|Special Public Works Programmes - SPWP - Planting Trees - An Illustrated Technical Guide and Training Manual (ILO - UNDP, 1993, 190 p.)|
|6. Maintaining plantations|
Planting trees is one thing, protecting them during the critical first three to six years, however, is something else. Far too many plants that have been raised and planted with care, effort and knowledge, die due to lack of maintenance of the plantations.
The maintenance operations and protection that might be needed are:
- Weed control
- Protection from grazing
- Fire prevention
- Protection from insects, diseases and rodents
- Replacement planting
Protection from grazing
Protection from insects, diseases and rodents
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 be:
2-3 weedings during the first year after planting;
1-2 weedings during the second year after planting;
0-1 weeding 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
- provides nutrition
Often both grass-cutting and hoeing is needed
Removal of climbers
Tree seedlings may also be harmed by animals. Cattle, sheep, goats and sometimes wild animals must be kept out of the plantation until the trees are big enough to withstand grazing. This problem is most acute in dry areas with sparse vegetation where animals turn to planted trees for food. Without the cooperation of the livestock owners protection will be difficult. It is therefore essential to discuss the problem very early during planning and to meet regularly after planting to sort out problems.
When bigger areas representing a large portion of the accessible grazing lands are being planted and where grazing is scarce, it might be necessary to divide the planting area into compartments and to plant them one at a time. The livestock is then allowed into the first compartment when the second one is being planted some years later, and so on. In this way the area where grazing has to be avoided is minimized. It may also be necessary to use species that are not readily grazed by the animals (for example prosopsis, ailanthus and some eucalyptus). If these measures are not sufficient, fences should be built before or during planting.
For smaller plantations fences can be built with branches cut from thorny trees or other suitable material to protect the plants for the first couple of years. However, these lands of fences require a large quantity of branches and may put an additional pressure on an already stressed forest or bushland.
Hedges of closely planted bushes and trees (live fences) can also be created. Thorny plants such as Cactus, Euphorbia, Aloe, Sisal, Acacia or Juniperus can be used. Species that can be grown from large cuttings are preferable. Live fences must, however, be planted some years before the trees are planted and be given time to reach a sufficient size to keep out the animals.
All types of fences have to be maintained. Where fences alone do not protect the plantation, a watchman can also be used to look after the plantation.
Protection from grazing
Bamboo fence combined with thorny branches
Bamboo fence combined with hedge
Bush fires in planted areas are almost always man-made. Fire is used to clear land, to improve grazing and to chase away wild animals. Fires may also be caused by carelessness during charcoal burning and honey collection.
Prevention of fire depends to a great extent on information and extension work. An understanding of the value and benefits of the forest for all members of the community must be reached. Where the plantation to be protected does not belong to individual private owners or to the local community, the interest of the local population can be increased by sharing the produce of the plantation. This can be done in several ways. Local people can be given the right to collect non-wood products like grass, mushrooms, honey, etc. They can also be offered a share of the wood or other products from the plantation. To protect large areas of state forest plantations, local people can be given private wood-lots to form a protective belt around the state forest.
Firebreaks combined with a well designed road system may keep the fire from spreading. Firebreaks consist of corridors about 20 m wide that are kept without vegetation cover. Maintenance of firebreaks is simple but labour intensive. They must be cleared at least once a year at the beginning of the dry season. Controlled grazing or cutting grass for stall-feeding can be used to minimize the amount of flammable dry grasses in the forest. Controlled grazing can also be used for clearing firebreaks.
Plantation staff and peasant association members may be trained in fire control. Small fires might be extinguished with water or plantation tools such as hoes or spades. If a fire has spread over a bigger area, the only practical way to control the fire is to remove flammable fuel from the path of the fire by opening up corridors without vegetation (fire lines). Already existing fire lines such as firebreaks and roads can be enlarged. Large forest fires can be fought with the help of backfire. A backfire is started on a strong fire line and directed towards the main fire. A wide corridor will be burned and when the two fires meet they will die for lack of fuel. Backfiring techniques need a lot of labour and should only be used under the supervision of an experienced fire fighting crew since there is always a danger that the fire can spread away from the back of the fire, starting new main fires.
Fire prevention depends upon information
Share benefits of the forest
Fire fighting crew
Tree seedlings may also be harmed by insects, diseases and rodents.
Species liable to insects and diseases should be avoided. The best form of protection is to diversify the plantation, using various tree species. Treatment with pesticides or dipping of plants (i.e. planting seedlings treated with pesticides) may also be used. Some safety guidelines for the use of pesticides are given in section 9.5.
Rodents may cause damage to saplings, especially at high altitudes. The best form of protection from rodents is to keep the soil around the seedlings bare, i.e. well weeded. Rodents avoid bare soil where they are visible to birds of prey. Therefore, weeding limits the damage that can be done by rodents above the soil surface. Mechanical protection of the lower stem of young trees also works quite well. A suitable protection would be a split bamboo tube. The two halves of the tube are placed around the stem and tied together with a string. Protecting seedlings from rodents that damage the roots underground is more difficult. Traps, repellants or poisoning may be used.
On poor sites a dose of manure or chemical fertilizer may be valuable. It should be applied during a rather dry period towards the end of the rainy season, preferably hi combination with weeding in order to avoid run-off or absorption by weeds. The simplest method is to apply about one tablespoon of chemical fertilizer in two small patches on each side of the tree, 15-30 cm from the stem, and hoe it in.
Protection from insects, diseases and rodents
Choose resistant species
A variety of species reduces risk of damage
Protection from insects
Rodents avoid bare soil
Rodent protection with bamboo tube
Protection from rodents
On poor sites fertilizer may be used
Even if the seedlings are of good quality, carefully planted and suitable to the site conditions, there will always be a number of seedlings which do not survive. Replacement or "beating up" is always expensive. Therefore it is necessary to decide carefully, whether replacement is required or not. This depends on the percentage of seedlings that died and on their distribution on the site.
Replacement will be necessary only if more than two in ten plants have died and only where at least two neighbouring seedlings have died. If the rate of failure is below 20 per cent, replacement will only have to be done if the failures are concentrated in particular areas of the site.
A method of establishing survival rates is described in Technical sheet 3. The survival count should be carried out at the end of the dry season following planting. Replanting is then done at the beginning of the rainy season that follows.
For replacement, big seedlings of the best quality should be planted at the beginning of the rainy season. If one person completes the whole replanting operation - carrying of the seedlings, digging the holes, planting the seedling - a minimum of time will be spent for walking and locating where planting is needed.
There might be a need for more than one replacement planting. But where after two replanting operations the area is still not adequately stocked, a thorough check is necessary as regards suitability of planting techniques, plant quality, weeding practices, choice of species and the quality of the work.
In the long run it is better to invest more in site preparation, planting and weeding than in replacement.
Less than 20% dead ® no replacement
Less than 20 % but concentrated ® replacement
More than 20% dead ® replacement
Common mistakes in maintaining plantations
Weeding too late.
Not continuing weeding long enough.
No, or insufficient, protection from grazing.
Protection from grazing and fire relies too much on technical means such as fences and firebreaks rather than on reaching agreement with the local population.