HORTICULTURAL CULTURAL PRACTICES

Introduction

• Cultural practices are agricultural methods used to enhance crop productivity through
conserving water and soil to improve crop health/ productivity by reducing weeds, pests
and diseases.
• Sustainable horticultural farming is a relatively high risk, high cost per acre business
requiring intensive management.
• Successful growers manage capital, and marketing competently.
• Growers design and implement systems of culture which include crop and variety selection,
crop rotation, soil fertilization, land selection, tillage, integrated pest management (insect,
disease and weed control), transplant production and/or use, seedbed preparation, seeding,
irrigation, windbreak management, pollination (bee management), harvesting, handling
and packaging and sales. These crops are perishable in nature, must be free from blemishes,
and, have narrow market windows.
• Consequently, cultural operations must be accomplished in a more precise and timely
manner to deliver high quality products to markets on schedule.
Grower profit and loss are affected by uncontrollable factors including weather, market
fluctuations, pest infestations, and legislation. Therefore, growers must pay close attention to
variables which they can control. Timely implementation of effective cultural practices enables
careful growers to minimize or totally avoid pitfalls. Wise selection of cultural practices improves
production efficiency, lowers production cost and increases profitability. As with most successful
businesses, careful planning greatly enhances the incidences of success.

1. Crop Selection
Selection of crop kinds and varieties for production is the initial step in the development of a
successful horticultural farming operation. This decision is difficult because producers have many
alternatives available to them. Successful production in a given area will be influenced by limiting
factors: water, hail, wind, temperature, light, nutrition and markets. Variable levels of limiting
factors limit yields or reduce potential for profitability..

2. Variety Selection
Once the decision which crops to grow is made, the variety selections must be made next. Always
select adapted varieties having the highest levels of disease and/or insect resistance, good
horticultural characteristics and market appeal.

3. Site Selection

Three major points should be considered in selecting a field for growing crops: site topography,
soil type, and water availability (quantity and quality).

Topography refers to the physical layout or characteristic of the field area. Elevation, contour, soil
depth, water and air drainage patterns as well as the presence or proximity of rock out cropping
and trees can significantly influence production. An optimum topography for a vegetable field is
one that is nearly flat to slightly sloping, well drained and free of low spots, rocks or trees. Fields
of this type are desirable because cultural practices such as cultivation, irrigation, pest management
and harvesting are performed more efficiently on level unobstructed land.

Soil type refers to the physical makeup of the soil. Basically, soils are composed of decomposed
mineral matter (sand, silt, and clay) and decomposed organic matter (plant residues). The optimum
soil conditions for most vegetables consist of a deep, friable, well drained, sandy loam. Clays and
other heavier soils are not well suited for horticultural production due to poor aeration, drainage,
nutrient liberation and restrictive root growth characteristic of such soil types.

4. Land Preparation

Most vegetables have small to medium size seeds. Consequently, proper seed bed preparation is
important. Optimum seed beds have mellow soils comprised of fine sized particles, free of clods,
weeds and previous crop residue. Such seed beds enable good soil to seed surface contact to soil
which is required to allow uniform water absorption, germination, and seedling emergence.

5. Crop Establishment

There are three basic methods of establishing vegetable crops in field situations: direct seeding
seeds; transplanting seedlings, and, planting vegetative plant parts.

a)Direct Seeding
Seeds planted too deep often do not emerge adequately to produce a desirable stand. For example,
bean and pepper seedlings are easily obstructed in their upward thrust and fail to emerge is planted
too deep. Because most vegetable seeds are relatively small, they do not have sufficient emergence
strength to push through deep soil. This is especially true under cold, wet soil conditions. Seeds
planted too shallow often dry out too rapidly causing poor germination.

Optimum planting depth for most horticultural crops is three times its width. For example, bean
seeds are generally ¼ inch in width. Therefore, bean seeds should be sown ¾ inch deep.

b)Transplanting

There are five primary advantages to transplanting:

• Enhanced earlier harvest

• Reduced impact of adverse environmental conditions during the early seedling growth
• Reduced seed quantity needed for crop establishment
• Eliminates thinning need
• Enhanced plant stands and faster maturity
High seed cost and poor germination ability under field conditions renders transplanting a must
for the establishment of many crops

Vegetative Propagation

Vegetative propagation entails the use of a plant part to regenerate new plants or to establish a new
crop.

Thinning

Thinning as cultural practice is the removal of weak plants from a stand, to give rise to one or two
vigorous crop plants. It is usually done by hand and practiced when the crop plants are very young.

