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An area with similar soil, climatic conditions and resource availability resulting in similar type of crops and cropping systems. Ex. Rice based cropping system, Ragi based cropping system, Wheat based cropping system, Cotton based cropping system etc.

Efficient cropping zone: An analysis of productivity efficiency of crop was made by Kanwar (1972) using relative yield index (RYI) and relative spread index (RSI).

A zone where both yield and spread indices are maximum that is above 90 per cent is called most efficient and in case of indices below 90 is the least efficient zone of a crop.

Agriculture is the most important sector in India in terms of the population dependent on it. Although agriculture now accounts for on 14 per cent of GDP, it is still main source of livelihood for the majority of the rural population. Rapid growth of agriculture is critical for development of rural economy and viable development of rural economy will leads to overall development of country. Diversification in agriculture is need of the hour, any cropping system comprising crops with varied maturity period, crop canopy and high yielding potential is need for an average farmer. Again cropping systems depending upon the soil type, total rainfall and arrival of monsoon in the region. Low cost technology is essential for reducing financial burden on farmers and to increase production on sustainable manner.

The crop production is affected by the plant type, climatic condition, soil type and management factors. The production of the plant might be increased by changing plant type and increasing the grain filling period under certain climatic condition where management and soil factors are not limited. There is a direct relationship between the plant type and crop yield because the orientation and number of leaves play an important role in carbon fixation (photosynthesis). Again any variety/cultivar will contribute 21-25 per cent to the total yield of any crop in general. In recent years due to development of photoinsensitive varieties and hybrids which are more fertilizer responsive and high yielding varieties lead to increase overall production in the country.

Plant ideotypes

Refers to plant type in which morphological and physiological characteristics are ideally suited to achieve high production potential and yield reliability. The concept of ideotype was given by Donald in 1968 and he illustrated that there should be minimum competition between the crops and crop must be competent to compete with weeds. Ideotype is defined as a biological model which is expected to perform or behave in a predictable manner within a defined environment. On the basis of environment, Donald and Hamblin (1976) identified two forms of ideotypes that is isolation ideotypes and competition ideotypes. Isolation ideotypes are suitable for mono/single cropping and competition ideotypes are suitable for mixed cultivation.

Crop diversification refers to the addition of new crops or cropping systems to agricultural production on a particular farm taking into account of the different returns from value-added crops with complementary marketing opportunities.

Major driving forces for crop diversification

Crop diversification provides better conditions for food security and enable farmers to grow surplus products for sale at market and thus obtain increased income to meet other needs related to household well being. Crop diversification enable farmers to gain access to national and international market with new products, food and medicinal plants. Diversification from the monoculture of traditional staples are important for nutritional benefits of farmers in developing countries and can support a country to become more self reliant in terms of food production. Diversification also manages price risk and compared to monoculture techniques. For diversification crops generally consists of more sustainable natural resources and again, diversified farms are usually more economically and ecologically resilient.

The stability of yield is an important characteristic to be considered when judging the value of a cropping systems when compared to others cropping systems. Here, we focus on multiple cropping and how this agroecological practice can be used to increase the sustainability of crop production. Strip, mixed and relay intercropping can be used to increase crop yields through resource partitioning and facilitation. In addition to achieving greater productivity, diversifying cropping systems through the use of strategic cropping systems will increase yield stability, reduce weeds, pests, disease and improve soil health. Several multiple cropping systems are already implemented in industrialized agricultural landscapes, including mixed intercropping with perennial grasses and legumes as forage and relay intercropping with winter wheat and red clover. Because multiple cropping systems will provide numerous benefits, researchers should be clear about their objectives and use appropriate methods so as not to draw spurious conclusions when studying multiple cropping systems. In order to advance the practice, experiments that test the effects of multiple cropping systems should use standardized methodology and researchers should report a set of common criteria to facilitate cross-study comparisons. Multiple cropping systems with two or more crops appears to be less common with annuals than perennials, which is likely due to differences in the mechanisms responsible for complementarity. One area where intercropping with annuals in industrialized agricultural landscapes has advanced is with cover crops, where private, public and governmental organizations have harmonized efforts to increase the adoption of cover crop mixtures.

When crops are grown in either intercropping or sequential cropping interaction between different component crops occurs which is essentially a response of one species to the environment as modified by the presence of another species is commonly referred to as interference or interaction.

The interaction are classified into three groups

1. Competitive interaction: One species may have greater ability to use the limiting factor and will gain at the expense of the other and this is called competitive interaction or when one or more growth factors are limiting, the species that is better equipped to use the limiting factor(s) will gain at the expense of the other and this is called competitive interaction.
2. Non competitive: If the crops are grown in association and the growth of either of the concerned species is not affected, such type of interaction is called non competitive interaction or if resources (growth factors) are present in adequate quantities, as a result of which, the growth of either of the concerned species is not affected, then it is non-competitive interaction or interference.
3. Complementary: If one species is able to help the other, it is known as complementary interaction or if the component species are able to exploit growth factors in different ways (temporal or spatial) or if one species is able to help the other in supply of factor (like legumes supplying part of N fixed by symbiosis to non-legumes), it is complementary interaction or interference and also referred to as Annidation.

