AGRICULTURE O LEVEL(FORM THREE)- AGRICULTURAL MECHANICS

Introduction: To perform work, ENERGY must be used. The rate of energy expenditure is proportional to the rate of doing work, which is known as POWER.

Forms of Energy

I) Animated Energy: Energy expended by using the muscular power of human beings and animals.

II) Inanimated Energy: Energy expended through transformation of natural resources, e.g., fossil fuel, wind.

Definition: The application of engineering principles and techniques in the agricultural sector involving utilization of all forms of energy through mechanical assistance in agricultural production.

Components: Tools, Implements, Machines.

Advantages of Mechanization

• Brings more intensive production.
• Allows more land to be put into use.
• Increases speed of work and capacity.
• Releases labor during peak periods.
• Increases labor productivity.

Limitations

• Not suitable on steep slopes, e.g., mountains.
• Requires technical knowledge.
• It is expensive.
• It is weather sensitive.

Definition: Power is proportional to the rate of energy expenditure and the rate of doing work.

Types of Power

I) Human Power: The ability to work by using hands and operating machinery using legs and hands in daily agricultural activities.

• When using hands in small-scale and simple tools called hand tools. These include:

• Hoe: A device used for turning the soil (digging), making ridges, uprooting stumps, etc. It varies in weight, size, and shape depending on the use.
• Rake: A short sponged tool used in soil leveling, removing stones and weeds, breaking clumps during seedbed preparation.
• Machete: A device used for lifting, inverting, leveling the soil, digging holes, and transplanting seedlings.
• Manure fork: A device whose prongs are spaced at regular intervals, similar to a spade but with no plane blade, used in spreading manure.
• Hand craft: A boat-shaped short blade tool used in digging shallow holes and transplanting.
• Mattock: Used in uprooting, digging, and cutting.
• Shears: Scissor-like tool used in trimming hedges.
• Secateurs: Similar to shears and used in pruning.
• Sickle: A curved iron blade with a short handle used for grass cutting.
• Watering can: A container with a perforated spout used for watering.
• Forked hoe: A strong sponged tool shaped like a fork used for rhizomatous weeds and loosening hard soil.

Caring and Maintenance

• Clean and wipe tools after use.
• Grease metal tools to prevent rust using grease or engine oil.
• Construct tool sheds or stores.
• Arrange tools in proper order in the shed or store immediately after use.

II) Animal Power: Power generated by use of oxen, buffaloes, and camels involving pulling of carts and ploughs under human guidance. Animals used are draught animals.

Limitations

• Farmers must possess draught animals.
• Animals may suffer from diseases and parasites.
• Availability of vegetation for grazing animals.
• Land topography should be reasonably flat with light soil.
• Advisory services are needed to train and advise farmers on the use of animals and equipment.

Qualities of a Draught Animal

• Should be healthy and strong.
• Should have short horns.
• Should be 2-3 years old.
• Selection should be done in pairs with similar size, strength, and temperament.
• Should be castrated male animals.
• Should have humps for a yoke.
• Should be of quiet temperament.

Note: Preferably nose-ringed to make it easy for people to control.

Harnessing

Meaning: The process of hitching implements to draught animals using a harness.

Types of Harness

Yoke Harness

Commonly used in Tanzania. It consists of a beam, skey, straps, and U-bolt.

• Beam: Usually about 1.5 m long, used in ploughing and harrowing. Other operations like cultivation (weeding and ridging) require a longer beam of about 1.4 m. It is a smooth piece of wood rested on the neck of an animal.
• Skeys: Pieces of wood fitted into beam perforations to keep animals in position.
• U-bolt: A device fixed at the center of the beam where an implement can be attached.
• Straps: Leather ropes tied under the animal’s neck to hold the skeys.

Collar Harness

A single animal harness consisting of a collar and straps.

Methods of Training Animals

• Far Eastern Method (Indian type): Uses one pair of oxen and one person controls both oxen and implement. Control is achieved by a rope passed through a hole and around the neck.
• Traditional Method: Involves two pairs of oxen guided by two people; one leads the animals and the other controls the implement. Training includes naming animals, restraining with ropes, tying pairs with a yoke daily, using commands, and gradually increasing work intensity.

Note: People training oxen should be calm, patient, and consistent.

Management of Oxen

To obtain maximum power output, the following are important:

• Utilize animals during cooler parts of the day and allow them to eat, drink, and rest.
• Working animals should rest under a shed to protect them from wind, sun, and rain.
• Control diseases and parasites such as tick-borne diseases.
• Check injuries daily and provide treatment immediately.
• Feed animals well on rich pasture, hay, green fodder, and recommended supplements.
• Feed supplements and minerals must be provided in well-cared paddocks.

Tools and Implements Used

Qualities of tools and implements used: simple, strong, light, durable, and inexpensive. Examples include:

• Plough: Both donkey and oxen – One furrow mould board plough commonly used, made of steel with double handles and a depth wheel in front of the beam.
• Cultivator: Aligned implements used for inter-row weeding.
• Ox-ridger: An implement consisting of two mould boards back to back for making ridges.
• Carts: A wooden box fixed on top of two wheels connected to an axle used for transportation of inputs and products.
• Toolbar: A light metal or wooden frame to which different pieces of equipment can be attached depending on the job to be done. Supported by wheels or skids.