Weeding

This is the removal of unwanted plants which grow among cultivated crops. Weeding or weed
control is done regularly on farmlands in order to prevent competition with crops for space,
sunlight, nutrients, soil moisture, soil oxygen, etc. Weeding can be done manually by hoeing,
cutlassing, etc or chemically with the use of specific herbicides, or mechanically with machine.

Spacing

Spacing refers to the distance within and between crop plants in a farmland. This ensures greater
yield of crops and prevents over crowding. and easy ventilation within and between rows of crop
plants For example, the spacing for maize could be 90 cm x 30 cm at one seed per hole or 75cm x
25cm at two seeds per ho1e.

Windbreaks

Windbreaks and nurse crops are essential to protect crops from wind and hail. Windbreaks permit
plants to grow faster and larger by lowering rate of water loss from soil and leaves and increasing

Mulches

Mulch is any material applied to the soil surface of a plant bed to modifying the microclimate just
above or below the soil surface. Depending upon the material used and the time of the year,
mulches can successfully suppress weed growth, reduce soil moisture loss, reduce fertilizer
leaching, overcome unfavorable soil temperature, manipulate insect populations and/or manage
disease problems.

Purpose of mulching

1. To conserve soil moisture- reducing evaporation

2. Ensure clean fruit-

3. Controls weeds-

4. Hastens maturity

5. Increases yields

6. Control soil temperature-temp under straw mulch may average several degrees lower than
those of unmulched soil. On the other hand, black paper or polythene usually increases soil
temperature which may be beneficial to early crops and especially to those requiring a warm
season.

Staking

Staking is the act of providing stakes or certain plant or wood to enable the crop plants stand erect
and prevent lodging. Stems are tied or trained to the stakes. Staking allows for good fruiting and
keeps fruits from disease attack arising from contact with soil. Staking is usually done before
flowering. Examples of crop plants that require staking are tomato and yam.

Trellising

Training vines to grow up a trellis is another effective means of forcing vegetable plants to grow
vertically. In addition to reducing diseases and aiding cultivation, harvest efficiency is greatly
improved by crop training techniques.

Pruning

Pruning is the removal of lower branches of crop plant using sharp cutlass. Pruning encourages
better canopy formation, more light penetration and improved air movement.

Pest and disease control

FLOWERING IN HIGHER PLANTS

One of the important roles of flowering in plants is that it offers a mechanism of genetic growth
which as a result can provide a greater variety of genetic recombination for the purposes of
adaptation of plants.

Ecologically, the timing of flowering plants can be related to the plant to complete the development
before onset of unfavorable conditions/environment stress.

The flowering process is

1. Internally programmed within the plant

 2. Environmental factors where a number of environmental factors are involved in flowering
responses.

Internal programming

1. Development responses involved in the flowering of plant- the growth rate has an
important role and in most perennial plants, the differentiation of flower buds in meristem
occurs after rapid growth rate has ceased hence those factors that would enhance early
termination of growth will tend to promote flowering in plant e.g.
Some cultural practices e.g. bending out of vertical oriented shoot induces early flowering.

Also application of growth retarding chemicals which enhance flowering e.g. paclobutrazol

Also husbandry practices like withholding irrigation after certain period, plants will tend
to come into flowering.

1. The age of the plant-during early stages of growth, most plants are in juvenile stage
and tendency to flower increases with plant age. Also in some plants, plant size has
effect in flowering e.g. in case of cabbage seedlings, if they are of the same age, the
tendency is for bigger seedling to flower early than small seedling.

External factors involved in flowering of higher plants

1. Photoperiodism

2. Temperature

3. Moisture

Photoperiodism

Day length effects are perceived by the leaves and stimulus of flowering is translocated to
the meristem where it will evoke morphological changes.

Plants are grouped into 3 classes

a. Short day plants- flower at day length of less than 12 hours

 b. Long day plants- flower at day length of more than 12 hours

c. Day neutral-plants flower irrespective of the day length but we consider some external
factors e.g. right age of the plant.

Short/long day plants may be termed as obligate or quantitative. Obligate short/long

day plants, the requirement for short/long day must be met e.g. chrysanthemums, soy
bean. Obligate long day plants-spinach, lettuce.

Quantitative short/long day- for this, long/short day conditions can promote flowering. The effect
can be replaced by other factors e.g. short day plants but give alternative conditions like low
temperature, a similar effect will be achieved.

