eChapters

Carbon may be present in soil in four different forms:

1. Carbonates: Mainly as CaCO₃ and MgCO₃, active CO₃ ^2- and HCO₃ ^- ions and gaseous CO₂.
2. Highly condensed elemental organic form: Charcoal, graphite.
3. Completely decomposed resistant organic residues: Humus.
4. Undecomposed and partially decomposed organic residues.

The latter three fractions constitute the total organic carbon of which last two are chemically active form.

20.1 Exchange Capacity

Soil colloidal particles carry both negative and positive charges on their surface which attract and hold equivalent amount of oppositely charged ions to their surface. The total number of negative charges present on a given mass of soil or capacity of a given mass of soil to exchange cations or total number of cation held by a given mass of soil is termed as cation exchange capacity (CEC). Similarly, the capacity of a soil to retain anions is known as anion exchange capacity (AEC). The ion exchange capacity of a soil depends upon the type and amount of colloidal particle (clay and organic matter) present in the soil. Ion exchange capacity (CEC/AEC) is expressed as milliequivalent ion (cation/ anion, respectively) per 100 g of soil (meq/100g). It is also expressed as centimoles of charge (positive/negative) per kg of soil [cmol (±) / kg]. Meq/ 100g = cmol (±) / kg of soil.

20.1.1 Determination of Cation Exchange Capacity of Soil Principle

Soil is first saturated with normal ammonium acetate (pH 7.0). Excess ammonium (NH₄⁺) ions and displaced cations are then removed by washing with alcohol. The amount of NH₄⁺ ions retained by the soil is measured by steam distillation of NH₄-saturated soil with MgO. During distillation evolved ammonia is absorbed in a boric acid solution as ammonium borate and the amount ammonium borate formed is determined by titration with standard sulphuric acid in presence of mixed indicator.

21.1 Determination of Total Nitrogen in Soil (Modified Kjeldahl Method)

Nitrogen mostly present in soil in organic form. Relatively small amount of nitrogen usually occurs in ammonium and nitrate form, the available form. The Kjeldahl method of total N determination includes both organic and ammonium forms and with modification nitrate form of N can also be included.

Principle

When soil is digested with concentrated sulphuric acid organic nitrogen is converted to ammonium sulphate. To speed up the reaction a digestion mixture composed of sodium (or potassium) sulphate (to raise the boiling point of H₂SO₄) and cupric sulphate (CuSO₄) - selenium powder (catalyst) is used.

Phosphorus is present in soil both in inorganic form and organic form. The inorganic P can be divided into different pools. The major active inorganic forms are: P bound to aluminium (Al-P), iron (Fe-P), calcium (Ca-P) and silicate minerals and relatively less active forms are occluded and reductant soluble forms of P. On the other hand, the principal organic P compounds present in soil are (i) inositol phosphate, (ii)phospholipids, (iii)nucleicacid and other unidentified esters and phosphoproteins.

22.1 Determination of Available Soil P

The availability of soil P to plant varies greatly depending upon the reaction, minerological composition and amount of the soil colloid. Very little P is present in the soil solution except in recently fertilized or sodic soils. The type of phosphate ions present in the soil solution depends on the soil pH. In soils of neutral to slightly alkaline pH, HPO₄^2-ion is the dominant form. In slightly or moderately acidic soils, both HPO^-and HPO^2-ions prevail. At strongly acidic soil HPO 244 24 ion tends to dominate, while above pH 9.0, the PO₄^3-ion becomes more important - than H₂PO₄ .

As the P is drawn from soil solution largely through diffusion by the plant, it is replenished from solid phase pool of available P. P fertilizer is added to recharge this pool.

23.1 Forms of Soil K

Ignoring potassium (K) in soilorganism, total K in soilmaybe classified as (i) water soluble K, (ii) readily exchangeable K (exchangeable K), (iii) slowly exchangeable K (non- exchangeable or fixedK) and (iv) mineral or lattice K. Thedifferentforms are in dynamic equilibrium with one another.

Sulphur (S) occurs in soil in both organic and inorganic forms. Inorganic S fraction may occurs as sulphate (SO₄^2-) and compounds of lower oxidation state such as sulphide (S^2-), polysulphide (S_n^2-), thiosulphate (S₂O₃^2-) and elemental sulphur (S⁰). In well drained soils inorganic S usually present as sulphate. Under anaerobic condition (reduced or waterlogged soil) inorganic S mainly occur as sulphide and under extreme condition as elemental S form. Estimation of S is carried out in two steps:

1. Extraction of different forms of S from soil by suitable extractant.
2. The filtrate is then analysed for S by the turbidimetric method.

