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Ground Cultivation Methods
The most important reason for cultivating ground prior to planting is to provide a suitable planting medium for the trees. Soil-type, slope and drainage conditions will dictate the most suitable method of cultivation.
Mechanical mounding
This is the most commonly used technique. It is carried out in areas where drainage is a problem or where there is a high water-table. A tracked excavator opens sloping-sided drains, using the spoil from the drains to form mounds into which the trees are later planted. The drains may be opened at 8 or 12 metre intervals. If the topsoil is shallow it is preferable to mound at 8 metre intervals as less sub-soil is brought up to form mounds.
There are a number of advantages associated with mechanical mounding:
• The closeness of drains improves overall site drainage and helps to lower the water-table.
• The soil in the mound is loose and aerated and provides a planting medium which encourages immediate root development.
• Trees on mounds are raised above competing vegetation and will generally stay clean for the first season thus reducing vegetation control costs.
• Rooting is not restricted in any direction so the tree develops a radial root system which will provide for good crop stability in later years.
• The greatest disadvantage of mechanical mounding is that access around the site is made more difficult.
Ripping
This technique is commonly used on sites where there is a layer such as an iron pan or a cultivation pan, beneath the surface. A bull-dozer pulls a tine behind it to a depth of 45 cm, shattering the pan layer. The trees are planted approximately 9 cm from the centre of the rip channel. This provides for better rooting through the pan which would have previously been impenetrable to tree roots. Ripping leads to good stability, however, initial establishment is slower than on mounded sites and weed control will be necessary from the outset. Care must be taken to provide adequate cut-off drains and to ensure that there is sufficient slope for water run-off while ensuring that erosion is prevented.
Planting machine
This system is only suitable for good soils that do not need cultivation and/or drainage.
There are a number of different types of planting machines in use but all of them operate on the same basic principle. A trench is opened by a tractor mounted plough. An operator sitting on the machine places the trees into the trench at the required spacing. The trench is subsequently closed and the tree is firmed in either by the machine or manually, by somebody walking behind the machine. This system may be used for planting conifers or broadleaves and generally results in very high survival rates and good subsequent growth.
Fencing
All plantations must be completely stock-proof and fenced to Forest Service specifications. It is very important to keep all livestock out of the site as losses and damage to trees will lead to higher filling-in and maintenance costs. Long–term rooting damage caused by stock is generally irreversible. It is often more economical in the long-run to erect a new fence rather than patch existing fences and risk damage from trespass. The type of fencing to be erected will depend on whether there are cattle or sheep outside the plantation. If there are rabbits or hares in the area, it is vital to erect rabbit proof fencing as damage can be very severe. Ensure that gates and entrances are wide enough to accommodate machinery in the future and that stiles are provided to make access to the site easier. All wire around forests should be stapled to the outside of the forestry fencing stakes i.e. on the side facing the livestock.
Fertiliser
Marginal sites generally require an application of Granulated Rock Phosphate. It is important to make provision for distribution of fertiliser around the site. Fertiliser must be applied between the months of April and August in order to maximise uptake and minimise environmental damage. Many midland peat sites may require an application of potash. Land which was farmed intensively before planting does not usually require fertiliser application.
Plants and Planting
Trees are generally planted during the dormant season when they are not actively growing. This normally runs from November to late April. It is possible to extend the season by using plants from cold storage.
Plant Quality
The quality of the plants used and the actual planting operation are vitally important. If poor quality plants are used or if the planting is of poor quality, trees may die. The size and species of tree required will be specified on your approval letter. It is a good idea to have your contractor or consultant check the health and quality of the trees when they arrive on site. Also check that the bags contain the correct number, grade and species as specified on the label.
Trees should only be bought from a registered nursery, which can supply both a Provenance Declaration Form/Suppliers Document and depending on the species, a Plant Passport.
Planting
The planting method used will be determined largely by site conditions and cultivation method. Specialised tree-planting machines may be used on level ground which does not require cultivation. However, many forestry sites are not suitable for this type of machinery, so planting by hand is still the most common method. There are a number of different planting techniques:
• Slit planting involves the opening of a slit into which the roots are placed and the slit is closed up afterwards. This technique is used largely on mechanically mounded and ploughed sites where the soil is already loosened.
• Angle notch planting involves the opening of an L or T shaped notch with a spade. The roots of the tree are placed in the angle and tightened in. This is carried out on ripped sites as it gives the tree a better start where the soil has not been loosened.
• Pit planting is done where cultivation is not possible and involves digging a hole for the tree. This is the most time-consuming and expensive planting method.
The number of trees to be planted will depend on the species. For conifers the required stocking is generally 2500 trees per hectare. Between 3,300 and 6,600 broadleaf trees per hectare are required, depending on species.
Regardless of the technique used, the principles of good planting are the same.
• Ensure the tree is planted upright,
• All roots must be underground & facing downwards,
• Plant tree to correct depth (root collar),
• Trees should be firm in the ground without compacting the roots,
• Don’t force roots into the soil with the spade.
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