15 Factors influence in the selection of agroforestry plants

Factors influence in the selection of agroforestry plants

In general the factors influence in selection of spices for agroforestry are as follows

1.  Site factors.
2.  Effect on annual crops.
3.  Purpose of plantation.
4.  Type of agroforestry system.
5.  Marketability of produce.
6.  Multipurpose trees.
7.  Availability of tree species.
8.  Types of tree and crop species.
9.  Tree function.
10. Minimum temperature.
11. Soil condition.
12. Light constraints.
13. Drainage and soil water.
14. Pest and disease.
15. Space availability.

1. Site factors 

Site factor include climate, soil, physiography, Biotic. In any plantation, the species selected should first be adapted to the site condition. The climate, soil and biotic factor affect the growth and performance of trees, shrub and other forms of vegetation directly while the physiographic factors affect the climate and the soil and thus affect the vegetation.

Climate: Several climatic parameters should be considered of species selection for various Agroforestry system as total annual rainfall, humidity, number of rainy day, mean minimum and mean maximum with extreme ranges of temperature, incidence of natural calamities. e.g. frost, drought, flood etc. Each and every locality has a specific parameters which determines the choice of a limited number of species. On the basis of temperature the climate of locality may be classified as under table

Zone	Mean annual Temperature	Mean January Temperature	Remarks
I) Tropical	Over 24	Over 18	Cold season short or none. Frost and snow absent.
II) Sub-tropical	17-24	10-18	Cold season define but not severe. Frost during winter.
III) Temperate	7-17	-1-10	Winter pronounced with frost and snow.
IV) Alpine	Below 7	Below -1	Winter long and severe, snow common.

Bangladesh mainly lies between the tropical and subtropical zones. Only Hill ranges constitute subtropical, temperate and alpine zones. Every zone has almost a specific flora and choice of species is limited within that flora. On the basis of rainfall, the climate of a locality could be classified into the following

 Arid when annual rainfall is below 500 mm.

 Semi-arid when rainfall is between 500 mm to 750 mm.

 Dry when the rainfall is between 750 mm to 1250 mm.

 Semi-humid when the rainfall is between 1250 mm to 2000 mm.

 Humid when the rainfall is over 2000 mm.

Soil: Soil is another site factor, which is quite important. Various soil conditions also affect the decision regarding choice of species. Several physical and chemical characteristics of soil such as texture, stoniness, drainage, pan formation, soil depth, aeration, water table, moisture regime, soil pH, soil nutrients etc. are important for selection of species. The ability of a species to establish and grow well depends on its root system and its ability to absorb moisture and nutrients. Some species indicate a preference for specific soil condition.

Sl no	Soil Type	Suitable tree species
1	Desert soils	Khejur, palm, Babla, khoir etc.
2	Recent alluvium	Sissoo, khoir, nut, shimul etc.
3	Old alluvium	A large number of tropical species.
4	Saline alkali soils	Neem, goraneem, eucalyptus, Babla etc.
5	Coastal and deltaic alluvium	Khoir, sundari, gaoa, nut, coconut etc.
6	Red soils	Eucalyptus, ipil-ipil, kanthal, sissoo, teak etc
7	Black cotton soils	Acacia, babla, bael, khejur, teak etc.
8	Laterite and lateritic soils	Eucalyptus, teak, rubber, bot etc.
9	Hill soils	Umloki, shal, teak, mahogoni etc.
10	Organic soils	Jamrul, jam, rubber, bot etc.

2. Effect of Trees on Annual crops 

In Agroforestry system, the effect of trees on the surrounding annual crops is an important consideration. The tree species, which cause no or least damage to agricultural crops should be given preference. The following consideration is important:

 Species selected for Agroforestry system, should possess self pruning properties.

 If not self pruning, they should be able to tolerate frequent pruning.

 They should have small canopy and their phyllotaxies should permit the penetration of light on the ground.

 Their phenology with respect to leaf fall should be advantageous to the growth of the annual crop.

 Their rate of litter fall and litter decomposition should have a positive effect on the soil.