The turbidimetric method is the most widely used one because of its simplicity and rapidity.

25.1 Determination of Available Micronutrient cations (Zn, Cu, Fe and Mn) in Soil

The available micronutrient cations (Zn, Cu, Fe and Mn) can be estimated in a single extraction with diethylene triamine pentaacetic acid (DTPA) as proposed by Lindsay and Norvell (1978). DTPA has the excellent property to combine with free metal ions in the solution forming soluble complexes. The stability constants of metal-DTPA complexes make DTPA as a most suitable extractant for simultaneous complex formation with Zn, Cu, Fe and Mn. In calcareous soil DTPAextractant may result overestimation due to excess dissolution of CaCO₃, causingrelease of occluded micronutrient cations which are not plant available. To avoid this excessive dissolution of CaCO₃, DTPA is buffered at pH 7.3 using triethanol amine (TEA). At this pH major part (3/4^th) of TEA is present as HTEA⁺ (protonation) and exchanges for Ca and Mg ion from the soil exchange site. This increases concentration of Ca and Mg in the solution phase and suppresses dissolution of CaCO₃. The DTPA has the capacity to form complex with each of the micronutrient cations 10 times of its atomic weight and it ranges from 550 to 650 ppm depending on the micronutrient cation.

The amount of cation in the extract is determined on an atomic absorption spectrophotometer (AAS). The experimental condition such as shaking time, DTPA concentration, pH and temperature during shaking influence the amount of Zn, Cu, Fe and Mn extracted. Increase in shaking time and temperature markedly influence the extractability of these cations.

26.1 Plant Available Fraction of Nickel, Cadmium, Lead and Chromium

The DTPA method was originally developed to extract Mn, Cu, Fe and Zn from slightly acidic to alkaline soils (Lindsay and Norvell, 1978), but in some cases it can be used for other metals also, such as Nickel (Ni), Cadmium (Cd), Lead (Pb) and Chromium (Cr). Among them Ni is considered as an essential micronutrient. The DTPA is used to extract soil metals by forming chelates with free metals in solution, which lowers their ionic activities so that additional quantities of metal are released from the soil colloids until equilibrium is attained. Triehanolamine (TEA) is used to buffer the extracting solution at pH 7.3 in an attempt to optimize the extraction of various metals. Calcium chloride is included in the extracting solution to minimize dissolution of CaCO₃.

Different diagnostic tools are designed to avert nutrient deficiency or sufficiency and if properly used both loss of yield and quality of crop can be minimized. Among several diagnostic tools, nutrient analysis of standing crop seems to be an efficient method in arriving at the need-based fertilizer scheduling for various crops.

Nutrient uptake by plants indicates the actual accessibility of nutrients in soil to the plants. Also, concentration of certain heavy metals in plant indicates their solubility in soil which leads to poor crop quality.Although, different plant species and even different varieties of same species may differ in their nutrient requirements, the concentration of nutrient element in plant can act as guide to support the soil test result in assessing nutrient supplying capacity of a soil and as a tool for correcting any deficiency if carried out early enough to prevent yield loss. However, analysis of harvested or mature crop is like a post mortem as this information only can help in nutrient management planning in subsequent years.

Like soil testingplant analysis also suffers from some limitations. Amongthem, the most important are the risk of sampling error as well as the chances of incorrect interpretation of test report in recommending fertilizers. Selection of right plant part and right stage of crop growth are very crucial for successful plant analysis.

Agroforestry is a new name for a set of old practices. The farmers have been practicing agroforestry since ancient times. The general concept of agroforestry is to integrate trees and agriculture so as to create a more diversified landscape, while providing the producers with new environmental and economic benefits. In other words, agroforestry is a method of farming that allows trees and shrubs to grow along with crops and/or livestock, therefore blending agriculture and forestry in the same production system. In fact, man’s association with forest is much older than with agriculture. First man was a food gatherer and hunter in forests. Then he realized that the seeds of the fruits he collected germinated, grew into plants and bore the fruits again and thus man started to cultivate foods. Man’s desire to live in a community created settled agriculture.

