on the surface, they are not anchored to the soil any more.
