CROP PRODUCTIONIII:(NURSERY PRACTICES)

CROP PRODUCTION III. (NURSERY PRACTICES.)

CROP PRODUCTIONIII:(NURSERY PRACTICES),Piece of land which has been prepared to receive planting materials.

• Nursery bed. Special seedbed prepared for raising seedlings before transplanting. Should not be more than 1M wide
• Seedling bed. Special type of nursery bed used for raising seedlings removed/pricked from nursery bed due to overcrowding.

Nursery practices.   All activities carried out during preparation and management of a nursery to raise planting materials.

IMPORTANCE OF A NURSERY IN CROP PROPAGATION.

• Facilitates production of many seedlings in a small area.
• Routine management practices are easily and timely carried out than in main seedbed.
• Facilitates raising of small seeds which develop into strong seedlings that are easily transplanted.
• Ensures transplanting of only the healthy and vigorously growing seedlings.
• Facilitates transplanting of seedlings that are already established thus reducing period taken in the field.
• Excess seedlings from the nursery may be sold thus becoming source of income to the farmer.
• Makes it possible to provide the best conditions such as fine tilth levelled field and shade.

CROP PRODUCTIONIII:(NURSERY PRACTICES)

SITE SELECTION

Factors considered when selecting a nursery bed site.

• Nearness to water source. For easy watering.
• Should be sited on a gently sloping area to prevent flooding and soil erosion through runoff.
• Soil type. Should be well drained, deep and fertile preferably sandy loam.
• Previous cropping. Avoid siting the nursery bed on an area where the same crop species had been planted to avoid build-up of pests and diseases.
• Well protected from theft and destruction by animals and birds.
• Well sheltered place. Wind breaks needed to prevent strong winds which can uproot seedlings and cause excessive evapotranspiration.

Categories of nurseries. 

• Tree nurseries.
• Vegetable crops nurseries.
• Vegetative propagation nurseries.

• Vegetable crop nurseries.

Vegetative crops with small seeds are established through the nursery.  Vegetation is cleared using pangs, lashers axes mowers etc.    Trash is removed and the site ploughed to remove all perennial weeds. In dry areas nursery beds are sunken to help in conservation of available moisture.

• Tree nurseries

The site is prepared and drills or furrows are made using specific spacing for each tree species. Seeds are drilled evenly in furrows and then covered lightly. Pre-germinated seeds are then planted in polythene sleeves. The sleeves facilitates transporting of tree seedlings when ready for transplanting.

• Vegetative propagation nurseries.

Used for inducing root production in cuttings before they are transplanted. Cuttings can be planted directly in the soil (bare root nurseries) or planted into containers (containerized nurseries.)

When preparing cuttings e.g. tea, the cuttings should be placed in water until they are planted.  The brown hard bottom part takes long to produce roots while the soft top part tends to rot if planted.  To avoid rotting leaf of cuttings should not touch the soil.  The cuttings in sleeves are covered in polythene sheets and shelter constructed over the units.  Sleeves are watered once every 3 weeks.

NURSERY MANAGEMENT PRACTICES.

1.  A light   mulch should be applied and is removed on the 4^th day or when seedlings begin to emerge. Mulching prevents excessive evaporation and moderate soil temperatures.
2. Should be watered regularly preferably in the morning and evening.

• Weed control. Should be kept weed free. Weeds should be removed through uprooting when soil is moist to avoid damage to the seedlings.

1. Pricking out. Where seedlings are overcrowded some of them should be removed and planted in a seedling bed 3-4cm apart. This allows the seedlings to grow strong and healthy without much competition.
2. Shade should be erected over the nursery bed. Dark conditions should be avoided as they cause seedlings to become etiolated and pale and predispose them to damping off disease.
3. Pest and disease control. Soil is sterilised through heat treatment or application of chemicals.

• Hardening off. Gradual reduction of shade and watering frequency 1-2 weeks before transplanting seedlings to enable them adapt to the prevailing ecological conditions in the seedbed.

CROP PRODUCTIONIII:(NURSERY PRACTICES)

GRAFTING 

Practice of uniting 2 separate woody stems i.e. the rootstock and the scion.

• The part with the rooting system.
• Part that is grafted to the rootstock.
• Ability of scion and rootstock.

Structures that are botanically related are compatible.

METHODS OF GRAFTING. 

• Whip/tongue grafting.

Used when the scion and the root stock are of the same diameter.  A slanting cut is made on both the scion and the rootstock and the two wrapped with grafting tape or a polythene strip.  It is done when they are pencil thick.

• Side grafting.

Done where the rootstock has a larger diameter than the scion.  The scion is inserted on the side of the stock.

Others types of grafting are.

• Bark grafting Ø Notch grafting.
• Approach grafting.

BUDDING.

Practice of uniting a vegetative bud (scion) into a seedling of another plant (rootstock.) Methods of grafting.