Since then, the pressure on the agricultural lands has increased manifolds due to the increasing population, expansion of urban area and the industrialization process. The environment has also been disturbed. Soil is losing its productivity and the biodiversity is threatened. Farming community is trying all means to increase the land productivity. Chemical fertilizers and pesticides are applied in higher proportion, causing environmental pollution hazards. Under all these circumstances agroforestry has shown that besides sustainable agriculture it can also help promote a better environment. This relatively young science known as agroforestry was brought from the realm of indigenous knowledge into the forefront of agricultural research four decades ago and was promoted widely as a sustainability-enhancing practice that combines the best attributes of forestry and agriculture.

The word ‘social forestry’ was coined by J. C. Westoby and used in the ninth Commonwealth Forestry Conference at New Delhi in 1968. In India the term was first used by the National Commission on Agriculture, Government of India in 1976, to denote tree raising programmes to supply firewood, small timber and minor forest products to rural population. Prasad (1985) defined social forestry as forestry outside the conventional forests which primarily aims at providing continuous flow of goods and services for the benefit of people. This implies that the production of forest goods for fulfilling the needs of the local people is social forestry. Thus, conceptually it deals with the people to produce goods such as fuel, fodder, small timber, etc. to meet the needs of local community particularly the underprivileged section (Shah, 1988).

A forest is a large area dominated by trees. Many definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing and ecological function. Although a forest is usually defined by the presence of trees, under many definitions an area completely lacking trees may still be considered a forest if it grew trees in the past, will grow trees in the future, or was legally designated as a forest regardless of vegetation type. According to the Food and Agriculture Organization, forests covered 4 billion hectares or approximately 30% of the world’s land area in 2006. Forests are the dominant terrestrial ecosystem of earth, and are distributed around the globe. Forests account for 75% of the gross primary production of the earth’s biosphere, and contain 80% of the earth’s plant biomass

Classification Of Forest

Forests have been classified in different ways. Forests can be classified on the basis of method of regeneration, age, composition, object of management, ownership, canopy density, stand density or growing stock.

The words ‘system’, ‘sub-system’ and ‘practice’ are commonly used in agroforestry literature. In a broad sense, a system is defined as a group of associated elements forming a unified whole and working together in a well defined regular relation for a common goal. An agroforestry system refers to a type of agroforestry land-use that extends over a locality to the extent of forming a land utilization type of the locality. Sub-system and practice are lower-order terms in the hierarchy with lesser magnitudes of role, content and complexity. However, these terms are used loosely, and almost synonymously.

Classification of agroforestry systems is necessary in order to understand and provide a practical framework for evaluating systems and developing action plans for their improvement. Any classification scheme should satisfy the following criteria (Nair, 2008).

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.

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 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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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:

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).

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.

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:

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

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.

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 :

Eukaryotic, spore – producing, achlorophyllous organisms with absorptive nutrition that generally reproduce both sexually and asexually and whose thallus is usually filamentous, branched somatic structures known as hyphae, typically surrounded with cell wall.

Mycology – Study of fungi

The fungi can be divided into two groups namely

True fungi: Chytridiomycota, Zygomycota, Ascomycota, Basidiomycota

Additional phyla: Myxomycota, Dictyosteliomycota, Acrasiomycota, Plasmodiophoromycota, Oomycota, Labyrinthulomycota, Hypochitridomycoya.

Algae are a large and diverse group of eukaryotic organisms that contain chlorophyll and carry out the oxygenic photosynthesis.

Study of algae is referred as phycology or algalogy

They vary from cyanobacteria or blue green algae by their eukaryotic nature.

Proto – first; Zoon – animal

Protozoa are single celled eukaryotic organisms, which lack cell wall and ability to move at some stage of their life cycle.

They are referred as the first animals.

There are about 65000 described species grouped into 7 phyla. Among them, 50 per cent are not available as living forms (as fossils) and out of remaining 50%, 22,000 species are free-living and 10,000 species are parasitic forms.

The protozoa are distinguished from other organisms by following characters

Virus can be defined as a genetic element containing either DNA or RNA that replicates in host cells as intracellular parasites but is characterized by having an extracellular state.

Virus can use the metabolic machinery of the host cell and can modify the genetics of the host cell. Virus has both extracellular and intracellular state.

Extracellular State

Outside the host cell, the virus is a minute particle containing nucleic acid surrounded by protein, which is referred as virions or virus particles. Virions are inert and have no biosynthetic and metabolic functions. Extracellular state or virus particle is the perfect stage of virus to study the morphology and chemistry.

