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FACTORS INFLUENCING AGRICULTURE.

FACTORS INFLUENCING AGRICULTURE.

FACTORS INFLUENCING AGRICULTURE. These are:

  • Human factors.
  • Biotic factors.
  • Climatic factors. S Edaphic factors.

Human factors.

Human characteristics that affect decision making and operations carried out..

Includes.

  • Level of education and technology.
  • Human health/HIV-AIDS.
  • Economy
  • Transport and communication.
  • Government policy.
  • Cultural and religious beliefs. S Market forces.

Human health/HIV-AIDS.

Effects of HIV-AIDS.

  • Shortage of farm labor.
  • Loss of family support.
  • Low living standards leading to despondency and hopelessness.
  • Time wasted looking after the sick and money used to buy drugs instead of farm inputs.

Government policy.

Are government laws enacted to protect farmers, land and livestock.

Includes:

  • Food policy.
  • Policies on control of livestock parasites and diseases. S Policy on marketing of farm produce.

Policies by the government that helps improve agricultural production.

  • Heavy taxation of imports in order to protect local industries. This makes importation more expensive and discourage sale of products similar to those produced locally.
  • Subsidizing the growing of locally produced commodities. This makes production cheap and affordable to most farmers.  g. reducing tax on inputs to make them cheaper to buy and use.
  • Quality control. This ensures production of high quality goods for both export and domestic market.
  • Conservation of natural resources. To make them sustain agriculture.  g.

conservation of forests, water catchment areas, wildlife and soil.

  • Stepping up control of diseases and parasites that affect crops and livestock. Such measures includes: quarantine, licensing of quality products and vaccination of animals against infectious and contagious diseases.

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FACTORS INFLUENCING AGRICULTURE.

Level of education and technology.

Low level of education results in farmers using poor methods of farming. They tend to rely on fate, superstitions and traditions.

Knowledge in mathematics helps in measurements and calculations leading to accuracy in apply inputs and assessing results.  It is necessary for proper accounting and analysis leading to proper decision making.

Knowledge in science helps in observation, interpretation and solving problems.

What can be achieved with this high level of education and technology?

  • Proper method and time of doing things such as planting at the proper time and spacing.
  • Use of the right type and amount of inputs.
  • Applying the inputs at the right place. E.g. foliar fertilizers on the leaves.
  • Making right decisions based on proper observation. It helps for example, in observing signs of disease and applying the right treatment or fertilizers.

High level of education leads to:

  • Accuracy in applying inputs and assessing results
  • Helps in proper decision making and organization
  • Better problem solution
  • Better utilization of livestock feeds and fertilizers
  • Understanding of technical language used in agriculture
  • Development of skills for operating machines and their maintenance
  • Increase in efficiency and minimizes costs

Biotic factors.

  • Pests
  • Pollinators
  • Parasites
  • Pathogens
  • Predators
  • Nitrogen fixing bacterias

Pests.

Destructive organisms. They cause the following.

  • Lowers the quality and quantity of agricultural produce.
  • They transmit crop diseases. Pests with sucking mouthparts feed on sap and in the process they transmit crop diseases especially viral diseases.
  • Some injure the plant parts which they feed on and as a result expose the plant to secondary infection. They may also lead to rotting of produce.
  • They increases the cost of producing crops. This is because control measures have to be undertaken such as chemical control which is expensive.

Parasites.

Invertebrates which live in or on other living organisms.  (Endoparasites and Ectoparasites.)

They suck blood from the animals and irritate them by biting on their skin.

Decomposers.

Micro-organisms that act on plant and animal remains.  They lead to decomposition thus adding organic matter to the soil.

Predators.

Animals that kill and feed on other animals.  Predators that feed on pests are beneficial to farmers as they reduce pest populations.

Pathogens.

Micro-organisms that transmit diseases. They cause death of plants and livestock.  They reduce both the quality and quantity of agricultural products.  Include: bacteria, viruses and fungi.

