eChapters

Integrated Method of Weed Management

Definition

1. An integrated weed management may be defined as the combination of two or more weed-control methods at low input levels to reduce weed competition in a given cropping system below the economical threshold level. It has proved to be a valuable concept in a few cases, though much is still to be done to extend it to the small farmers’ level.
2. When more than one method is employed for controlling weeds, it is termed as integrated method weed management.

FAO Definition

It is a method whereby all economically, ecologically and toxicologically justifiable methods are employed to keep the harmful organisms below the threshold level of economic damage, keeping in the foreground the conscious employment of natural limiting factors.

IWM is the rational use of direct and indirect control methods to provide cost-effective weed control. Such an approach is the most attractive alternative from agronomic, economic and ecological point of view.

Herbicide History and Development

Common salt, ash, smelter waste, and like cheap materials have been used for centuries to control weeds on roadsides, fence rows, and pathways. But Chemical weed killing was born in 1896 when Bonnet, a French grape grower, observed that the Bordeaux mixture which he used against downy mildew of grape turned the leaves of Sinapis arvensis (a weed) black. Soon it was found that copper sulphate present in the Bordeaux mixture was responsible for its weed killing effect. Further tests in France, Germany, and U.S.A. established that copper sulphate could indeed be used for selective control of broadleaf weeds in small grains; wheat, barley, and oat. Between 1896 and 1908, several other inorganic salts, as also sulphuric acid, were found selective to small grain cereals. Of these, in Europe, a 6 to 10 per cent solution of sulphuric acid continued for considerable time as a satisfactory herbicide for broadleaf weed control in cereals, but it corroded the containers and sprayers. In the U.S.A., salts like sodium chlorate, carbon bisulphide, sodium arsenite, kainite, and calcium cyanamide were developed for non-selective eradication of perennial weeds, particularly, Convolvulus arvensis ‘field bind weed’ and Cirsium arvense ‘Canada thistle‘. In Hawaii, sodium arsenite solution was found highly effective for weed control in sugarcane plantations. Between 1930 and 1940, some boron compounds, thiocyanates, dinitro phenols (DNC and DNBP), ammonium sulphate, and certain mineral salts were developed in the west for selective and non-selective weed control. DNC and DNBP wereused extensively in Europe in small grains for broadleaf weed control, even though these chemicals dyed the hands and clothes of the users to yellow colour, almost permanently. Further milestones in weed control were introduction of organic chemical, 2-methyl-4, 6-dinitrophenoll (DMOC), in 1932 and discovery of hormone type selective weed killers. Selective residual chemicals such as substituted phenyl ureas and triazines, and non-residual chemicals diquat and paraquat are more recent discoveries.

The discovery of the herbicidal activity of 2, 4-D (2, 4-dichlorophenoxyacetic acid) first synthesized in 1941, triggered the development of modern herbicide technology. 2, 4-D proved to be an outstanding herbicide.

History on Classification of Herbicides

Copper sulphate (CuSO₄) was the earliest inorganic salt used as selective herbicide for controlling dicot weeds in cereal crops during 1896 in France, Germany, and USA. Sulphuric acid (H₂SO₄) was used as herbicide in cereals during 1909. In selective killing action depends on the fact that it runs off the leaves of the cereals and scorches rough surfaces of certain seeds. Sodium chlorate (NaClO₃) under the name mort-herbs is used in France for killing deep rooted perennials. Another non-selective herbicide, ammonium sulphamate (NH₄SO₃NH₂) was introduced in 1945 as ammate for the control of woody plants. Organic herbicides are more effective and selective.

Classification of Herbicides

Classification of herbicides is modified periodically as and when new herbicides are developed. Herbicides are classiûed based on their method of use (soil and foliage applied), mode of action (systemic or translocated and non-systemic or contact herbicide) and chemical key structure (aliphatic-aromatic, dinitrophenal, etc. Some herbicide molecules contain more than one classifying key structure and they are put into the group most likely to be contributing activity.

Any approved herbicide is known by three names: common name, chemical name and trade name. Common name of herbicide is a technically accepted abbreviation of its chemical name. Chemical name reads out its full molecular structure. Trade names refer to their formulations offered by the chemical companies for the consumers.

