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The human body consists of trillions of cells and to be healthy it needs variety of foods and nutrients. The food around the globe includes a variety of spices which have many health benefits. It has been found that spices and vegetables in the diet are very important for living healthy. The traditional foods, nuts, seeds, wild fruits and vegetables which are used in the diet are grown in specific areas. Traditional food system plays a significant role towards maintaining the well-being and the health of people in any specific region.

According to Indian Philosophy (Bhat, 2012) the physical body is called Annamaya Kosha.A body, when well nourished grows well by absorbing the energies from the food consumed. Fasting is another aspect of traditional food system. It is meant to purify the mind and the body.

We all eat food because it provides the nutrients that are needed for the various functions of the body. Energy is required for growth and repair of tissues, to maintain body temperature and for physical activity. Energy comes from foods which are rich in carbohydrates, proteins and fat. This provides energy to the body from other nutrients and helps to keep the skin and nervous system healthy. They help towards the various biological activity in the human body. These nutrients are grouped into carbohydrates, proteins, lipids (fat), water, vitamins and minerals. These are used for growth, maintenance, repair and other needs of the body. Protective foods are which contain adequate amounts of vitamins, minerals and high-quality proteins which protect against the development of a deficiency disease. There are various chemical reactions taking place within each cell of a living organism. These provide energy for vital processes and for synthesizing new organic materials. This process is known as Metabolism. Living organisms get energy from the environment and use it for movement, growth, development and reproduction.

We get energy from food. We need energy for all the activities which we get by eating. The body structures as muscles, organs and bones are composed of the nutrients contained in food which are absorbed by the body.

Nutritional requirement of the major nutrients

Nutrients are the substances which are found in food and drive biological activity. They are essential for the human body. These are categorized into proteins, fats, carbohydrates (sugars, dietary fiber), vitamins and minerals (Sugishima, 2019). They perform the vital functions like building all parts of the body as muscle, bone, teeth and blood. Out of the 20 different kinds of amino acids that make up proteins nine are not synthesized in the body and are therefore called essential amino acids. These essential amino acids have to be supplemented through food. High-protein, low-carbohydrate diets have been found to be effective.Protein is an important component of every cell in the body. Large part of hair and nails are made up of proteins. The human body uses protein to build and repair the tissues, helps in making enzymes hormones and other body chemicals. Protein is an important building block of bones, muscles, cartilage, skin and blood.

To look into the nutritional security around the globe, FAO and WHO, have undertaken the analysis of policies. They have covered many issues which include; World Summit on Food Security, pillars of food security and availability, access, utilization, stability, effects of food insecurity, stunting and chronic nutritional deficiencies, depression, anxiety and sleep disorders. There are many challenges to achieve food security. These include global water crisis, land degradation, climate change, agricultural diseases, food versus fuel, politics, food sovereignty, food wastes, risks to food security, population growth, fossil fuel dependence, homogeneity in the global food supply, price setting, land use change, global catastrophic risks, agricultural subsidies and role towards children.

Indian Spices: These are dried, fragrant, aromatic or pungent vegetables or plant substances. They can be whole, broken or in ground forms. Primary function in food is seasoning rather than nutrition and which contributes to the flavour and piquancy in foods and beverages. These have been used as food additives widely since ancient times [http://www.imedpub.com/articles/herbal-medicines-possible-risks-andbenefits.pdf,https://www.ncbinlm.nih.gov/pmc/articles/PMC3170500/pdf/nihms307509.pdf). They also exert digestive stimulant action of food enhancing the taste. A few medicinal properties of spices are as being a tonic, carminative, stomachic, diuretic and antispasmodic (Aboaba et al., 2011; Achi, 2006 and Adefegha et al., 2012). This has led for pharmacological applications in the indigenous systems of medicine as digestive stimulants and to relieve digestive disorders and makes the food more palatable. In many countries around the world these are grown and reared for the purpose of trade and distribution. In the ancient times the spice merchants have been the most popular traders. India is well known for spices with a wide variety of recipes that are laced with them.