Various types of cropping systems are practiced in a farm or region. They should be evaluated to find out their stability and relative advantages in yield. Again, comparisons may be made with reference to land use efficiency, biological potential and economics. Following are the important indices for assessment of competition and yield advantage:

1. Relative yield total (RYT): The oldest establishment measure of the yield advantage of crop mixtures is the Relative Yield Total. The RYT index was designed as a measure of the extent to which various crop components shared common resources, rather than as a direct measure of yield advantage.

Classifications of cropping systems

Depending on the resources and technology available, different types of cropping systems can be adopted on farms and which are as below.

Mono cropping /single cropping: Mono cropping refers to growing only one crop on a particular land year after year or practice of growing only one crop in a piece of land year after year. Example, growing only crops during kharif in rainfed areas and this is due to lack of irrigation facilities and crops depend on rainfall alone.

In sustainable agriculture the word sustain is derived from the Latin word sustinere (sus-from below and tinere-to hold), to keep in existence or maintain, implies long term support or performance. As it pertain to agriculture, sustainable describes farming system that are capable of maintaining their productivity and their usefulness in society indefinitely. Such system should be resource conserving, socially supporting, commercially competitive and environmentally sound. Systems approach is essential for understanding sustainability and it gives us tools to explore the interconnections between farming and other aspects of our environment and sustainability implies at the following,

1. Meeting the basic needs of all people and giving this priority over meeting the greeds of a few
2. Keeping population densities if possible below the carrying capacity of the region
3. Adjusting consumption patterns and the design and management of systems to permit the renewal of renewable resources
4. Conserving, recycling and establishing priorities for the use of non- renewable resources
5. Keeping environmental impact below the level required to allow the systems unaffected to recover and continue to evolve.

Various definitions have been provided for what constitutes sustainable agriculture ranging from the narrow focus on economics or production to the incorporation of culture and ecology. Wendell Berry has simply said A sustainable agriculture does not deplete soils or people.

Multiple cropping includes both inter and sequential cropping systems and here the main objective is to utilize the available resources effectively in a given environment. Number of indices are available for assessing land use and the yield advantage of crop mixtures compared to pure stands. These indices not only reflect the difference in criteria used to appraise advantages often encompassing aspects of quality or values as well as yield, but also reflects the different reasons for which an assessment is made.

1. Rotational intensity (RI): Crops are grown in a recurring sequence on the same piece of land with sufficient diversity and intensity. Crop rotations to control erosion/ to improve or maintain soil fertility and to manage weeds, insects and disease. Lower values of rotational intensity indicate mono cropping and higher values of rotational intensity indicates more rotation.

The main objective of any cropping system is to utilize available resources efficiently viz., land, water, solar radiation by maintaining stability in production in order to obtain higher net returns. The efficiency is measured by the quantity of produce obtained per unit resource used in a given time. The objective of traditional agriculture was to increase the production by two means

1. By increasing area under cultivation
2. By increasing the productivity per unit area of the crop

But two more dimensions are added to modern agriculture

1. To increase the production per unit time
2. To increase the production per unit space

In the traditional cropping systems, mixtures and rotations were developed by the farmers over years of experience by trial and error to suit specific ecological and sociological conditions to attain yield stability, whereas modern scientific cropping has three pillars viz.

A system is a unit which possess a group of interacting components, operating together for a common purpose, capable of reacting as a whole to external stimuli. It is unaffected directly by its own outputs and has a specified boundary based on the inclusion of all significant feedbacks. For example, the human body is a system-it has a boundary (skin) enclosing a number of components (heart, lungs) that interact (the heart pumps blood to the lungs) for a common purpose (to maintain and operating the living body).

Ecosystem: Any collection of organisms that interact or have the potential to interact along with the physical environment in which they live form an ecological system or ecosystem. Ecosystems are not static entities but, they are dynamic systems with characteristic pattern of energy flow, nutrient cycling and structural change.

Agro ecosystem: Agro ecosystems are ecological systems modified by human beings to produce food, fibre or other agricultural products. Like the ecological systems, agro ecosystems are structurally and dynamically complex. But their complexity arises from the interaction between socio economic and ecological processes.

Crop system: An arrangement of crop population that transform solar energy, nutrients, water and other inputs into useful biomass that produce food, feed, fuel and fibre. Crop system comprise of soils, crop, weed, pathogen and insect subsystems. The crop can be of different species and variety, but they only constitute one crop system if they are managed as a single unit.

Cropping systems: It is defined as the order in which the crops are cultivated on a piece of land over a fixed period of time. Cropping system is the way in which different crops are grown. In the cropping systems, sometimes a number of crops are grown together or they are grown separately at shorter intervals in the same field.

Growing more than one crop in sequence or simultaneously as a mixed crop is an ancient practice. In Indian Vedas, there is a mention about double cropping. In early periods, the objective to adopt sequential cropping practices was to reduce the risk of total crop failure due to uncertain monsoon and to have a variety of produce to meet food requirement of farmer’s family, fodder to animals and to meet his cash requirements. Other benefits of yield increase was due to complementary effects of the component crops in improving the soil fertility, spreading the labour requirement throughout over a period of time and to reduce damage caused by weeds, pests and diseases were only incidental.

