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Cleaner Technology Projects in Denmark 1997
Mekanisk renholdelse af kulturer plantet på agerjord
Miljørapport nr. 353, 1997, Miljøstyrelsen
The Danish Research Centre for Forest and Agriculture has carried out a number of
investigations into methods for reducing the use of pesticides in forestry and the
decorative greenery business. The purpose was to demonstrate the effective and economical
results which can be gained by using three different harrow types for weeding of newly
planted trees on former agricultural fields and compare the principles with chemical
weed control and no treatment at all. Another purpose was to study whether there is a
need for developing new machines or improving machines for mechanical weed control.
Two investigations were made with mechanical weed control in tree plantations on former
agricultural fields. One trial with noble fir on sandy soil and one trial with common oak
on clay soil. The experiments were running for three years. The effects from three
different tractor-mounted harrows on survival and height growth of the trees were compared
with no treatment at all (control) and weeding with a herbicide.
Only 13 percent of the noble fir in the control plot survived. All the other treatments
gave a very satisfactory and significantly better survival with more than 90 percent
surviving trees. In all the mechanical treatments and in the chemical treatment the trees
had a significantly better height growth.
On the clay soil all of the common oaks in the trial had a satisfactory survival rate.
Even the oaks that did not get any treatment at all had a survival rate of 89 percent.
Only one of the treatments, the HPH Skovharve caused a significantly better survival with
a survival rate of 98 percent. None of the mechanical treatments gave the oaks a
significantly better height growth than the untreated tress.
The mechanical treatments only caused small damages to the trees. One harrow, the Einböck Langfingerharve, caused significantly more small damages to
the noble fir than the other harrows. The LOFT
Spaderulleharve caused significantly more damages to the oaks than the other harrows. None
of the injuries were considered essential for the future survival and growth of the trees.
The costs of weeding with the HPH Skovharve and the LOFT Spaderulleharve are exactly
the same as long as the row spacing fits the harrows. The costs of weeding with the
Einböck Langfingerharve are lower than the other methods because this harrow is wider.
All the empirical experiences that were gained during the research period showed that
careful planning is essential for the successful application of mechanical weeding in new
plantations. The layout of the planting must fit the tools and the machinery that are to
be used later on. Because none of the harrows known today can handle weeds that are bigger
than 5 or perhaps 10 centimetres, inspections must be made frequently to determine when to
weed.
Author/ institution
Bent Keller, Forskningscentret for Skov og Landskab
This report is subsidised by the National Council for Recycling and Cleaner Technology
ISSN no. 0105-3094
ISBN no. 87-7810-740-7
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