With increasing food production, availability and accessibility the global agro-industrial food system has improved.However, malnutrition, biodiversity loss and climate change are newer challenges. The best solution to this is the utilization of indigenous and traditional crops which will bring a transformative change in the food system. There is a need to look into the development of smallholder producers. The agro-industrial food system has improved the food supply and has made way for significant trade-offs with agro-biodiversity, dietary diversity, environmental sustainability and socio-economic stability mainly amongst the rural poor. Now is the time to mainstream the underutilized indigenous and traditional crops into the food system. This will provide opportunities to develop a sustainable and healthy food system.It will also help towards the societal goals which include employment creation, wellbeing and environmental sustainability.

Food fortification is the procedure in which micronutrients (essential trace elements and vitamins) are added to the food. As a public health policy fortification can be carried out by the food manufacturers or by the governments to help people in combatting dietary deficiencies within a population. Fortification can be done in food even if these nutrients are originally present or not. However, it improves the nutritional status of a population by overcoming the deficiencies of micronutrients. Deficiency of micronutrients is known as hidden hunger which is a serious health risk. Access to safe and nutritious food is a must.Due to the lack of consumption of a balanced diet, adequate micronutrients are not supplied to the body. Therefore, there is a considerable loss of nutrients during the processing of food. One of the strategies to address this problem is fortification of food.

For Indian foods

Food processing industries are the fastest growing in India. India is the largest producer of milk, bananas, mangoes, guavas, papaya, ginger and okra. It is the second largest producer of wheat, rice, fruits, vegetables, tea, sugarcane and cashew nut. It is the third largest producer of cereals, coconut, lettuce, chicory, nutmeg, mace, cardamom and pepper at the global level (Highlights of Agriculture Census, 2010-11, http://pib.nic.in/newsite/PrintRelease.aspx?relid=132799). Most part of the income is spent on foods. It is important to establish and nurture mutually beneficial relationships with global food processing, food retail and related supply chain organizations. This will in turn help in the realization of significant business growth opportunities in India, through newer technologies, innovations and ways of value additions. The geographical location of India helps in the export of items to other countries. It is connected to Europe, Middle East and Africa from the western coast and to Japan, Singapore, Thailand, Malaysia, Korea, Australia and New Zealand from the eastern coast. Food processing is a priority sector for the Indian Government, especially in recent times with “Make in India” initiative.The country is considered as one of the most favourable markets because of the easy and affordable credit and other fiscal incentives. The total consumption of food and beverages in India is US$ 369 billion which is expected to increase to US$1.142 trillion and the output in the food processing sector might increase to US$ 958 billion by 2025. This offers a vast market opportunity by the Indian food processing, food retail, transport, logistics and related infrastructure sectors to players in the food processing value chain. The market for plant and machinery in the food processing sector is estimated in the year 2024-25 to be USD 51.41 billion as compared to the current value of USD 17.3 billion (2016-17).

It has been found that at the household level the health of female members in any family suffers to a large extent. It could be encountered to low health care, poor housing or/and environmental conditions. Due to malnutrition it affects the health to such an extent that it gives rise to many diseases. For a sustainable nutritional status food and various aspects of health needs attention. Looking into that, nutrition is directly related to the health status. For food and nutrition security it is vital to see the availability, accessibility and utilization of food. The World Food Programme (WFP) developed the Vulnerability Analysis and Mapping (VAM) project to analyse the vulnerability to food insecurity of target populations. A prominent part of VAM is related to food access. The demographic and Health Survey (DHS), funded by USAID, provides health data for many countries to help them design their national policy. FAO has developed the Global Information Early Warning System (GIEWS), which collects data related to temporary food insecurity. Under the leadership of WHO, several health surveillance systems have been developed and implemented to monitor the epidemiology of various forms of malnutrition and of selected diseases. At the meso or sub-national level, food market surveys provide data on the availability of food. Agricultural production surveys, intra-household food frequency interviews, immunization surveys and anthropometric surveys of children under five can be used to assess the availability, accessibility and utilization of food and its stability at micro level. Most common Food and Nutrition Security (FNS) indicators at different social and administrative levels depends on the supply and demand. To determine the national situation of food availability data on the production of different food commodities, fertility rate and the trends in internal population needs to be seen. Food prices and per capita food consumption are indicators for national food accessibility. The rates of stunting, wasting and underweight in children, low Body Mass Index (BMI) in adults and low birth weight are FNS impact indicators that designate the extent to which food is adequately being used, utilized and converted into a satisfactory national nutrition situation. Fluctuations and shortages of food availability or accessibility in food prices make the national FNS unstable. Sensitive indicators for accessibility of food are the prices in the market. The sewage disposal and diarrheal diseases (DD) rates affect food utilization.A temporal food and nutrition insecurity arises due to pre and post harvest food availability and accessibility along with low BMI.If the food is in shortage leading to the consumption of more wild foods indicates reduced food availability at household level. Also if the number of meals per day goes down and unemployment increases it indicates low food accessibility.Malnutrition indicators like wasting, goitre or anaemia among the household members show reduced food utilization at micro level. Finally, changes in pre-harvest food consumption practices are good indicators for temporal food insecurity.

