eChapters

A primary objective of extension and development workers is to deliver presentations that are engaging, dynamic, and memorable for their audience. This objective can be most effectively achieved through the use of audio visual aids, which enhance the communication of knowledge and the teaching of skills. Extension teaching methods are defined as the tools and techniques that create environments conducive to the exchange of knowledge and skills between extension workers and their audience. Similarly, audio-visual aids play a significant role in enhancing the effectiveness of learning by facilitating the communication of knowledge and the teaching of skills.

People predominantly learn through seeing, hearing, and doing by looking, listening, and acting. Audio-visual aids provide extension workers with unique opportunities to enhance the effectiveness and clarity of the developmental concepts being conveyed. These aids allow learners to engage more fully with the material by seeing and hearing, thus fostering a deeper understanding. The success of extension workers and the progress made by their learners are largely dependent on the workers' ability to effectively communicate ideas. For progress and development to occur, it is essential that extension workers communicate clearly and that their learners comprehend the information. Audio-visual aids are crucial in this communication process, guiding learners through the steps of the teaching-learning process.

In light of this, the current unit discusses the important audio-visual aids that are beneficial in extension teaching, aiming to enhance your understanding of their application and impact.

Understanding Audio-Visual Aids

People's attention is captured by various senses in the following proportions: seeing (87.0%), hearing (7.0%), smell (3.5%), touch (1.5%), and taste (1.0%). Consequently, seeing and hearing are the primary senses involved in attracting attention and enhancing learning.

12.1 Introduction

Allowing certain plants from the population to reproduce, while barring others, comprises selection. This permission for reproduction may be granted by nature or by the plant breeder. In the other words, both nature and breeder exert selection pressure. Natural selection operates through differences of fertility among the adult individuals of parent generation as well as through differences of viability among the individuals of offspring generation. Artificial selection, i.e., the selection from action of the plant breeder in the choice of parents, produces its change of gene frequency by separating the adult individuals of parent generation into two groups, viz., the selected and the discarded, that differ in gene frequency. So, selection simply implies the retaining of desirable types or culling of unwanted or undesirable types.

Combining Ability Estimation
Crosses made in a definite fashion are a prerequisite for combining ability estimation. Estimated by half-sib (GCA) and full-sib (SCA) mating. Various steps like parent selection for crosses, performing crosses, their evaluation, and interpretation are involved while estimating of combining ability. For analysis of crosses, biometrical techniques like diallel analysis, partial diallel, and Line x tester analysis are used. If GCA variance is higher than SCA variance the importance of AGA & parent selection will be effective for the improvement of such traits. If SCA variance is higher than GCA variance there is importance of NAGA( dominance & epistasis) & Heterosis breeding may be rewarding. If GCA=SCA variance then AGA & NAGA are equally important in the expression of character, In this situation reciprocal recurrent selection may be adopted for population improvement.
Selection for GCA
General combining ability (GCA) is the average value of the inbred line based on its behavior in crosses with other lines. The mean performance of the line is expressed as deviation from the mean of all crosses.GCA is owing to the activity of genes which are largely additive in their effects as well as additive × additive interactions.

The selection of individual animals from a group is very important in a livestock farming business. While creating a herd, every farmer should buy animals from a trustworthy disease-free herd and learn as much as they can about the animals. Once the herd is established, the selection of gilts and boars for replacement in the breeding herd should be based on type and performance. The following are important criteria to consider while creating a healthy sow herd:

• Size of litters
• Strength and vigour of litters
• Milking ability
• Temperament

One of the objectives of experiments in cultivators’ field is to test technology for adoption in a targeted area i.e. NARP Zone, or a district. In that case interaction between district x treatment within a zone or between blocks x treatment within a district should not be significant. If the targeted area is a district, an experiment in cultivators’ fields must occur in at least two blocks. Also, if the targeted area is a zone, an experiment should occur in at least two districts in order to estimate interaction.

Analysis of cultivators’ field experiment

The on-farm trials were conducted in 25 villages on kharif rice during 1992-93. The treatments viz. T1-Farmers’ practice with local variety, T2-Farmers’ practice with improved variety, T3-Farmers’ practice with improved variety +recommended fertilizer and T4-Improved practice with improved variety +recommended fertilizer. Farmers level of NPK fertilizer was 40:0:0 and local variety was Suzata while recommended NPK fertilizer was 80:40:20.