Multiple cropping in simple terms refers to the practices that increase production in a unit area of land through two or more growing crops simultaneously. The importance of intensive cropping in sustainable agriculture has been well understood by the agricultural scientists of late and there has been surge of interest in the research community to explore these complex systems in detail and to see what can be learnt from the farmers in our quest to make cropping system more sustainable progress made in the past through intensive research carried by the various agricultural universities, ICAR, research institutes/ coordinated research projects and international research institutes such as IRRI, ICRISAT, IITA and CIMMYT, it has shown that and more efficient utilization of the natural resources is possible by suitably modifying the present cropping systems in the various regions of the world.

The present cropping intensity in India is 136 per cent. There is a great prospect for increasing the cropping intensity both in irrigated and rainfed areas. In many irrigated areas, cropping intensity can be increased to 200-300 per cent. There is good scope to increase cropping intensity to 180-200 per cent with proper policies and technology options in rainfed conditions also.

Agricultural extension is a term that has long been used to describe a non-formal educational system aimed at improving the livelihood of farmers. Extension education aims at three main types of behavioural changes in relation to knowledge (things known), attitudes (things felt) and skills (how to implement the things). This can be achieved through persuasion and motivation for the changes. The core activities in extension are education and training. Extension is now being regarded as a much wider task of integrating indigenous and new skills and techniques, derived from study or research, into an overall framework of discussion and cooperation between the people and the extension organisation. The extension worker is primarily engaged in the ‘selling’ of ideas to bring about changes in the knowledge, attitudes and skills of the individual. Functions of extension in a broader sense include

Economic analysis provides a rational basis for making decisions in allocating scarce resources among various options to achieve competing goals. If resources were not limiting, there would be no need for economic consideration.

PRINCIPLES OF ECONOMIC ANALYSIS

Optimization criteria

The additional return obtained from using one additional unit of an input should be considered to optimize net income from several possible production options. If option ‘x’ gives a higher return to land than other options, then additional units of land should be allocated to option ‘x’.

Agroforestry systems are more complex than the agricultural systems. The long-term nature of trials involving woody species and the varying objectives of agroforestry trials demand that adequate caution be exercised in their design. Several characteristics of the trees like slow growth, long term effects on their surroundings, long life, age of trees, the area over which the influence of trees extend, etc. complicate the issue of designing experiments for these systems. Agroforestry experiments are often established on marginal sites which include sloping lands, and sites with infertile and degraded soils. It is thus difficult to find homogeneous sites of such problem areas, especially sloping lands where plots along contour lines are long and linear. Germplasm of many agroforestry tree species are usually collected from different origins which lack uniformity. Therefore, experimental materials in an agroforestry experiment may not be of uniform quality.

There are several features of agroforestry systems that require some modification of the methods usually used in agricultural experiments. Important issues related to agroforestry experiments include

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.

Human societies over the ages have depleted natural resources in different ways and degraded their local environments. Indiscriminate cutting down of trees and accelerating the construction works lead to global warming and climate change. Climate scientists believe that human-induced deforestation is responsible for 18-25% of climate change. Accumulation of greenhouse gases in the lower atmosphere is the main cause of global climate change. The concentration of these gases in the earth’s atmosphere is increasing, mainly due to deforestation and the combustion of fossil fuels which release carbon dioxide.

The earth receives heat energy constantly from the sun through radiation. Some of the heat is absorbed and some is reflected. Carbon dioxide works like an invisible blanket that wraps around the earth and traps the heat inside, similar to the function of a greenhouse. A greenhouse is a structure that is used in colder climates to grow plants. Even when outside temperatures drop below freezing point, greenhouses are still warm enough inside to grow plants. Greenhouses are made of glass, which allows solar radiation to enter. The heat is trapped inside the greenhouse, allowing plants to grow all the year round. Increasing concentrations of carbon dioxide in the earth’s atmosphere insulate it like a greenhouse, leading to a gradual warming of the earth’s atmosphere. Carbon dioxide is the major greenhouse gas, but there are others as well, including methane and nitrous oxide.

India shares 17.4% of the world population, while its land is only 2.4% of the total geographical area of the world. Naturally, the pressure on the land is often beyond its carrying capacity. Therefore, the productive lands, especially the farmlands in India are in the constant process of various degrees of degradation and are fast turning into wastelands. At present, approximately 63.85 million hectare area of the land is lying as wastelands in India (NRSA, 2005). Out of these lands, about 50% lands are such non-forest lands, which can be made fertile again if treated properly. In the last 50 years India’s lush green village forests and woodlots have been deforested to the maximum. To restore this ecological imbalance by developing the degraded non-forest wastelands, Government of India had created the Department of Wasteland Development during July, 1992 under the Ministry of Rural Development, which has been subsequently reorganized and renamed Department of Land Resources, with a broader mandate.

National Wasteland Development Board was established in 1985 mainly to tackle the problem of degradation of lands, restoration of ecology and to meet the growing demands of fuelwood and fodder at the national level. The Board was reconstituted in August, 1992 and was made responsible for development of wastelands mainly in non- forest areas in totality by involving local people at every stage of development. It aims at creating a scenario where the Government acts as a facilitator and the people at the grass root level become the real executioner of the programme. The degradation of environment in the fragile Indian subtropical ecosystem is basically attributed to the following factors.

A watershed is a geohydrological unit or all the land and water area bounded by a divide which contributes runoff to a common point. Watershed is considered to be synonymous with ‘catchment basin’ and ‘drainage basin’. In watershed management approach, development is not only confined to agricultural lands but also covers the area, starting from the highest point of the land to the outlet of the natural stream. Watershed management becomes increasingly important as a way to improve livelihood of people while conserving and regenerating their natural resources.