A number of innovations have taken place towards ready to eat instant food mixes of traditional origin. These have helped people to eat traditional food in which ever part of the world they go.

MTR Company

In India the best example is of MTR company which manufactures a range of packaged foods which includes breakfast mixes, ready to eat meals, masalas and spices, snacks and beverages. Snacks, such as kodubale, khara boondi and masala groundnut are very popular as they are ready to eat packets and contain healthy food with less oil. The different spices used for mixes are procured from famous countries which give the perfect taste and avoid rancidity.As a summer launch, milkshake with canned chikoo, banana and cold filter coffee are available. MTR Foods Pvt. Ltd. is a subsidiary of Norwegian conglomerate Orkla and is an acronym of Mavalli Tiffin Rooms. According to the company, India is on the verge of explosive growth in packaged instant foods. MTR has an aim to target a market of Rs 30, 000 crore with their products of traditional meals, breakfast, snacks and desserts. The Nielsen India study has shown that in 2020, the number of consumers in this category will be 2.7 times than the current base.

Mother’s Recipe is a brand which make traditional pickles in bottles with a distribution network to 20 states in India and exporting the products globally. The manufacturing is done in-house and the raw materials are procured seasonally in large quantities. After cleaning they are cut according to the recipe. Each variety of mango pickle has its own cutting process. Some are automatically cut, while others need manual work. The use of right oils, spices roasted inhouse, and marination of the pickles according to the practices of the particular region allow many consumers to relish them. Bottling and packaging are done only when the orders come.

Benjamin et al., (2016) have focused on the small-scale food processing enterprises (SSFPEs) as one of the important measures for national development and addressing food security challenges, particularly in Nigeria. The authors have explained the need for food processing as there has been tremendous food losses and wastages in the country. Enhancing the food processing and productivity for mechanization of food processing unit operations, development of new and existing technologies, design and development of machinery, systems for processing and preservation of different agricultural produce of high target have been undertaken. SSFPEs have played an important role in the economy of a developing country, particularly in terms of employment creation, income generation, post-harvest losses reduction, food preservation, value addition, improvement of food safety, nutritional quality, increase in shelf-life of a product and to act as training grounds for entrepreneurs before they invest in large scale enterprises. SSFPE’s around the world and especially in Nigeria are faced with significant challenges that compromise their ability to function and contribute optimally to the economy. Financial constraints and lack of management skills are the major constraints. It is important that governments and non-governmental organizations must encourage and facilitate the development of SSFPE’s. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO or GAIN in preference to others of a similar nature that are not mentioned. FAO’s Nutrition and Food Systems Division (ESN), in collaboration with the Global Alliance for Improved Nutrition (GAIN) 2018,