Herbicide Application

Generally, herbicides are applied in the form of solution or granules. Of the two, spraying solutions of herbicides formulated as wettable powders, soluble powders and emulsifiable and solution concentrates is more common. When herbicides are formulated as granular or encapsulated materials, they are applied by hand or with the help of a granular applicator.

Mode of Action

The term mode of action refers to the sequence of events from absorption into plants to plant death. The mode of action of the herbicide influences how the herbicide is applied. For example, contact herbicides that disrupt cell membranes, such as acifluorfen (Blazer) or paraquat (Gramoxone Extra), need to be applied post emergence to leaf tissue in order to be effective. Seedling growth inhibitors, such as trifluralin (Treflan) and alachlor (Lasso), need to be applied to the soil to effectively control newly germinated seedlings.

To be effective, herbicides must 1) adequately contact plants; 2) be absorbed by plants; 3) move within the plants to the site of action, without being deactivated; and 4) reach toxic levels at the site of action. The application method used, whether pre-plant incorporated, pre-emergence, or postemergence, determines whether the herbicide will contact germinating seedlings, roots, shoots, or leaves of plants.

Mode of Action of Herbicides

Herbicides perform a vital role in the management of weeds. As the name indicates, herbicides are chemicals that kill or control vegetation. Although the ultimate effect of most herbicides is the same (usually death of weed), the way they control weeds is vastly different. Physiologists use the term mode of action to describe the way the herbicides affect weeds. It includes the entire sequence of events that occur from the time the weed absorbs the herbicide to the final plant response (usually death). The term mode of action is the broad term under which all aspects of herbicidal action including the mechanism of action is included, while the mechanism of action refers to only the biochemical and biophysical responses of plants that appeared to be associated with herbicidal action.

Thus, mode of action includes absorption, translocation to an active site, inhibition of a specific biochemical reaction, degradation or breakdown of the herbicide in the plant and soil and the effect of the herbicide on plant growth and physiology.

Although two herbicides may differ chemically, they may still possess the same mode of action example trifluralin (a dinitroaniles herbicide) and propanamide (an amide herbicide) are inhibitors of microtubule/spindle apparatus. Each herbicide family (class or group) has a primary site of action which may be different in its action from others example sulfonylureas herbicides are ALS or AHAS inhibitors while glyphosate and sulfosate are ESPS inhibitors. Some may have more than one site of action, but the mostinhibitory of these will be affected first. The other site(s) may be considered secondary. Fluometuron, a urea group herbicides act by inhibiting photosynthesis at photosystem II and carotenoid biosynthesis.

Herbicide Mixtures

A mixture of two or more herbicides could be more effective for controlling different weed species. In horticultural and plantation crops, weed free situation is needed during the entire year over several years. In such situations, herbicides are to be rotated to take care of all the species of weeds. A mixture of herbicides, due to chemical reaction, may enhance or reduce the efûciency of one or more compounds. Hence, knowledge of herbicides interactions is essential for efûcient use of herbicides in weed control.

Persistence of Herbicide in Soils

Most of the herbicides are applied to soil as pre-emergence for weed control under different situations. For effective weed control, herbicides must remain in soil in active and available form until their purpose is served. Larger persistence poses hazard to subsequent land use and is undesirable. The length of time that an herbicide remains active in the soil is called persistence or soil residual life. The quantity of herbicide that remains in the soil after its mission is accomplished is referred as residue. The term residue infers the continued presence of herbicide in the soil in very small quantities even though it may not be present in herbicidal quantities or available for plant absorption. Herbicide residues in soils are undesirable mainly because they may

Injure sensitive crops in a cropping system,

Be absorbed by succeeding crops and residues accumulated in unlawful amounts in the produce,

Result in building up of herbicide residues following repeated treatments that exceed their rate of dissipation, and

Inhibit growth of soil micro-organisms.

Knowledge of persistence and carry over residual effect of herbicides is essential to use them safely and effectively. Persistence of herbicides in soils pose hazard when

Highly persistence herbicides are used,

Crop failure necessitates replanting,

A susceptible crop follows a short term crop which received a persistence herbicide, and

Decomposition of the applied herbicide proceeds very slow.