Intracellular State

The active state in which the virus replicate in the host cell. When the virus nucleic acid is introduced to host cell and replication starts, the process is referred as infection. The cell in which infection of virus and replication takes place is referred as host cell.

The essential nutrients and their function in microbial cells

Sterilization refers the complete removal or elimination of microorganisms from an environment. Physical and chemical agents are available to remove the microorganisms from the environment. Heat, irradiation and filtration are the three physical agents and various chemicals are available for sterilization.

Terms related to control of microorganisms

Cide or cidal means to kill the microorganism (Ex. Bactericidal refers the killing of bacteria).

Static or stasis means inactivation or inhibition, but not killing. They prevent multiplication of the organism. (Ex. Fungistatic refers the inhibition of growth of fungi.).

Sepsis refers break down of a living tissue by organisms and is accompanied by inflammation and pus formation.

Antispetic is an agent applied externally on living tissues to kill or inhibit the growth of the organisms.

Disinfectant is an agent applied externally on inanimate objects (not living tissues) to destroy harmful pathogens in their vegetative stage.

(Antiseptics are milder than disinfectants because to avoid the side effects)

Sanitation refers removal of organisms from a location by cleaning but not by sterilization.

Genetics is the study of what genes are, how they carry information, how their information is expressed, and how they are replicated and passed to subsequent generations or other organisms.

DNA in cells exists as a double-stranded helix; the two strands are held together by hydrogen bonds between specific nitrogenous base pairs: A-T and C-G.

A gene is a segment of DNA, a sequence of nucleotides, that code for a functional product, usually a protein.

When a gene is expressed, DNA is transcribed to produce RNA; mRNA is then translated into proteins. This is also referred as Central Dogma of Life. The DNA in a cell is replicated before the cell divides, so each daughter cell receives the same genetic information.

Industrial Microbiology is the discipline that uses micro organisms, usually grown on large scale, to produce commercial products or carry out important chemical transformations.

The products derived from such processes are

1 Alcohols and alcoholic beverages.
2 Production of pharmaceutical agents like antibiotics, vaccines etc.
3 Food additives
4 Enzymes
5 Chemicals
6 Single cell proteins

The pathogenicity of an organism varies form mild attack to severe fatal attacks. The host has many mechanisms to resist or to avoid the pathogens apart from immune systems. One or few of these will be activated when the pathogen enters into the body. Following are some of the listed natural host defense mechanisms.

Development of sophisticated procedures for the isolation, manipulation and expression of genetic materials is a field called genetic engineering. Genetic engineering has applications in both basic and applied research. In basic research, genetic engineering techniques are used to study the mechanisms of gene replication and expression in prokaryotes, eukaryotes and viruses. For applied research, genetic engineering used for development of microbial cultures capable of producing valuable products such as human insulins, growth hormones, interferons, vaccines, enzymes etc. The commercial application of genetic engineering is sometimes referred as Biotechnology. In broad sense, Biotechnology refers the use of living organisms to carry out defined chemical processes for industrial application.

The process of isolation, purification and replication of specific DNA fragment is called molecular cloning or gene cloning. Molecular cloning is the base of most of the genetic engineering procedures. The purpose of molecular cloning is to isolate large quantity of specific genes in pure form. Thus molecular cloning is very important in genetic engineering and can be divided into several steps depends on the purpose. The steps are as follows:

Microorganisms live as single cells in nature in association with other cells in assemblage that we call “Population”. Such populations are composed of group of related cells generally derived by successive cell divisions from a single parent cell. The location in an environment where a population generally lives in association with other populations of cells called “Microbial communities”. Environmental microbiology deals with the study of these microbial communities in different habitats, naturally occurring on earth.

Natural habitats of microorganisms are exceedingly diverse. Any habitat that is suitable for the growth of microorganisms can also support the growth of other microorganisms. But in addition, there are many habitats where, extreme environment, due to chemical and physical factors, higher organisms cannot grow but microorganisms can grow and flourish. In this chapter, different habitats of microorganisms are discussed briefly.

Because microorganisms are so small, their habitats are also small. The term microenvironment is often used in ecology to describe where a microorganism actually lives and metabolites within its habitat.