Pollinators.

Can be insects or birds. They lead to cross pollination which helps in the production of new and improved varieties of crops.  Include: bees, butterflies.

Nitrogen fixing bacteria.

Found in the nodules of leguminous crops roots.  Convert nitrogen from air into nitrates.  Their presence in soil make soil more fertile when leguminous crops are grown.

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FACTORS INFLUENCING AGRICULTURE.

Climatic factors.

Include:

  • Rainfall
  • Temperature
  • Relative humidity.
  • S Light.

Weather. Atmospheric conditions of a place at a given period of time.

Climate.  Weather condition of a place observed and recorded for a period of 30-40 years.

Rainfall.

Water is required by the plants for the following reasons:

  • Acts as a solvent for plant nutrients.
  • Cools the plant during transpiration.
  • Raw material for photosynthesis.
  • Makes plant turgid hence providing support.

Plant responses to lack of adequate water.

  • Closing stomata to reduce water loss.
  • Hastens maturity.
  • Some will roll their leaves.

Aspects of rainfall.

  • Rainfall reliability.

It is the dependency on the meteorological timing on the onset of the rains.  It determines time for land preparation and planting.

  • Rainfall amount.

Quantity of rainfall that falls in a given area within a given year measured in millimeters

It determines the type of crops to grow and type of livestock reared in an area.

  • Rainfall distribution.

Refers to the number of wet months in a year.  Influences the choice of crop varieties grown in an area.  Annual rainfall indicates the amount of rainfall available during the year though it does not tell about how it is spread throughout the year.

  • Rainfall intensity.

Amount of rain that falls in an area within a period of one hour and is measured in MM per hour.  Rainfall of high intensity damage crops and causes soil erosion.

Temperature.

The hotness or coldness of a place measured in degrees Celsius or centigrade

Topography is the surface feature of an area and it affects the temperatures of a place.

Effects of temperatures on crop production.

Low temperatures.

  • Slows growth rate of crops as the process of photosynthesis is slowed.
  • High incidences of disease infection to crops such as Elgon die back, CBD and hot and cold diseases of coffee.
  • Quality of some crops such as tea and pyrethrum improves with the lowering of temperatures.

 High temperatures.

  • Increases evaporation leading to wilting of crops.
  • Increase rate of growth or hastens maturity of a crop.
  • Improves the quality of some crops such as pineapples and oranges.
  • Increases incidence of disease infection and pest attack in crops. For example, leaf lust in coffee and aphids in vegetables.
Ecological zone. Range of altitude. Livestock. Crops.
High altitude. (high potential) 2100 m and above. v  Exotic dairy breeds of cattle and wool sheep breeds.

v  Exotic beef breeds.

Tea, pyrethrum and high altitude maize varieties.
Medium altitude. (High to medium potential.) 1500-2100m v  Exotic dual-purpose breeds. (boran and sahiwal)

v  Exotic dairy breeds such as Guernsey and jersey.

v  Dairy goats.

Coffee, maize hybrids of medium altitude, bananas and beans.
Low altitude.

(Low potential.)

900-1500m Zebu cattle, meat goats. Katumani maize, bananas, sorghum, pigeon peas, cassava.

Wind.

Refers to air in motion.

Effects of strong wind in agriculture.

  • Increasing the rate of evaporation of moisture from the soil.
  • Causing lodging in cereals and damage to crops. S Blowing away and bringing rain-bearing clouds.
  • Acting as agent of seed dispersal.
  • Acting as agent of soil erosion.
  • Increasing evaporation rate.
  • Increasing the spreading of pests and diseases.
  • Destroying farm structures.
  • Areas with high humidity tend to be hotter but when wind takes away atmospheric water, a cooling effect occurs.

 Relative humidity.

It is the amount of water vapor held by air at a given temperature, compared to what it would hold when saturated. It affects the rate of evaporation and transpiration.

