eChapters

Size – Shapes - Arrangements – Morphology

Bacteria are very small, most being approximately 0.5 to 1.0 mm diameter. Smallest bacteria are Mycoplasmas, as small as 0.2 micrometers (almost as small as largest poxviruses).

Accepted wisdom is that bacteria are smaller than eukaryotes. But certain cyanobacteria are quite large; Oscillatoria cells are 7 micrometers diameter, size of red blood cells. And certain eukaryotes (e.g. Nanochlorum eukaryotum) are very small, only 1 to 2 micrometers, but true eukaryotes (nucleus, chloroplast, mitochondrion are present). So size difference is, like many generalizations, only a useful yardstick, not an absolute truth.

Epulopiscium fishelsoni, discovered in 1985 in intestinal tract of sturgeonfish, is an enormous, cigar-shaped cell, as large as 80 x 600 micrometers (that’s 0.6 mm, large enough to be seen by the naked eye). Amazingly, this cell is prokaryotic! Initial evidence by EM was hard to believe, but confirmed rRNA comparisons with other organisms, a cousin of Gram-positive Clostridium genus.

The relative size of the bacteria are as follows :

Place of Microorganisms in Living World

Haeckel’s kingdom Protista

E.H. Haeckel, 1866 proposed this concept. Apart from plant and animal kingdom, the third kingdom “Protista” was developed by him. The protista includes unicellular organisms that are typically neither plant nor animal. These organisms, the protists, include bacteria, algae, fungi and protozoa. Bacteria are referred as lower protists and others are called as higher protists.

Whittaker’s five kingdom concept

R.H.Whittaker (1969) proposed the concept of five kingdom. He divided the living things in to 5 kingdoms.

Microscope is an instrument to magnify and enable to see the microorganisms by us.

Microscopes are of two types. Light and Electron microscope.

Basic Principles of light microscope

The light is the primary source on which magnification is performed. The magnification is obtained by a system of optical lenses using light waves. These light microscopes can be further classified into

Obviously human have had to deal with microbes even before the recorded history. The first record of human using microorganisms comes from ancient tablets from mid east.

Babylonians were using yeast to make beer over 8000 years ago and acetic acid bacteria to make vinegar over 6000 years ago. About 5000 years ago, Persia (Now Iran) region recorded the wine making.

The Romans had God for specific microorganisms. The roman God of mold and mildew were “Robigus” and “Robigo” which mean crop rust. (Rust is one of the plant disease caused by fungus). God Robigus was very much feared because of crop lost. About 2000 years ago, Romans proposed that diseases were caused by tiny animals. But, fundamentalist religions had a strong hold over the progress. The real microbiology history starts from 1600s, when people began to make crude lenses and microscopes.

The following are the scientists and their role in the development of microbiology:

Microbiology

Study of microorganisms, a large and diverse group of microscopic organisms, that exist as single cell or cluster. It also includes virus, which are microscopic, but not cellular.

Development of Agriculture in the World and in India

Agricultural ecosystems will increasingly be called on to deliver food and fiber for a demanding and expanding global population. Until recently, increased production relied on expansion of the amount of land under cultivation and irrigation. Since World War II, production advances have relied on genetics and plant breeding, advances in fertilizer and pesticide use and improved cultural management (Matson et al., 1997). Since 1950, agriculture worldwide has expanded cereal production by an average of 2% per annum while population has increased by 1.9% per year (Borlaug and Dowswell, 1994).

Modern science-based agriculture had its beginnings in the late 19^th century with improved traction and tillage equipments. However, it was not until after World War II that the research findings that led to the modern-day productive systems in the United States and later in European and other developed countries. The expansion was directly related to the great demand for food to support the Allied war effort. Knowledge bases developed in plant genetics, physiology and pathology, along with a ten-fold increase in fertilizer use, advances in seed technology, weed control, irrigation and cultural methods allowed the development of the systems that dominate agriculture in many of the countries today. Corn or maize responded dramatically to the advances in production technology. Maize yield in the United States has increased more than 300 per cent over the past 50 years and continues to rise. Maize production technology has been delivered worldwide (Borlaug and Dowswell, 1994).

Agroecology : Agroecology can be defined broadly or narrowly. “Loosely defined, agroecology often incorporates ideas about a more environmentally and socially sensitive approach to agriculture, one that focuses not only on production, but also on the ecological sustainability of the productive system.

or

The science of applying ecological concepts and principles to the design and management of sustainable agroecosystems.