A sustainable and healthy food system is one which can provide food and nutrition security for all, in an economical way which is socially and environmentally sound for future generations. Underutilized indigenous and traditional crops can support and strengthen the existing food system, as they are in particular economical and friendly with the environment. Several underutilized indigenous and traditional crops are nutrient dense and adapted to marginal conditions, suggesting that they could be used to champion sustainable and resilient agriculture and food systems for smallholder farmers residing in these environments. The mainstreaming of underutilized indigenous and traditional crops and foods should be recognized for their attributes to make them desirable and to conserve them. In this regard, the fact that value chains for underutilized indigenous and traditional crops are poorly developed at present has created many opportunities to diversify the current food systems. This will create a new employment, market and distribution opportunities.It will also help to combat poverty. It will be if the smallholder farmers and women in rural areas are given the opportunity to utilize underutilized indigenous and traditional crops and re-enter the manistream system. A significant role which is played by the women for the production and conservation of underutilized indigenous and traditional crops offers opportunities for women empowerment through their inclusion in the food system. Promotion of gender equality and empowerment of women is directly linked for strengthening the sustainable food systems that can fight hunger and malnutrition and improve the lives and livelihoods of rural populations. The mainstreaming of underutilized indigenous and traditional crops into the food system would support women to diversify in a sustainable way, feed their own households and to provide nutritious food into the local markets. This will also help in addressing, the Sustainable

Sustainable agriculture’s benefit to farm and community economies is grounded in four well-established economic development principles and a fifth, concern for the community:

Lower input farming system (LIFS)

Lower input farming system means reduced production levels with larger area of land used in order to maintain the same revenue; or reduced dependency on external inputs with similar production structure but improved valorization of the product through transformation and or direct marketing, cutting the length of the production chain is a sustainability concept (produce and consume locally). LIFS are seeking optimization of on-farm resources, minimization of off-farm resources use. It also leads to mixed farming system, characterized by animal valorization of vegetal production on farm and organic manure restitution to farm soil from farm husbandry. Mixed character of farming system optimally combines annual and perennial crops and animal production on the same farm. Lower input farming also maintains ecological infrastructures (at least 5% in integrated farming)-which prove to be very beneficial for biodiversity – can provide shelter for organisms providing biological control and also be a source of raw material (wood) for producing on-farm energy.

Introduction

Nature is dynamic; it causes inheritable changes in all living organisms. For thousands of years, farmer around the world have been selecting and conserving varieties of different crop plants that they cultivated. This process has generated a rich wealth of varieties in each crop plant, seen to be most abundant in countries near the equator and India is no exception. In the world there are Mega centers of biodiversity of which aware present in India, this is because in India, the different soils and agro-climatic situations are present, so Indian farmers grow a large number of crops. Generation of Indian farmers, with their continued selection and conservation, has created a rich wealth of varieties in many crops. Therefore India is the original home of many crops such as rice, little and kodo millets, red gram, moth bean, jute, pepper, cardamom, many vegetables and fruit species. These plants were identified from the wild, selected and cultivated by Indian farmers over hundreds of years. The present wealth of varieties in India includes both crops that originated in the country and those that were introduced from the other countries during the distant and recent paste are soybean, sunflower, oil palm and kiwi fruit.

The Indian economy is predominantly rural and agriculture oriented. In agriculture, 85% of the holdings are less than two hectares and the declining trend in the average size of the farmer holdings, poses a serious problem. Majority of them are dry lands, which depend on erratic monsoon rains. The rest of the area is cultivated with supplemental irrigation. The farmers concentrate mainly on crop production, which is invariably subjected to a high degree of uncertainly income and employment.

In India the cultivable land is 143.8 million hectares and there is very little possibility of extending it further. Therefore, to meet the requirement of food grains for increasing population, the only option open is through time and effective space utilization in agriculture. The time concept relates to increasing the intensity of cropping under assured irrigated conditions, whereas space utilization pertains to building up of vertical dimension through multi-tier cropping and farming system approach. Thus by making use of these time and space concept either in irrigated or in rained areas, the productivity per unit area per unit time can be substantially enhanced. Therefore the only way to increase an agricultural production in the small/marginal units of farming is to increase the productivity per unit time and area. This may be achieved of quicker maturing varieties with equal yields or by improving techniques of culture, fertilizer use, weed and pest control.

Introduction

Solid waste management is a worldwide problem and it is becoming more and more complicated day by day due to rise in population, industrialization and changes in our life style. Large quantities of organic wastes are produced from agricultural production and farming systems which include animal manures, sewage biosolids, food wastes, and industrial organic wastes. Globally, these wastes have the potential of increasing soil and water pollution as because they are currently disposed of by land-spreading, incineration, or into landfills. As much as 50%-60% of the total wastes that are disposed into landfills are organic wastes. If these were turned into materials useful in farming system, there would be great savings in primary plant nutrients and metabolic energy.

