Trees planted on farms may be labelled farm forestry, agroforestry or landcare planting, depending on their main purpose. However, the distinction is often artificial, as the names have considerable overlap, especially where trees are managed for multiple purposes. There are many things to consider when planting trees which will depend on why you are planting them. If it is purely a commercial timber crop, a uniform block of trees will be most efficient for harvesting, but if crop trees are being incorporated into a windbreak or amenity planting, something less formal will be required.
Farm forestry
A broad definition of farm forestry includes any trees on farm land which are managed to produce saleable products such as timber, oil, tannin, charcoal or carbon credits. The farm forestry label is now being used to include the commercial management of native forest on farms as well.
Agroforestry
The purpose of agroforestry is to incorporate trees and shrubs into farming systems to gain from their positive interactions with agriculture. Benefits gained from trees and shrubs may be direct (timber), indirect (shade, shelter and fodder), or a mixture of both. The terms agroforestry and farm forestry are often used interchangeably.
Landcare
Landcare plantings are a form of agroforestry at the non-commercial end of the spectrum. Trees and shrubs are grown with the primary aim of protecting land and water, and enhancing nature conservation. The benefits to agriculture are usually indirect, through improved farm productivity and sustainability.
Tree layouts in farm forestry
Many different tree layouts have been developed by farmers trying to find the optimum way to fit trees and other farming enterprises together. Typical layouts range from large plantations, to smaller blocks or woodlots, belts, windbreaks, alley farming and widely spaced trees. Since each farmer has a unique set of goals, and a unique piece of land, the optimum farm forestry layout varies from farm to farm.
Woodlot or small plantation:
With a woodlot or small plantation, timber production and agriculture are managed as separate enterprises though there may still be a degree of interaction between the two. Stock may graze and shelter beneath the trees, and the trees may enhance the productivity of part of the farm by lowering ground water, or providing protection from prevailing winds. This layout is suitable for producing pulplogs or sawlogs with minimum management.
Because competition between trees in plantations produces tall, straight crop trees with small side branches, labour requirements for pruning are lower than in more integrated layouts. Plantations are suited to areas where tree farming is a more profitable long term pursuit than other agricultural activities.
Shelter belts:
Trees planted in this way are integrated into the farm to achieve land management goals. Typical examples are protection from wind, ground water control, erosion prevention, drainage line protection, aesthetic enhancement, and provision of wildlife corridors. As well as producing commercial products, tree belts can increase farm income indirectly by raising the productivity of adjoining agricultural enterprises.
Trees grow faster in belts than in blocks, because more of the trees are at the edge, where there is less competition from other trees. However, edge trees grow larger side branches and are more likely to need pruning to produce high quality sawlogs, or logs suited to mechanical harvesting for pulp. The fencing requirement is also greater than for a plantation.
Alley farming:
In alley farming, narrow belts of trees are planted in straight rows or along contours, with grazing and cropping between the rows. The aim is to maximise returns per hectare from an integrated system. This type of layout is ideal where the trees enhance agricultural production by sheltering stock, lowering ground water or reducing wind erosion. Alley layouts with a standard width of trees are especially suited to tree crops such as oil mallees, where the foliage will be harvested regularly by machine. Timber trees can also be grown successfully in alley layouts. With good access to light, water and nutrients, they can grow very quickly. However, the trees are more likely to develop curved and forked trunks, and produce large side branches because of the reduced competition for light. Intensive management, especially form pruning and branch pruning, may be needed to produce high value timber.
Windbreak design
Windbreaks can produce valuable timber, even earning more per hectare than other farm enterprises. Total farm profit can be increased by putting windbreaks closer together than the usual recommendation of 20 to 30 times tree height. Having a greater number of windbreaks than needed for wind protection alone, allows some windbreaks to be harvested from time to time without jeopardising wind protection on the farm. Windbreaks managed for timber production are likely to be harvested after 10 to 12 years (for pulpwood or posts), or 20 to 40 years for sawlogs.