Alternative Farming/Alternative Agriculture : These are essentially synonymous terms encompassing a vast array of practices and enterprises, all of which are considered different from prevailing or conventional agricultural activities. “They include:

Agricultural practices in India remained virtually unchanged for over 2000 years till 1950-60. With technological advancement in medicine and improvement in health care services, population in India substantially increased in the post independence period. The result was that there was acute shortage of food during 1960s and India had to import massive quantities of wheat from USA to avert famine. Most of these food shipments were in the form of aid. It was then that Government of India realised the gravity of situation and invested heavily in agricultural research. Fortunately, during this period food research laboratories in the West developed hybrid varieties of seeds to suit various types of soil and climatic conditions. At the same time new types of fertilizers and pesticides were introduced which showed dramatic increase in the yield. The agricultural research laboratories in India were able to build on this research and provided extension services to adopt new agricultural techniques to farms in India. This led to dramatic improvement in agricultural production which was hailed as “Green Revolution”. Within two decades a country perennially deficient in food and subject to cyclic famines became a food surplus country in spite of the fact that there was a continuous rise in population which doubled in 30 years after independence. This trend continued into 1980’s when Government built huge buffer stocks of wheat and rice to meet the needs during lean production years.

However the momentum of Green Revolution could not be maintained and certain disturbing trends were noticed in 1990s. The growth rate in productivity declined from 2.99 per cent per annum to 1.21 per cent This was not because we had come to a technical plateau our yields of various products are still quite low as compared to those achieved by developed countries and even some of the developing countries.

Leisa

Sustainable agriculture is an important element of the overall effort to make human activities compatible with the demands of the earth’s eco-system. Thus, an understanding of the different approaches to ecological agriculture is necessary if we want to utilise the planet’s resources wisely.

While sustainable agriculture is based on long-term goals but not a specific set of farming practices, it is usually accompanied by a reduction of purchased inputs in favor of managing on-farm resources. A good example is reliance on biologically-fixed nitrogen from legumes versus manufactured nitrogen fertilizers. Low-input agriculture is one of several alternative farming systems whose methods are adaptable to sustainable agriculture.

Low-input farming is based on a reduction—but not necessarily elimination—of chemical fertilizers, insecticides, and herbicides. Farmers are adopting these practices primarily to reduce costs, but also because they want to minimize impact on the environment or because they perceive future pesticide regulations.

In a search for information on how to farm with fewer chemicals, it is helpful to examine alternative farming systems in existence that largely exclude chemicals in favor of biological farming practices. Experiences of producers who have successfully practiced these methods are valuable to farmers considering a transition to low-input sustainable agriculture.

Concept of Agro-ecology

Ecology and environment

The word environment is derived from the French verb environner, which means “encircle” or “surround”. Thus, our environment can be defined as the physical, chemical and biological world that surrounds us, as well as the complex of social and cultural conditions affecting an individual or community. This broad definition includes the natural world and the technological environment, as well as the cultural and social contexts that shape human lives.

The earth is the only known planet habited by man and other life forms, plants and vegetation. Man and nature have lived together and so long as man’s wants were in conformity with nature, there was no problem. But unfortunately, man’s ambition for limitless enjoyment and comfort has led him towards the exploitation of nature’s wealth so indiscriminately and so shamelessly as to reduce nature’s capacity for self stabilization. The indiscriminate exploitation of nature over centuries has created numerous environmental problems. Man’s voracious appetite for resources and his desire to conquer nature has put him on collision course with environment. The demands of his explosive technological society impose intense stress on the state of equilibrium with the environment.

Ecology is the branch of biological science concerned with the relationships and interactions between living organisms and their physical surroundings or environment. Living organisms and the environment with which they exchange materials and energy together make up an ecosystem, which is the basic unit of ecology. An ecosystem includes biotic components – the living plants and animals and abiotic components the air, water, minerals and soil that constitute the environment. A third and essential component of most natural ecosystems is energy, usually in the form of sunlight.

Familiar examples of land based or terrestrial ecosystems include forests, deserts, jungles and medows. Water based or aquatic ecosystems include streams, rivers, lakes, marshes and estuaries. There is no specific limitation on the size or boundaries of an ecosystem. A small pond can be studied as a separate ecosystem, as can a desert comprising hundreds of square kilometers. Even the entire surface of earth can be viewed as an ecosystem; the term biosphere is often used in this context.

Sustainable agriculture can be defined as a tool of using the natural resources for meeting the present needs without jeopardizing the future potential, increasing per capita productivity without causing degradation of soil and water resources, enhancing profitability without reducing total production and reducing excessive dependence on off farm inputs. Thus the holistic view of sustainability is an approach which is ecologically sound, economically profitable and socially equitable. Theoretically this is an ideal concept and of recent origin. But the real danger to sustainable agriculture stem from the compelling needs of increasing population for food, fuel, fodder on one hand and limited natural resource base of land and water on the other.