Temperature

The most commonly observed feature about temperature is regard to low temperature whereby a
good of number of biennial and perennial are promoted to flower by low temperature. There are
few exceptional cases where flowering is induced by increased temperature e.g. spinach and rice.
Vernalization is used to refer to the promotive effect of low temp on flowering.

a. The actual induction of flowering by low temp. The plant will actually require to be
subjected to low temp for it to flower e.g. cabbage, beet, and celery.

b. The low temp are involved in hastening the flowering process (Quantitative) whereby the
plant will flower at certain conditions but when subjected to low temp, the flowering is
enhanced e.g. lettuce.

The role of moisture

Its effect on flowering may be seem to be indirect and some cases as direct.

The indirect effects are attributed e.g. where plants are subjected to a drought stress/moisture stress
hence slow growth rate hence less vegetative materials e.g. smaller leaves or senescence of leaves
and dry out hence plants defoliate hence most of buds are exposed better to light.

The direct side of it is where we find that most plants when they are in water stress conditions,
they undergo certain physiological changes e.g.(a). Greater accumulation of carbohydrate reserve.
(b). in other plants the effect may be through the level of plant growth regulators e.g. in those
plants where gibberellic acid inhibit flowering where they are produced in actively growing shoots
and meristems and when plants are suppressed, the level of gibberellic acid drop hence better
chance for flower bud to differentiate.

SEX EXPRESSION IN HIGHER PLANTS

It is the types of the flowers that are borne by plants. Generally, flowers can either be
perfect/hermaphrodite whereby the flower has both stamens and pistils parts and the staminate-
carries only the male part or pistillate carries only the female part.

Sexuality of plants in terms of horticultural production, we’re concerned with 2 categories of plants

1. Monoecious-male and female flower are borne on the same plant but at different positions.

2. Dioecious- male and female flowers occur on separate plants.

The sexuality of plant determines the production of that plant.

Importance of different sexual expressions in production

1. Monoecious plants-it is important in 3 crops; cucumber, maize and banana.

Cucumber- different flowers are produced in a specific flowering pattern. In the basal
nodes, we have male flowers. Towards the middle, we have perfect flowers and towards
the tip you’ve got female flowers and on the apex, we have parthenocarpic flowers.
Usually, the fruits are formed by the perfect flower which means the ratio of perfect
flowers: male: female will determine the productivity.

Maize-the female flower is found in the middle while the male flowers will appear at the
tip of the plant. The filling of cob and formation of grain will depend on extent of
pollination. In production of hybrid seeds, it is important to determine the variety that will
act as a source of pollen.

Banana- monoecious character is manifested within the inflorescence itself. As banana

plant is growing, eventually the inflorescence will shoot out at the apex of the plant. The
flowers that are formed at the upper part are female. Towards the middle, we have perfect
 or hermaphrodite flowers and towards the tips, we have male flowers enclosed in a male
bud. The good quality fruits of good size are from female flowers

2. Dioecious plants

This character is important in the productivity of crops like spinach, asparagus, papaya.

Asparagus-the edible portion (spear) is determined by the sex of the plant and male plants
tend to produce more spears of smaller size in contrast to the female plants that produce
thicker and few in number spears. The survival rate in field is also dependent on size where
we have female plants have got a shorter life span than males since they have thicker spears.

Spinach- the plant either produces a female or have perfect flowers and not unless a
situation for seed production, spinach is grown for leaves and female plants are more
vegetative and more productive than perfect plants.

Papaya- the plant may either have male flowers, female flowers or perfect flowers. The
edible fruits are produced from female and perfect plants. The male plants are required for
pollination purposes. In establishment of crop in the field, it is good to maintain a certain
ratio of male: female plants for pollination purposes.

Environmental factors that favor sex expression

1. Temp- low temp increases femaleness. In case of papaya, very high temp results in sex
reversal. E.g. in case of hermaphroditic plants whereby the female plants reverse and
become male plants as a result of pistil abortion. The situation is temporarily.

2. Short day have been shown to increase femaleness. If you have short day length in
cucumber, most fruits are parthenocarpic.

3. The nutrition of plant e.g excessive nitrogen application increases maleness in plants.

4. Artificial chemical regulators can also be used like GAs when sprayed in cucumber,
have a tendency to increase the number of male flowers while auxins increases
femaleness.
FRUIT FORMATION (FRUITING)

For most crops, the process of fruit formation is initiated when pollination takes place as in most
plants. It is a requirement we have pollen from anther and deposited on pistils. These plants require
pollination. The plants may be self-pollinating or cross pollinating plants.