Tree height is the main factor governing a windbreak's effectiveness, so the taller the trees, the further windbreaks can be spaced apart. Windbreaks give protection to the area around them where wind speed at ground level is reduced by at least 20 per cent. Using this yardstick, windbreaks can protect land for at least 20 tree heights in their lee, and up to four tree heights upwind. The area of greatest protection is between two and 10 tree heights downwind. Windbreaks have little or no effect beyond 30 tree heights.
On soils prone to wind erosion, or in hilly areas with complicated wind patterns, spacings of 20 times tree height or less are recommended. Use even closer spacings where high levels of shelter are needed, for example, around horticultural crops, feedlots, dairies, buildings, and paddocks for lambing or for off-shears sheep.
Windbreaks are most effective for wind approaching at right angles.
Choose a planting layout that suits the species, site, timber products wanted, and the type of management intended.
For example, to grow tall slender pines for round posts, plant them in rows 3 m apart, with trees at 2 m spacing along the rows (1667 per hectare).
Eucalypts to be harvested for pulpwood are usually planted in rows 4 m apart, with trees 2 to 3 m apart in the rows (1250 to 833 per hectare). The closer spacing is suitable for areas with rainfall over 800 mm, while the wider spacing is recommended for drier areas. No thinning is needed before harvest.
Use similar spacings when planting trees for sawlogs, but thin them early, to retain only the best trees for timber production. Thinning eucalypts to 200 per hectare and pines to 500 per hectare by age six gives a good balance of timber production and shelter. To grow sawlogs even faster, eucalypts can be thinned to 150 to 200 and pines to 200 to 400 per hectare at this first thinning, but shelter is reduced
Trees in the outer rows of windbreaks can grow at twice the rate of trees in the centre rows, due to reduced competition for light, water and nutrients. However, they usually need more management. For example, most edge trees develop large branches that need pruning to produce sawlogs, or to be suitable for mechanical harvesting for pulpwood.
Eucalypt edge trees may also produce lower quality timber, due to curvature and growth stresses. The trees tend to grow towards the open paddock and develop curved trunks. Also, because most of the branches and foliage grow on one side, the outer side of the trunk grows more rapidly than the side facing inwards, producing elliptical growth rings. Because eucalypt edge trees are more likely to develop growth stresses, more care is needed when sawing and seasoning them, to minimise splitting and warping.
Farm forestry
A broad definition of farm forestry includes any trees on farm land which are managed to produce saleable products such as timber, oil, tannin, charcoal or carbon credits. The farm forestry label is now being used to include the commercial management of native forest on farms as well.
Agroforestry
The purpose of agroforestry is to incorporate trees and shrubs into farming systems to gain from their positive interactions with agriculture. Benefits gained from trees and shrubs may be direct (timber), indirect (shade, shelter and fodder), or a mixture of both. The terms agroforestry and farm forestry are often used interchangeably.
Landcare
Landcare plantings are a form of agroforestry at the non-commercial end of the spectrum. Trees and shrubs are grown with the primary aim of protecting land and water, and enhancing nature conservation. The benefits to agriculture are usually indirect, through improved farm productivity and sustainability.
Tree layouts in farm forestry
Many different tree layouts have been developed by farmers trying to find the optimum way to fit trees and other farming enterprises together. Typical layouts range from large plantations, to smaller blocks or woodlots, belts, windbreaks, alley farming and widely spaced trees. Since each farmer has a unique set of goals, and a unique piece of land, the optimum farm forestry layout varies from farm to farm.
Woodlot or small plantation:
With a woodlot or small plantation, timber production and agriculture are managed as separate enterprises though there may still be a degree of interaction between the two. Stock may graze and shelter beneath the trees, and the trees may enhance the productivity of part of the farm by lowering ground water, or providing protection from prevailing winds. This layout is suitable for producing pulplogs or sawlogs with minimum management.
Because competition between trees in plantations produces tall, straight crop trees with small side branches, labour requirements for pruning are lower than in more integrated layouts. Plantations are suited to areas where tree farming is a more profitable long term pursuit than other agricultural activities.
