Multi-Species Tree Gardens and Alley Cropping
c) Multi-species tree Gardens:
d) Alley cropping (Hedge row intercropping):
- In this system of agroforestry, various kinds of tree species are grown mixed.
- The major function of this system is production of food, fodder and wood products for home consumption and sale.
- Alley cropping, also known as hedgerow intercropping,
- In this perennial, preferably leguminous trees or shrubs are grown simultaneously with an arable crop.
- The trees, managed as hedgerows, are grown in wide rows and the crop is planted in the interspace or 'alley' between the tree rows.
- During the cropping phase the trees are pruned and leaves and twigs are used as mulch on the cropped alleys in order to reduce evaporation from the soil surface, suppress weeds and/or add nutrients and organic matter to the top soil.
- The primary purpose of alley cropping is to maintain or increase crop yields by improvement of the soil and microclimate and weed control. Farmers may also obtain tree products from the hedgerows, including fuelwood, building poles, food, medicine and fodder, etc.
Plate 3.3 Alley croppingLayout of Alley:
- The position and spacing of hedgerow and crop plants in an alley cropping system depend on plant species, climate, slope, soil conditions and the space required for the movement of people.
- Ideally, hedgerows should be positioned in an east to west direction so that plants on both sides receive full sunlight during the day.
- The spacing used in fields is usually 4 to 8 meters between rows and 25 cm to 2 meters between trees within rows. The closer spacing is generally used in humid areas and the wider spacing in sub-humid or semi-arid regions.
Plate 3.4 (a) Alley croppingPlate 3.4 (b) Alley cropping
Characteristics of species for hedgerow intercropping: Alley cropping usually includes leguminous trees to improve soil fertility through nitrogen fixation; hence an ideal alley cropping tree or shrub species should have following characteristics:
- It should have a sparse, small crown to permit sunlight penetration into the cropped area
Plate 3.5 Hedgerow intercropping
- It should re-sprout rapidly after pruning, coppicing, pollarding or lopping.
- It should form a deep taproot system so that it takes moisture and nutrient from deeper layers and will not compete with agricultural crops.
- It should have shallow lateral roots that are easily ‘pruned’ by ploughing along the hedgerow, without serious damage to the plants.
- Fast decomposition rate of leaf litter.
- Ideally, trees and shrubs used for alley cropping should fix nitrogen.
- Trees/shrubs should be non-exacting in nature.
- Gliricidia sepium, Flemingia macrophylla, Leucaena, Calliandra calothyrsus, Erythrina subumbrans, Albizia saman, Pithecellobium dulce, Paraserianthes falcataria, Acacia spp., Paraserianthes falcataria and Cajanus cajan.
Advantages of Alley Cropping:
e) Multipurpose trees and shrubs on farmlands:
- Improved crop performance due to the addition of nutrients and organic matter into the soil/plant system,
- Reduction of the use of chemical fertilisers,
- Improvement in the physical nature of the soil environment.
- Reductions in erosion losses.
- Provision of additional products such as forage, firewood or stakes when a multipurpose tree legume is used as the hedgerow, and
- Improvement in weed control.
f) Crop combinations with plantation crops:
- In this system various multipurpose tree species are scattered haphazardly or according to some systematic patterns on bunds.
- The major components of this system are multipurpose trees and other fruit trees and common agricultural crops.
- The primary role of this system is production of various trees products and the protective function is fencing and plot demarcation. Examples of multipurpose trees employed in agroforestry are: Leucaena leucocephala, Acacia albida, Cassia siamea, Casuarina equisetifolia, Azadirachta indica, Acacia senegal, Cocos nucifera, etc.
Perennial trees and shrubs such as coffee, tea, coconut and cocoa are combined into intercropping systems in numerous ways, including:
i. Integrated multistory mixture of plantation crops;
ii. Mixture of plantation crops in alternate or other crop arrangement;
iii. Shade trees for plantation crops
iv. Intercropping with agricultural crops.
g) Agroforestry for fuelwood production:
- Tea (Camilia sinensis) is grown under shade of Albizia chinensis, A. odoratissim, A. lebbek, A. procera, Acacia lenticularis, Derris robusta, Grevillea robusta, Acacia spp., Erythrina lithosperma and Indigofera tesmanii.
- Coffee (Coffea arabica) is grown under the shade of Erythrina lithosperma as temporary shade while, permanent shade trees include Ficus glomerata, F. nervosa, Albizia chinensis, A. lebbek, A moluccana, A. sumatrana, Dalbergia latifolia, Artocarpus integrifolius, Bischofia javanica, Grevillea robusta.
- Cacao (Theobroma cacao) is grown under the shade of coconut and areca nut, and Dipterocarpus macrocarpa (in forest).
- Black pepper (Piper nigrum) is grown with support from Erithrina indica, Garuga pinnata, Spondias, Mangifera, Gliricidia maculata and Grevillea robusta.
- Small cardamom (Elettaria cardamomum) and large cardamom (Ammomum subulatum; A. aromaticum) grow in forests under temporary shade tree of Mesopsis emini.
- Large cardamom is grown under the shade of natural forest as well under planted shade treesviz., Alnus nepalensis, Schima wallichii; Cinchona spp.; Lagerstroemia spp., Albizia lebbek; Castanopsis tribuloides; C. hystrix; C. indica; Terminalia myriocarpa; Bischofia javanica.
- In this system, various multipurpose fuelwood/firewood species are inter-planted on or around agricultural lands.
- The protective role is to act as fencing, shelter belts and boundary demarcation.
- Tree species commonly used as fuelwood are: Acacia nilotica, Albizia lebbek, Cassia siamea, Casuarina equisetifolia, Dalbergia sissoo, Prosopis juliflora, Eucalyptus tereticornis, etc.