Characterisation of Natural Resources

The objective of food security can be met by promoting sustainable agricultural production systems. Increasing agricultural production should not be at the cost of degrading soil and depicting the water bodies. If the basic needs of people are to be met on a sustainable basis, the earth’s natural resource base must be conserved and enhanced. In other words, for food security and sustainable livelihoods, ecological security is necessary. Areas under ecological stress need attention, pressure on natural resources increases with population increase in order to fulfill the demand.

A systems perspective is essential in understanding sustainability. The system is envisioned in its broadest sense i.e., from the individual farm to the local ecosystem and to communities affected by this farming system both locally and globally. An emphasis on the system allows a longer and thorough view of the consequences of farming practices on both human communities and the environment. A systems approach gives us the tools to explore the interconnections between farming and other aspects of our environment.

Towards Sustainability

Sustainability means preserving human life on Earth. Meeting human needs is thus vital in creating a sustainable society. It follows that one of The Natural Step’s principles of sustainability is to meet human needs worldwide.

The concept of multiple dimensions of a sustainable agriculture is more broad which has to be viewed with awareness of potential technologies, fragile ecosystem and human interference to disrupt with limited resource availability. All these aspects have to be taken into account for proper understanding of sustainable agriculture.

The major aspects are,

1. Agriculture must be increasingly productive and efficient in resource use.
2. Biological processes within agriculture systems must be controlled from within (rather than by external inputs of pesticides) and
3. Nutrient cycles within the farm must be closed.

Within this frame work a sustainable model has to be developed. The proposed concept of sustainable agriculture which is best suited for developing and developed countries and is a viable model for the present and future is depicted schematically (Fig. 1).

In its purest form sustainable agriculture would be a complete reversion to subsistence agriculture relying on organic wastes and manures within farms without applying

Preserving the productivity of agricultural land over a long term requires sustainable food production. Sustainability is achieved through alternative agricultural practices informed by in-depth knowledge of the ecological processes occurring in farm fields and the larger landscape of which they are a part. From this foundation, we can move towards the social and economic changes that promote sustainability of all sectors of the food system. Sustainability means different things to different people, but there is a general agreement that it has an ecological basis.

In recent years, all eyes seem to be focused on visions of the future. High-tech, bio-tech, and info-tech are the key words most frequently used among those who are concerned with future agriculture development. Many also forecast increasing vertical integration of production, processing distribution functions-including activities from molecular level to consumer preference i.e. from seed to table, thus increasing dependence on biotechnology and information technology at all levels in world agriculture.

Conventional farming systems vary from farm to farm and from country to country. However, they share many common characteristics viz.,rapid technological innovation; large capital investments in order to apply production and management technology; large-scale farms; single crops/ row crops grown continuously over many seasons; uniform high-yielding hybrid crops; extensive use of pesticides, fertilizers, and external energy inputs; high labour efficiency; and dependency on agribusiness. In the case of livestock, most production comes from confined, concentrated systems.

Agricultural development in independent India can be divided into 3 distinct phases. The phase I started during 1950, wherein local cultivars, indigenous technology, green manuring being the inputs and the expected output was quite low. Alarming rise in the population rate forced the scientists to think of alternatives to the local cultivars with higher response to fertilizers & jump in yield levels. This marked the beginning of phase-II (1965), wherein high yielding varieties, fertilizers, mechanistion & irrigation were used as the inputs and production increase was lucrative. And this phase was popularly called as ‘Green Revolution’ phase in the History of Indian Agriculture. But after 20-25 years the impact of high input technology was reflected in the degradation of agro-ecosystem & once again forced the scientists to think of a viable option to keep intact the resource base & to harvest more/sustain yield levels to feed the burgeoning population. This being the third phase is popularly called as phase of sustainable agriculture organic farming phase started from 1980’s onwards. This gave an impetus to environmentalists, to think seriously regarding protection of the ecosystem.

Multipurpose trees and shrubs are defined as all woody perennials that are purposefully grown to provide more than one significant contribution to the production and/or service functions of a land-use system that they occupy. In agroforestry systems, different species of trees and shrubs can be planted with many types of crops in a variety of patterns. Thus, it is required to know about the methods of propagation and nursery raising, planting and other silvicultural management practices along with the diverse uses of multipurpose trees and shrubs of tropical and subtropical areas before their selection for forestry and agroforestry activities. It is important to select the most suitable tree species since it is not easy to replace them once they have been planted.

