eChapters

20.1. What?

Sprayer is equipment used for applying insecticides, fungicides, herbicides and in some cases fertilizers as foliar sprays to agricultural crops. Sprayers range in size from man-portable units (backpacks) to Self propelled units with boom mounts covering 60-150 feet length. Sprayers include the ones used for spraying liquid formulations, dusters for dusting dust formulations and granular applicators for delivering granules.

20.2. Principle of working

Sprayers work based on Bernoulli’s principle. Basically, the sprayers have a storage tank, a plunger, lance and a nozzle. When the plunger is pushed in, the air flows at a high velocity through the nozzle. The flow of air at high velocity creates a region of low pressure just above the lance. The higher atmospheric pressure acts on the surface of the liquid insecticide causing it to rise up the lance and the insecticide leaves out through the nozzle as a fine spray.

Sprayers are fitted with hollow cone nozzles for spraying pesticides and with flat fan nozzles for herbicides.

19.1. Need for weeding

Weeding is the critical operation to be carried out to obtain a good crop. Weeds are plants which grow in places where they are not wanted. They grow in the fields competing with crops for water, soil nutrients, light and space and thus reduce crop yields. They also harbor insect pests and micro-organisms. Certain weeds release the inhibitors or poisonous substances into the soil which are harmful to plants, human beings and livessecks. They increase the expenditure on labour and equipment, render harvesting difficult and reduce the quality and marketability of agricultural produce. When grown in water channels, they block and or reduce the flow of water.

The weed seeds germinate earlier and grow faster than the crop plant. This phenomenon is more pronounced when coupled with favourable environment like fine soil tilth and the soil receiving adequate water and fertilizers. Weeds flower earlier and produce seeds profusely ahead of the crop. So, these seeds get mixed up with the harvested crop and are distributed to the next season or transported to other places along with the harvested produce.

18.1. What?

The basic objective of sowing is to place the seed in rows at the desired depth, to maintain proper spacing between seed to seed, cover the seeds with soil and provide proper compaction over the seed if required. Precise sowing/planting helps in better crop stand. This helps to achieve optimum yields. Traditional sowing methods include broadcasting manually, opening furrows by a country plough and dropping seeds by hand (i.e.) dibbling. In the present day, improved seed-cum-fertilizer drills are used for sowing and fertilizer application. These are provided with seed and fertilizer boxes, metering mechanism, furrow openers, covering devices, frame, ground drive system and controls for variation of seed and fertilizer rates.

18.2. Types of sowing/planting equipment

Sowing equipment include seeders and transplanters. Various types of sowing equipment, viz., manually operated, animal drawn, power operated and tractor drawn are used throughout India.

18.2.1. Seed drills

Seeders are available for sowing seeds of various crops. Some seeders have been designed with adjustable metering mechanism which makes them versatile for sowing two or three kinds of seeds. For example, a multicrop planter developed by CIAE is used for sowing garlic, maize, moong, peas and groundnut. Similarly, the institute has developed a small seed sowing drill which is used for sowing small seeds such as bajra, rapeseed and mustard.

17.1. What?

The soil is prepared to a fine tilth, which is referred to as land preparation or preparatory cultivation. This enables proper sowing of seeds, planting of seedlings and precise application of fertilizers to the crop. Various implements are used to prepare the land. The basic ones are ploughs, harrows, cultivators or tillers, and land levellers. These implements are manually operated or by animals or tractors. Various improvements have been made to increase the efficiency of each one of the implements by research workers. Many products are also available to suit the local regions and soil condition.

17.2. Plough

It has been the basic implement used for decades in agriculture to open up and invert the soil for initial cultivation. While inverting the soil, it also buries the weeds and the remains of the previous crops and allows them to decay. In the process of inverting, it also aerates the soil. Ploughs were initially used with animal power. Later on, many improved implements with heavy weights have been developed. These are drawn by tractors.

1. Introduction

Agricultural mechanization refers to usage of any improved tool, implement and machine by the farm workers to improve the efficiency of any operation to increase productivity. It also helps to reduce drudgery or stress which adversely affects human mental faculties leading to errors, imprecision and hazards and eventually loss of efficiency if done manually. In developed countries, however, mechanization is synonymous to automation. There is scope to mechanize every operation of crop production, post harvest and agro-processing.

Farm tractor designs and styles differ greatly. Tractors are often used on a daily basis for several agricultural and non-agricultural tasks by attaching or operating light, medium to heavy implements, equipment and machineries according to the requirement and hp of tractors. Tractors are very versatile and can be used on sandy (light textured), loamy (medium textured) and clayey (heavy textured) soil at different topographic and agro-climatic conditions. Earlier, the proportion of tractor usage in agricultural and non-agricultural work was 70:30. This proportion has increased to about 55: 45 over the past two to three years. It is expected to reach 50:50 in (agricultural:non-agricultural applications) in the coming years. The major application of farm tractors for agricultural and non-agricultural sectors is given below.