Introduction

Agriculture occupies a prominent place in Indian economy and rural livelihoods. But, it is faced with the challenge of producing food for a rapidly growing population whilst maintaining the nation’s fragile resources.Efforts through green revolution brought out significant increase in food grain production by concentrating on the potential farms in terms of irrigation and other basic resources.Nationally and globally, it is necessary that the growth rate of food production must remain higher than the population growth rate to avoid hunger and overcome famines. But, food security one of the basic human rights is in jeopardy, today. Agriculture is crucial for ensuring the food and livelihood security of the country and hence it is important that this sector with diversified farming systems becomes resilient to increasing climatic variabilities and global economic changes. This concept encourages the farmers towards efficient utilization of natural resources and also proper channelization of by-products of one enterprise to the other enterprise in farming. The integrated farming systems, therefore, assume prime place for sound management of farm resources to enhance the farm productivity, reduce the environmental degradation, and improve the quality of life of resource poor farmers and to maintain the sustainability to meet the challenges of food security. In order to meet the soaring demand for food there is a need to go for integrated faming system.This approach facilitates in strengthening the socio-economic status of Indian farmers besides strengthening ecological balance. Integrated farming system is common to Indian farmers simply because of the preponderance of small farm systems which form the backbone of traditional agriculture. For small farmers, these systems enable a means of diversifying the use of meagre resources in the context of a rational means of reducing risk. Additionally, it also enables increased efficiency in the use of these same resources in a manner that there will be livelihood security and stability to farming systems. There is no scope for increasing the farm size. Yet steady increase in population with shrinkage of cultivated land as a result of industrialization and urbanization would pose serious hurdle for agricultural development. Only vertical expansion is possible by integrating appropriate farming components requiring lesser space and time ensuring continuous income to the farmers.

Rice is the most important cereal crop of India occupying about 44.0 million hectares land. It provides food and employment to millions of people in the country. Despite development of high yielding varieties and technological interventions the yield of rice is still low (3.20 tonnes/ha) in India. The reasons for low yield of rice are:

Lesser area under high yielding varieties

Limited availability of quality seed

Increased acidity/ sodicity in some parts of the country

Declined soil fertility

Unavailability of inputs, like fertilizers and seed, in time

Inefficient nutrient management including imbalanced use of nutrients

Improper crop rotations

Reduced availability of irrigation water

Inefficient management of weeds, diseases and insect-pests

India ranks third after China and Canada in the world in production of edible oilseed crops. Average yield of rapeseed-mustard in the world is 2043 kg/ha. Average yield of European Union, Canada and China is higher than India. Higher yield in these countries is due to cultivation of long duration varieties suitable for their local climatic conditions. Duration of favorable climatic condition to grow rapeseed-mustard is shorter in India as compared to EU, Canada and China, which enforces cultivation of short duration varieties (130-145days). Rapeseed-mustard contribute one third in the production of edible oils in India. These crops ranks second in area and production after soybean. Total area and production under these crops is 5.80mh and 6.28mt respectively. It is necessary to mention that total water requirement of these crop is 80-240mm, which is very low as compared to other crops. These crops pay higher return by utilizing low inputs, thus, are highly remunerative for the farmers.

Rapeseed-mustard group of crops are mainly cultivated in irrigated areas where at least one irrigation facility is available and only 24.0% of area is under rain-fed situation. Five states of India namely, Rajasthan, Uttar Pradesh, Haryana, Madhya Pradesh and West Bengal contribute 82.00% and 85.67% in total area and production, respectively, under these crops. In Madhya Pradesh 53.2% of total area is irrigated with average yield of 1006 kg/ha, however, 76.6% of total area of country is irrigated even then average yield is only 1083 kg/ha. The lower average seed yield can be attributed to (i) cultivation of very short duration and low yielding B. rapa genotypes in Eastern and North-Eastern states; (ii) susceptibility of varieties to different pests; and (iii) high temperature stress at seedling and reproductive stage. Out of total area under these crops, Indian mustard (Brassica juncea) is grown over more than 80% area. Cultivation of Indian mustard has also been taken up in non-traditional areas of southern states of India viz., Karnataka, Tamilnadu and Andhra Pradesh, recently. This has become possible due to its higher average yield, tolerance against different biotic and abiotic stresses, availability of varieties with 100-152 days maturity, and non-shattering behaviour.