Evaporation is the loss of water from the soil surface in form of water vapor while transpiration is the loss of water vapor through the leaf pores.  At high relative humidity, the rate of evapotranspiration is low.

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FACTORS INFLUENCING AGRICULTURE.

Light.

Light provides the energy required for photosynthesis.

Aspects of light.

1) Light intensity.

Strength with which light is harnessed by chlorophyll for the purpose of photosynthesis. Rate of photosynthesis increases with increase in light intensity. Low light intensity makes plants especially seedlings to become etiolated (thin and pale in colour).

Ways of increasing amount of light harnessed by crops.

  • Prunning
  • Thinning
  • Weeding
  • Use of a wider spacing.

2) Light duration.

Refers to the period during which light is available to plants per day.

Photo periodism.  Plant response to light duration.

  • Short-day plants. Requires less than 12 hours of day light to flower and seed.  g. soya beans, rice and tobacco.
  • Long-day plants. Requires more than 12 hours of daylight to flower and seed.  For example; some wheat varieties.
  • Day-neutral plants. Requires 12 hours day light to flower and seed.  Include tropical plants like; coffee, maize and beans.

3) Light wavelength.

Chlorophyll absorbs certain wavelength of light which are not present in artificial light unless incase of ultra-violet or infra-red.

S Green houses or Glass houses can be used to control temperatures, relative humidity and light intensity and duration.

EDAPHIC FACTORS.

Soil is the natural material on the uppermost layer of the earth’s crust which support plant growth.  Consist of a mixture of weathered rock and decayed organic matter. Supports plant’s life by providing anchorage, nutrients and water.

Soil formation.

Soil is formed through weathering process.  Weathering is the breakdown and alteration of the parent rock near the earth’s surface.

A series of complex changes occur and alter the form, colour, texture and composition of rocks.

Weathering is a combination of disintegration (breakdown down process) and synthesis (building up process.)  Weathering is brought about by physical, biological and chemical processes.

Soil forming factors.

  • Climate
  • Parent materials.
  • Living organisms.
  • S Time.

 Physical agents of weathering.

These includes: wind, water, moving ice and temperatures.

  • Strong winds carry materials which hit against each other making surfaces of the materials break off into smaller fragments.
  • When rocks or other materials are moved along the ground, they have a grinding effect.
  • Moving ice also has a grinding effect.
  • Rainfall of high intensity erodes rock surfaces.
  • In places of high altitude, the temperatures are low and when water gets into cracks, it freezes and become ice. This increases the volume of water by 9%. The increase in volume exerts pressure on the walls of the cracks in the rocks widening them and dislodging mineral grains from small fragments.
  • In arid and semi-arid areas, temperatures are very high during the day. This makes the rocks to expand starting from the outside to the inside. At night, temperatures drop. This makes the rocks to cool and contract starting from the surface. This unequal expansion and contraction of the rocks causes the outside part of the rocks to flake off.
  • This physical or mechanical weathering in time causes the disintegration of rocks without any chemical changes being involved.

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FACTORS INFLUENCING AGRICULTURE.

Biological agents of weathering.

Living organisms play a very important role in soil formation.

  • When large animals such as elephants, buffaloes, cattle, horses, camel and man move, they exert pressure on the rocks causing the small fragments to disintegrate.
  • Man’s activities like mining, earth moving, cultivation and construction of buildings, railways and roads reduce the size of the rocks into smaller particles.
  • Bacteria and fungi initiate the breakdown of plant tissue on the surface and within the soil. Organisms such as ants’ termites are also important in tropical soil formation.
  • Termites bring to the surface large quantities of fine materials. This promotes weathering as lower materials become aerated.
  • Earthworms feed on plant tissues and their waste matter helps to cement soil particles.
  • Roots of growing vegetation force their way into cracks on the rocks exerting pressure which eventually splits the rocks. When the plants die, the roots decay leaving gaps in rocks which are then occupied by water and air that forms acids that dissolve minerals from rocks and corrode rocks weakening them.
  • Roots produce acids in the soil during respiration, which dissolves minerals from rocks.