Use of Tractor (Tractor Power)

• Conversion of chemical energy of fuel to mechanical power for use on the farm. Examples of fuel used include petrol, diesel, coal, etc.
• Liquid fuel engines called internal combustion engines produce power through a combination of steam engines and a boiler steam generator.

Factors to Consider When Applying Tractor Mechanization

• Farms must be large with plenty of work throughout the year.
• Preparation of enough capital for buying and operating a tractor.
• Finding skilled personnel for operating, repairing, and maintaining a tractor.
• Availability of spares and services at a reasonable price.
• Justification of tractor running costs with expected returns.

Limitations of Tractorization

• Tractors and spares (equipment/implements) are very expensive.
• Needs fuel and lubricants which increase cost.
• Requires highly skilled labour for operation and maintenance.
• Economically not suitable for peasants as it requires large farms with plenty of work.

Importance

• Transporting products/produce, fertilizers, seeds, and building materials.
• Opening up new land with subsequent fertilizer application.
• Weeding and harvesting.
• Processing food and livestock feed by transmitting power to grinding machines through P.T.O.

Classes of Tractors

• 2-wheeled tractor: Single axle tractor, small in size, operated by an individual behind it. Used in small jobs around the home, e.g., garden.
• 4-wheeled tractor: Two axle tractor whose engine power is transmitted to both axles. Usually big in size depending on horsepower (Hp), e.g., medium 15-16 Hp, large 75 Hp and above. Used in ploughing, transport, etc.
• Track-laying tractor: Uses endless tracks instead of wheels. Commonly used for land clearing, farming operations, deep tillage, and working in difficult soils such as swampy and soft soils.

Implements Used by Tractor

A. Cultivation

Machinery used to prepare the soil for planting, e.g., ploughs.

• Mould board ploughs: Produce a more even surface so that use of harrow may not be necessary.
• Disc plough: Preferred in farms with tree stumps; a rotating disc rolls over the obstruction instead of being caught up.

B. Ridgers

Used to make ridges for crops, e.g., potatoes. Types include disc and mould board ridgers.

C. Fertilizer Distribution

Used to achieve even distribution of fertilizer in the field.

D. Planters

Implements maintained by a tractor for the purpose of planting.

E. Cultivators

Used as a follow-up after ploughing.

• Tined cultivators: For inter-row weeding.
• Rotary cultivators: A P.T.O shaft-driven implement used in breaking up soil.

Main Parts of an Engine

A tractor engine is divided into four main parts:

1. Stationary parts: Include engine block, crankcase, cylinder head, and oil sump. These parts do not move relative to their position on the tractor.
2. Reciprocating parts: Include pistons, inlet and outlet valves, and connecting rods. These parts move back and forth.
3. Rotating parts: Include crankshaft, shaft, and flywheel.
4. Auxiliary parts: Facilitate smooth engine function by coordinating the stationary, reciprocating, and rotating parts. These include cooling system, fuel system, electrical system, lubricating system, transmission system, and hydraulic system.

Major Parts of the Tractor

The tractor can be divided into five major parts:

1. Engine: A group of parts assembled in a specific order used to convert the energy given off by burning fuel into useful mechanical form. It may be classified according to cylinder placement (e.g., V placement, inline placement), valve placement, camshaft placement, cooling system (air or liquid), fuel type (diesel, petrol), number of cylinders, and principle of operation (2 or 4 stroke).
2. Clutch unit: A device used to connect or disconnect the flow of power from the transmission unit.
3. Gearbox: A system of gears which transfer and adapt the engine power to the drive wheels, allowing selection of speed ratios and reversing the travel direction.
4. Different units: Transmit power to the drive axle and allow each drive wheel to rotate at different speeds.
5. Final drive: The last phase in the power chain; it provides the final reduction in speed and increase in torque to the drive wheels.

Internal Combustion Engines

1. Stationary parts:
   • Cylinder head: The cap that attaches to the top of the engine block, covering the upper cylinder openings, forming the combustion chamber. A gasket seals the engine between the block and cylinder head.
   • Engine block: A unit usually made of cast iron containing cylinders and a water jacket for cooling.
   • Cylinders: Tubes inside the engine block with smooth finishing, serving as guides for pistons.
   • Crankcase: The lower part of the block that confines lubricating oil near the moving parts.
   • Oil pan/sump/reserve: Aids the crankcase in confining oil near moving parts.
2. Rotating parts:
   • Crankshaft: Converts the reciprocating action of pistons to rotational movement.
   • Flywheel: A heavy metal wheel attached to the crankshaft that smooths out engine power impulses, can be connected to the starter, provides a place to mount the clutch, and provides extra turning force.
3. Reciprocating parts:
   • Pistons: Receive the force of exploding gases and transmit it to the piston pin, connecting rod, and crankshaft.
   • Rings: Seal combustion and compression pressure and prevent lubricating oil from entering the combustion chamber.
   • Valves: Open and close to allow air intake and exhaust gases.
   • Connecting rod: Connects pistons to the crankshaft.
4. Engine accessories: Components of four separate systems needed to operate an internal combustion engine: electrical, lubricating, fuel, and cooling systems.