Watershed management is the process of creating and implementing plans, programmes and projects to sustain and enhance watershed functions that affect the plant, animal and human communities within a watershed boundary. It implies the judicious use of all the resources i.e. land, water and vegetation in an area to prevent soil erosion, improve water availability and increase food, fodder, fuel and timber on sustained basis.

Ecology of a place is influenced by a number of biotic and abiotic factors. An agroecological zone is broadly homogeneous in climatic and edaphic factors, but not necessarily contiguous, where a specific crop exhibits roughly the same biological expression. On the other hand, the characteristics of an agroecological zone influence the crops and cropping patterns of the zone. Thus, there are considerable variations in the types and management practices of agroforestry systems being followed in different agroecological zones.

AGROFORESTRY FOR HUMID AND SUBHUMID TROPICS

Humid and subhumid tropical regions have much variation in biological, social and economical parameters. The characteristics of humid tropics include high mean annual rainfall of more than 1500 mm, dry season of less than four months in a year and mean annual temperature of more than 22oC. Rainfall usually exceeds the evapotranspiration. However, demographic pressure has caused excessive deforestation and overgrazing which developed soil related problems like low soil fertility, low organic matter, high acidity and high rainfall erosivity. The agroforestry practices designed for this region should aim for improved fallows, soil fertility improvement and conservation, food production, etc. Thus, the common agroforestry systems in this zone are taungya, homegardens, alley cropping, plantation-crop combination, windbreaks, silvipastoral systems and various intercropping systems. Shifting cultivation is a common practice in tropics which should be discouraged as it causes environmental degradation and ecological imbalance, soil erosion and soil nutrient loss.

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 practice 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.

Trees that provide materials for propagation are called mother trees. Selection of mother trees is important because the young trees will be expected to inherit the favourable characteristics from the mother tree, such as fast growth, upright or spreading shape of the tree crown, good flowering and fruiting, and tolerance of diseases or pests. There may be sexual propagation by seed or vegetative propagation by using other parts of the tree. The genetic make-up of the seeds differs due to recombination of the genes, resulting in seedling variation. Thus, all the seedlings may look like the mother tree in some respects, but no two seedlings are the same. In case of vegetative propagation through cutting, layering, grafting or budding, the genetic make-up of the young tree is exactly the same as that of the mother tree. Consequently, all new trees grown vegetatively from one mother tree have the same set of gene pairs and therefore the same characteristics; they form a so called clone. Differences between plants of a clone can only be caused by different growing conditions.

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 belowground resources such as nutrients and water. In some cases inhibitory effect may also result from allelochemicals secreted by some of the tree species.

Management approaches to soil, including problems of soil degradation and low soil fertility, have recently undergone major changes. The earlier concept was to concentrate on achieving high levels of production from the more fertile areas, leaving the marginal lands for extensive use only. Steeply sloping and highly drought-prone areas were mostly left without any cultivation as production from these areas was hardly cost effective. Soil constraints were to be overcome by inputs like improved crop varieties, fertilizers, chemical control of pests and diseases, and the use of irrigation.

The approach of use of newly developed high yielding crop varieties, improved agronomic management practices, use of chemical fertilizers, efficient water management and timely plant protection measures has been successful in achieving large increases in crop productivity in recent years. On the other hand, continuous application of fertilizers at higher rates leads to environmental problems. Yield responses to fertilizers have declined because of soil physical degradation and micronutrient deficiencies. Above all, large numbers of poor farmers simply can neither afford high levels of fertilizers and other purchased inputs, nor do they have the capital to take on the risk involved in their use. Increasing the area under irrigation has also run into severe constraints in the form of limits to available freshwater resources.

The word 'social forestry' was coined by 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).

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 is a new name for a set of old practices. 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.

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. Trees have always played an important role in mankind's survival. This relatively young science known as agroforestry was brought from the realm of indigenous knowledge into the forefront of agricultural research three and half decades ago and was promoted widely as a sustainability-enhancing practice that combines the best attributes of forestry and agriculture.

Abstract

Anaerobic microorganisms occur in oxygen-free environments as they possess biomolecules and metabolic processes that have adapted to sustain them in the stressed environments. These biomolecules and metabolic processes are harnessed and employed in various biotechnological applications. Anaerobes are abundant in various ecological niches such as freshwater or marine sediments, subsurface aquifers, deep thermal vents etc. where, in the absence or limitation of oxygen, they utilise reduced ions such as nitrate, sulphate, ferric, carbonate and certain organic compounds like degrading organic matter, fatty acids or alcohols as electron acceptors during respiration/fermentation to produce more or fewer reduced products such as, alcohols, ammonia, organic acids, hydrogen and carbon dioxide as the oxidised product. Diversity of substrates that can be fermented and the wide range of products that can be formed make anaerobic processes useful in biotechnological applications. Their substrate versatility and flexibility, for example, they can utilize simple sugars as well as many of them can utilise complex renewable biomass make their biotechnological applications sustainable and environment friendly. Anaerobes have been employed in food, chemical and material industries for the production of food items, preservative, additives, chemical intermediates, solvents, catalysts and polymers. They find widespread usage in energy sector for generation of various kinds of biofuels that can mitigate our reliance on non-renewable sources for fuel production. An emerging aspect of anaerobic biotechnology is waste valorization that involves treatment of any kind of waste (industrial, municipal, agricultural, pharmaceutical), where organic fraction of the waste is converted into valuable products. Anaerobes play key role in maintaining the global cycles of carbon, nitrogen, and sulfur, and also facilitate bioremediation by breakdown of persistent compounds. Lately, role of anaerobes in medicine and health care sector is widely explored as they are found to produce several bacteriocins, antibiotics, immunomodulators, vitamins and anti-tumor compounds. Some of the anaerobes have also been employed as probiotics. In the present chapter, we discussed these and many more biotechnological applications of anaerobes in white, green, red and blue biotechnology.