General Selection Procedures for Dairy Breeds
Selection of Dairy Cows
Selecting a calf in calf show, a cow in cattle show by judging is an art. A dairy farmer should build up his own herd by breeding his own herd. Following guidelines will beuseful for selection of a diary cow. Whenever an animal is purchased from cattle fair, it should be selected based upon its breed characters and milk producing.
History sheet or pedigree sheet which are generally maintained in organized farmsreveals the complete history of animal.The maximum yield by dairy cows are noticed during the first five lactations. So generally selection should be carried out during First or Second lactation and thattoo are month after calving.?Three successive complete milkings has to be done and an average of it will givea fair idea regarding production by a particular animal.
A cow should allow anybody to milk, and should be docile.?It is better to purchase the animals during the months of October and November.?Maximum yield is noticed till 90 days after calving.

Choosing the appropriate construction materials requires evaluating their properties, cost, availability, and how well they suit the particular project. Common materials include concrete, steel, bricks, wood, stone, glass, and various plastics. Key specifications often considered are strength, durability, fire resistance, and environmental impact.
MATERIALS OF CONSTRUCTION FOR TRADITIONAL GREENHOUSE
Traditional greenhouses are built using a variety of materials that ensure durability, insulation, and protection for plants, while also allowing sunlight to penetrate. The selection of materials depends on factors such as cost, climate, and the greenhouse’s intended purpose. Here are some of the common materials used in constructing traditional greenhouses:
1. Wood: Wood has been a traditional and widely used material in greenhouse construction due to its affordability and ease of use. Treated wood, such as cedar or redwood, is commonly chosen for its resistance to decay and insects. Wood offers good insulation and stability, making it suitable for different climates.
2. Galvanized Steel: Steel frames provide exceptional structural support and are known for their strength and durability. Galvanized steel is coated to prevent rust and corrosion, extending its lifespan. Steel frames are capable of withstanding heavy loads and harsh weather conditions.
3. Aluminum: Aluminum frames are lightweight and resistant to corrosion, making them a favored choice for greenhouse construction. They are easy to assemble and require little maintenance over time.
4. PVC Pipes: PVC (polyvinyl chloride) pipes are cost-effective and simple to work with, making them ideal for smaller or temporary greenhouses. They provide a basic, lightweight framework that is easy to assemble.

Proper records can be maintained and individual performance can be noted.

Disadvantages: A number of males should be maintained which is not economical.

Advantages of polygamous mating: Economical because 1 male can be used for 4-5 females. We can use postpartum estrus effectively.

Immediately after parturition after 7 days they come to heat. Breeding can be done 7 days after parturition after separating the young ones. [Weaning age 21 days]

But this is usually not followed because the number of young ones born reduces subsequently.

Disadvantages: Proper records cannot be maintained.

Selection is a phenomenon of giving preference to certain individuals in a population to reproduce over other individuals that are deprived of the opportunity to reproduce. In common parlance, it is the process to choose individuals from the herd that are going to produce the next generation and influence the performance of the herd. Performance of a herd is guided by the genes of the parents. In a herd, males give rise to more off springs and hence selection of males is an opportunity to boost cattle husbandry. The contribution of males to the inheritance of polygenic traits is equal with that of females. Hence, it is central to pay equal emphasis while selecting males and females. Selection of sire is more important than dam selection due to numerous reasons. The first reason is that a sire produces more numbers of progenies compared to one dam. Since a sire is called “half the herd”, it determines the performance of the herd. Modern initiatives like artificial insemination and frozen semen technology has further extended the use of sire and highlights the importance of sire selection. Artificial insemination has allowed the superior traits to reach different corners of the globe and this has benefitted the present generation at large. Frozen semen technology together with artificial insemination is milestone to the field of genetics and breeding. It is now possible to

Seed is defined as a ‘matured ovule’ or a reproductive unit formed from a fertilised ovule consisting of an embryo, food store and protective coat. These essential constituents are common to all seeds in different groups of seed bearing plants. The knowledge of seed morphology is essential for artificial regener ation as it can influence the collection, processing, storage and treatment of seeds. The external and internal morphologies of seeds are stable. Therefore, they provide reliable criteria for the positive identification of unknown seeds.

Importance of Tree Seed

Farmers have been growing trees for different purposes for thousands of years. Tree species that are grown to provide more than one significant function are called multipurpose trees. These functions may be productive such as producing fuelwood, timber, fibre, fodder, food, medicine, etc. and/or protective such as soil conservation, shade, shelterbelt, microclimate amelioration, land sustainability, biodiversity preservation, etc. All trees are multipurpose; some, however, are more multipurpose than others. Tree species can be multipurpose in two ways.