Engine Cycles

• Four-stroke engine cycle: Involves two complete revolutions of the crankshaft.
• Two-stroke engine cycle: Involves one complete revolution. This is accomplished by eliminating valves used in four-stroke engines. Instead, two ports enter the cylinder wall.

Engine Accessories

• Cooling system: Removes unwanted excess heat, maintains efficient temperature under all operating conditions, and brings the engine to operating temperature when starting up.

Components:

• Water-cooled engine radiator: Made of brass and copper to facilitate cooling and protect from rust and corrosion. It consists of a series of fine tubes with fins providing a large surface area for air. Water is confined in tubes and cooled rapidly by air drawn through the radiator by a fan. A thermostat controls water flow to achieve operating temperature. Hoses connect the radiator and water pump. The water pump circulates water through the engine.

Care of Radiator

• Keep fan and pump belts at proper tension (about 20 mm deflection when pressed at middle length).
• Hoses should be in good condition.
• Check pressure cap for proper operation.
• Keep all connections tight.
• Keep radiator core free from insects and dirt.

• Fuel system: Supplies the engine with clean fuel in the correct ratio.

Diesel: Fuel passes to the injector pump, filtered by gravity or pump, then sent at high pressure into cylinders with compressed air. Fuel ignites due to high temperature of compressed air.

Petrol: Fuel passes through filters, mixed with air in a carburetor at a ratio of 1:15, then sucked into the engine cylinder for combustion.

Carburetor

Mixes petrol and air in the right proportion.

Components:

• Fuel tank: A fuel storage unit, well protected from flying stones and accidents. It has a vent to allow air to avoid vacuum creation and a drainage valve for cleaning.
• Fuel lines: Diesel uses low-pressure fuel lines (tank to injector pump), petrol uses high-pressure fuel lines (injector pump to tank).
• Fuel filter: Removes impurities from fuel.
• Fuel lift pump: Sucks and pushes fuel to the injector pump through the filter.
• Injector pump: Times, measures, and delivers fuel under pressure to the cylinders.
• Injector nozzles: Atomize and spray fuel in the cylinders.
• Air cleaners: Prevent dust and dirt from entering the engine.

Maintenance: Check tank for leaks and repair; change filter elements regularly.

• Lubrication system: Reduces friction between moving parts, absorbs heat, seals piston rings, cleans and flushes moving parts, and helps reduce engine noise by supplying a thin film of oil on moving surfaces.

Classes:

• Force feed lubrication: Oil is fed under pressure from a pump to all bearings.
• Splash feed lubrication: Common in single-cylinder engines where moving parts are lubricated by splashing oil over them.

• Electrical system: Supplies electricity for starting the engine and lubrication.

Components:

• Battery: Source of electrical energy for ignition system.
• Ignition switch: Connects and disconnects electricity flow.
• Resistor: Controls current to the coil.
• Coil: Transformer that raises battery voltage.
• Breaker points: Connect and disconnect current flow in the circuit.
• Condenser: Provides a place for primary current flow when points are open.

• Transmission system: Mechanical system consisting of clutch, gearbox, differential unit, and final drive. It transmits power from the engine to the tractor wheels and provides varying speeds.
• Hydraulic system: Consists of oil reservoir, pipeline, and control valves. Oil pumped under pressure transmits power to control implement settings and external operations.

Tractor Control

Important controls include starter, starter switch, clutch pedal, gear selector, accelerator pedal/throttle, brake pedal, steering wheel, and hand brake.

• Starter switch: Starts the engine.
• Clutch pedal: Connects and disconnects engine power from the gearbox for gear selection.
• Gear lever/selector: Selects appropriate gear.
• Accelerator pedal/throttle: Controls speed by regulating fuel supply.
• Brake pedal: Stops the tractor.
• Steering wheel: Controls direction of movement.
• Hand brake: Secures the tractor when parked.

Daily Service and Maintenance of the Tractor

• Lubricate all grease nipples, especially front wheel bearings.
• Check oil and fuel levels.
• Check current type, pressure, and battery condition.
• Check and top up water in radiator.
• Check for excessive fuel or oil leaks.
• Ensure brakes are latched and nuts and bolts are tightened.
• Check and clean air cleaning system.

Tillage Implements

Tillage is the practice of modifying the state of the soil to provide suitable conditions for crop growth.

Objectives:

• Production of suitable tilth.
• Control and destruction of pests and diseases.
• Facilitate incorporation of fertilizer, manure, and weed control.

Types

• A. Primary Tillage: Initial major soil working operation designed to loosen soil, bury plant material and residues, and rearrange soil aggregates.
• B. Secondary Tillage: Intended to create well-retained soil condition.

Implements

• Primary tillage implements: For primary tillage.
• Secondary tillage implements: For secondary tillage.

I. Primary Tillage Implements

Ploughs

Ploughing is the basic tillage operation in which a layer of soil is separated from subsoil and inverted. This can be accomplished by disc plough, mould board plough, and chisel plough.

Disc Plough

An implement with concave discs mounted on bearings which rotate as they cut through soil.

