6.1 Weed control
Grasses, herbs and other vegetation on the planting site compete
with the seedlings for light, water and nutrients. Cutting or removing the
vegetation from around the seedlings reduces the competition. If weeding is
neglected, the seedlings will die. How often and in which way the weeding is
carried out depends on the climate, the soil, the species planted and the size
and quality of the seedlings used.
The more hot and humid the climate, the more weeding operations
are needed. Depending on weed competition in some places it will be enough to
weed once during the first year. In other places three or more weedings per year
might be needed. If small and poor quality seedlings are used, the number of
weeding operations needed will increase. As a general rule of thumb there should
2-3 weedings during the first year after
1-2 weedings during the second year after planting;
during the third year after planting.
Weeding must be carried out early, before the seedlings suffer
from being smothered by weeds. Since the growth of grasses is fastest during the
rainy season, the first weeding should begin immediately after the planting is
finished at the end of the rainy season. If the weeding is carried out too late,
the seedling will not be able to survive the sudden exposure to light after the
weeding and it will die.
Cutting grass and other vegetation is a less effective form of
weeding, since the grass roots remain in the soil and keep competing with the
roots of the trees. On sites where competing vegetation is less vigorous and
where more weed-tolerant tree species have been planted, however, cutting weeds
in a 1m-wide circle around each tree seedling is sufficient.
2-3 weedings during the 1st year
1-2 weedings during the 2nd year
0-1 weeding during the 3rd year
If weeding is too late, the seedling
will die because of the sudden exposure
Grass-cutting on the entire site is also a way of harvesting the
grass. It is recommended in areas where the grasses grow high and are
hard-stemmed, and also when seedlings are small, because the light competition
and physical damage of the tall grass can suppress seedling growth. It also
helps to reduce the risk of bush fires. If grass is cut for fodder the nutritive
value will be highest when the grass is young and green immediately after the
rains, before flowering. If the grass is not carried away from the plantation
and used it should be mulched around the seedling. If thick enough the mulching
layer will suppress the further growth of weeds, reduce water loss and provide
the seedling with nutrients. Mulching may, however, attract termites and rodents
and should be avoided in areas where such damage is common.
Cutting the vegetation alone is not adequate on sites with heavy
grass competition, when the seedlings are small and for some weed-sensitive
species (teak, some eucalyptus species). Hoeing should also be done, preferably
in dry weather. At least one square metre around the plant should be hoed.
A very effective way to ensure that the weeding is carried out
well and that the seedlings are protected is to intercrop trees and agricultural
crops for the first 1-2 years after planting. For a description see section 7.4.
Tools required for grass-cutting are the same as for clearing. They are
described in section 2. 1.
A sickle is an additional tool, useful for cutting soft
stem grasses. It should be used if the seedlings are small and difficult to
locate, because the cut is easy to control. The scythe is otherwise preferable
since it permits work in an upright position. A sickle weighs about 0.3 kg and
the length of the sickle blade is about 0.3 m. It is used with one hand and the
cutting swing is made away from the seedling.
It might be necessary to remove climbing vines in moist and
humid regions. The best method is to use a Y-shaped stick to push the vine up.
The vines thus removed from the tree should not be cut, as they would sprout
again, but curled up and deposited at the base of the tree.
Grass-cutting decreases competition
and provides fodder
- suppresses weedgrowth
- reduces waterloss
Often both grass-cutting and hoeing