Vermicomposting has been arising as an innovative eco-technology for the method by which compost or mixed manure of organic origin or conversion of various types of waste is prepared by the use of earthworms. It is a controlled degradation (non-thermophilic, boioxidative process) of the organic wastes for the consumption of earthworms, helps in the recycling of food wastes, reduces the waste bulk density and the final product may contain hormone-like substance which accelerates the plant growth. Vermicompost is humus like, finely granulated and stabilized material which can be used as a soil conditioner to reintegrate the organic matter to the agricultural soils. Industrial wastes remain largely unutilized and often cause environmental problems like ground and surface water pollution, foul odours, occupying vast land areas etc. Non-toxic and organic industrial wastes could be potential raw material for vermitechnology. In the last two decades, vermin-technology has been applied for the management of industrial wastes and sludges and to convert them into vermicompost for land restoration practices. The success of the process depends upon several process parameters like quality of raw material, pH, temperature, moisture, aeration etc., type of vermicomposting system and earthworm species used. Vermicomposting and vermiculture are two interlinked and interdependent processes where vermiculture can be done in the presence of decomposable waste organic matter

Introduction

Cyanobacteria are often called “blue-green algae”, this name is convenient for talking about organisms in water that make their own food, but does not ref lect any relationship between the cyanobacteria and other organisms called algae. Cyanobacteria are relatives to bacteria, not eukaryotes, and it is only the chloroplast in eukaryotic algae to which cyanobacteria are related. Some cyanobacteria are aquatic and photosynthetic, that is, they live in water, and can manufacture their own food. They are quite small and usually unicellular, though they often grow in colonies large enough to see. In fact, it may surprise you then to know that the cyanobacteria are still around; they are one of the largest and most important groups of bacteria on earth (Berry et al., 2008). The great contribution of cyanobacteria is the origin of plants chloroplast with which plants make food for themselves is actually a cyanobacterium living within the plant’s cells. Sometime in the late Proterozoic or in the early Cambrian, cyanobacteria began to take up residence within certain eukaryote cells, making food for the eukaryote host in return for a home. This event is known as endosymbiosis, and is also the origin of eukaryotic mitochondrion (Issa et al., 2002).

Introduction

Plant growth in agricultural soils is inf luenced by a myriad of abiotic and biotic factors. As a routine practice growers normally use physical and chemical approaches to manage the soil environment to improve crop yields while the application of microbial products for this purpose is less common. An exception to this is the use of rhizobial inoculants for legumes to ensure efficient nitrogen fixation; a practice that has been occurring in North America for over 100 years (Smith, 1997). The region around the root, the rhizosphere, is relatively rich in nutrients, in expense of as much as 40% of plant photosynthates from the roots (Lynch and Whipps, 1991). Consequently, the rhizosphere supports large and active microbial populations capable of exerting beneficial, neutral, or detrimental effects on plant growth. The importance of rhizosphere microbial populations for maintenance of root health, nutrient uptake, and tolerance of environmental stress is now recognized (Bowen and Rovira, 1999; Cook, 2002). These beneficial microorganisms can be a significant component of management practices to achieve the attainable yield for in other words a crop yield limited only by the natural physical environment of the crop and its innate genetic potential (Cook, 2002).

The prospect of manipulating crop rhizosphere microbial populations by inoculation of beneficial bacteria to increase plant growth has shown considerable promise in laboratory and greenhouse studies however, responses have been variable in the field (Bowen and Rovira, 1999). The potential environmental benefits of this approach, leading to a reduction in the use of agricultural chemicals are fitting the sustainable management practices. Realizing the biological interactions occurring in the rhizosphere, recent progress are in need to fulfill the practical requirements of inoculant formulation and timely delivery which would increase the technology’s reliability in the field and facilitate its commercial development.

