Silviculture and Methods of tree cultivation



Silviculture refers to the raising of trees. When trees are introduced into farms along with field crops, it is known agrisilviculture or agroforestry system. Tress provides many benefits to mankind. They play protective role by making available a variety of products for human consumption, for livestock and for industrial raw material needs.

E.g., fruits, nuts, fuel, fodder, timber, wood, wax, resin, etc. They also play a protective role through soil and moisture conservation, enrichment of soil fertility through nutrient recycling and protection of environment.

(i) Methods of tree cultivation

Block culture: Large area is planted with selected species of tress suitable for fuel, timber, wood or industrial use (multipurpose tree species). It is also known as wood lots or energy plantations when planted for fuel. e.g., Eucalyptus, Acacia, Prosophis.

Staggered planting: Trees are grown scattered in the field with annual crops raised in the interspaces. Multipurpose tree species suitable for fuel, fodder, wood and timber can be planted at 20–50 trees per ha. E.g., Acacia + fodder sorghum, Neem + pulses/sorghum.

Border trees: Trees can be grown along farm boundaries and field borders for economic use as well as boundary markers. E.g., Palmyrah, Neem, Tamarind, Eucalyptus.

(ii) Different systems of tree culture

1. Agrisilviculture (Agroforestry): Trees and annual crops are raised in an intercropping system in the same field. Trees are planted at 5-8 m spacing and field crops are sown in the interspaces during rainy reason. E.g., Leucaena + sorghum/pearl millet/castor/pulses, neem/vagai + fodder sorghum/pulses.

2. Silvipasture: Leguminous fodder trees are raised with fodder grasses and legumes as intercrops. E.g., acacia + cenchrus + stylosanthes, vagai/sisoo + cenchrus + stylosanthes.

3. Alley cropping or hedgerow intercropping: Annual field crops are grown in alleys formed by hedgerows of trees and shrubs. The trees or shrubs in hedge rows are cut back to short height (0.5–1.0 m) at sowing of annual crops with onset of rains and kept pruned during crop growing season to reduce shade effect and competition with field crops. The width of alley (space between hedges) is about 4–6 m. e.g., leucaena or desmanthus as hedge row with sorghum, maize, pigeon pea and sunflower as intercrop. Alley cropping offers many benefits.

• Green fodder from hedgerows during dry season, and food and dry fodder from annual crops during rainy season.

• Off season rainfall is utilized by hedgerow trees or shrubs.

• Hedge rows check runoff and erosion when formed along contour or across slope.

• Loppings and prunings from hedgerows can be used as fodder, fuel wood or for mulching.

• Yield of crops raised in the alleys is improved due to better microclimate through reduction in temperature and wind speed, increase in humidity and reduction in evapotranspiration loss.

Success in alley cropping depends on alley width and height of hedgerows. Alley width of 5–6 m has been found to be effective. Low height of 45–50 cm is desirable. Usually one cutting of hedgerow shrubs at the time of sowing of annual crops and subsequent prunings at monthly interval during cropping season are optimal. During dry season, cutting is done depending on fodder requirement.

4. Timber-Fibre system (TIMFIB system): It involves growing trees and perennial fibre crops together. E.g., Leucaena + agave.

(iii) Choice of trees for dry lands

Trees suitable for dry lands must have the characters like multipurpose tree species (fodder, fuel, timber, wood), adaptable to wide variations in soil and climate, rapid growth and withstanding against severe pruning.

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