Components

• Main frame: Large steel tubes to which a top link, mask, and cross shaft are attached.
• Standards: Where disc bearings are fixed; discs are fixed on the hub of the bearing assembly.
• Scraper: Attached to each disc to cut soil close vertically.
• Disc: For cutting and inverting the furrow slices.

Note: The orientation of the disc is determined by the disc angle and the tilt angle.

• Disc angle: The horizontal angle between the plane of the disc face and the direction of travel.
• Tilt angle: The angle between the disc face and the vertical axis.

When disc angle is increased, the plough penetrates deeper but more power is used. Adjustment for appropriate depth is done by adjusting the top link.

Disc plough is used in areas where mould board plough will not work satisfactorily, e.g., dry land, rough and stony ground, sticky soil with hard pan, deep ploughing, peaty and leafy mould soils.

Mould Board Plough

Used to give good residue coverage and soil pulverization, especially in areas where soil is soft and free from roots and rocks.

Components

• Body: Used for attachment of other tools.
• Share: Makes a horizontal cut separating the furrow slice.
• Slade: Receives downward pressure due to weight.
• Land slide: Counters sideway forces.
• Disc coulter: Makes the vertical cut to the furrow slice.
• Skin coulter: Assists in complete burial of crop residue and trash.

Chisel Plough

Used to break through compacted or impermeable soil layers to improve water penetration. Best results are obtained when the soil is dry.

Components

• Heavy-duty frame: Where a number of tines are bolted.
• Tines: For opening up the soil pan.
• Shear bolt: Incorporated at the foot of the tine which breaks on underground obstruction.
• Tines are arranged in 3-4 rows depending on work type, soil conditions, and power available.
• Rigid tines are common, but spring-loaded or heavy-duty (flexible) tines are also available.

II. Secondary Tillage Implements

Harrows

Types

• Disc harrows:
  • Offset harrow: Has two gangs (left and right) throwing soil to opposite sides.
  • Single acting disc harrow: Two opposed gangs of disc blades throw soil outwards.
  • Tandem disc harrow: Has two additional gangs that throw soil backward to the center.

Adjustment: Done by varying the disc angle and working depth. The hand lever or hydraulic vane on the harrow is used to adjust cutting depth.

Maintenance of Tillage Implements

• Rotary components require daily greasing.
• Implements should be checked before starting the day’s work.
• Loose nuts and bolts should be tightened.
• At the end of each day, clean the implements.
• At the end of each season, check for distortion and wear.
• Replace components, sharpen or resurface, and proof soil-engaging parts.

Planting Equipment

These can be hand-operated equipment (e.g., hoe) or tractor/animal-drawn planters.

Advantages of Drawn Planters over Hand-Operated Planters

• Saves labor and time.
• Facilitates post-planting operations such as weeding, spraying, and harvesting due to uniformity.
• Ensures uniform distribution of seeds.
• Ensures uniform planting depth.

Ways of Seed Planting by Machine Planters

• Broadcasting: Random scattering of seeds over the field surface.

Broadcaster

Implements that distribute seeds reasonably uniformly over a given area.

Demerits

• Difficult to estimate seed rate.
• Other operations such as weeding cannot be carried out effectively.
• Poor seed coverage; sometimes thinning is required.

• Row planting: Accurate planting pattern with seeds covered at equal intervals in rows.

Row Planters

Distribute seeds at equal intervals in rows.

Components

• Seed and fertilizer hoppers.
• Metering devices for seeds and fertilizer.
• Delivery tubes.
• Furrow openers.
• Press wheel for covering and firming soil around seeds.

Note: Generally, planters open furrows, deposit seeds and fertilizer, then cover and firm the soil.

The most common metering devices consist of a seed plate with seed cells. The seed plate is at the bottom of the hopper and receives its drive from the ground wheel of the planter. Seeds are picked up in the seed cells and rotated until they reach a hole at the hopper’s bottom.

• Seed drilling

Seed Drill

Works on the same principles as a row planter. The main difference is in metering mechanism and delivery tubes, where the seed drill is placed close by.

Calibration of Row Planters

Involves selection of a correct seed plate, belt, or wheel and checking its performance.

Steps to Calibrate a Single Seed Selection Plate

1. Select a suitable seed plate, belt, and wheel for the seed to be planted and fit it to the planter unit.
2. Sack up the planter unit so its drive wheel rotates freely.
3. Fill the planter unit with seeds.
4. Turn the drive wheel a number of revolutions representing a known distance, calculated as: Distance = Number of revolutions × drive wheel circumference (cm).
5. Collect seeds for the same number of revolutions.
6. Count seeds collected and use data to calculate within-row spacing.

Within-row spacing: Distance represented by known number of revolutions of drive wheel divided by number of seeds collected for the same revolutions.

Within-row spacing can be adjusted by changing the drive sprocket ratio until the desired rate is obtained.

Operating Procedures for Planting Equipment

• Seed should be graded to uniform size to fit seed cells.
• Set or calibrate equipment to provide desired plant spacing.
• Select the correct seed plate for the seed size.
• For row planters, correct spacing between rows is obtained by moving the planter unit along the toolbar.
• Adjust depth of furrow openers.
• Operate equipment at reasonable speed (4-10 km/h) to maintain seeding rate.
• Fields should be level, free of trash and obstacles.
• Grease and oil equipment regularly.
• Clean after use.