Resistance

The intensive and continuous use of herbicides over the last five decades has resulted in the development and evolution of weeds resistant to the normally phytotoxic chemicals. Although herbicide resistance was reported as early as 1957 against 2, 4-D from Hawaii the first confirmed report of herbicide resistance was against triazine herbicide in common groundsel (Senecio vulgaris) was reported in l968 from U.S.A. Over the years, more than 150 weed species have been identified as having developed biotypes resistant to at least one or more herbicide classes. Resistance to at least 15 classes of herbicides have been noted. Moreover, the area of land infested with resistant weeds is increasing rapidly. Reports of evolution of newly resistant biotypes continue to emanate from all over the world, including developing countries, e.g., India, where extensive use of herbicides in grain crops began only in the late 1970s. These reports indicate that herbicide resistance problems are accelerating and, consequently, management of weeds is becoming increasingly more difficult and complex.

The phenomenon of herbicide resistance in plants, especially in weeds, is analogous to the evolution of changes that arise in insects and pathogens in response to the continuous use of insecticides and fungicides. Herbicide resistance is the result of selection for traits that allow weed species to survive specific herbicide usage, which would otherwise cause mortality. Herbicide resistance contributes a trait of resistance within the plant species to a herbicide and resistant weeds are those plant species that express the genetic variation required to evolve mechanisms to escape control. Like other crop pests (insects, pathogens, etc.) with reference to pesticides (insecticides, fungicides, etc.), herbicide-resistant weeds are the result of intensive selection pressure in weed populations.

Generally, resistance is defined as the ability of a plant species to withstand the phytotoxicity of a chemical. This is the trait normally found in crop plants, as against weeds, thus forming the basis for herbicide selectivity. Crop resistance to a herbicide is often different from the one that exists in the phenomenon of herbicide resistance in weeds.

Herbicide resistance in the context of weeds is defined as a characteristic of the weed species to withstand a herbicide dosage substantially higher than the wild type of the same plant species can withstand. It is the inherent or acquired ability to withstand the dosage of herbicide normally used for satisfactory weed control. Resistant weed populations are unharmed by a concentration of herbicide that completely kills all unselected populations. This herbicide concentration is the one that in field practice produces an effective kill.

Herbicide susceptibility represents the other end of the scale, encompassing natural variability in sensitivity to herbicides within the unselected populations. Tolerance, on the other hand, indicates reduced susceptibility (or conversely enhanced resistance) which may sometimes result from selection by herbicides. It is a response rather less than 100% survival accompanied by zero reduction in growth at herbicide concentrations, which normally give 100% Kill of susceptible biotypes. Tolerance may also be considered the natural or normal variability of response to-herbicides that exists within a species and can easily and quickly evolve.

Shifts or changes in the abundance and types of weeds within agricultural systems are common. These shifts can occur for a number of reasons and may result from cultural, mechanical, or chemical weed management strategies. The right combination of weeds and relying too heavily on any one practice is often the most common cause. Some of the concepts associated with weed species shifts are discussed below.

A weed shift is the change in the composition or relative frequencies of weeds in a weed population (all individuals of a single species in a defined area) or community (all plant populations in a defined area) in response to natural or human-made environmental changes in an agricultural system. Weed shifts occur when weed management practices do not control an entire weed community or population. Some species or biotypes are killed by (or susceptible to) the weed management practice, others are not affected by the management practice (tolerant or resistant), and still others do not encounter the management practice (dormant at application).

Those species that are not controlled can grow, reproduce, and increase in the community; resulting in a weed shift. Any cultural, physiological, biological, or chemical practice that modifies the growing environment without controlling all species equally can result in a weed shift. Weed shift may be due to introduction of new species or change in relative proportion of members of the existing community. Latter is the most common.

A. Species shift: Change in density of one or more species in field

B. Biotype shift: Change in density of biotypes within a species. These shifts often found noticed since biotypes typically are similar in appearance. Herbicide resistantbiotypes are the most frequently studied.

Weed Management

The productivity of crops much depends on intercultural and weeding operation. The efficient management practices ultimately increases the yield level. The productivity is much dependent on various attributes starting from the variety, climate including human resource management and other factors known well to the farmers. It is estimated that nearly 30-50 per cent of the crop is lost due to weed menace in the agricultural fields. The farmers use various methods of weed control like cultural, mechanical, chemical and manual means. Encompassing all these control measures is known as integrated weed management.