Introduction

Water is a vital component of agricultural production. It is essential to maximise both yield and quality. Water has to be applied in the right amounts at the right time in order to achieve the right crop result. At the same time, the application of water should avoid waste of a valuable resource and be in sympathy with the environment as a whole. Understanding, measuring and assessing how water f lows around the farm, and recognising how farming practices affect f lows, will help farmers to manage water efficiently and reduce pollution risks. Land management and advanced technologies can help maximise the “crop per drop” that farmers produce worldwide. Water used in irrigation accounts for 90% of agricultural water demand. Improving irrigation systems is therefore crucial to making contributions to water savings in agriculture. In any agricultural production system the promotion of good agricultural practices and product stewardship is fundamental for sustainable agriculture. Industry is part of various multi stakeholder partnership initiatives that support efforts to protect water quality. These include reducing soil erosion, avoiding pesticide run-off and maintaining wildlife habitats as part of a holistic farm or land management approach.

Is it possible to feed a world population projected to reach 8.5 billion by 2030, 9.7 billion by 2050 and exceed 11 billion in 2100? India expected to surpass China as the most populous country in the world within seven years (UN report July 2015). Besides that there is an immense decline in yield and quality over the past three decades may be at the point of diminishing returns (Bouis 1993; Cassman et al. 1995; Flinn and De Datta 1984). Furthermore, the soil is partially under tremendous pressure to sustain yield and production. The excessive and exhaustive agriculture practices have not only declined the soil quality but it’s also reported for different human and animal health issues. Thus, keeping pace with population growth and health safety appropriate soil management practices must be addressed. Now burgeoning population load, declining yield, soil health diminution, and effect on human and animal health arises the opportunity for sustainable soil management to cater the problem at the right time. Figure 1 clearly indicates the tremendous load on soil and subsequent results. Burgeoning increase in population and a load of food production intensification, sustainable soil management will become increasingly important in future. Soil being the powerhouse of the mineral nutrients also retains most living organisms within it. The appropriate soil management practices ensure the critical level of mineral elements which finally come into the human body.

Biodiversity is a magnificent contribution of nature on our planet. The great variety of life forms on earth has catered for man’s needs over thousands of years. This diversity of living creatures which forms a support system has been used by each civilization for its growth and development. Those that used this “bounty of nature” carefully and sustainably survived. Those that overused or misused it disintegrated. The attempt to classify and categorize the variability existing in nature for over a century has led to an understanding of its organization into communities of plants and animals. This information has helped in utilizing the earth’s biological wealth for the benefit of humanity and has been integral to the process of development. This includes better health care, better crops and the use of these life forms a raw material for industrial growth which has led to a higher standard of living for the developed world. However, this has also produced the modern consumerist society, which has had a negative effect on the diversity of biological resources upon which it is based. The diversity of life on earth is so great that if we use it sustainably we can go on developing new products from biodiversity for many generations. This can only happen if we manage biodiversity as a precious resource and prevent the extinction of species.

The sustainable management of biodiversity is one of the most important challenges facing humanity. Biological diversity, abbreviated to biodiversity, refers to the variety of life forms at all levels of organization, from the molecular to the landscape level. These are the legacy of billions of years of evolution, shaped by natural processes and increasingly, by the activities of humans. Losing biodiversity has eroded the basis for social and ecological resilience, which has resulted in reducing the capacity for adaptive responses in a rapidly changing world. However, human activities still continue to have a large impact on the environment and on biodiversity. Agricultural, urban and infrastructural developments and climate change has exacerbated biodiversity loss. As a result, ecosystem functions and services are affected with serious consequences. The Sustainable Development Goal should be devoted to “protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss”. It is high time to realize the linkages between the severity of global biodiversity loss and degradation of ecosystems and the negative impact that this situation have resulted on food security, nutrition, access to water, health of the rural poor and people worldwide.

Agroforestry: At a Glance

Agroforestry as a landuse system is gaining wide importance and acceptance in the current global scenario to mitigate global climatic conditions. It is a highly efficient system of sustenance for the rural population with ample livelihood opportunities. The benefits from agroforestry is immense for socio-economic as well as in ecological perspective. From the vivid ecosystem services like climate regulation, carbon sequestration, soil productivity and biodiversity conservation to food security and sustainable livelihood enhancement, agroforestry envisages immense services. The implication of the agroforestry system and practice varies from area to area. Traditional agroforestry can be modified by implementing different species combinations suitable for vivid regions thus enhancing the long term productivity. An important specification of agroforestry is with a minimal labour input maximum production and utilization of resource could be attained. National Agroforestry policy, implemented is a big step forward for new agroforestry initiatives in the country. Conduction of region specific agroforestry studies and policy implementations with involvement of rural populations will be an effective breakthrough approach for a sustainable future.