Crop Protection Equipment

Main crop protection is against weeds (herbicides) and insects (insecticides). Types of equipment used include sprayers and dusters.

Sprayers

Types

• Syringe sprayers: Simple hand-operated sprayers consisting of piston cylinder with inlet/outlet valves.
• Knapsack sprayers: Three types: Hydraulic, Pneumatic, and Motorized.

Components

• Consist of tank, strainer, boom, and nozzle. Sophisticated ones have agitator, pressure regulator, and pressure gauge.
• Rate of work depends on walking speed.
• Knapsack sprayers are more expensive than syringe sprayers but more efficient and suitable for large farms and tree crops.

• Tractor operated sprayers (Boom sprayers):

Components include tank, pressure cylinder, pump, filter, boom, and nozzles. Tanks are made of fiberglass (strong, light, resistant but expensive) or steel. Boom length varies from 5 to 17 meters.

Note: The effective working width of the boom is referred to as boom width.

Operating Procedures / Precautions

• Spray when weeds/pests are most susceptible to chemicals.
• Avoid spraying during rain and strong winds.
• Spray from leeward towards windward side.
• Avoid inhaling chemicals; use body protection.

Calibration of Tractor Operated Sprayers

Setting up and adjusting the sprayer to achieve desired application rate.

• Fill tank with chemicals and set pressure to desired working pressure.
• Use graduated containers to collect solution from several nozzles over a known duration.
• Determine volume of chemical solution collected.
• Calculate application rate (L/ha) based on delivery rate, forward speed, and boom width.

Application L/ha = total delivery rate (L/min) ÷ operating rate (ha/min), where total delivery rate = volume of chemical delivered by nozzles per minute, and operating rate = area covered in one minute.

Factors Affecting Application Rate

• Forward speed.
• Nozzle size.
• Type and ratio of water to chemical.

Dusters

Dusting is the application of powdered chemicals to crops or livestock.

• Dusting of crops is most effective when leaves are damp and atmosphere is relatively dry.
• Avoid dusting in strong winds.

Types

• Small hand-operated: Cheap, effective, suitable for applying large volume of gas in short time.
• Machine duster: Tractor or aircraft operated.

Care and Maintenance of Sprayers and Dusters

• Clean all parts with clean water; use the right chemicals.
• Flush all parts with clean water after dusting/spraying; flush with Na₂CO₃ after using acidic chemicals.
• Detach all parts and dry them; treat metal parts with oil or grease.
• Store in a cool, dry, and safe place.

Harvesting Equipment

Types

• Manual/hand harvesting.
• Machine operated/harvesting by combine harvester.

Combine Harvesters

• Cut the crop, convey it to the threshing mechanism which separates grains or seeds from straw and chaff. Straw is left in a swath behind the combine and chaff is blown out.
• Clean grain is elevated to the tank. Combines are either self-propelled or tractor-drawn.

Functions of a Combine Harvester

• The reel, located over the cutter bar, helps pull crops over the cutter bar.
• The screw auger behind the cutter bar feeds the crop to the elevating mechanism and threshing cylinder.
• The threshing unit consists of a rotating cylinder and stationary concave drum between which the crop is fed.
• The high-speed cylinder knocks grain loose from the heads.
• The concave can be raised or lowered to adjust the gap and control threshing effectiveness.
• Grains remaining in straw are carried back to the beater which fluffs the straw to shake out remaining grain, then pushes straw into grain walker which shakes out any remaining grain.
• Below the sieves, a fan blows air upward to lift material resting on them.
• Clean grain is conveyed by elevator to the grain tank.

Forage Harvesting Equipment

• Involves cutting pasture grass to be fed as hay, silage, or green feed. Grass is cut and left in the field to dry before collection and storage as loose or baled hay.
• Grass may also be collected green and fed directly to animals using tools like slashes, sickles, or tractors.
• For hay making, equipment includes mowers, swath turners, and balers; for silage making, flail-type harvesters are used.

Mowers

Two types:

• Reciprocating mowers: Consist of a knife moving back and forth to cut grass with a shearing action.
• Rotary mowers: Rotate horizontally and cut grass by impact. Suitable for light vegetation on fairly level land and stronger for thick vegetation on rough ground. The cutting action chops and accelerates grass into pieces, making baling difficult.

Swath Turners

• Grass for hay making is cut and left to dry in a swath. Swath turners turn the swath.
• Common type: finger wheel swath turner or rake wheel turner.

Balers

• Used for picking, compressing, and tying cut grass into neat bundles for easy transportation, storage, and feeding. Usually driven by P.T.O shaft.

Flail Type Forage Harvesters

• Suitable for harvesting all types of green material for silage making. Cheap and simple.
• Works on the same principle as rotary mowers, except blades called flails are hinged to a vertical cylinder rotated at high speed through a P.T.O shaft.
• Flails cut vegetation on impact and throw it into a trailer.

Other sources of power include wind, water, sun, nuclear, fossil fuel, charcoal, and biogas.