The possibility of the drifting of continents was first suggested by the French scholar Antonio Snider in 1858, but this was so much opposed to the scientific view then prevailing that nobody took notice of it. In 1910 F.B. Taylor of America invoked the hypothesis of horizontal displacement of continents or continental drift with a view to explaining the distribution of mountain ranges, but for various reasons the hypothesis of Taylor received scant attention. German Professor Alfred Wegener was the first to put forward this idea in the form of a theory in 1912 and published a detailed discussion of it in 1915. But an account of the First World War (1914-18) this could not attract the attention of many scientists. In 1924 an English translation of Wegener’s book was published. Since then it has attracted much attention and publicity, and a huge literature has grown around this theory.

Wegener was primarily a climatologist and the main problem he wanted to explain was the change of climates in the geological past. There are several geological evidences to show that there have been important and large scale changes in the climates of the world in the geological past. The occurrence of coal in the cool middle latitudes indicates that the climate of these regions was hot and humid in the carboniferous times and the natural vegetation was dense forest which ultimately resulted in the formation of huge coal deposits. On the other hand, in India, South Australia, Brazil or South Africa where the climate is warm today, there are evidences of cold climate and the presence of glaciers in the carboniferous period. The only conclusion that can be reached from this is that either the climatic zones have moved or if they have not, then there has been movement of the landmasses. There are several difficulties in postulating shifts in the climatic belts of the world as their geographical distribution is governed primarily by the sun. It, therefore, appears to be more probable that the landmasses have changed their position.

Isostasy is derived from the Greek word isostasios meaning ‘in equipoise’ or in a state of balance. American geologist Dutton was the first to use the term isostasy in 1889 for the state of gravitational equilibrium that exists between continents and ocean floor and the mountains, plateaus and plains on a rotating earth, in accordance with densities of their underlying rocks. Dutton was of the view that the height of these different features was related to their density. In other words, the higher features were composed of rocks of lower density and the features of lesser to height were made of rocks of higher density. For instance, the continental blocks whose average height is about 5 kms above the ocean floor are composed of lighter rocks than the latter, and to compensate for their higher height the continental blocks go deeper into the earth so that the continents and ocean basins may remain in equilibrium. The same argument applies to the mountain ranges. The excess mass of lighter materials which rises in the form of mountain chains on the earth’s surface is compensated by light materials extending as roots into the denser strata below. In other words, the upper part of the earth’s crust is built of lighter rocks which is floating on the substratum of denser rocks. The hypothesis of the sialic rocks floating over the sima of the sub-stratum had been first put forward by Sir George Airy of Britain in 1855. The use of the word floating, of course, did not imply that the sub-stratum was in a liquid condition.

The analysis of land use patterns has long been one of geography’s basic concerns. At first, it might appear as if agricultural land use is little affected by relative location, once the factor of a suitable market has been acknowledged. Indeed, the farmer does adapt his land use to site conditions, climate, land forms, and soils.

However, the effects of the market situation cannot be disposed of as easily as all that. Johann Heinrich Von Thunen (17831850), a German economist and estate owner of the early 19th century, developed a theory of agricultural location that is still worth considering.

This model is based on an econometric analysis of his estates in Mecklenburg, near Rostock in Germany. Most of the data used in explaining his theory were obtained by him through practical experience. He attempted to construct a theoretical model of land use pattern, giving a particular arrangement of towns and villages in a situation experienced in Mecklenburg.

The main aim of Von Thunen’s analysis was to show how and why agricultural land use varies with the distance from a market.

The study of crop combination regions constitutes an important aspect of agricultural geography as it provides a good basis for agricultural regionalization. The crops are generally grown in combinations and it is rarely that a particular crop occupies a position of total isolation other crops in a given area unit at a given point of time.

The distribution maps of individual crops are interesting and useful for planners, but it is even more important to view the integrated assemblage of the various crops grown in an area unit.

For example, the demarcation of India into the rice region or wheat region does not explain the agriculturally significant fact that very often the wheat region also has a rice crop and vice versa, or wheat is often grown with gram, barley, mustard, lentil, peas and rapeseed.

For a comprehensive and clear understanding of the agricultural mosaic of an agroclimatic region and for the planning and development of its agriculture, a systematic study of crop combinations is of great significance.

In recent years the concept of crop combination has engaged the attention of geographers and agricultural land use planners. The studies made so far in this field range in approach from topical to regional and vary in extent from small areas of minor political units to the entire country.