NB: In another crops the process of fruit formation can be initiated in the absence of pollination
and fertilization and these are parthenocarpic fruits. For most of these fruits, the resultant fruits are
seedless e.g. banana pineapple.

Cross pollinating plants- there are a number of mechanism that favor the occurrence of cross
pollination

1. Nature of plant- either monoecious or dioecious.

2. Floral morphology- have flower, where we have stamens far below stigma, the plant
cannot self pollinate. In other plants, it is the timing of flower formation or maturity of
pistils e.g. avocado, the plant open in a very peculiar ways. 1st day plant behave like female
2nd day behave like male hence need to intercrop different varieties to cross pollinate.

3. Incompatibility reactions within the plants- e.g. in apple cultivars, we have some pollen
tube growth inhibitors, and pollen from the same flower when grows downward the stem,
it is inhibited.

Once pollination and fertilization is complete, we have the commencement of fruit development.
The process that are associated with early fruit developmental growth we have Fruit set.

The final size of mature fruit can either be considered as a

1. Factor of cell size (once the fruit has set, a number of cells can remain fairly constant and
subsequent increase in size may be due to increase in cell size.
2. The development of the fruit is also highly influenced by the seeds that are in a fruit. The
developing seeds serve as a very rich source of growth promoting substances. In certain fruit
crops, the more the number of seeds, the bigger the fruit e.g. strawberry, apple where you have
increase proportion of fertilized seeds, the fruit is also bigger.
Geometry/shape of fruit –can also be influenced by seeds. In developing fruit, the side with
more seeds tends to grow faster than the side where seeds have been aborted or damaged hence
results to emaciated fruit due to retarded growth due to absence of seed.

When we talk of growth and development with regard to commodity, we are essentially
concerned with the edible part e.g. in tree, our main stage is that when fruit forms, tubers/bulbs-
swelling of the edible part commences and plant continues to grow and develop until it matures.

When we talk of maturity

1. Physiological maturity

2. Commercial maturity/horticultural maturity.

Physiological maturity is the stage during the development of fruit, vegetable when we have
maximum growth has occurred and that plant part continues with normal metabolic process
even if it is detached.

Commercial maturity/horticultural maturity- the stage of development of plant organ when

it shows the characteristics that are required by the consumers. Examples;

Cucumber-the cucumber fruit is essentially used in two ways;

a. Can be used for pickling (preservation of fruit in vinegar). It is very small and young fruits.

b. Can be used for slicing-fruits used as dessert sliced and used. The fruits are much bigger
and in more advanced stage.

At both cases, even if they are in different development stages, they have achieved their
commercial maturity.

Beans –e.g. French beans required when pods are young and green (commercial maturity).
Dry beans- the pods are allowed to go through the whole process until they dry. Dry beans are
the one utilized (commercial maturity).

How do you determine the maturity of commodity?

The maturity of a commodity will depend on its usage. Therefore, the plant part should develop
certain characteristics that are required by consumer. These characteristics that are needed by
the consumers are referred to as maturity index/indices. For a maturity index to be useful,
should have certain characteristics

1. Simple and easy to determine especially in the field.

2. The index that one uses should consistently relate to the quality of the commodity i.e. not
character that is variable from season to season, different locality.

Maturity indices may involve objective measurements or may be subjective (descriptive). In

most cases, both subjective and objective measurements are utilized to determine optimum
maturity stage of plant. Indices may vary from crop to crop.

Examples of indices

1. Skin/fresh color- useful in fruit crops where maturation is attributed to changes in color
e.g. a fruit start to develop yellow or red color depending on the species e,g. tomato, papaya,
mango.

2. Firmness of the commodity- may be determined subjectively by just pressing, feeling

with hands or determined objectively by use of penetrometer which can be pushed through the
plant organ and get reading.

3. Chemical measurement esp. in some processed commodities where the processor can be
very specific on the level of certain chemicals e.g. the acidity or sugar levels -can be determine
brix by taking sample and measure using refractometer and can tell sugar level.

4. Size and shape of the particular plant organ- e.g. French beans, maturity based on the
size of pod. In terms of shape, some fruit like banana, the shape changes as the fruit matures
e.g. in young fruit, cross section is angular, maturity-cylindrical.

5. The calendar date- the grower can tell since he knows how long it takes and can time
when flowers are formed and know maturity age. For vegetable crops, in certain regions, one
can tell how long they will take. Experience in crop, market requirement is needed. In most
cases, a grower may utilize more than 1 index to determine when the crop is ready for
 harvesting. Also harvesting date can be influenced by a number of factors e.g. planting time,
flowering date. If prevailing weather is warm, subsequent growth is faster as compared to cool
weather where we have delayed maturity.