Abstract

Hundreds of bacterial taxa makes up human gut microbiota and it is comprised primarily of anaerobes belonging to four main phyla which are Firmicutes, Bacteriodetes, Actinobacteria, and Proteobacteria. Anaerobes colonizes the human body, including oral cavity, small intestine, vagina, skin but the majority of them are housed in the colon. The composition and distribution anaerobes varies along the length of gastrointestinal tract because of variation in oxygen gradient, anatomy of intestinal tract and other host physiological factors. Human gets colonized by anaerobes during the birth and these initial colonizers have impact on infant’s health status. The colonization and development of the gut microbiome is responsive to variety of factors including the mode of delivery, feeding methods, environment etc. The human gut microbiota plays an important role in healthy status of host. It plays an important role in nutrient metabolism and absorption, synthesis of vitamins and production of short-chain fatty acids (SCFAs). In turn these metabolites have positive effect on host immunity and overall host fitness. Studying, the anaerobes using culturing method remains critical in microbiology. However, culturomics approach, combined with sequencing technology, provides new insights in studying anaerobes of human gut microbiota. In this chapter we have discussed that, how human gut is an ideal habitat for the colonization and growth of anaerobes and their impact on host health. We also tried to shed light on latest technical advancement in sequencing culturing technology and their application in studying gut anaerobes.

Abstract

Gastrointestinal tract (GIT) harbors mixed microbial community, these are highly diversified, as revealed by molecular and phylogenetic studies. It is also estimated that microbiota of the GIT is composed of over 35,000 species and play a crucial role in human health and diseases. Thus are now of great interest to both the industrial and scientific communities. The microbes exhibit health benefits are known as probiotics. Anaerobic bacteria dominate in the GIT environment and genera like Bifidobacterium, Clostridium, are strict anaerobes while Lactobacillus, Lactococcus, is facultative anaerobes implicated in the probiotic effects.

For developing anaerobic bacterial based bio-products, it is necessary to cultivate large-scale biomass production that could be done using a modern manufacturing practice. Information on detailed understanding of the perfect growth medium and other bioprocessing parameters for the growth and viability is must. Also high cell viability is a prerequisite during downstream processing and storage of probiotic formulation. In this work we review the latest information about the history, mechanism of action, benefits of probiotic, selection criteria, sources of anaerobic probiotic bacteria, industrial cultivation medium along with biomass production, downstream processing.

Abstract

The normal human microbial flora comprises of both aerobes and anaerobes at various sites. Anaerobes are recognised as pathogens causing simple abscesses to life threatening human infections like gas gangrene. They are also incriminated in a large number of mixed bacterial infections and their diagnosis and specific therapy is important for better patient outcomes. The emergence of Clostridioides difficile as an important pathogen causing antibiotic associated diarrhoeas and its emerging resistance to antimicrobial agents has brought anaerobic microbiology into the forefront. Unfortunately, anaerobic clinical microbiology is difficult to practice with long turnaround time, difficult to grow pathogens, new genera and species being discovered based on 16S rRNA sequencing methods and increasing incidence of antimicrobial resistance being reported in anaerobes. This chapter delves into the important aspects required to improve utilization of anaerobic microbiology services and the variety of human infections we encounter in clinical practice due to anaerobic bacteria.

Abstract

Anaerobes are a diverse groups of microorganisms which do not require oxygen or energy for respiration/metabolism and are one of the important components of nitrogen cycle. They are capable of using various other organic and even inorganic materials as electron acceptors during respiration. Anaerobic based wastewater treatment is a biological approach where microorganisms degrade organic contaminants (i.e. rich in carbon and nitrogen) in the absence of oxygen. In this chapter, the role of anaerobes in wastewater treatment has been discussed as it offers an alternative, cheap and eco friendly treatment technology among different biological treatment methods. Anaerobic biological treatment of wastewater is well developed, understood, and frequently used in anaerobic digesters to treat complex organic carbon and nitrogen compounds such as primary and secondary wastewater sludge. The anaerobic sludge contains diverse groups of anaerobic microorganisms that work together in association via a multistage processe consisting of the following biochemical reactions like hydrolysis, acidification, acetogenesis, and methanogenesis thereby converting the organic matter to biogas. The composition of biogas includes 70% methane (CH₄) and 30% carbon dioxide (CO₂) in addition to traces of other gases (e.g., H₂ and H₂S). The methane produced as a by-product can be used as an energy source. The potentiality of anaerobes in anaerobic based bioreactors for its maximum efficiency can be implemented in a variety of ways. The chapter discusses about the working principle, performance, treatment potential, and cost implication in the application of anaerobic treatment technology. The main bioprocess parameters such as pH, temperature, mixing, organic loading rate (OLR), and hydraulic retention time (HRT) have also been discussed in brief. Anaerobic treatment offers several benefits over aerobic treatment, including lower energy requirements, less chemicals, low capital, operation, and maintenance costs, and less sludge production. Hence, it saves money and the environment and overall simplifies the whole process.

