AGROFORESTRY AGRICULTURE FORM FOUR
AGROFORESTRY AGRICULTURE FORM FOUR: agroforestry. Collective term used to cover a variety of land uses that combine tree growing, pasture and crop production practices on the same piece of land.
Forms of agroforestry.
- Agrosilviculture.
Growing of tree/shrubs and crops. It is practised in high rainfall areas. ii. Silvopastoral.
Growing of trees/shrubs and keeping livestock. It is suitable for ASAL where indigenous and improved breeds of livestock and hardy tree species do well. iii. Agrosilvopastoral.
Combination of growing trees/shrubs together with pastures for livestock and crops. Done in high potential areas.
Importance of agroforestry.
- Remedy to deforestation (source of wood)
Agroforestry provides sustainable source of fuel wood helping to ease wood shortages and reduce environmental degradation.
- Source of income.
Products from trees/shrubs e.g. fruits, poles, timber and fodder can be sold. They also help in saving cash that would have been used to acquire them.
E.g. leucaena leucocephala and calliandra calothyrsus provide excellent fodder.
- Environmental benefits.
Trees protect soil from strong wind, rain and sun reducing soil erosion.
Litter from leaf fall add organic matter to the soil.
On large scale, agroforestry improves water catchment. iv. Labour saving.
Time spent looking/fetching firewood could be employed on other productive work in the farm.
- Aesthetic value.
Trees/shrubs helps to beautify the environment and make the place more pleasant to live in.
AGROFORESTRY AGRICULTURE FORM FOUR
Important Trees and Shrubs.
Trees and shrubs should be selected properly according to their specific purpose.
Trees and shrubs compete with crops for soil nutrients and space but with correct spacing management may increase the yields of the crops.
Characteristics of Trees and Shrubs to use in Agroforestry.
- Fast growth.
Should have fast growth rate so that one do not need to wait too long to get the end products. E.g.
- Eucalyptus
- Grevillea
- Calliandra
- Croton
- Deep rooted.
To reduce competition for minerals, nutrients and moisture with crops. It also enables them to tolerate drought. E.g.
- Eucalyptus
- Grevillea iii. Nitrogen fixing.
Should be capable of fixing nitrogen into the soil. E.g.
- Cajanus cajan
- Sesbania sesban
- Leucaena spp
- Calliandra calothyrsus
- Good in by-product production.
Trees should produce by-products without harming the crop plant. E.g. timber, fruits and poles. E.g.
- Markhamia lutea
- Grevillea robusta
- Croton macrostachysus
Trees and shrubs to avoid at certain sites.
- Cypress and eucalyptus leaves have allelopathic effects on crops and should not be planted in arable land.
- Bushy trees should not be planted near homestead because they may harbour predators.
- Trees and crops should be in multi-storey structure to avoid tall trees from shading other crops.
- Soil fertility restoring species should be planted on land left to fallow.
AGROFORESTRY AGRICULTURE FORM FOUR
Tree Nursery.
Types of Nurseries.
Nursery bed is a special seedbed prepared for raising seedling before transplanting. They should be 1M wide.
- Direct Nurseries.
Seeds are planted directly on the ground without any container. It is called bare root or Swaziland beds.
They are easy to establish but survival rates of seedlings is low due to root injury when uprooting.
- Containerised Nurseries.
Seeds are sown directly in containers filled with soil. Containers include; pots, poly bags, plastic or tins.
Seed collection and preparation.
Acquiring seeds.
High quality seeds ensures a good start in the nursery. Seeds should be free from diseases and pest and fresh to ensure high viability.
Seed treatment.
Reasons for treatment.
- To break seed dormancy and ensure rapid germination. ii. Seed inoculation which improves vegetative growth associated with Nitrogen Fixing bacteria.
Methods of seed treatment.
- Hot water treatment.
It softens the seed coat and makes it more permeable to water. The temperature is 80 degrees Celsius for 3-5 minutes then water is drained and soaked in cold water for 24 hours until it swells.
Examples. Acacia, Calliandra and leucaena.
ii. Mechanical breaking.
Done by filling or nickling the seed coat with a knife to facilitate water entry.
Examples. Croton megalocarpus
iii. Light burning.
Applied to seeds of wattle tree. Trash is spread over the seeds covered with a thin layer of soil and burnt.
Nursery management.
- Mulching.
A light mulch should be applied on the nursery bed and should be removed as soon as seedlings starts to emerge. Mulching reduces excessive evaporation and moderates soil temperatures.
ii. Watering.
Should be watered regularly preferably in the morning and evenings.
iii Pricking out.
Overcrowded seedlings should be removed and planted on another nursery bed to allow seedlings to grow strong and healthy without competition.
iv Weed control.
Weeds should be removed through uprooting.
v Root pruning.
Long tap roots makes lifting of seedlings difficult and increase the chances of damage to seedlings.