Farm Surveying and Mapping

Meaning: Process of observing and measuring to determine positions, distances, boundaries, size, and elevations of various physical features of the land.

Purpose of Surveying

• To determine vertical and horizontal distances between two or more points on the land.
• To locate physical and non-physical features on the land surface.
• To locate the direction of various features on the land.
• To determine the area of a given piece of land.

The Process of Surveying: Done in Three Stages

1. Reconnaissance survey: Taking a general view of the area to get an overall picture of the work to be done, done by visual observation.
2. Observing: Measuring and recording direction, angles, and elevation using surveying equipment to determine relative positions and sizes of land features.
3. Presenting the data: Collected in a form that allows understanding and interpretation, such as drawings, written reports, tables, or any convenient form.

Basic Surveying Equipment

• Odometer (perambulator), plumb bob, chain, arrows, surveyor’s rod/leveling staff rod, tape.
• Plane tables, ranging pole, predetermined length of rope, range finder, plan meter.
• Compass, altitudes, ruler, pantograph, field notebook, erasers, sharpeners, pencil.
• Calculators, Abney level, slide rulers, hand level, box sextant, umbrella, clinometers.

Methods of Surveying and Mapping

• A. Linear Surveying: Determination of horizontal distance between two points using pacing, odometer/land wheel, and chaining/taping.

Pacing

Counting the number of paces/strides made over the distance to be determined.

Advantages: Simplest method, rapid rough distance checking.

Disadvantages: Not very accurate; pace length varies with walking conditions.

Note: To improve accuracy, determine the number of paces in an accurately measured 100 m distance on the same ground before pacing.

Odometer/Land Wheel

Simple devices measuring distance by counting wheel revolutions. Can be pushed by hand or pulled by vehicle. Suitable for flat smooth surfaces (odometer) or rough grounds (land wheel).

Chaining/Taping

Instruments used include chains and tapes.

Types of Chains

• Gunter chain: 66 yards long, divided into 100 links of 7.92 inches.
• Standard/Engineers chain: Similar to Gunter chain but 100 feet long with 12-inch links.
• Metric chain: Usually 20-30 m long with 20 cm links.

Tapes

Used when greater accuracy is needed, e.g., in building roads and other measurements. Marked in hectares, centimeters, feet, or inches.

• Linen tape: Made of linen with steel wire woven into fibers.
• Steel tape: More accurate than linen tape.

Arrows

Made of steel, about 350 cm long, used to mark temporary stations during surveying.

Ranging Poles

Usually made of wood with pointed ends and alternate bands of white and black, used to align survey lines on the ground.

Plumb Bob

Used to indicate vertical position of a point, e.g., in chaining long slopes. Made of solid metal with one pointed end and a ring fixed to a flat base.

Field Notebook

A book in which field notes are recorded.

• B. Triangulation: Survey method dividing an area into several triangles. Lengths of sides are measured and recorded.
• C. Leveling: Process of determining difference in elevation between two points.

Types of Leveling

• Differential leveling: Determines difference in elevation of several points apart.
• Profile leveling: Determines elevation of a series of points at measured intervals.

Instruments/Equipment

• Level: Various types selected according to accuracy required, e.g., dumpy level, Abney level.
• Leveling rod: Long rod graduated in meters, used with a level to measure vertical distances.

Compass Traversing

Method to establish positions of successive points. Types include closed traverse (from one known point to another) and open traverse (does not close into a known point).

Scales and Calculation of Areas

The scale of a map is the ratio of the plotted length on the map to the actual length on the ground. Used to present large survey features on a map or plan.

Ways of Showing Scales on a Map/Plan

• Imperial scales: Length in inches on paper equivalent to some units on the ground, e.g., 1 inch representing 100 feet.
• Metric scales: Similar to imperial but units are metric, e.g., 1 cm represents 100 m.
• Natural scales: Represented as a ratio, e.g., 1:100,000 means 1 cm on map represents 100,000 cm on ground.
• Scale bars: Graphical representation of scale on map or plan for ready distance measurement.

Calculation of Area

Area of land surveyed plots can be calculated by:

1. Dividing the map or plot into geometrical figures such as triangles (triangulation) and squares.
2. Using ordinates by trapezoidal or Simpson’s rule.
3. Using a planimeter.

Trapezoidal rule: Total area = d × (½O₁ + O₂ + O₃ + … + Oₙ₋₁ + ½Oₙ), where d is the common distance apart and O are ordinates.

Simpson’s rule: Total area = d/3 × (O₁ + 4O₂ + 2O₃ + 4O₄ + … + 2Oₙ₋₂ + 4Oₙ₋₁ + Oₙ).

Planimeter: A device to mechanically obtain area by reading off a graduated unit.

Errors in Measurement

Three kinds of errors:

1. Systematic or cumulative errors: Sources include wrong tape/chain length, poor straightening, poor ranging, temperature variations, slope, sag.
2. Compensating/accidental errors: Sources include variation in tape tension, wrong holding of tape, station marking.
3. Gross errors: Sources include displacement of arrows/station marks, miscounting tape/chain lengths, misreading tape/chain, wrong booking of field notes.