Introduction

Lentil is one of the important Rabi pulses. It is one of the oldest pulses crops and the most nutritious of the pulses. It has the potential to cover the risk of dryland agriculture. It is also used as a cover crop to check the soil erosion in problem areas. It is mostly eaten as ‘dal’. Lentil can also be used as green fodder. Its straw is also used as cattle. Being a leguminous crop, it restores the soil fertility.

Area of cultivation

Lentil is mostly cultivated in the northern and central parts of India. The important lentil growing states are Madhya Pradesh, Uttar Pradesh, Bihar, West Bengal, Orissa, Haryana, Rajasthan, Punjab and Assam. Uttar Pradesh and Madhya Pradesh together contribute 78% towards total national area as well as production.

Climatic requirements: Lentil requires cold climate during growth and warm temperature at the time of maturity. It can tolerate cold and frost winter up to great extent. The optimum temperature for growth is 18-30 degree centigrade. Excessive drought and/or high temperatures during the flowering and pod-fill period also reduce yields.

Soil: Lentil can be grown on a variety of soils such as light loams; alluvial soils and black cotton soils. This crop is also suited to the poorer types of soils, low lying areas such as paddy fields. Lentil does not tolerate flooded or waterlogged soils. Good drainage is required, because even short periods of exposure to waterlogged or flooded field conditions kill plants. A soil pH near 7.0 is best for lentil production. Acidic soils are not fit for growing lentil.

Rice is the most important crop in India occupying about 43.7 million hectares area with a production of 136.5 million tonnes (rough rice/ paddy). As the human population is increasing, so is the demand for rice, yet yields of the crop are leveling out. At present, the rice yield in India is 3.12 t/ha as against the world average of 4.11 t/ha. Not only this, the rice yield in India is exactly half than that of China (6.26 t/ha). The World Development Report 2008 predicts that cereal production would have to increase by 50% by 2030 to meet the escalating worldwide demand. The additional rice for increasing population will have to be produced on less land with less water, less labour, and reduced inputs.The major constraint in rice production in India is the lack of suitable crop management practices and sufficient irrigation facilities. The water crisis is threatening the sustainability of the irrigated rice system and food security in many parts of the world. Despite efforts on a variety of fronts, including genetic engineering of rice strains for improved yield and nutrition, no concrete solution has been found yet. There is a challenge to develop novel technologies and production systems that allow rice production to be maintained or increased in the face of declining water availability. To produce 1 kg of grain, farmers have to put 2 to 3 times more water in rice fields than in those growing other cereals.

The increasing water need for agriculture poses a potential threat to natural water resources and climatic change scenarios in the near future. The great challenge will be to increase food production with less water, particularly in countries with limited water and land resources, by promoting techniques and cropping systems of higher water-use efficiency (WUE).There is also much evidence that water scarcity already prevails in rice-growing areas in India, where rice farmers need technologies to cope with water shortage and ways must be sought to grow rice with less water.The farmers, especially those, who are resource-poor, are losing interest in rice cultivation as its profitability is declining with the rise in input costs. But, system of rice intensification (SRI) and aerobic rice culture appear to be a viable alternative of rice cultivation that may save the expensive inputs, improve soil health/ quality and protect the environment substantially.

Sugarcane is the most important sugar crop contributing more than 62% of the world's sugar production. With increasing human population in the world, sugar requirement has also gone up. Molasses is an important by-product of sugar industry. It is used for the production of alcohol by the distillaries. Alcohol serves as a base material in pharmaceuticals and several other industries. The manufacture of gur (jaggery) and khandsari as alternative sweetening agents in India from sugarcane also plays considerable role in the Indian economy, particularly in rural area. Nearly 40 % of the sugarcane produced is utilised for manufacture of gur and khandsari. Sugarcane is bound to play a greater role in the Indian economy in the years to come by offering a stable income to the farmers by way of cane price, by providing employment to rural masses, by realising excise duty, Cane Cess/ purchase tax and foreign exchange earning.

Acreage and production

Sugarcane is grown in tropical and sub tropical regions. Brazil has largest area and production of sugarcane.India is second to Brazil in sugarcane production. It is followed by Cuba and China. Other important cane growing countries are Pakistan, Mexico, South Africa, Australia, Indonesia etc. So far, as average sugarcane productivity is concerned Peru ranks first in average sugarcane yield. To meet the sugar requirement of increasing population in future, it is essential that sugarcane production is stepped up. Since there is no scope at present to bring additional land under sugarcane, productivity of sugarcane, the targets have to be achieved only through increased productivity.