Root pruning encourage the development of a strong tap root.
vi Shading
Dark conditions should be avoided.
vii Pest and Disease control.
Soil should be sterilised through heat treatment or application of chemicals (Furadan-banned) Use appropriate chemicals.
viii. Hardening off.
Helps seedlings to adapt to prevailing ecological conditions in the seedbed.
Involves gradual reduction of shade and watering frequency 1-2 weeks before transplanting.
ix Transplanting.
Holes should be dug long before transplanting (3 months before) The top soil is kept separate to be used for refilling the hole halfway.
Transplant at onset of long rains.
Water seedlings well a day before transplanting for the following reasons:
- Makes the soil to stick around the roots.
- Eases the removal of polythene sleeves during transplanting.
Seedlings should be planted on the same depth they were in the nursery bed and soil firmed around the seedlings.
After transplanting they should be watered, mulch applied and a temporal shade erected to conserve moisture.
AGROFORESTRY AGRICULTURE FORM FOUR
Care and management of trees.
- Protection
Young trees should be protected from damage by animals for one year. To protect trees from being browsed on.
- Pruning and training.
Pruning is the removal of extra or unwanted parts of a plant. Unwanted parts may be due to breakages, overcrowding, pest or disease attack and low productivity.
Tree branches may be pruned for use as fuel wood or for fodder.
- Grafting old trees.
Compatibility is the ability of scion and rootstock to form a successful union.
Agroforestry practices.
- Alley cropping/ Hedgerow/intercropping.
This is growing of trees and crops. Trees are cut regularly and the leaves used to mulch the crops.
Tree species should be leguminous to fix nitrogen.
Aims.
Improvement of the soil.
The spacing should be wide enough to avoid competition for growth resources. Trees should have an open crown to let sunlight through. Roots should be lateral and shallow but with deep tap roots system. Tree species include: Leucaena and calliandra.
- Multi-storey cropping.
Based on crops that tolerates shading.
Trees and crops form different levels that look like storeys.
Trees are spaced widely and left to grow unchecked. Spacing of 8-20M by 4M (between crops)
Trees should be planted running east to west to reduce the effect of shade.
Species ideal for thus include:
- Whistling pine (Causurina equisetifolia)
- African Blackwood (Dalbergia melanoxylon) v Muhugu (a hardwood in ASALS) v Acacia species.
3) Woodlots.
Plots of land set aside for trees only. Produce large volume of fuel wood, timber, poles and fodder.
AGROFORESTRY AGRICULTURE FORM FOUR
Sites for Agroforestry Trees.
1) Boundaries.
Planting trees and shrubs or hedges on boundaries neighbouring other farms.
Importance.
- Protect the farm as a fence.
- Mark/demarcate the boundary.
- Form wind breaks.
- Provide wood and timber for fuel.
Ideal tree species include:
Jacaranda mimosifolia
Eucalyptus spp Silky oak.
- River banks.
Woody plants help to decrease water velocity along river banks and protects exposed soils.
- Teraccess
Trees planted on terraces and other soil conservation structures makes them more permanent by reducing speed of water run-off holding soil in situ.
Roots of trees hold the soil together reducing erosivity, the tree canopy intercepts raindrop reducing raindrop erosion.
Ideal tree species include.
- Silky oak.
- Mangifera indica
- Persea american v Papaya carica 4)
Woodlots should be established in slopy areas to control erosion. Areas with slope of more than 55% should not be cultivated (de jure).
Ideal species include:
- Silky oak v Blue gum. v Croton v
5) Homestead.
Trees around the house provide shade and aesthetic value.
However, they should not be too near the house to avoid damage in case it falls.
Tree harvesting Methods.
1.Prunning
Removal of branches from the lower part of the tree crown.
It is done to reduce shade and improve quality of the trunk.
It should be done towards the end of dry season to avoid damage to crops. Pruned materials can be used as fodder and wood.
2.Lopping
Removal of branches from trees in haphazard manner. It is common technique used for harvesting fodder where emphasis is on good green leafy biomass.
3.Pallarding
Cutting of all the branches and the top part of a tree.
Common pollared tree species are:
- Croton spp
- Jacaranda mimosifolia
- Causuarina equisetifolia v Silky oak v
4. Coppicing.
Cutting of the whole tree about 30cm above the ground.
Coppicing is done to provide fodder, wood fuel and mulching materials.
Commonly coppiced tree species include:
- Calliandra calothyrsus
- Eucalyptus spp
- Leucaena leucocephala
- Markhamia lutea
Some coppice well when young e.g. silky oak and casuarina spp
5. Thinning.
Cutting down of some trees to avoid overcrowding. It is done where tree have been established by direct seeding. It is common in woodlot
AGROFORESTRY AGRICULTURE FORM FOUR
ALL AGRICULTURENOTES FORM 1-4 WITH TOPICAL QUESTIONS & ANSWERS
PRIMARY NOTES, SCHEMES OF WORK AND EXAMINATIONS
