BLE 211: Principles of
Agriculture and Forestry
Lecture 2
Agricultural Practices
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Crop production systems vary with the crop, time,
location and the level of technology of the particular
area.
 In pre-agricultural societies gathering wild plants was
the only way to obtain crop products.
 The management of natural stands of some useful
plant species has continued to play an important role
in tropical crop production.
 Many practices have also evolved with the evolution
of man. They may be:
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Extensive on large areas of land or
Intensive in gardens.
Agricultural practices involve the use of choice
cultivars and manipulations of soil and other
resources to obtain desired yields from plants
Types of Cultivation practices
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Shifting cultivation: With increased population,
shifting cultivation has been replaced by sedentary
occupation and reduced length of fallow period.
Mono-cropping: This is the growing one crop to
maturity on a piece of land. Not common in the
tropics except in plantations and swamp rice,
sugarcane or large-scale maize production.
Mixed-cropping or multiple cropping: It is
growing of two or more crops on the same piece of
land, simultaneously. Most common of the farming
practices in the tropics usually associated with
under-developed farm technology.
Crop Rotation: A given combination of crops is
grown in a particular sequence on the same piece
of land for several years without loss of soil fertility
or reduced yields
Types of Mixed cropping
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Inter-cropping: Short-term annuals planted
through long-term annuals or biennials and
harvested before the main crop matures.
 Inter-planting: Long-term annual or biennial
crops planted through short-term annuals.
 Phased Planting: Planting dates are
systematically arranged to ensure continuous
sequence of growth and harvesting.
 Relay Planting: Following one crop with
another immediately before harvesting the
former crop.
Advantages of Mixed Cropping
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Reduces susceptibility to diseases and pests as
well as risks of crop failure.
Allows for adaptation of plants to changing soil
conditions because of differences in peak demand
by associated crops for nutrients and water.
Facilitates vertical and horizontal variations thus
allowing cultivation of crops adapted to light and
shade.
Permits phased harvesting and even distribution of
workload
Provides reasonable soil cover that protects the soil
against erosion, while suppressing weed growth.
Provides higher yields that mono-cropping
Adaptable to small-scale hand operated farming
Principles of Crop Rotation
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Alternate growing of crops with differential
ability to absorb nutrients from the soil or
having different depths of rooting system.
Alternating crops susceptible to certain
diseases with those that are resistant.
A Planned succession of crops that takes
into account any detrimental or beneficial
effects of one crop on the following crop.
Alternating soil-exhausting crops with crops
that contribute to the improvement of soil
fertility.
Alternating crops with peak requirements of
labour, water etc.
Agricultural Systems
Characteristics
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Reducing farm sizes although some large-scale
farms are still in existence.
Use of human labour and simple tools. Animal
power limited to only a few operations.
Permanent cultivation usually restricted to
homestead and to tree crops but with increasing
population permanent cultivation especially on
flood plains and other productive soil regions is
emerging.
Mixed cropping is widespread. There are usually
more crops and crop combinations on the
homestead farms than on outlying farms.
Cropping is almost entirely dependent on rainfall.
Irrigation is mainly practised for the high-value cash
crops.
Agricultural Systems
Characteristics
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Burning is widely used as a means of clearing the
land in preparation for planting.
Limited use of manufactured chemical fertilisers
due to cost. Soil fertility is maintained through
regular fallowing or application of household and
animal refuse.
Animals, especially poultry are kept on free range.
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Farm animals are fed on fodder while kitchen wastes
provide food for a few animals kept in the household.
Extensive animal husbandry relies on continuous
movement of livestock in search of forage and water
throughout the year.
Low level of capital investment since primary
objective of most farmers is subsistence.
Agricultural Systems
Characteristics
 With
the increase in availability of
industrial consumer goods, the
traditional objective of self-sufficiency in
food is gradually giving way to an
exchange economy.
 In
this economy the level of capital
investment in farming determines to some
extent the level of income and ability of the
farmer to acquire consumer goods.
Changes in Agricultural Systems
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Shifting cultivation has been considerably
modified resulting in more settled land
occupation as opposed to constant
migration by cultivators.
Nomads continue to move with their
animals particularly cattle, sheep, goats and
camels, in search of grazing
Intensive production of poultry and pigs is
practised.
Dairying as an intensive practice and
ranching as an extensive practice are also
found in the tropics.
Changes in Agricultural Systems
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With the development of large-scale and
small-scale irrigation projects, arable
farming of cereal, vegetable crops, fruits
and flowers has gradually developed.
Large-scale, arable, rain-fed as well as
tree-crop plantation has been developed in
the more humid areas in response to
market demands for industrial and food
crops.
Intensive production of vegetables, fruits
and flowers has increased tremendously.
Reasons for these Changes
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Increase of human population, which impose
a greater demand for food and other
agricultural products.
 Rapid urbanisation attracts labour away from
agriculture and encourages intensification.
 Technical progress raising the demand for
agricultural raw materials and
 Changed outlook of farmers from subsistence
to commercial production aimed at
maximisation of income.
Branches of Agriculture
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Animal science: This is concerned with the study
of animal breeding and husbandry including
aspects of animal health.
Crop Science: The study of crops, their
management, harvesting and storage.
Soil Science: The study of the classification
survey, conservation and management of the soil
for crop and animal production.
Mechanisation - The study of agricultural
machinery and tools together with the development
of improved implements and methods of managing
crops, animals and their products.
Horticulture – This is the study of cultivation of
fruits, vegetables and ornamental plants.
Branches of Agriculture
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Forestry: Science of forest resources and their management
and conservation as well as utilisation of forest and forestry
products.
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Wildlife and range management - Concerned with the study
of wildlife resources in the forest ecosystem.
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Fisheries - study of the wildlife resources of aquatic systems.
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Agricultural economics - Demand-and-supply relationships
in agriculture and the economics of agricultural production
including financing, land tenure, marketing of agricultural
products, co-operatives, project development and evaluation.
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Agricultural extension and Rural Sociology - Development
and dissemination of agricultural information; the transfer of
technology to farmers and the study of the lifestyles of rural
farming populations.