The scale of human settlements is dynamic; it ranges from farmstead to village to town to city and to metropolis. There is thus, a broad hierarchy of settlements. These hierarchies can be grouped according to size and function. Size hierarchies are ranked from the highest to the smallest settlements only in terms of population while functional hierarchies are essentially based on the extent to which settlements have an economic impact on their surrounding areas. Functional hierarchies rank the settlement according to the number of shops, the number of specialised services available or the most dominant financial organisations. Such hierarchies mayor may not have similar sized market areas. Despite their having the same population, one town might surpass another in functional importance.

In this context, two theories have been propounded-the Central Place Theory by Walter Christaller and its modified version by August Losch. These theories are two of the most important examples of the scientific approach to the study of settlements. These theories suggest that there is a definite link between the functions of a settlement and its spatial locations with regularity in the distribution pattern within an urban system.

Introduction

The characteristic features of a city are the result of the combination of various factors like topography, climate, history, economy, culture, etc. since these characteristics vary; every town/city is unique and has certain distinctive characteristics. These urban characteristics are, however, never static. They change both over time and space.

With the development of the economy, other factors like population growth, urbanization and improved technology have a combined effect on urban settlements, which grow bigger and more complex. The study of the internal structure of cities by urban geographers is a study of the structural and demographical variations (i.e., variations in building size, shape, height, function and social status) of urban settlement.

Theories on the Internal Structure of Cities

The internal structure of cities has attracted many generalizations in the form of theories. These theories have attempted to explain the city structure by examining cities at any location in a country largely from sociological viewpoint. The different theories on the internal structure of cities are the Concentric Zone theory of Burgess, Sector Theory of Hoyt, the Multiple Nuclei Theory of Ullman, the Social Area Analysis of Murdie and the Exploitative Model of William Bunge.

Introduction

The search for order in the location and size of settlements continues. Certain geographers examined the size of distribution of settlements and described in graphical form the relationship between the number and size of settlements. Their methods were radically different in that they were not deterministic, rather than making a set of assumptions, deriving a theory and testing it against reality, they observed the size and number of settlements in various countries and noted a common characteristic, which was called the rank size rule. Having once observed this order in the real world, they then sought to explain it. A relationship which is observed on several occasions is called an empirical regularity. The rank size rule is one such empirical regularity.

The rank size rule was first observed by Auerbach in 1913 but was proposed and popularized by G.K. Zipf in his book “Human Behaviour and the Principle of Least Effort”. Since then, many writers have attempted to explain it but the basic aim has always remained the same: to find a graphical description to the size distribution of cities which would apply to the situation prevailing in many countries.

Rank Size Rule: Theoretical Base and Concept

Rank size rule is a theory describing numerical distribution of settlement, which recognises an empirical regularity whereby the product obtained by multiplying a city’s rank by its size is equal to a constant, the population of the country’s largest city such that for a given settlement system

The social area analysis model of urban structure incorporates all three aspects of city structure, namely concentric zones, sectors and multiple nuclei. It is a more comprehensive statement of urban forms. The model was developed by R.A. Murdie in 1969. According to this model, the physical space of streets, buildings and roads are superimposed by three dimension of social space (Fig. 8.1). The social criteria are the following:

Family Status

Family status indicators include population and age variables, house ownership and age characteristics, family size and marital status and other life cycle. These exhibit a concentric zonal or ring pattern with older, smaller renter households located near the city centre and owner occupied newer larger family households near the outer fringe.

Economic Status

Economic status tends to include measure of income, occupation and education. This portrays a distinct sectoral pattern with definite high income and low income sectors.

This theory belongs to the ‘market area’ or ‘profit maximisation’ approach and has focused on spatial variations in scales potential. August Losch was a German economist and he proposed his theory in 1939 in a book entitled Die taumliches Ordnung Derwirt’s Chaff.

He disregarded spatial variations in production costs by holding them constant, and instead depicted optimal location as occurring where the largest possible market area is monopolised – that is, where sales potential and total revenue potential are maximised. Losch sought to explain the size and shape of market areas within which a location would command the largest revenue.

Walter Isard had given the location theory in 1956 vided publication entitled, Location and the Space Economy. Isard has modified the Loschian schema, in the attempt to make it more realistic. Isard linked location theory to the general theory of economics through the substitution principle.

In economic theory, capital can be substituted for labour, for example. Similarly, the selection of a manufacturing site from among alternative locations can be viewed as substituting expenditures among the various production factors such that the best site is chosen. (Fig.10.1) provides one simple illustration of Isard’s substitution principle.