Shelter belts:
Trees planted in this way are integrated into the farm to achieve land management goals. Typical examples are protection from wind, ground water control, erosion prevention, drainage line protection, aesthetic enhancement, and provision of wildlife corridors. As well as producing commercial products, tree belts can increase farm income indirectly by raising the productivity of adjoining agricultural enterprises.
Trees grow faster in belts than in blocks, because more of the trees are at the edge, where there is less competition from other trees. However, edge trees grow larger side branches and are more likely to need pruning to produce high quality sawlogs, or logs suited to mechanical harvesting for pulp. The fencing requirement is also greater than for a plantation.
Alley farming:
In alley farming, narrow belts of trees are planted in straight rows or along contours, with grazing and cropping between the rows. The aim is to maximise returns per hectare from an integrated system. This type of layout is ideal where the trees enhance agricultural production by sheltering stock, lowering ground water or reducing wind erosion. Alley layouts with a standard width of trees are especially suited to tree crops such as oil mallees, where the foliage will be harvested regularly by machine. Timber trees can also be grown successfully in alley layouts. With good access to light, water and nutrients, they can grow very quickly. However, the trees are more likely to develop curved and forked trunks, and produce large side branches because of the reduced competition for light. Intensive management, especially form pruning and branch pruning, may be needed to produce high value timber.
Windbreak design
Windbreaks can produce valuable timber, even earning more per hectare than other farm enterprises. Total farm profit can be increased by putting windbreaks closer together than the usual recommendation of 20 to 30 times tree height. Having a greater number of windbreaks than needed for wind protection alone, allows some windbreaks to be harvested from time to time without jeopardising wind protection on the farm. Windbreaks managed for timber production are likely to be harvested after 10 to 12 years (for pulpwood or posts), or 20 to 40 years for sawlogs.
Tree height is the main factor governing a windbreak's effectiveness, so the taller the trees, the further windbreaks can be spaced apart. Windbreaks give protection to the area around them where wind speed at ground level is reduced by at least 20 per cent. Using this yardstick, windbreaks can protect land for at least 20 tree heights in their lee, and up to four tree heights upwind. The area of greatest protection is between two and 10 tree heights downwind. Windbreaks have little or no effect beyond 30 tree heights.
On soils prone to wind erosion, or in hilly areas with complicated wind patterns, spacings of 20 times tree height or less are recommended. Use even closer spacings where high levels of shelter are needed, for example, around horticultural crops, feedlots, dairies, buildings, and paddocks for lambing or for off-shears sheep.
Windbreaks are most effective for wind approaching at right angles.
Choose a planting layout that suits the species, site, timber products wanted, and the type of management intended.
For example, to grow tall slender pines for round posts, plant them in rows 3 m apart, with trees at 2 m spacing along the rows (1667 per hectare).
Eucalypts to be harvested for pulpwood are usually planted in rows 4 m apart, with trees 2 to 3 m apart in the rows (1250 to 833 per hectare). The closer spacing is suitable for areas with rainfall over 800 mm, while the wider spacing is recommended for drier areas. No thinning is needed before harvest.
Use similar spacings when planting trees for sawlogs, but thin them early, to retain only the best trees for timber production. Thinning eucalypts to 200 per hectare and pines to 500 per hectare by age six gives a good balance of timber production and shelter. To grow sawlogs even faster, eucalypts can be thinned to 150 to 200 and pines to 200 to 400 per hectare at this first thinning, but shelter is reduced
Trees in the outer rows of windbreaks can grow at twice the rate of trees in the centre rows, due to reduced competition for light, water and nutrients. However, they usually need more management. For example, most edge trees develop large branches that need pruning to produce sawlogs, or to be suitable for mechanical harvesting for pulpwood.
Eucalypt edge trees may also produce lower quality timber, due to curvature and growth stresses. The trees tend to grow towards the open paddock and develop curved trunks. Also, because most of the branches and foliage grow on one side, the outer side of the trunk grows more rapidly than the side facing inwards, producing elliptical growth rings. Because eucalypt edge trees are more likely to develop growth stresses, more care is needed when sawing and seasoning them, to minimise splitting and warping.