AGROFORESTRY

Introduction

  • In Kenya land use is changing from extensive methods of farming to more productive and sustainable intensive methods.
  • Agroforestry is a method of farming which has become increasingly important.

Definition

  • This is the practice of integrating a variety of land use
  • It combines tree growing, pasture and crop production practice on the same piece of land to improve the output of the land.

Forms of Agroforestry

Agroforestry;

  • It is a combination of trees/shrubs and crops in agricultural production.

Silvopastoral:

  • It is a combination of growing tree/shrubs, pastoral and keeping of livestock.

Agrosilvopastoral:

  • It is a combination of growing trees/shrubs, animals, pastures, and crops.

Importance of Agroforestry

  • Environmental protection.
  • Source of income.
  • Afforestation for timber production.
  • Maintenance of soil fertility.
  • Aesthetic value.
  • Labour saving in firewood collection.
  • Source of food and feed.
  • Source of fuel wood.

Important Trees and Shrubs for Particular Purposes

Eucalyptus Spp;

  • Timber,
  • Bee forage,
  • Fuel wood,
  • Medicinal,
  • Production of essential oils.

Acacia Spp;

  • Leaves and pods eaten by animals,
  • Provision of shade.

Cajanus cajan (pigeon peas);

  • Proteinous feed for human,
  • Used as fodder

Croton megalocarpus(croton);

  • Fuel wood timber for poles
  • Handles for hand tools.

Erythrina abyssinica (flame tree);

  • Wood carvings,
  • Bee forage,
  • Nitrogen fixation

Markhamia lutea (markhamia tree)­;

  • Timber for construction,
  • Shade,
  • Soil protection,
  • Bee forage.

Grevillea robusta (silky oak.)

  • Timber,
  • Fuel wood,
  • Fodder,
  • Bee forage,
  • Soil protection,
  • Wind breaker

Sesbania sesban (sesbania);

  • Fodder,
  • Nitrogen fixation,
  • Shade,
  • Fuel wood.

Calliandra calothyrsus (calliandra);

  • Fuel wood,
  • Fodder,
  • Nitrogen fixation,
  • Shade,
  • Bee forage.

Persea american (avocado) ;

  • Fodder,
  • Fruit production,
  • Shade,
  • Fuel wood.

Mangifera indica (mango);

  • Fruit production,
  • Shade trees,
  • Wind break,
  • Soil protection,
  • Fuel wood.

 Characteristics of Agroforestry Tree Species:

  • Fast growth rate.
  • Deep rooted.
  • Nitrogen fixation ability.
  • By-product production ability.
  • Be multipurpose in nature.
  • Should not possess competitive ability with main crop ..
  • Have coppicing and lopping ability.
  • Have appropriate canopy – should not shade others.
  • Nutritious and palatable.

Trees and Shrubs to Avoid at Certain Sites and Reasons

  • Eucalyptus Spp.-should not be planted near water sources because it would absorb the water.
  • Eucalyptus Spp. -should not be planted on the arable land as the roots have allelophathic effects on other vegetation including crops.
  • Tall trees should not be planted near farm buildings because they may fall and damaging the buildings, their roots will break the building stones gradually.
  • Bushy trees or shrubs should not be near farm buildings as they may harbour predators.
  • Tall trees planted with main crop of a lower canopy intercept the rainfall, affecting the growth of the main crop.
  • Cypress trees have leaves which produce acidity in the soil preventing undergrowth beneath the tree.
  • These trees should not be planted within the farm but at the periphery.

Tree Nursery

  • Tree nurseries are structures used to raise tree seedlings until they are ready for transplanting.
  • There are 2 main types:

Bare root nurseries:

These are also known as ‘Swaziland’ beds where the seedlings are raised directly into the soil.

Advantages

  • Cheap and less time consuming.
  • Require less labour
  • Occupy a small space.
  • Many seedlings are raised in a small space.
  • Transportation of seedlings is easy.

Disadvantages

  • Root damage when uprooting the seedlings.
  • Difficult to transport.
  • Lower survival rate after transplanting.

Containerized nursery:

  • The seedlings in this type of nursery are raised in containers such as pots, polythene bags or tubes and tins.

Advantages

  • Higher survival rate after transplanting.
  • No root damage.
  • Successful in arid areas.

Disadvantages

  • Labour intensive.
  • Difficult to get containers.
  • Sometimes it may be difficult to get the right type of soil to use in the containers.

Seed Collection and Preparation

Seed Collection

Seeds should be collected from;

  • Adaptable trees,
  • High yielding,
  • Healthy
  • Resistant to pests /diseases.
  • The mother plant should be identified first.

 

The following methods used to collect seeds.

  • Shaking the tree.
  • Gathering from under the tree.
  • Lopping of the tree.
  • Climbing on the trees.
  • Hooking method.

 

Seed Preparation

  • This done when seeds are collected from a fresh fruit, they should be soaked in water, then washed and dried.

Cleaning and sorting: done to remove immature seeds, rotten seeds, broken or damaged seeds.

Drying: Done by sun-drying or oven drying.

Seed testing: this determines;

  • Seed quality for percentage purity,
  • Seed weight,
  • Moisture content,
  • Germination percentage.
  • Seeds should be stored in dry containers at room temperature.