Alfred Weber first introduced his famous theory of industrial location in 1909, in his book entitled, Uber den Standort der Industrien and its English translation was published in 1929 as The Location and Theory of Industries. His theory is known as ‘LeastCost Location Theory’ or ‘LeastCost Minimization Approach’. The basic objective of the Weber’s theory is to find out the minimum cost location of an industry.

The demographic transition theory is one of the most important population theories which is the best documented by the data and statistics of recent demographic history. In its original form, the demographic transition theory was put forward by W. S. Thompson (1929) and Frank W. Notestein (1945). These scholars based their statements and arguments on the trends in fertility and mortality, being experienced in Europe, North America and Australia.

The theory postulates a particular pattern of demographic change from a high fertility and high mortality to a low fertility and low mortality when a society progresses from a largely rural agrarian and illiterate society to a dominantly urban, industrial, literate and modern society. The three very clearly stated hypotheses involved in the process are:

1. The decline in mortality comes before the decline in fertility.
2. The fertility eventually declines to match mortality and
3. Socio - economic transformation of society takes place simultaneously with its demographic transformation.

In the present – day world, as would true of any point in time, different countries of the world are at different stages of the demographic transition. In the opinion of Trewartha, this is largely due to the dual nature of man. According to him, biologically, man is same everywhere and is engaged in the process of reproduction but culturally man differs from one part of the world to another. It is the cultural diversity of man that gives rise to varying fertility patterns in different areas resulting in different stages of demographic transition.

The demographic transition theory is characterized by conspicuous transition stages. The transition from high birth and death rates to low rates can be divided into stages. In the words of E.G. Dolan, “Demographic transition refers to a population cycle that begins with a fall in the death rate continues with a phase of rapid population growth and concludes with a decline in birth rate”.

Thomas Robert Malthus enunciated his views about population in his famous book, Essay on the Principle of Population as it affects the Future Improvement of Society, published in 1798. Malthus revolted against the prevailing optimism shared by his father and Godwin that a perfect state could be attained if human restraints could be removed.

Malthus’ objection was that the pressure of increasing population on the food supply would destroy perfection and there would be misery in the world. Malthus was severely criticised for his pessimistic views which led him to travel on the continent of Europe to gather data in support of his thesis. He incorporated his researches in the second edition of his Essay published in 1803.

The Malthusian theory of population is the most well-known theory on population in economics. Malthus pointed out that an accelerated increase in population would outweigh the increase in food production. This would have an adverse impact on the development of an economy. The Malthusian theory explains the relationship between the growth in food supply and in population. It states that population increase faster than food supply and if unchecked leads to vice or misery. This theory is explained in the following propositions

The growth pole theory was developed by French regional economist, Francois Perroux, in 1955. He was concerned with the phenomenon of economic development and with the process of structural change. Growth pole is a central location of economic activity. It is an urban location where economic activity ignites growth and better quality of life in the urban periphery.

He attempted to explain how modern process of economic growth deviated from the stationary conception of equilibrium growth. His arguments were based on Schumpeter’s theories of the role of innovations and large scale firms.

In Schumpeter’s analysis, development occurs as a result of discontinuous spurts in a dynamic world. The cause of discontinuous spurts is the innovative entrepreneur whose activities take place in large-scale firms. These firms are able to dominate their environment in the sense of exercising reversible and partially reversible influences on other economic units by reason of their dimension and negotiating strength, and by the nature of their operations.

Scale of operations, dominance and impulses have close relationship to innovate. This is the most important feature of Perroux’s theory and leads to the concepts of dynamic propulsive firm and leading propulsive industry. The dynamic propulsive firm is relatively large and belongs to a relatively fast growing sector. It has a high ability to innovate and intensity of its interrelation with other sectors of the economy is important enough for the induced effects to be transmitted to them.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

12.1. Instruments panel

12.1.1. Oil pressure gauge

Indicates oil pressure in Kgf/cm²

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.

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.

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.

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.

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.

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.

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.

21.1. What?

Harvest is the process of gathering the end produce from mature crops in the fields. Harvest marks the end of the growing season, or the growing cycle for a particular crop. Harvesting is the most labour-intensive activity. Moreover, timely harvest before shattering of the produce or before rain assumes significance. As adjacent fields sown at the same time come to harvest simultaneously, farmers face great problem in getting manual labour for harvesting and cleaning their produce. To overcome these difficulties, different types of harvesters have been developed from time and again to suit different crops, situation and conditions.