13.1. Types

Lamps: Head lamp, plough lamp, indicators

Switches: Safety switch, starter switch, etc

13.2. Components

Battery: A battery provides power to electrical or electronic circuits. The voltage rating of a battery tells how much electrical “pressure” the battery can provide. Battery energy is used to operate starter motor and to provide current to the ignition system during cranking. The electrolyte should always be maintained just below the maximum level, but should not go down below the 1/4^th level.

Alternator: Alternators are electromechanical devices used to convert mechanical energy to alternating current electrical energy. While some of the alternators use rotating magnetic field, some use linear. The functioning of alternators is similar to that of direct current generators. As the magnetic field around a conductor changes, a current is induced in the conductor. The rotating magnet or the rotor turns and cuts the field across the conductors. Thus, an electrical current is produced which causes the rotor to turn. This rotating magnetic field causes an AC voltage in the stator windings. In tractors, alternators are used to charge the battery and to power the electric system when its engine is running. An alternator is superior to a dynamo as it provides more precise output control, requires lesser maintenance, is more compact and requires no cut-out.

12.1. Instruments panel

12.1.1. Oil pressure gauge

Indicates oil pressure in Kgf/cm²

11.1. Hydraulic system

It is a mechanism in a tractor to raise, hold or lower the mounted or semi-mounted equipment by hydraulic means. All the present day tractors are equipped with a hydraulic control system for operating three point hitches. Some of the tractors are fitted with a hydraulic brake system and a few others are fitted with a hydraulic steering system. Tipping trailers, front mounted loaders or dozers are examples of multi use of hydraulics.

11.2. Principle

The working principle of a hydraulic system is based on Pascal’s law (Fig 11.1.) This law states that the pressure applied to an enclosed fluid is transmitted equally in all directions. A small force acting on a small area can produce higher force on a surface of larger area.

10.8.1. Function

A power take-off (PTO) is a splined drive shaft on a tractor that can be used to provide power to an attachment or a stand alone machine. PTO shaft gets the drive from hydraulic pump shaft. This in turn gets drive from engine. PTO is designed to be easily connected and disconnected (Fig 10.8.1.). It is used to operate implements, viz., rotavator, fertilizer spreader, duster and many more machines which are stationary such as threshers, water pump and portable flour mill. These shafts either run at 540 rpm with 6 splines in the shaft or at 1000 rpm with 21 splines in the shaft. But many old tractors have 540 rpm PTO. The present day equipment is designed to operate with 1000 rpm PTO shaft. The manufacturers of old tractor models provide an auxiliary gear box which increases the speed of PTO to 1000 rpm. Selection of implements, equipment and machinery should be done on the basis of available tractor PTO speed.

9.7.1. Function

The front axle is the unit on which the front wheel is mounted. This wheel is an idler wheel by which the tractor is steered in various directions. The function is to assist the steering and support the tractor. It is a rigid tubular or I-section steel construction, pivoted at the centre. The pivot pin is housed on bushings on a support bolted to the front of the engine. As the track width of a tractor is adjustable, the front axles have provision to be extended on both sides. The tubular front axles have telescopic arrangement for extension, whereas the I-section type of front axles are three-piece axles.

8.6.1. Function

It steers the tractor in the required direction. The rotation of the steering wheel moves the steering column, which in turn rotates the sector shaft. This rotation pulls the pit man arms on one side and pushes at the other side. This motion is conveyed to the wheels by the drag link and makes the front wheel turn in the requisite direction.

7.5.1. Functions

The two primary functions of tyres, especially rear ones, are to provide maximum work output while ploughing the field and for haulage.

6.4.1. Function

The brake is used to stop or slow down the motion of a tractor. It is mounted on the driving axle and operated by two independent pedals. Each pedal can be operated independently to assist turning of the tractor during field work or both the pedals can be locked together.

6.4.2. Principle of operation

The brake works on the principle of friction. When a moving element is brought into contact with a stationary element, the motion of the moving element is affected. This is due to frictional force which acts in the opposite direction of the motion and converts the kinetic energy into heat energy.

5.3.1. Main components

Shear tube: It absorbs heavy shocks and protects the components of rear transmission and main transmission from breaking.

Crown wheel and pinion: It transmits the drive from the main shaft to the rear axle shaft and inverts the direction of rotation to 90° from the main shaft. It reduces the speed and multiplies the torque.

Rear axle: It is a semi floating type. It transfers the drive from the sun gear to the rear wheel.