Mangium (Acacia Mangium)

Acacia mangium is a single-stemmed evergreen tree that grows to 25-35 m in height and up to 60 cm in diameter. The bole is usually straight, often fluted near the base, free of branches for up to half its height. Mangium is native to Australia, Indonesia and Papua New Guinea. However, it tolerates varied site conditions and has adaptability to different planting objectives. Mangium shows most vigorous growth on well-drained, fertile soils in high rainfall areas in the humid tropics. It is valued for its rapid growth and has been planted throughout the humid tropics and is a major plantation species in the Asia Pacific. Provenances from Papua New Guinea consistently show better growth in height and diameter.

Trees have been used in cropping systems since the beginning of agriculture. Throughout the world, at one period or another in its history, it has been the practice to cultivate tree species and agricultural crops in intimate combination. In the tropics, human beings underwent a transition from hunting/gathering to the use of domesticated plants and livestock. As a part of the process they cut down trees, cleared the debris by burning and sowed crops in the ash- enriched soil. It was the ‘slash-and-burn’ agriculture, a primary forerunner of the present day agroforestry and a practice that might have originated in the Neolithic period, around 7000 BC.

There are innumerable examples of traditional land-use practices involving combined production of trees and agricultural species on the same piece of land in many parts of the world. Trees were an integral part of these farming systems and they were deliberately retained on farmlands to support agriculture. These practices are now known as agroforestry. However, the ultimate objective of these practices was not tree production but food production.

In agroforestry systems the various components like tree, crop and pasture exist in different proportions and orientations. It is difficult to find out which agroforestry system is the best suited for a given land situation. Similarly, it is to be decided which technologies are required for refinement and improvement of the existing agroforestry practices. But without sufficient knowledge of the existing system in a particular land situation, it is very difficult to set the research priorities for modification and development of this system.

Diagnosis and Design (D & D) is a systematic and objective methodology developed by International Centre for Research in Agroforestry (ICRAF) to initiate, monitor and evaluate agroforestry programmes. D & D is based on the philosophy that knowledge of the existing situation (diagnosis) is essential to plan and evaluate (design) meaningful and effective programmes in agroforestry research for development. The methodology plays a strategic role in all the phases of the agroforestry research process. D & D in agroforestry is unique and it has been specially developed for the following purposes.

Agroforestry is a land use system that involves two or more plant species at least one of which must be a woody perennial. When perennial woody and herbaceous components are grown together on the same piece of land their performance would largely depend on their ability to share various growth resources in a given environmental situation. Due to difference in growth pattern and resource requirement of the components in agroforestry situation, a close interactive relation is obvious. Thus, careful management practices for the components are required to establish a successful agroforestry system. The characteristics of the trees and crops, and their interactions, can be modified with good management practices in order to take advantage of the positive characteristics and minimize the effects of the negative ones. Effective and efficient agroforestry management may be divided into two groups - tree management and agricultural crop management.

Factors Affecting The Selection Of Tree Species

Trees in an agroforestry system contribute significantly to the total output of the system and therefore, success of the system depends on the selection of the tree species. The following factors are to be considered to choose the best tree species for the agroforestry systems in a particular site.

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.

Agroforestry systems are not simply systems where trees and crops or animals give useful products to the farmers, rather systems where trees and crops and/or animals interact. Interaction literally means influence or mutual or reciprocal action. So component interaction refers to the influence of one component of a system on the performance of other component as well as the system as a whole.

In agroforestry systems, trees are grown in close proximity to crops and pasture. Their performance would largely depend on their ability to share various growth resources in a given environmental situation. Various interactions take place between the woody trees and herbaceous plants (crops or pastures) which is referred to as tree-crop interface. These interactions take place through the media of soil and microclimate and may exert favourable or adverse effects on the crop. Study of interaction helps to know how the components of agroforestry utilize and share the resources of the environment, and how the growth and development of any of the components will influence the others. Interaction occurs both above and below the ground and includes a complex set of interactions relating to radiation exchange, the water balance, nutrient budget and cycling, shelter and other microclimatic modifications.

The success of an agroforestry system relies heavily on exploitation of the component interactions. In an ideal relationship, production of trees as well as crops or grasses in combination could be comparable to their sole performance. Agroforestry could be even more advantageous if the production of associated components is increased due to influence of trees. This is possible because trees are capable of improving productivity of soil in many ways. A large number of trees are known to fix nitrogen symbiotically. Nevertheless, instances of crop inhibition in association of trees are not uncommon. Such inhibitions are primarily caused by shade effect as well as competition for below-ground resources such as nutrients and water. In some cases inhibitory effect may also result from allelochemicals secreted by some of the tree species.