Abstract

Solid Waste Management (SWM) has become a significant global concern, specifically for developing countries like India because of increasing population, rapid urbanization and high rate of municipal solid waste generation. Bio-composting and anaerobic digestion are the methods majorly used for solid waste management. Present chapter comprises detailed information on methods, microbiology involved and pros and cons of these methods to provide the detail information of solid waste management processes to the readers. Variable nature of substrates are available for bio-composting process. It includes sludge from effluent treatment plant (ETP), sewage treatment plant (STP) and bio-toilets, municipal solid waste, food waste and garden waste etc. Nutritional content, carbon /nitrogen (C/N) ratio of the substrate, available space and cost of the process are the main factors that affect selection method for waste management. Anaerobic digestion is the preferred method of solid waste management in comparison to other processes of composting due to methane generation as biogas and bioconversion of organic compounds to manure.

Abstract

Rise in global energy demand has led to an increase in consumption of fossil fuels. In recent years, there has been an increasing awareness about the consequences of pollution and global warming caused by burning of fossil fuels. This has led to an increased interest in the search for sustainable energy. Transportation sector is a major consumer of world’s energy resources. n-Butanol is one of the most promising alternative bio-fuels which has various advantages over other biofuels. The microbial n-butanol is produced by anaerobic conversion of the substrate to n-butyric acid and subsequently utilized to form n-butanol. The present chapter explores the scope of bacterial butanol production as need of the hour and its use as an alternative biofuel.

Abstract

Hydrogen synthesis from bioprocesses a good approach for generation clean of fuel for world's development. Throughout the ancient and current periods, most of the developmental activities are completed by consumption of non-renewable fossil fuel energy that which has resulted in multiple environmental issues or challenges (Climate change and pollution by toxic gases or byproducts formation) at global level. Biohydrogen synthesis from anaerobic bacterial fermentation could be a good effort for sustainable energy production without any toxic byproduct formation. For production of hydrogen, lignocellulosic material can be utilized as cheap raw substrates. This would help the farmers in providing surplus benefits to farmer for their agriculture residues that normally burnt and cause the serious air pollution. Utilization of agro-waste residues can help in development of sustainable biofuels for world energy need. Burning of agrowaste residues by farmer's can be discouraged via utilization as raw carbon substrates thereby reducing air pollution.

Abstract

Grazing animals have developed symbiotic relationship with anaerobic microorganisms, which survive in their rumen and help in the oxidation of complex molecules of feed containing lignocellulosic materials into volatile fatty acids. The consortium comprises anaerobic bacteria, fungi and protozoans. The rich microbial diversity of rumen remains constant after its establishment and does not get affected by intruding contaminants along with feed or water. The rumen contains a wide range of microbes such as Fibrobacter spp., Ruminococcus spp., Clostridium spp., Prevotella spp., Eubacterium spp., Methanobacterium spp., Treponema sp. Lachnospira sp., Bacterioides s pp., fungi: Anaeromyces s pp., Neocallimastix spp., and protozoa: Enoplastron sp., Eudiplodinium spp., Ostracodinium sp. They often have a variety of enzymes, glucanases, xylanase, glucuronidase, pectinase and amylase, etc. These enzymes inhabit the microbes and even break down complex molecules into simpler forms like; glucose and volatile fatty acids. The present chapter discusses on the role of microorganisms of rumen.

Abstract

Anaerobic sulfur compound reduction processes make use of sulfur, thiosulfate, trithionate, tetrathionate, and sulfite during the reduction process. Complete reduction of these sulfur compounds leads to production of H₂S. Isolation of sulfur compound reducers requires a suitable electron donor and one of the sulfur compound as a sole electron acceptor during the reduction process carried out in anaerobic conditions. Anaerobic sulfur, thiosulfate and tetrathionate reductases identified to date are molybdopterin binding oxidoreductases that extract out electron during the reduction process. The electron transport chain during the reduction process involves cytochromes and menaquinones. Dissimilatory sulfite reductases include conventional siroheme dissimilatory sulfite reductase and the nonconventional sulfite reductases including ASR sulfite reductase, F₄₂₀ dependent sulfite reductase and the MccA sulfite reductase. Anaerobic sulfur compound reduction process are almost ubiquitous in nature and are important part of the biogeochemical cycle. They occurs in aquatic systems, are found in extreme environments such as hydrothermal vents, acid mine drainage sites and are also found in important human and animal pathogens.