5.3.2. How does it work?

The drive from the main shaft of the gear box is taken to the rear drive shaft through the coupler planetary. Depending on the position of the high–low gear and lever which moves the coupler, power is transmitted directly or through epicyclic gear train. The drive from the rear drive shaft is transferred to a safety coupling also known as shear tube. The coupling is a safety device. In case the rear wheels encounter any shock loading, the coupling breaks and disconnects the gear box from the rear transmission. This prevents damage to costly parts in the transmission, clutch and engine. Power is transmitted from safety coupling to a pinion which has a spiral bevel gear at one end. The bevel pinion is supported on two tapered roller bearings carried in a housing which is mounted in the centre housing.

4.2.1. Gear boxes

It is a unit fitted after the clutch. Forms a part of transmission and provides speed and torque conversions from a rotating power source to another device using gear ratios. Its primary function is to change the speed of the tractor to cater to varying field, road and load condition. It also helps in reversing the tractor.

Gears are usually made of alloy steel. Since the tractor has to transmit heavy torque all the time, the best quality lubricants, free from sediments, grit, alkali and moisture, are used for lubrication. SAE 90 oil is generally recommended for gear box.

The description about gear boxes stated below pertains to major tractors manufactured in India. The number of teeth in each of the gear and the engagement between gears of the main shaft and the corresponding gear on the counter/lay shaft also change in different tractors evolved over a period of time. Hence, information hosted in this section is only indicative.

3.1.1. Introduction

Clutch is a device which is used to connect and disconnect the tractor engine from the transmission gears and drive wheels. It is fitted in between the engine and gear box. The clutch transmits power by means of friction between driving members and the driven members.

2.1. Introduction

The engine is the source that generates power. It transforms chemical energy in fuel into mechanical energy for power. Diesel internal combustion engines are invariably used in all the tractors. In these engines, very high compression of the air ignites the fuel as compared to spark plug that ignites fuel in petrol engines. The air in the diesel engine is compressed with a compression ratio typically between 15 and 22 resulting in a 40 bar (about 600 psi) pressure as compared to 8 to 14 bar (about 200 psi) in the petrol engine. This high compression heats the air to 550°C (1022°F). At about this moment, small droplets of fuel are sprayed in an atomized form directly into the compressed air in the combustion chamber.

2.2. How does it work?

Any engine will work with four strokes, namely suction, compression, power and exhaust (Fig 2.1). It will also complete two revolutions of the crankshaft. In the suction stroke, pure air is drawn into the cylinder through the inlet valve. The exhaust valve gets closed and the crankshaft completes half a revolution. In the compression stroke, the piston moves up while the valves remain closed. The air which is drawn into the cylinder during the suction stroke is compressed. There is a rise in temperature. The hot air ignites the fuel injected into the cylinder. The crankshaft again completes half a revolution. In the power stroke, the hot products of combustion, viz., carbon dioxide and nitrogen expand. The piston is forced down. The valves remain closed and the crankshaft completes half a revolution. In the exhaust stroke, the exhaust valve opens while the piston reaches the lowest point of travel. Then the burnt gases are swept out.

1.1. Definition

A tractor is a specific vehicle designed to deliver a high tractive torque at slow speeds, for the purposes of haulage or for pulling an agricultural implement or equipment or machinery. This vehicle is also used as a source of power for stand-alone agricultural machineries. The word tractor is taken from Latin being the agent noun of trahere “to pull”.

1.2. History of evolution

The first engine-powered farm tractors used steam and were introduced in 1868. These engines resembled small road locomotives. They were used for general road haulage and in particular for timber trade. The most popular steam tractor was the Garrett 4CD.

In 1887, gasoline-fuelled engines were tried as an alternative to steam engines. Later, Henry Ford produced his first experimental gasoline powered tractor in 1907, under the direction of his chief engineer Joseph Galamb. It was referred to as an “automobile plow”. While unpopular at first, these gasoline powered machines began to catch on. In the 1910, the size of the tractor was smaller than the earlier introductions and also became more affordable. In 1917, Henry Ford introduced the first mass-produced tractor. These were built in the U.S.A., Ireland, England and Russia. The unique feature of these tractor consisted of the strength of the engine holding the entire machine together. By 1920, tractors with a gasoline powered internal combustions engine had become a norm.

1.3. History in India

The level of mechanization in Agriculture was very low at the time of independence in 1947. But, the initial few five-year plans implemented by the Government of India gave an impetus to the improvement in the production and productivity of major crops including mechanization via joint ventures and tie-ups between local industrialists and international tractor manufacturers. It was three decades after independence that the domestic production of 4-wheel tractors grew slowly. In 1990, the tractor production was nearly 2,70,000 units per year and by the 2013, the volume approached to about 6,96,000 units per year. India has presently overtaken the United States as the world’s largest producer of four-wheel tractors with over 16 national and 4 multinational corporations engaged in its production. But still the Food and Agriculture Organization estimates that from out of the total agricultural area, less than 50% is under-mechanized land preparation. This indicates that potential for large tractorization still exists. Credit facilities for farmers have been improving steadily over the years. This is one of the prime drivers of the sale of tractor in India.