Chemical weathering.

  • It is the actual decay or decomposition of rocks. Involves various chemical reactions which take place between rock minerals, water and certain atmospheric gases like oxygen and carbon( iv) oxide.
  • The chief agent of chemical weathering is water.
  • As rain water falls through the atmosphere, it dissolves some carbon iv oxide forming very weak carbonic acid. This acid reacts with the mineral particles of the rocks particularly calcium carbonate causing decomposition.

Rain water + carbon (iv) oxide= weak carbonic acid.

H2O  + CO2                                   H CO

Weak carbonic acid + limestone                                    calcium bicarbonate.

H2CO3    + CaCO                                                   3 2

  • The calcium bicarbonate formed is soluble in water and this process dissolves the rocks.
  • Oxygen reacts with many elements such as iron from olivine rocks forming ferrous and ferric oxides that produces red soils.

Factors influencing soil formation.

Parent rock material.

  • Influence physical properties and chemical constituents of the soil.
  • Texture of the soil affects rates of soil formation. Freely drained parent materials form soils faster than dense impermeable parent materials.
  • Mineral composition of the soil depends on the nature of the parent material. Rocks containing calcite, feldspar and Ferro magnesium minerals are likely to produce deep heavy soils rich in plants nutrients.
  • It influences the type of natural vegetation in an area.

Climate.

  • Rainfall provides water which is an important reactant in all forms of weathering. The precipitation: evaporation ration is important.  If precipitation exceeds evaporation, there will be loss of ions in drainage water.  If surface evaporation exceeds precipitation, there will be accumulation of salts either on the surface or within the soil profile.
  • High temperatures speed up the rate of chemical reactions. In cold regions, chemical reactions are slow and activity of micro-organisms is also slow limiting soil formation.
  • Wind acts as a transport agent and carries weathered materials from one place to another. Where a lot of weathered materials are deposited, soils are deep and where wind carries away the top soil, the soil remain shallow or bare rock is left.
  • Dry areas have soils with carbonate accumulation in the profile.

Topography.

It is the shape of land in relation to the underlying rock of the earth’s surface.

  • Factors such as elevation, slope and degree of exposure or shelter may influence the degree of soil erosion.
  • Slope affects the depth of the soil and kind of vegetation growing in an area. Soils found in flat land and low lying areas tend to be more fertile than those on higher slopes.
  • On steep slopes there is soil erosion that leads to shallow soils.
  • In flatter areas, there are deeper soils that are richer in minerals due to deposition. The soils tend to be darker in colour and well drained.

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Time.

  • Where soil forming process have taken place over a long period, deep mature soils can be found.
  • Where erosion has been severe there is a tendency of soil to remain shallow and youthful with a poorly differentiated profile.
  • In flatter areas, soil erosion is less and this makes the time factor have a greater effect on the soil, giving rise to mature soils. If parent material is not easily weathered, it may take a long time for soil to grow to maturity and develop in depth.

 SOIL PROFILE.

Vertical arrangement of various soil layers/horizon.

1) Superficial layer.

Thin layer consisting of dry decaying and decayed origin matter covering the soil’s surface.

2) Top soil (Horizon A)

Uppermost soil layer.

  • Darker in colour than other layers due to its high humus content.
  • It is well aerated and contains active micro-organisms.
  • Well drained and contains most of the plant nutrients.

Sub-soil. (Horizon B)

  • More compact and less aerated than the top soil.
  • Hardpan which is an impervious layer may be found in this region. Hard pan impedes drainage and root penetration.
  • Downward movement of clay colloids are deposited in this region hence called layer of accumulation.

Substratum/weathered rock. (Horizon C) S Made of partly weathered rock with no humus.

  • It is hard and impervious to water.
  • Roots of large trees may reach this layer to draw water in dry season.