21.2. Harvester and reaper

Harvesters are used to cut the crop after they mature. In such cases, threshing is to be done separately. Harvesters are available for a wide range of crops belonging to cereals, pulses, millets, oilseeds, fruits and plantation crops. Reapers are used to harvest crops such as rice, wheat, soybean, mustard, rapeseed, safflower and other thin stemmed crops. Reapers are operated using power tiller.

22.1. What?

Threshing is the process of separating grains from the straw or pod by impact, friction or both. Threshing should be done at an appropriate time after harvest. Delayed threshing causes rapid deterioration of the grains, especially during field drying or when the crop is stacked in the field. Improper threshing leads to wastage of grains and reduces the quantity of final marketable produce. After threshing, the produce has to be winnowed to remove lighter materials such as unfilled grains, chaff, weed seeds and straw using a blower, air fan or wind. Winnowing improves the ability of the grain to be safely stored, milling output and quality.

22.2. Methods employed

Traditionally, threshing is done by beating the harvested crop on a threshing floor directly or with a stick. Another traditional method of threshing is to make a bull walk in circles on the grain on a hard surface. In some areas, the harvested panicle with grain is spread on the surface of a country road so that the grain may be threshed by the wheels of passing vehicles. In these methods winnowing is separately performed. However, with the development of technology, now it is mostly done by machine referred to as threshers, shellers and stripper. Some of these threshers have inbuilt facility for threshing. Thus, threshing and winnowing are completed in a single process.

23.1. What?

Post harvest and agro-processing refers to activities carried out after harvesting a crop. These include milling, grading, processing and packing of the produce before it reaches the end users. This is also referred to as value addition, as it increases the marketable quality of the harvested produce.

23.2. Milling

It is the process of separating edible portion of the grain after removal of the husk or seed coat. This converts the products into a form that can be readily used for cooking, e.g. rice milling and dal milling.

23.3. Grading

Grading is the process of segregating the harvested produce based on the physical appearance including size and colour. Grading increases the market value of the crop.

24.1. What?

Most of the horticultural crops are raised by following special techniques such as budding and grafting. In case of landscape horticulture, frequent pruning and mowing are required to maintain the architecture. When new area is brought under cultivation, either jungle or unwanted plants have to be cleared. To perform all these operations, certain set of special tools are used. Some tools, though small, are of great need in raising and maintaining horticultural crops at various growth stages.

24.2. Special tools for horticultural crops

24.2.1. Manual

Axe, Dah, Hand shovel, Garden rake, Crow bar, Felling dao, Tea pruning dao, Billhook, Budding knife, Grafting knife, Budding and grafting knife, Pruning and slashing knives, Multipurpose chopping knife, Pruning secateurs, Pneumatic secateurs, Hedge shear, Hedge trimmer, Lopping shear, Forester shear, Grass shear, Garden sword, Flower scissors and coconut tree climber

This chapter deals with equipment and machineries that are used in certain specific operations/ areas.

25.1. Lac cultivation

High-capacity scraper cum grader, scraper cum grader

25.2. Mushroom production

Grain Cleaner, Grain boiler, Boiled grain and Chalk powder mixer, Bag/bottle filler, Spawn inoculators, Substrate mixer - manually operated

26.1. What?

These devices are used to lift water to a height that allows access to water. Lifting devices can be used to lift groundwater, rainwater stored in an underground reservoir and river water. For agricultural use, water is lifted either from a borewell or open well to irrigate the crops. According to power sources, lifting of water can be accomplished either manually or by animal or electricity sources of power.

26.2. Human-powered devices

Man has a limited physical power output, which may be in the range of 0.08 to 0.1 hp. This power can be used to lift water from shallow depths for irrigation. These include swing basket, counterpoise lift, don, Archimedean screw and paddle wheel. However, nowadays these are not commonly used.

26.3. Animal-powered devices

Animal power is abundantly available in India. They are used to lift water, besides being put to use for other field operations and processing works. A pair of bullocks may develop approximately 0.80 horsepower. They can lift water from a depth of 30m or more. Of course, the rate of discharge will go down with increase in the lift. These include rope and bucket lift, self emptying bucket, two bucket lift, Persian wheel and chain pump.