Abstract

Methane is the second most important green-house gas and has a major role in global warming. Aerobic oxidation of methane is known for more than 100 years. Anaerobic methane oxidation (AOM) was recently discovered before ~25 years, first in marine sediments. The first discovered AOM was found to be mediated by anaerobic methanotrophic archaea (ANME) in association with sulphate reducing bacteria (SRB) and termed as sulphate dependent anaerobic methane oxidation (S-DAMO). Three main groups of ANME are present which perform methane oxidation by reverse methanogenesis pathway. Later on, methane oxidation by using nitrate or nitrite as the electron acceptor was discovered from a freshwater sediment. N-DAMO or nitrate/ nitrite dependent AMO can be carried out by an archaeal or a bacterial member, respectively. Members of Ca. Methylomirabilis oxyfera are bacteria, and use nitrite as the electron acceptor and methane monooxygenase to carry out methane oxidation. Whereas, members of Ca. Methanoperedens nitroreducens are archaea, and use reverse methanogenesis coupled to nitrate reduction. Metals like FeIII or Mn IV can also be used as electron acceptors for AOM, a process recently discovered (M-DAMO). In this case, one archaeal partner and one bacterial partner could be involved, although more research is going in this area. S-DAMO is the main methane oxidation process in the marine sediments and accounts for the major methane oxidation in the marine sediments. In fresh water sediments, aerobic methane oxidation and processes like N-DAMO seem to play an important role.

Abstract

Microorganisms that produce methane as their metabolic end product are known as methanogens. Methanogens are prokaryotic, unicellular, obligate anaerobes having fastidious growth requirements making them difficult to isolate and preserve. They catalyse the terminal step in anaerobic breakdown of organic substances. Even though methanogenic archaea or methanogens show very limited metabolic diversity, they are one of the most phylogenetically and ecologically diverse group of Archaea. Methanogenic community varies greatly with respect to temperature. Methanogens have been reported from permanently frozen habitats like permafrost to hyperthermophilic environments such as hydrothermal vents. However, the metabolic and phylogenetic diversity of methanogens in these habitats vary greatly. Methanogens are the biocatalysts, having the ability to provide a solution to help solve energy crisis by producing methane as storable energy carrier. Methane being a flammable gas, can act as a clean and renewable source of energy. The biogenic methane gas thus produced may serve as an efficient alternative for fossil fuels in the future.

Abstract

The anaerobic fungi are one of the early organisms in evolution which are commonly found in the digestive tract of ruminating and non-ruminating animals, (including herbivores) deep sea and earth, dumping sites, etc. In animals, these are considered the primary colonizers of the plant biomass ingested by them. Still their taxonomy was unclear for a long period of time. However, with the help molecular techniques, they are now classified under a separate phylum Neocallimastigomycota. There are 38 species known so far belonging to 11 genera. These have been identified based on both morphological data (like thallus, rhizoids, flagella per zoospore, etc.) and phylogenetic analysis. There is a need to explore the undiscovered anaerobic fungi and look for their potential in industrial applications and solutions to the present environmental problems. It can be achieved by improving techniques of sampling, isolation, maintenance and long term preservation. Animals like herbivores do not have the ability to produce enzymes for degrading the plant biomass and anaerobic fungi help them by producing a range of extracellular enzymes. This ability of anaerobic fungi are of use to humans in bioenergy (biogas production) and biomass degradation (by producing cellulases). Recent advances in metagenomics coupled with new methods of cultivation are helping immensely to know the uncultivated anaerobic fungal populations from the animal gut. The present book chapter discusses the past and present of anaerobic fungi, lacunaes and need for more work on this group of fungi, It focuses on the progress in sampling, isolation and preservation techniques, simultaneously discussing the advances in the application these fungi in biotechnology.

Abstract

Anoxygenic phototrophic bacteria (APB) are having the genetic potential of converting radiant energy into chemical energy useful for growth and metabolic activities without evolving oxygen. They are physiologically, metabolically and phylogenetically versatile group of organism spread in five distinct phyla; Proteobacteria (purple bacteria), Chlorobi (green-sulfur bacteria), Chloroflexi (green non-sulfur bacteria), Fir micutes (heliobacteria) and Acidobacteria. Different group of APB harbors distinct photosynthetic pigments, carotenoids, and a photosynthetic reaction center. These group of bacteria succeeds in a natural environment with light availability and presence of anoxic conditions as the pigment, and the molecular oxygen inhibits bacteriochlorophyll synthesis whereas few APB can grow in hypooxic as well as in aerobic conditions. Calvin-Benson-Bassham (CBB) pathway, reverse tricarboxylic acid (rTCA) cycle, and hydroxypropionate cycle are reported pathways for carbon assimilation in APB to fix carbon dioxide. Photosynthesis occurs in either intracytoplasmic membrane (ICM) or membrane bound chlorosomes and in the cytoplasm for few APB. APB have a wide range of potential applications including removal of H₂S from wastewater and gas streams, hydrogen production, degradation of xenobiotic, toxic metals and radioisotopes, work as host for the production of challenging membrane proteins, source of carotenoids and terpenoids, single cell protein, extensive applications in agriculture and production of bioactive compounds with antimicrobial, antioxidant and anticancer activity. The chapter is focused on the diversity of different types of APB, habitats, their growth requirements, photosynthetic machinery and biotechnological applications of APB.

Abstract

Microbes are key ingredients of various ecosystems and backbone of modern biotechnology and industry. In addition to their cultivation, purification and characterization, preservation of microorganisms is equally important. Different preservation methods and protocols have been developed for long term preservation of microbes. Microbial Resource Centers (MRCs) are providing active services in the field of life sciences. National Centre for Microbial Resource (NCMR) at National center for Cell Science (NCCS), Pune is one of the MRCs. Unlike aerobes little work has been done in the area of cultivation and preservation of anaerobic microbes. In the previous chapter we have discussed the technicalities and problems of anaerobic cultivation. The aim of current chapter is to provide the recent overview of preservation of anaerobic microorganisms like methanogens, sulfate and metal reducers and the obligate anaerobes of clinical and industrial importance with fermentative mode of life style.