Seed treatment: seeds are treated first to break the seed dormancy and ensure rapid germination;

Hot water treatment: used to soften the seed coat to make it more permeable to water.

  • Examples of seeds which require this treatment are leucaenia, calliandra and

Mechanical breaking: done by nicking the seed coat with a knife for easy entrance of water for example seeds of croton

Light burning: applied to the wattle tree seeds.

 

Nursery Management

The following are the practices carried out in the nursery when the seedlings are growing:

Mulching:

  • Aim is to reduce excessive evaporation,
  • Moderates the soil temperature,
  • When it decays it improves the soil structure,
  • Reduces the impact of the raindrops.

Weeding:

  • Done to reduce competition for growth factors by uprooting the weeds,
  • Use a sharp pointed stick.

Watering:

  • Done by use of a watering can
  • Done twice a day in the morning and in the evening.

Pricking out:

  • It is the removal of seedlings in an overcrowded area to another nursery bed,
  • This allows the seedlings to grow strong and healthy.

Root pruning:

  • It is the cutting of the roots longer than the pots.

              Root pruning is done for the following reasons;

  • Make lifting easier
  • Encourage fast establishment.
  • Reduce damage to the seedlings.
  • Encourage development of a short dense and strong rooting system.

Shading:

  • Done to reduce the intensity of sunlight .
  • Dark conditions should be avoided.

Pest and disease control:

  • Use of appropriate chemicals,
  • Sterilization of soil through heat treatment,
  • Fencing to protect seedlings against animal damage.

Hardening off:

  • It is the practice of preparing seedlings to adapt to the ecological conditions prevailing in the seedbed.
  • It involves gradual reduction of shade and watering 1-2weeks before transplanting.

Transplanting:

  • The practice of transferring seedlings from the nursery bed to the main field where they grow to maturity.

Procedure of Transplanting

  • Holes are dug early before transplanting.
  • Topsoil is mixed with compost manure.
  • The seedlings are watered well a day before transplanting.
  • The seedlings are removed from the nurseries carefully with a ball of soil for the bare root seedlings and roots trimmed for the containerized seedlings.
  • The seedling is placed in the hole at the same height it was in the nursery.
  • The container is removed carefully.
  • The soil is returned into the hole and firmed around the seedling.
  • The seedling is watered and mulched.

Care and Management of Trees

Protection:

  • From damage by animals such as goats and cattle by eating the leaves.
  • It is done by fencing the fields or using small poles around each seedling with or without wire nettings, can be done for individual trees or an entire field.

Pruning and trimming:

  • Pruning is the removal of extra or unwanted parts of a plant.
  • The unwanted part may be due to breakage, overcrowding, pests or disease attacks and over production.
  • Pruning initiates growth of shoots and trains the tree to have the required shape.
  • Regular cutting back of the trees is known as coppicing,
  • It is done at the beginning of each cropping season to reduce competition for water, minerals, nutrients and sunlight with crops.
  • The materials pruned or coppiced are used as fuel wood or for fodder crops.

Grafting old trees:

  • This is the practice of uniting two separate woody stems.
  • The part with the rooting system is known as root stock (base)
  • The part which is grafted onto the rootstock is called a scion which has buds that develop into the future plant.
  • The ability of the scion and the rootstock to form a successful union is known as compatibility.
  • Methods of grafting include whip or tongue grafting, side grafting and approach grafting.

 

Agroforestry Practices

Alley Cropping/Hedgerow Inter­cropping:

  • The growing of multipurpose trees and shrubs together with crops.

   Benefits

  • Improve soil fertility through nitrogen fixation and organic matter.
  • Provision of green manure.
  • Used as fence and mark boundaries.
  • Acts as windbreaks.
  • Suppress weeds.
  • Source of timber and fuel wood.

 Multi-storey cropping ;

  • This is the growing together of trees of different heights.
  • The system is based on crops which can tolerate shading.
  • The trees and crops form different levels of canopy which look like storey.

         Benefits

  • Increases water conservation for pastures.
  • None of the crops or trees included will be shaded.
  • Act as windbreak for crops.
  • Creates suitable micro-climate in the area.
  • Trees are used for timber, fuel wood and forage.

 

Woodlots (farm forests)

  • These are plots of land set aside for trees only.
  • They are established in the hilly and less productive parts of the farm.
  • Fast growing tree species such as Eucalyptus spp. should be grown.

 

Sites for Agroforestry:

  • Farm boundaries – provide live fences.
  • River banks – protect water catchment areas.
  • Homesteads – provision of shade and windbreak
  • Terraces – for soil conservation.
  • Steep slopes – as contour hedges to encourage water seepage.

Tree Harvesting Methods

Pollarding;

  • This is the extensive cutting back of the crown of the tree about 2-3 meters above the ground level to harvest all the side branches.
  • It stimulates the development of a new crown and branches.

Coppicing;

  • Cutting the main stem of the tree completely at a height of 10 – 50 cm above the ground.
  • The tree should be cut in a slanting angle.

Lopping or side pruning ;

  • The removal of selected branches of the tree
  • Done to produce fuel wood and fodder.

Shaking of the tree ;

  • This is a method of harvesting pods and seeds from trees without cutting the tree.

Cutting back;

  • The tree is cut from the base to allow new growth as done in coffee when changing the cycle.

Thinning;

  • The removal of some of the trees growing in lines to give the remaining trees enough space to grow.
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