 Their root system and root growth characteristics should be such that it offers less competition to
agricultural crops for nutrient and water.

 They should be efficient in nutrient pumps.

3. Purpose of plantation 

Selection of trees for plantation in Agroforestry system must serve the purpose of the growers. The following needs should be kept in mind before selection:

A. Social needs: Social need include the firewood, small timber, poles, fruits, fibres etc. Several species like neem, goraneem, Acacia etc. meet variety of needs of the community. These species serve the multi-purpose requirement of the society. Therefore, multipurpose trees should be selected.

B. Industrial needs: As the natural forests are degrading day by day, selection of trees should be made in such a way that is also the requirement of the industry like plywood furniture, packing cases, sports goods etc. For this purpose, the small and marginal farmers should be encouraged to grow on marginal/degraded lands the wood species required by the industries along with the species of fuel and fodder required for their own used.

C. Environmental protection: Trees are playing and important role in keeping the environment conducive for both human and animal being. Therefore, from the viewpoint of environmental conservation, the following points need to be considered

 The species should be able to improve the site condition through conserving soil and water. Improving the nutrient cycling and regenerating the site ecologically.

 The species should be able to favorably modify the micro-climate in the area.

 The species should be able to maintain the ecological balance in the system.

 The species should be able to withstand adverse condition.

4. Types of Agroforestry systems 

Selection of species depends on Agroforestry systems. For example, under the agrisilvicultural systems such species are preferred which are multipurpose, fast growing and have commercial importance. For the silvipastural system, tree species which can yield fodder are preferred. Similarly for village woodlots, species having higher fuel wood and fodder values are generally recommended.

5. Marketability of produce 

With the intensification of the demand of fuel wood, fodder and timber, there is always a crisis for these plant products and such as its market price is increasing day by day. Therefore in Agroforestry, only such species have become popular which is fast growing and capable of giving a return within about shorten possible period. Species which are able to give return in terms of timber within a period of 10 to 15 years are especially suitable for Bangladesh condition as it’s farmers are poor.

6. Effect on site 

The effect of a species on the site is important in the long run. The species selected should be such that it is able to protect and improve the site condition. In Agroforestry, such species need to be selected which produce leaves that are easily decomposed to form the right type of humus. The nitrogen fixing trees (NFT) having desirable characters are best as it offering the following benefits:

 NFT contribute to sustainable Agroforestry production through maintaining soil productivity. Some NFT. i.e. A c a c i a have a long and deep tap root system. While Sesbania , Gliricidia posses small leaflets that decompose more rapidly which add organic matter to the surface soil.

 Several NFT have multiple uses and provide a combination of benefits. Several species like Acacia , leucaena , Dalbergia etc provide fuel timber, green manure, living fences etc.

 NFT litter fall and moisture conserving shade also improves grass yield.

 Protein rich leaves and pods make many NFTs excellent forage that animals readily eat.

 Plantation crops such as coffee, cocoa and tea often benefit from the shade and nitrogen rich litter fall provided by such NFTs as Erythrina , Gliricidia , leucaen a and others. Some farmers use NFT to fertilize shade and support crops such as pepper, vanilla and vam.

 Many NFT are planted for erosion control, watershed protection, wind breaks, leaving fences and ornamentals and for production of timber products such as tannins, gum and medicine.

 Some of the NFT are extremely fast growing.

 Some NFT have the capacity to establish in area despite heavy grazing pressure.

 A lot of NFT are specially suitable in the degraded site like saline soil, acidic soil, alkaline soil, soil with drainage and drought affected soils where other species rarely withstand.

7. Multipurpose Trees (MPTs)

The term ” multipurpose tree ” refers to all woody perennials that are purposely grown so as to provide more than one significant contribution to the production or service functions (food, fodder, fuel, timber, shelter, shade, land sustainability) of the land use system they implement. Accordingly, a tree which will serve more than one purpose is a multipurpose tree. A single tree may serve more than one purpose. For example, Gliricidia sepium that in addition to green manure provides fuel, fodder and acts as live fence