1. A single tree can provide more than one function. For example, Gliricidia sepium is grown as living fences that provide fuel, fodder and green manure for agricultural crops - all at the same time.

2. Trees of the same species, when managed differently, can provide different functions. For example, Leucaena leucocephala is managed so that some trees will mainly yield wood while others mainly produce leaf fodder.

All animals with cataract are not suitable candidates for surgery. Pre-surgical assessment of a candidate is essential to make a safe judgement for surgical procedure to perform lensectomy. Failure in canine cataract surgery can be associated with poor case selection. A thorough ocular and physical examination should be performed to rule out other ocular diseases prior to cataract surgery. The cataractous lenses in both eyes must be mature to cause functional loss of vision. (24).

The following prerequisites should be fulfilled before cataract extraction is recommended (6):

1. The affected eye should have a significant visual deficit.
2. For the patient to regain vision, its retina must be healthy and functional. if the fundus cannot be examined thoroughly (because of the cataract), retinal function should be evaluated with electroretinography (ERG) to ensure that retinal degeneration is not present as the patient history, signalment, and the speed of pupil contraction

Phytochemicals from various parts of a plant or tree such as the leaves, the flowers, the seeds, the barks, the roots and the shrubs can be isolated. Once one comes in from collecting plants in the field, it is good idea to freeze them immediately in a freezer at – 20°C or a commercial freezer held at – 80°C (Kaufman et al., 1999). According to Harborne (1984, 1998), fresh plant tissues should be used for phytochemical analysis and the material should be plunged into boiling alcohol within minutes of its collection. Alternatively, plants may be dried before extraction.

Phytochemicals from various parts of a plant or tree such as the leaves, the flowers, the seeds, the barks, the roots and the shrubs can be isolated. Once one comes in from collecting plants in the field, it is good idea to freeze them immediately in a freezer at – 20°C or a commercial freezer held at – 80°C (Kaufman et al., 1999). According to Harborne (1984, 1998), fresh plant tissues should be used for phytochemical analysis and the material should be plunged into boiling alcohol within minutes of its collection. Alternatively, plants may be dried before extraction. It is essential that the drying operation is carried out under controlled conditions to avoid too many chemical changes occurring. Once thoroughly dried, plants can be stored before analysis for long periods of time. It is possible to isolate some of the compounds from herbarium samples. One example of the use of the herbarium material is the essential oil analysis that was carried out on type specimens of Mentha leaf, the material being obtained from the original collection of Linneaus made before 1800 (Harborne, 1998). An obvious point to follow by the research worker is freeing of the plant tissue under study from contamination with other plants. While collecting roots, care must be taken that we are collecting roots from one plant. It is essential to use plants which are free from disease, i.e. which are not affected by viral, bacterial or fungal infection. In phytochemical analysis, at some stage in the investigation, a botanist of an acknowledged authority must authenticate the botanical identity of the plants studied and a voucher specimen of the plant may be deposited in a reputed Herbarium for future reference. It is advisable to keep a logbook of the plants that have been collected and used for phytochemical analysis. A backup inventory on the computer is also a good idea.

Pump is a mechanical device to increase the pressure energy of fluid. Aquacultural enterprises often find it necessary to move fluid against an energy gradient. Most commo n may be filling or emptying of tanks. For performing an assigned job, the best selection of pumps should be such that it should work at its peak efficiency. Unfortunately, there is only one head and discharge condition for each pump where the peak efficiency is obtained and therefore, it is rarely possible to achieve the highest efficiency for a pumping condition. Manufacturers cannot design and build so many varieties of pumps to meet all operating conditions. They have therefore, settled upon some standard designs which are generally required for most of the head and discharge conditions.

Homoeopathic treatment is based on an overall understanding of the symptoms in the body and mind created by a sickness. Dr. Samuel Hahnemann, the founder of the homoeopathic science of healing, after years of experiment and trial, came to finding that symptom - similarity is the curative method of medically curable diseases. In paragraph 25 of the 'Organon of Medicine⁷, he formulated the principle of 'like cures like' in these words: " Now, however, in all careful trials, pure experience, the sole and infallible oracle of the healing art, teaches us that actually that medicine which, in its action on the healthy human body, has demonstrated its power of producing the greatest number of symptoms similar to those observable in the case of disease under treatment, does also, rapidly, radically and permanently remove the totality of the symptoms of this morbid state, that is to say, the whole disease present, and change it into health; and that all medicines cure, without exception, those diseases whose symptoms most really resemble their own, and leave none of them uncured."