• T-Budding.

The rootstock is prepared by making a T-shaped incision through the bark down to the wood. (15-20cm above the ground.) Using a budding knife.  The bark is raised and the scion inserted, the bud is then tied firmly (using adhesive tape, rubber strips or polythene paper.). The wrapping should be removed 2 weeks later to check for compatibility.   The rootstock is cut a few cm above the union and the scion should be staked when 25cm long to prevent being blown and broken by the wind.

• Top budding.

Budding young or small tress where the buds are inserted at desired locations.

It allows production of many compatible fruit varieties on the same rootstock

• Patch budding.

The bark with a bud is removed from the scion stem and inserted into a patch where the bark of rootstock has been removed. The union is tied on top and bottom to hold it tightly

CROP PRODUCTIONIII:(NURSERY PRACTICES)

IMPORTANCE OF BUDDING AND GRAFTING.

• Plants with desirable root characteristics e.g. disease resistance, vigorous root system but with undesirable products may be utilised to produce desirable products. E.g.

lemon-orange graft.

• Facilitates the changing of the top of the tree from undesirable to desirable.
• Makes it possible to grow more than one type of fruit or flower on the same plant.
• Helps to propagate clones that cannot be propagated in any other way.
• Grafting helps to repair broken tress.
• Helps to shorten the maturity age. Grafted mangoes take 3_1/2 years to mature while un grafted mangoes takes up to 7 years to mature.

LAYERING.

Process by which part of the plant is induced to produce roots while still attached to the mother plant.

TYPES OF LAYERING.

• Marcotting/aerial layering.

Used on hardwood plants where the stems cannot bend easily to reach the ground. Section of the branch whose bark and cambial layer has been removed and moist rotting medium is wrapped with a polythene sheet to hold soil and maintain the soil moist.

Auxins accumulate thus induce development of roots.  The rooting medium quickens the process of rooting.

• Tip layering.

Shoot bearing terminal bud is bent to the ground and then covered with moist soil. It is held in position by use of pegs and induced to produce roots.

Branch of stem is bent, laid in a trench and held in position by use of pegs.  The trench is covered with moist soil.  The bud develop shoots that grow upward and roots are produced at the base of each shoot.

4) Compound/serpentive layering.

The branch is bent several times and held in position with pegs.  Produces several new rooted planting materials from the same branch.

 TISSUE CULTURE FOR CROP PROPAGATION.

It is based on the ability of plant tissues/cells to regenerate other parts of the plants.

Tissues /propagules/explants are derived from shoot tips where cells are undergoing rapid cell division and are not differentiated.  Cells are provided with right conditions which enables them to multiply and develop roots and shoots. The conditions are:

• Culture medium (correct nutrients and growth regulators)
• Correct light intensity, temperatures and relative humidity.

STAGES OF TISSUE CULTURE PROPAGATION.

Establishing aseptic culture and developing the propagules by enhancing cell division and enlargement. Contamination is eliminated by using disinfectants such as: alcohol, calcium or sodium hypochlorite.

Ingredients are:

• Inorganic minerals
• Energy source (sugar) Ø Growth regulators.
• Sub-culturing to rapidly multiply the propagules through somatic development of embryos to produce auxiliary buds and adventitious root.
• Preparation of propagules for establishing in the soil. By:
• Rooting of regenerated plantlets.
• Hardening the plantlets by imparting some tolerance to moisture stress and pathogen attack.
• Converting the plantlets from heterotrophic mode of nutrition to autotrophic.
• Rooting of plantlets is promoted by omitting growth hormone or using Auxins.

CROP PRODUCTIONIII:(NURSERY PRACTICES)

IMPORTANCE OF TISSUE CULTURE IN CROP PROPAGATION.

• Used to recover and establish pathogen free plants especially in control of viral diseases.
• Used in mass propagation of propagules.
• Fast and requires less space than cultural methods.

Limitations

• Requires highly skilled manpower.
• Requires special structures where humidity and temperatures can be controlled hence it is expensive.

 TRANSPLANTING OF VEGETABLE CROP SEEDLINGS.

Seedlings are ready for transplanting at 4 weeks old or when they have 4-6 true leaves.  The nursery is watered 3-4 hours before lifting the seedlings.  To ensure seedlings are lifted with a ball of earth/soil around the roots to minimise root damage.  Select healthy and vigorously growing seedlings and lift them using a garden trowel.  Transplant when the weather is cool.  Seedlings should be transplanted at the same depth they were in the nursery bed to avoid rotting of the soft parts of the seedlings. Apply a light mulch and shade if necessary.

ALL AGRICULTURENOTES FORM 1-4 WITH TOPICAL QUESTIONS & ANSWERS

PRIMARY NOTES, SCHEMES OF WORK AND EXAMINATIONS