The Process of Chaining

1. The head chain man unrolls the chain towards the reference point; the rear chain man holds the other end at the starting point.
2. For the first 100 m measurement, the head man has 10 pins.
3. The rear man aligns the chain by sighting the head man; the chain should be straight and stretched.
4. When the rear man reaches the 100 m mark, he calls “stick,” and the head man places a pin.
5. The rear man picks up the pin and walks forward while the head man pulls the chain to the next point.
6. Repeat until the head man has no more pins or the reference point is reached.

Note: Both men should count pins. The distance to the 11th pin is 1000 m.

Example of Chain Surveying and Booking

1. Set offset to the chain line; offsets are measured perpendicularly to the chain line.
2. Using an optical square or right triangle method.

Assumption: The ABCD farm with a fence boundary, farmhouse, and garage. Procedure:

1. Chain line AB and book readings at 10, 20, 30, …, 90 m.
2. Take offset of fence 10 m from points A and B on the chain line.
3. Take offset of the end of the fence 70 m from A and 15 m from chain line.
4. Take offset of the other end of the house 40 m from A and 25 m from chain line.
5. Book readings and repeat until all survey lines are completed, booking each line on separate record sheets.

Leveling

Differential leveling: Finding difference in elevation between points A and B.

Terminologies

• Bench Mark (BM): Fixed reference point with known height above datum.
• Datum (D): Any level surface to which elevations are referred.
• Reduced Level (RL): Height or elevation relative to the foresight.
• Back Sight (BS): Height or elevation reading taken behind the foresight.
• Fore Sight (FS): Height or elevation reading taken at succeeding stations before shifting instrument level.
• Height of Instrument (HI): Reading taken at station added to elevation of that point (HI = BM + BS).

Procedure for Intermediate Sight (IS) and Turning Point (TP)

1. Staff held at point A; instrument level set at point PX.
2. First reading at A is back sight (BS), e.g., 1.5 m.
3. HI = BM + BS, e.g., 400 + 1.5 = 401.5 m.
4. Staff moves to station S1; fore sight (FS) reading taken, e.g., 0.9 m.
5. Elevation of S1 = HI – FS, e.g., 401.5 – 0.9 = 400.6 m.
6. Staff moves to P2; BS reading taken, e.g., 1.2 m.
7. New HI = previous HI + BS, e.g., 400.6 + 1.2 = 401.8 m.
8. Staff moves to S2; IS reading taken, e.g., 1.4 m.
9. Elevation of S2 = HI – IS, e.g., 401.8 – 1.4 = 400.4 m.
10. Staff moves to S3; FS reading taken, e.g., 2.9 m.
11. Elevation of S3 = HI – FS, e.g., 401.8 – 2.9 = 398.9 m.
12. Level moves to PY (turning point); BS reading taken, e.g., 0.5 m.
13. New HI = elevation of S3 + BS, e.g., 398.9 + 0.5 = 399.4 m.
14. Staff moves to S4; IS reading taken, e.g., 0.9 m.
15. Elevation of S4 = HI – IS, e.g., 399.4 – 0.9 = 398.5 m.
16. Staff moves to S5; IS reading taken, e.g., 1.4 m.
17. Elevation of S5 = HI – IS, e.g., 399.4 – 1.4 = 398.0 m.
18. Staff moves to B; FS reading taken, e.g., 2.3 m.
19. Elevation of B = HI – FS, e.g., 399.4 – 2.3 = 397.1 m.

Note: When the level was at PX, the instrument man could not read the staff beyond S3 because staff was below line of sight. The instrument was shifted to PY and readings continued. All elevation readings are called Reduced Levels (RL).

Profile Leveling

Process of determining elevation of a series of points at measured intervals along a survey line.

Procedure

1. Select a benchmark where staff is stationed; take BS reading.
2. Place instrument at PX; take BS reading from benchmark.
3. Staff moves to station A; IS reading taken; elevation of A = HI – IS.
4. Staff moves to S1; IS reading taken; elevation of S1 = HI – IS.
5. Staff moves to S2; IS reading taken; elevation of S2 = HI – IS.
6. Staff moves to S3; FS reading taken; elevation of S3 = HI – FS.
7. Level moves to PY (turning point); BS reading taken; new HI = elevation of S3 + BS.
8. Staff moves to S4; IS reading taken; elevation of S4 = HI – IS.
9. Staff moves to S5; IS reading taken; elevation of S5 = HI – IS.
10. Staff moves to B; FS reading taken; elevation of B = HI – FS.

Contouring

Contour: An imaginary line of constant elevation on the ground surface.

Contour line (on a map): A line connecting points on the map with equal elevation on the ground. Elevation is represented by numbers on the contour line.

Examples of natural contours: Ocean/sea, lake shores, and rivers.

Uses

Used by farmers for:

1. Contour ploughing.
2. Contour planting.
3. Laying out terraces.
4. Laying out grass strips.
5. Laying out water control structures.

Requirements

• Instrument level (Abney level) and level man.
• Staff and staff man.

Procedure

• Select a point on a contour line; level man stands on the contour line.
• Staff man moves 15-30 m up and down along approximate contour as directed by level man.
• When level man locates point on contour line, staff man stakes it and remains beside stake while level man moves further.
• Level man sights back; staff man moves up and down slopes until on contour line.
• Repeat until entire contour is established.