Parent rock. (Horizon D) S Called the bedrock.

  • Soil is formed from this rock.
  • Ponds of water are also found here.
  • A transitional zone is found between any two bordering soil layers which reflects properties of adjoin horizons.

Differences between soil formed in situ and soil formed in deposition.

Soil formed in situ. Soil formed in deposition.
S Shallower. S Deeper.
S Less rich in plant nutrients. S Picher in plant nutrients.
S Easily eroded. S Not easily eroded.
S Has the colour and characteristics of the parent rock. S Has the characteristics of where it came from.
S Less silty. S More silty.
S Has the same chemical composition as that of underlying parent rock. S Differs in chemical composition from the underlying parent rock.

Soil depth.  Distance between top soil layer and the bottom soil layer in a soil profile.

  • Deep soils are suitable for crop growth since they contain more nutrients.
  • Deep soils facilitate good drainage and aeration.
  • Deep soils have larger surface area for root expansion.
  • Loosely packed sub-soil allows easy penetration of roots, drainage and aeration. This ensures soil erosion does not take place.
  • Nature and composition of bedrock influences mineral components of the whole soil.

SOIL CONSTITUENTS

Soil is made up of the following:

  1. Mineral matter
  2. Soil water
  3. Soil air
  4. Organic matter
  5. Living organisms
  6. Mineral matter

These are inorganic compounds formed from the weathering of rocks. They differ in size ranging from clay to gravel. They include:

  • Clay
  • Silt
  • Sand
  • Gravel

FACTORS INFLUENCING AGRICULTURE.

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Influence of mineral particles on crop production

They make the main frame work of the soil

They hold plant roots firmly together

How to determine the mechanical composition of the soil

Using various sieves of different diameter

  1. Soil water

Soil has water which comes from rainfall and also from irrigation in dry lands

Forms of soil water

  • Superfluous water
  • Capillary water
  • Hygroscopic water

Superfluous water

  • This is water which is held by gravity. It is also called gravity water.
  • Its easily lost because its loosely held by soil particles
  • Its readily available to plants but not useful because too much of it limits aeration

Capillary water 

  • This is water occupying the micro pores. It is held by soil particles
  • It’s the water available to plants. It is also referred to as available water

Hygroscopic water

This is water which forms a thin film around the particles. It is not available to plants

Functions of water to plants

  • Soil water maintains the life of plants
  • It is used as a raw material for protein for diffusion of mineral salts and oxygen into the root hairs and the mineral salts dissolved in water are conducted upwards to the leaves.
  • It is also acts as a solvent for the diffusion of other substances from one part of plant to another
  • It makes protoplasm and cell sap of the growing plants
  • It keeps the cell turgid and thus supports plant
  • Also cools the leaves of the plant during transpiration

Experiment 1 to find the percentage of soil water content

Apparatus: – dish, stirring, weighing balance, soil sample and heater or oven

Procedure: 

  • Measure the mass of the dish
  • Pour soil in the dish and weigh
  • Half fill the dish with water
  • Heat up to about 105oc
  • Cool the sol with a desiccator then reweigh and repeat the process until you get a constant mass
  1. Soil air

The spaces between the soil particles are filled with air. These include

Oxygen —————– 20.6

Carbon dioxide ——- 0.6

Nitrogen ————– 78.6 Other rare gases.

The amount of air available in the soil is inversely proportional to the amount of water in the soil pore spaces.

