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.