Abstract

Based on oxygen requirement, microorganisms have been classified into different groups, like facultative anaerobes, micro-aerophilic, aerotolerant and strict/obligate anaerobes. Obligate or strict anaerobes are the key components of anoxic environments and provide valuable ecosystem services like methanogenesis, sulphate reduction, metal reduction, degradation of pollutants etc. Apart from being valuable for the ecosystem, they are causative agents of human infections. They are the key players of human-gut microbiology, and can be used in bio-toilets, solid waste management, anaerobic digestion of waste, wastewater treatment processes and generation of waste to energy etc. Only few anaerobic microorganisms are pathogenic in nature. A mechanistic understanding about physiology and metabolism of anaerobic microorganisms is imperative for their industrial applications. Cultivation of these organisms is the first and very important step for the basic and applied study of anaerobes. Unlike cultivation of aerobic microorganisms anaerobic cultivation needs special care and facilities for successful handling of anaerobes. In the current chapter, We tried to incorporate the components and technicalities of anaerobic pre-reduced media preparation, cultivation and successful isolation of strict anaerobes. In addition, we also tried to discuss the different tools used for cultivation of anaerobes.

Harvesting: “Removal of entire plant or economic parts after maturity from the field" is called harvesting. It includes the operation of cutting, picking, plucking or digging or a combination of these for removing the useful part or economic part from the plants / crops. The portion of the stem that is left in the field after harvest is called as stubble. The economic product may be grain, seed, leaf, root or entire plant.

Harvest Index: (H.I): It is the ratio of the economic yield to the total biological yield expressed as percentage.

H.I = Economic yield / Biological yield x 100

Time of Harvesting: If the crop is harvested early, the produce contains high moisture and more immature ill filled and shriveled grains. High moisture leads to pest attack and reduction in germination percentage and impairs the grain quality.

Late harvesting results in shattering of grains, germination even before harvesting during rainy season and breakage during processing.

Growth is the development of a plant as a whole or of a specific organ. Besides the genetic factors, the environmental factors grouped as climatic factors and soil factors influence plant growth. The supply of mineral nutrient elements to the plants is discussed in this chapter.

A complete analysis of plants detects large number of elements. But only certain elements are essential. An element is said to be essential if the plant cannot complete its life cycle without it, and if the malady (deficiency) that develops in plants in its absence can be remedied only by that element.

Earlier 16 elements were considered as essential for plant growth. They are carbon, hydrogen, oxygen, nitrogen phosphorus, potassium, calcium, magnesium, sulphur, iron, manganese, zinc, copper, molybdenum, boron and chlorine. Recently, sodium, cobalt, vanadium, silica, selenium, gallium, aluminium and iodine are added to the above list. One or the other of these elements (recently added) has been found to be essential for a particular species of plants.

Carbon dioxide, water and molecular oxygen are the forms in which C., H and O are assimilated by plants. Others are taken up by plants from the soil. Nutrient uptake by plants accounts for about 10 percent of total dry weight of crops, the remaining percentage being water. The chemical symbol and the ionic forms in which the essential elements are absorbed by the plants are as follows.

Irrigation

Irrigation is defined as the artificial application of water to the soil for the purpose of crop production in supplement to rainfall and ground water contribution.

Time of Irrigation

The time schedule which indicates when irrigation water is to be applied and the quantity of water to be applied at that time is called irrigation schedule. There are several approaches for scheduling irrigation:

1. Soil moisture depletion approach based on the available soil moisture in the root zone.
2. Climatological approach based on the amount of water lost by evapotranspiration.
3. Combination approach based on soil moisture depletion and climatological approaches.
4. Critical stage approach which indicates the growth stages at which moisture stress leads to yield loss. These stages are known as critical period or moisture sensitive period. In cereals and millets panicle initiation and flowering stages are moisture sensitive stages. In pulses and oilseeds, flowering and pod development stages are critical stages. In sugarcane active tillering or formative stage is critical and in cotton boll development is the critical stage.

Weeds are the plants, which grow where they are not wanted. Jethro Tull (1731) coined the word weed. Weeds can also be referred to as plants out of place.

Definition

Weeds are unwanted and undesirable plant that interfere with utilization of land and water resources and thus, adversely affect crop production and human welfare.

In organic agriculture weeds are treated as childrens of the soil.

In the world 30,000 species of weeds have been listed, of which nearly 18,000 cause serious damage to agricultural production. Eighteen weeds are considered as the most serious in the world and about twenty six species have been listed as principal weeds in crop fields of India, and are listed in annexure V

Crop Stand Establishment

Good crop establishment is one of the most important features in better crop production. The better crop establishment is in turn expressed as optimum plant population in fields.

Plant population is the number of plants per unit area in a cropped field. It indicates the size of the area available for individual plant.

Optimum Plant Population

It is the number of plants required to produce maximum output or biomass per unit area. Any increase beyond this stage results in either no increase or reduction in biomass.

Crop geometry is the pattern of distribution of plant over the ground or the shape of the area available to the individual plant, in a crop field.