Once the fruit has matured, we have fruit ripening. During ripening process we have qualitative
changes that make fruit edible.

a. Softening of fruit- this is due to hydrolic changes occurring in cell content e.g. cell walls
are made up of pectin, cellulose which is broken down by enzymes leading to softening of
fruit.

b. Change in composition of fruit- the starch is hydrolyzed to form sugars. It increases

sweetness of fruit.

c. Changes related quality of fruit-(i)- change in fruit pigments –ripening there is

disappearance of green color, decrease in chlorophyll pigments and fruit acquires yellow-
red color depending on fruit. Yellow color is a result of synthesis of carotenoids pigments,
red-anthocyanin pigments. Phenols contribute to astringent (bitter taste which decreases
with ripening.(ii) respiratory changes- depending on how respiratory pattern changes, fruit
can be classified as climacteric fruits- the onset of ripening is associated with a rapid
increase in respiration and also at the same time there is autocatalytic production of
ethylene (ripening hormone) e.g. banana, avocado.

Non climacteric fruit-the ripening process occurs without significance changes in

respiration e.g. oranges, lemons, citrus fruits.

Changes that do occur in harvested horticultural commodities

Once the plant part has been detached from parent plant, it will continue with life process since
the plant organ is still living. There are various physiological and biochemical process that will
occur in harvested commodities. Some of the changes may result of improvement of quality and
appearance of crop. Others may be deteriorative changes that may result in loss of quality of
commodity.
 Change process involved significance
negative effects e.g. shrivel of
commodity and loss of
Water loss transpiration, evaporation
appearance
loss in weight
positive changes e.g. banana;
conversion of starch to sugar
result in sweetening
in potatoes, conversion of starch
Carbohydrate
Enzymatic process to sugar is negative aspect
conversion
in sweet corn/green maize, the
quality is attributed to sweetness
but when sugar is converted to
starch, loss of taste (-Ve).
Development of beneficial in fruit crops since the
flavor Enzymatic process fruit acquires aroma
positive changes (oranges
developing yellow colour to
Colour Synthesis of some pigments synthesis of Carotenoids
negative changes - kales turning
destruction of pigments yellow.
negative (potato tubers/onion
bulbs which may sprout when in
sprouting, rooting growth and development storage
pathological factors (infection
in harvested produce negative attribute
Decay/rotting
physiological process e.g. tissue
breakdown negative attribute

Harvested plant organ during storage period

We do realize that the quality of harvested produce will be influenced by pre-harvesting factors
that were prevailing in the field e.g. sugars- the final level is determined by the conditions of the
plant in field. These factors include

Temperature and light intensity-the development of some pigments especially red

pigment require exposure to full sunlight and if commodity grows underground situation,
colour development is inhibited. In case of temperature e.g. in atmosphere, the yellow color
develops when night temperature are cool and if temperature remains continuously high,
the fruit retains its green colour although has acquired maximum sugar.

Pruning in the field- proper pruning is required to expose most of fruit to light and avoid
shading of the plants.

The rootstock and scion also influences quality of commodity.- most fruits and
vegetables are propagated by budding and grafting and the type of rootstock that is used
influences quality of commodity e.g. Valencia oranges, if grafted on rough lemon, the size
of fruit and vitamin c content is lower compared to when the same cultivar is grafted on
Cleopatra mandaur.

Field management practices e.g. irrigation. If you have got a crop grown in waterlogged
conditions, it will result from faster shriveling of crop in storage. The irrigation regime can
negatively influence quality of commodities. When it comes to accumulation of sugars in
fruit crops, rapid accumulation of sugars occurs at the final stage of fruit maturation and is
possible to subject the trees to period of stress which result in enhanced accumulation of
sugar e.g. color development in grape is enhanced by cutting down water amount toward
maturation stage. Nutritional of the plant in field e.g. K is involved in decrease acidity of
ripening fruits.

The way you control pest can also impact when commodity is harvested- chemical
residues decreases quality of commodity. For some fruits they may be bagged to protect
them from damage and when fruits have been bagged, for some, colour development does
not occur normally.
Use of some growth regulators applied prior to harvesting so as to influence quality
e.g in tomato, ethylene is sprayed to enhance uniform maturity. Cytokinins- used to delay
senescence of some vegetable crops since when they are sprayed, the degradation of
chlorophyll is delayed and harvest produce remain much more green even after post
harvesting.