Compass Traversing

Traverse is a surveying method to establish control networks by placing survey stations along a line or path and using previously surveyed points as bases for observing next points.

Advantages

• Less reconnaissance and organization needed.
• Traverse can change shape to accommodate different terrains.
• Fewer observations needed at each station compared to other networks.
• Traverse networks are free from strength of figure considerations of triangular systems.
• Scale errors do not accumulate as traverse is performed.
• Azimuth swing errors can be reduced by increasing distance between stations.

Types of Traverse

• Link traverse.
• Polygonal/Loop traverse.
• Open/Free traverse.
• Closed traverse (useful for marking boundaries of woods or lakes).

Soil and Water Conservation

Reasons for studying soil and water conservation:

• Poor rainfall distribution and excessive soil movement.
• Too much or too little rainfall, moisture retention, and control of excess water.
• Low soil fertility due to poor soil structure and absence of essential nutrients.

Soil Conservation: Practices aimed at preventing excessive soil movement to maintain soil properties such as fertility.

Water Conservation: Practices aimed at retaining needed soil moisture and controlling excess water for effective use of rainfall.

Soil Conservation

Soil Erosion

Wearing and removal of soil particles by water and wind.

Effect of Soil Erosion

• Reduces land productivity due to decline in soil fertility.
• Renders large tracts of land unusable due to gullies.
• Causes silting of dams and rivers.
• Decreases water available for crops due to excessive runoff.
• Encourages floods due to silting of rivers and dams, destroying land, crops, and property.

Signs of Soil Erosion

• Appearance of gullies.
• Appearance of muddy rivers and streams.
• Silting of dams and waterways.
• Appearance of bare soil.

Causes of Soil Erosion

• Deforestation: Cutting trees indiscriminately without replanting.
• Overgrazing: Continuous grazing causing weakening of plant root systems and trampling of soil.
• Bad farming practices such as planting crops on steep slopes, clean weeding of plantation crops, uncontrolled burning of bush, ploughing along slopes, and destruction of vegetation along river banks.
• Living organisms loosening soil, making it susceptible to erosion.

Agents of Soil Erosion

• Water: Main agent in high rainfall areas.
• Wind: Main agent in dry areas with sandy soil.

Water Erosion Forms

• Sheet erosion: Uniform removal of soil from a wide area.
• Rill erosion: Removal of soil forming small channels (rills).
• Gully erosion: Removal of soil through well-developed deep channels (gullies).

Wind Erosion Forms

• Saltation: Suspension of soil particles in air and skipping/bouncing on surface.
• Surface creep: Rolling/skidding of soil particles in continuous contact with soil surface.

Examples of Soil and Water Conservation Schemes in Tanzania

• HASHI-HIFADHI ARDHI SHINYANGA
• HESAWA – LAKE ZONE CONSERVATION SCHEME
• HADO – HIFADHI ARDHI DODOMA
• KAEMP – KAGERA CONSERVATION SCHEME
• LOWER MOSHI IRRIGATION SCHEME – KILIMANJARO
• RUBADA – RUFIJI BASIN DEVELOPMENT ASSOCIATION
• KIHANSI CONSERVATION SCHEME – MTERA
• MALDO IRRIGATION SCHEMES

Methods of Soil Erosion Control

Goal: Regulation of movement of water and wind on soil surface, achieved by:

1. Mechanical measures
2. Agronomic measures

A. Mechanical Measures

Measures that break up slope and intercept runoff before it causes erosion, mainly construction of structures such as:

• Hillside ditches: Small ditches with a gradient of 0.5% to 1%, earth removed from ditch placed on lower side to form ridge. Usually 3 cm deep, spaced 20-30 m apart along contour.
• Terraces: Small walls of stones or earth, reinforced with vegetation, forming barriers against soil movement. Types include:
  • Narrow based terrace: Narrow banks with permanent grass, spaced 15-30 m apart, slope about 6%.
  • Broad based terrace: Wide banked terrace used on slopes of 2-4%, spaced about 30 m apart.
  • Bench terrace: Land reshaped into steps spaced 7.5 m apart; steeper parts kept under permanent grass or protected by stones.
• Storm drains or diversion ditches: Channels constructed around slopes with slight gradient to direct water to desired outlet. Design varies with soil type, slope, and peak runoff.

B. Agronomic Measures

Farming practices to reduce severity of water and wind erosion, including:

• Minimum tillage: Minimal soil disturbance.
• Contour strip cropping: Growing crops with little soil cover (e.g., maize) in alternate strips with dense crops (e.g., cassava) along contour lines.
• Vegetative buffer crops: Leaving strips of uncultivated land between cultivated strips as barriers.
• Mulching/Use of cover crops: Covering soil with straw, cut herbage, or leaves to protect soil from rain, wind, sun, and retain moisture. Adds organic matter when decomposed.
• Windbreakers: Trees or shrubs grown in wind direction to reduce wind velocity.
• Reforestation: Growing trees on bare land to protect soil and crops; roots bind soil.
• Avoid indiscriminate slashing and burning.
• Avoid deforestation.
• Avoid overgrazing.
• Avoid cultivation on very steep slopes.