Oxygen present in the air is essential for the respiration of roots and other living organisms in the soil

Nitrogen in the soil is converted into nitrates by the nitrogen fixing bacteria

Air is also needed by the micro- organisms living in the soil

Excess carbon dioxide in the soil is poisonous to plants

Experiment 2: To find the percentage of air by volume in a soil

Apparatus

  • Small tin
  • Graduated cylinder
  • Knife and stirring rod

Procedure

  • Turn the empty tin upside down and press firmly into the ground until the tin is completely filled with soil
  • Turn the tin upright and level the soil to the brim of the tin with a ruler
  • Pour 250cm3 of water into a cylinder and scrap off soil into the water until no bubbles comes out
  • Record the final volume of soil and cylinder
  1. Soil organic matter
  • Organic matter in the soil is the remains of the dead plants and animals plus their waste products
  • Humus is the decayed organic matter

Importance of organic matter

  • Decomposes to release nutrients to plants
  • Makes the soil lighter to cultivate
  • Also improves the soil structure

Experiment 3: To find the % of humus content in the soil 

  • Apparatus
  • Dish
  • Garden soil
  • Tripod stand
  • Wire gauze
  • Bunsen burner

Procedure

  • Weigh the empty dish
  • Put the garden in the dish and reweigh
  • Place in an oven at about 105oc
  • Cool in a desiccator and reweigh
  • Repeat the process several times until a constant weight is obtained  Note the difference weight
  1. Soil living organisms

There are two types of living organisms in the soil namely:

  • Macro organisms
  • Micro organisms

Macro organisms are large organisms found in the soil e.g. rodents, earthworms, ants, termites, plant roots etc.

Microorganisms are tiny organisms which can only be seen with the help of a microscope they include bacteria, fungi, protozoa etc.

Importance of soil living organisms

  • They barrow in the soil and aerate the soil and improve drainage
  • They help in the decomposition of organic matter
  • Some also fix nitrogen in the soil e.g. the nitrogen fixing bacteria

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Experiment 4: To show the presence of living organisms in a soil sample

Apparatus

  • 2 flasks
  • Rubber cork
  • Muslin bag
  • Heater
  • Lime water
  • Garden soil

Procedure

  • Put a handful of garden soil in two muslin bags labeled A and B
  • Heat the soil in muslin bag B strongly to kill the micro organisms
  • Suspend the two bags in the flasks also labeled A and B, the flasks should contain lime water  Leave the apparatus for 4hrs

Observation

  • Lime water in flask A turns milky
  • Lime water in flask B remains clear

Conclusion

  • Lime water in flask A turns milky because of the presence of carbon dioxide produced during respiration. Carbon dioxide turns lime water milky
  • Lime water in flask B remained clear since the living organisms were killed during heating so no respiration took place Physical properties of soil

These include:

  1. Soil structure
  2. Soil texture
  3. Soil colour

Soil structure

This is the way in which the individual soil particles are arranged

Types of soil structure

  • Single grained structure
  • Crumby structure
  • Granular structure
  • Platy structure
  • Blocky structure

Single grained structure

In this structure, the particles are not cemented together. They exist as individual grain. They form no aggregates and are non-porous.

They are mostly found in top soils of sandy soils and in arid climate and in alkaline soils

  • Crumby structure

This type consists of small, soft porous aggregates of irregular shapes. They are not closely fitted together

  • Granular structure

This is made of friable rounded aggregates of irregular shapes called granules. It is formed when particles coagulate and are cemented together to form rounded aggregates whose diameter is not more than 15cm

When wet it becomes porous since the spaces are not readily closed by swelling. The structure is found in top horizon in cultivated soils and in the sub- soil under grass. The structure is not porous and is usually affected by tillage.

  • Prismatic structure

This is where the structure aggregates are arranged vertically. The primary particles are vertically oriented forming distinct columns which vary in length depending on the type of soil.

The structure is found in sub soil of arid and semi arid soils

N/B: If the tops are rounded, they are called columnar. But if the tops have clear cut edges, the it is called Prismatic

  • Platy soil structure

In this structure, the aggregates are arranged on top of one another on thin horizontal plates. The plates overlaps and impair permeability and hence drainage and root penetration. The structure is found in top soils of clay soil and forested area.