The aforesaid indicates the importance of symptoms in the diagnosis and treatment in homoeopathy. If a drug creates a symptom during the course of proving, then it can be cured by a potencised dose of the drug; whatever may be the name of the disease. For instance, in proving GLONOINE produces a bursting, throbbing sensation in the head in a healthy person. Conversely any surging of the blood to the head requires GLONOINE. This can happen in a sun - stroke, in high blood pressure, in cerebro - spinal meningitis. KALI BICROMICUM produces in proving, a tough, stringy discharge of mucus. In homoeopathy, KALI BICROMICUM cures a similar discharge whether from the nose inwards from mouth, from fauces, from pharynx, from larynx, trachea, bronchi, vagina, and uterus or from any mucus membrane. CACTUSGRANDIFLORUS produces in pure form and gross doses, constriction of the heat and a constriction, anywhere in the body, which is like an iron band being tightened. The same sensation of constriction leads us to the use of CACTUS in a homoeopathic dose and it need not be confined to the heart. There can be constriction of the scalp, in the oesophagus, in the chest, in the abdomen, bladder, uterus, vagina or rectum.

The selection of the site has great importance for the establishment of a fruit orchard successfully. Establishment of orchard is a long term activity with huge investment. Hence, any mistake committed during site selection, it is difficult to rectify it later. Successful orchard is not only related with yield but also its economic production and efficient disposal of produce. For economic orchard establishment; some of the points which need to be considered, while selection of site. These are as follows.

1. Climate and soil: These are two important natural factors, which decide the success or failure of orchards. Before selection of site, climate and soil requirement for selected fruit crops needs to be studied thoroughly and accordingly site must be selected. On the other hand if a site has already been selected; then fruit crop selection needs to be done as per the existing climate and soil of that selected site.
2. Topography: Slope of site more than 15% makes the land almost unsuitable for cultivation. Land with 4% slope may be kept clean without much loss. Uneven land involves heavy expenditure in leveling. Southern slopes are generally warmer and affect the plant growth in a manner different from the northern slopes. It is due to the difference in quantum of receiving sunlight. Hence, the site with southern slopes may be selected for sun loving plants.

Farmers have been growing trees for different purposes for thousands of years. Tree species that are grown to provide more than one significant function are called multipurpose trees. These functions may be productive such as producing fuelwood, timber, fibre, fodder, food, medicine, etc. and/or protective such as soil conservation, shade, shelterbelt, microclimate amelioration, land sustainability, biodiversity preservation, etc. All trees are multipurpose; some, however, are more multipurpose than others. Tree species can be multipurpose in two ways. 1. A single tree can provide more than one function. For example, Gliricidia sepium is grown as living fences that provide fuel, fodder and green manure for agricultural crops - all at the same time. 2. Trees of the same species, when managed differently, can provide different functions. For example, Leucaena leucocephala is managed so that some trees will mainly yield wood while others mainly produce leaf fodder.

Farmers have been growing trees for different purposes for thousands of years. Tree species that are grown to provide more than one significant function are called multipurpose trees. These functions may be productive such as producing fuelwood, timber, fibre, fodder, food, medicine, etc. and/ or protective such as soil conservation, shade, shelterbelt, microclimate amelioration, land sustainability, biodiversity preservation, etc. All trees are multipurpose; some, however, are more multipurpose than others. Tree species can be multipurpose in two ways.

1. A single tree can provide more than one function. For example, Gliricidia sepium is grown as living fences that provide fuel, fodder and green manure for agricultural crops - all at the same time.
2. Trees of the same species, when managed differently, can provide different functions. For example, Leucaena leucocephala is managed so that some trees will mainly yield wood while others mainly produce leaf fodder.

Farmers can grow multipurpose trees (MPT) in various combinations with other crops, as in agroforestry, in block plantations of trees or in naturally regenerating tree farms. In certain cases, multipurpose trees are grown and managed for only one purpose. For example, Gliricida sepium is grown only to provide shade in coffee plantations. The same species may be planted in some other places and is managed differently for a very different use.

Farmers have been growing trees for different purposes for thousands of years. Tree species that are grown to provide more than one significant function are called multipurpose trees. These functions may be productive such as producing fuelwood, timber, fibre, fodder, food, medicine, etc. and/or protective such as soil conservation, shade, shelterbelt, microclimate amelioration, land sustainability, biodiversity preservation, etc. All trees are multipurpose; some, however, are more multipurpose than others. Tree species can be multipurpose in two ways.