  • Blocky structure

Here the aggregates are in form of rectangular blocks. The aggregates easily fit together a long vertical edges

Influence of soil structure on crop production

  • A loosely packed structure ensures good air circulation in the soil

Good structure also ensures proper water holding capacity

Good structure also gives proper root anchorage

  • Good structure also reduces then soils liability to erosion

Factors that influence the soil structure

  1. Parent material

The physical and chemical properties of the parent rock will determine the type of structure being formed

  1. Soil forming processes

Processes which lead to soil formation will determine the type of structure being formed c) Climate

In areas where a lot of rainfall is followed by dry periods cracks tend to form giving rise to good structure which is well aerated

  1. Organic matter

Presence of organic will stabilize the soil structure

  1. Living organisms

Living organisms also help to decompose organic matter which intern improve structure f) Cultivation

The nature of cultivation e.g. digging channels results in a better structure

  1. g) Inorganic compounds

Presence of compounds like iron oxide have binding properties and help in the formation of granules

  1. Soil texture

This refers to the relative proportion of various sizes of mineral particles in a soil.

Particles                                                      Diameter

  • Clay                                   002mm and below
  • Silt 002 —— 0.02
  • Fine sand 02 ——- 0.2
  • Coarse sand 2 ——– 2mm
  • Gravel 2 ———- 20mm
  • Stone                                    20mm and above

Determination of soil texture Can be determined by:

  • Mechanical analysis
  • Chemical analysis

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FACTORS INFLUENCING AGRICULTURE.

Mechanical determination of soil texture

Apparatus

  • Sieves of different diameter
  • Containers
  • Weighing balance

Procedure

  • Put a known amount of soil sample in a container
  • Pass the soil through a sieve of the smallest diameter and shake
  • Weigh the soil that remains in the sieve
  • Repeat the process using sieves of different diameter until all the soil I passed through

Observation

After every sieving it will be observed that a certain amount of soil remains in the sieve

Conclusion

Soil is made up of different sized particles of different diameter

Experiment 6: to show that soil is made up of different sized particles

Apparatus

  • Measuring cylinder

Sodium carbonate

Garden soil

Procedure

  • Put some soil sample in a measuring cylinder
  • Add about 4 times its volume of water with sodium carbonate to aid in dispersion of particles  Cover the mouth of the cylinder with the hand and shake vigorously for about 2min.
  • Place cylinder on the bench for about 1hr or more to allow the contents to settle down

Observation

  • At the end of the period, it will be seen that fractions have settled in layers
  • The heavy, coarse gravels settle first, then followed in succession by sand, silt and clay
  • The humus and organic matter remain floating in the water or on top of the clay

Conclusion

From the above observations, it can then be concluded that soil is a mixture of particles of different sizes.

Influence of soil texture on crop production

  • Coarse soils have poor water holding capacity
  • Very fine textured soils also have poor aeration

Soil colour

  • Soil colour depends mainly on the mineral composition of the soil
  • If the soil was made from a rock containing a lot of iron compounds, it tends to be brownish yellow, reddish or orange in colour
  • Humus content also gives dark brown colour
  • Soil colour influences temperature of the soil

 Soil classification

Soil can be classified based on the following

  • Soil structure
  • Soil texture
  • Soil colour
  • Soil pH

According to structure, soils could be classified as granular, crumby, blocky, or platy soil structures

According to texture, a soil containing high proportion of sand particles is called sandy soils, if it contains high amount of clay then it is called clay soils

In terms of colour, soils could be either dark coloured soils or light coloured soils

Types of soils

  1. Sandy soils
  2. Silty soils
  3. Clay soils
  4. Clay loams
  5. Loamy soils
  6. Sandy soils
  • They have bigger particles
  • Contains 50 – 80% sand, and 20 -50% silt and clay
  • Organic matter content is 0.1 – 3%
  • Are well drained
  • Are more prone to soil erosion have low water holding capacity
  • They are slightly acidic
  • Easy to cultivate but less fertile

How to improve sandy sols

  • Add organic matter
  • Addition of fertilizers
  1. Silty loams
  • They contain 20 – 30% sand
  • Also contains 70 – 30% clay

Has 0.1 – 4% organic matter

They are fine textured, well drained and have  a good water holding capacity  They have moderately acidic pH.  Moderately fertile and aerated

  1. Clay loams
  • They contain 20 – 50% sand
  • Clay and silt is 20 -60%
  • Has organic matter content of 0.1 – 6%
  • They are fine textured
  • Poorly drained and aerated
  • Has capillarity and water retention
  • They are rich in plant nutrients
  • Are suitable for flood irrigation for rice growing  This soil can be improved through drainage
  1. Clayey soils
  • Have clay content of more than 40%
  • Have high water holding capacity
  • Have crystalline and platy structure
  • Expand when wet
  • Crack when dry
  • Get water logged easily
  • Also suitable for flood irrigation  Have high capillarity
  1. Loamy soils
  • They contain 30 -50% sand, 50 -70% silt and clay and 0.4% organic matter
  • Are moderately textured and drained
  • Are slightly acidic
  • Have good water holding capacity
  • Can be improved by planting cover crops and adding organic manures

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FACTORS INFLUENCING AGRICULTURE.

Experiment 7: To compare the porosity and water holding capacity of sand, loam and clay Apparatus

  • Measuring cylinder
  • Funnels
  • Cotton wool
  • Dry sand, loam and clay

Procedure

  • Place equal volumes of each soil in each funnel plugged with cotton wool
  • Tap all the funnels persistently until all visible air spaces are filled up
  • Stand each funnel in the open end of measuring cylinder and add 50cm3 of water into each funnel
  • Note the time taken for the first drop of water through into the cylinder

Observation

After some time, it will be seen that water level is high in sand than the rest

Conclusion

Sandy soil is more porous than the other 2

Clay soil has the highest water holding than the other 2

Experiment 8: To compare the capillarity of sand, loam and clay

Apparatus

3 long cylinders

Dry sand, clay and loam

Water trough

Clock

Ruler

Procedure

  • Close the lower end of each tube with a plug of cotton
  • Fill each tube with different soils
  • Tap the end of each tube gently in the bench to tightly pack the soils
  • Stand and clamp each tube with a clamp and put in an empty water trough
  • Poor water into the trough to a depth of 5cm
  • Measure the height of water in each tube after 3 – 5min
  • Take as many readings as much as possible
  • Record the readings

Observations

  • Water will be seen to be rising up the tubes
  • It rises very fast in sand and loam in the first 3 – 5min. but very slow in clay
  • After 2hrs water level will be higher in loam than in clay soil and least in sand
  • Water rise continues in clay soil but stops after some time in loam Conclusions
  • Clay and loam have higher capillary action due to their fine pore spaces
  • Sand has poor capillary action due to their large pore spaces
  • Clay soil has the highest capillarity

Chemical properties of soil

  1. Soil pH
  2. Soil mineral content
  3. Soil pH
  • This is the acidity or alkalinity of soil solution
  • Acidity is determined by hydrogen ion concentration while alkalinity is determined by hydroxyl ion concentration

Influence of soil pH on crop production 

  • Soil pH affects the availability of various nutrients e.g. low pH makes P, and molybdenum less available and high pH. makes Mn, K, Fe and zinc less available
  • Very low pH affects the activities of microorganisms e.g. nitrogen fixing bacteria  Different crop species require different pH ranges

Ways of modifying pH

  • Apply lime to raise the pH
  • Apply basic fertilizers
  • Apply sulphur to lower the pH
  • Apply acidic fertilizers to lower the PH

FACTORS INFLUENCING AGRICULTURE.

ALL AGRICULTURENOTES FORM 1-4 WITH TOPICAL QUESTIONS & ANSWERS

PRIMARY NOTES, SCHEMES OF WORK AND EXAMINATIONS

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