Introduction

During the past 60 years, conventional agriculture has become increasingly dependent upon petroleum-based. Chcmically-synthesized fertilizers and pesticides for crop protection and to supply plant nutrients. Certainly, these energy intensive technologies have contributed greatly to this Nation’s agricultural productivity. However, sharply escalating production costs associated with the increasing cost and uncertain availability of energy i.e., fuel and fertilizers, have generated considerable interest in less expensive and more environmentally compatible production alternatives such as organic farming (USDA, 1980). The apparent decline in soil productivity throughout the world from excessive soil erosion, nutrient runoff and loss of soil organic matter; the impairment of environmental quality from sedimentation and pollution of natural waters by agricultural chemicals and the potential hazards to human and animal health and food safety from heavy use of pesticides, have also stimulated interest in organic farming systems of food production.

Use of organic wastes and residues in agriculture

Most countries have traditionally utilized various kinds of organic materials to maintain or improve the fertility, and productivity of their agricultural soils. However, several decades ago organic recycling practices were largely replaced with chemical fertilizers which were applied to high yielding cereal grains that responded best to a high level of fertility and adequate moisture, including irrigation. Soil cultivation was also intensified to improve weed control and seedbed conditions. Consequently, the importance of organic matter to crop production received less emphasis, and its proper use in soil management was neglected, or even forgotten. As a result of this and failure to implement effective soil conservation practices, the agricultural soils in a number of developed and developing countries have undergone serious degradation and decline in productivity.

Introduction

Chemical pesticides play an important role in plant protection in India and most of the developing countries of the world. These synthetic organic insecticides provide spectacular control of insects. Chemical control is one of the effective and quicker methods in reducing pest population. However, over reliance and injudicious use of pesticides resulted in a series of problems in the agricultural ecosystem mainly, the development of resistance in insects to insecticides, pest resurgence, outbreak of secondary pests into primary nature, environmental contamination and residue hazards, destruction of natural enemies of insect pests etc. All these problems aggravate the pest problem in agricultural crops. Thus, the importance of eco-friendly pest management techniques is being realized more and more in the recent past. The modern concept of pest management is based on ecological principles and involves the integration of different control tactics into a pest management system. This is not altogether a new concept. It was practiced before the advent of modern chemicals. Integrated Pest Management is an ecological approach in which utilization of all available techniques of pest control to reduce and maintain the pest population at levels below economic injury level. The UN’s Food and Agriculture Organisation defines IPM as the careful consideration of all available pest control techniques and subsequent integration of appropriate measures that discourage the development of pest populations and keep pesticides and other interventions to levels that are economically justified and reduce or minimize risks to human health and the environment. IPM emphasizes the growth of a healthy crop with the least possible disruption to agro-ecosystems and encourages natural pest control mechanisms. A well-defined Integrated Pest Management (IPM) is a program that should be based on prevention, monitoring, and control which offers the opportunity to eliminate or drastically reduce the use of pesticides, and to minimize the toxicity of and exposure to any products which are used. So, IPM is an eco-friendly approach which encompasses cultural, mechanical, biological and need based chemical control measures.

Introduction to sustainable disease management

Plants and pathogens are involved in ongoing interactions over millennia that have been modified by coevolutionary processes to limit the spatial extent and temporal duration of disease epidemics (Zhan et al. 2015). These interactions are disrupted by modern agricultural practices, such as intensified monoculture using high yielding varieties. Agricultural intensification and monoculture coupled with globalization disrupt the coevolutionary dynamics of plant-pathogen interactions which escalating the evolutionary rate of pathogens and increasing the risk of plant disease epidemics. These activities, when supplemented with high resource inputs, create unique conditions which is conducive to widespread plant disease epidemics and rapid evolution of pathogen. Disease management requires a significant shift to include ecoevolutionary principles in the design of adaptive disease management strategy for minimizing the evolutionary potential of plant pathogens by reducing their genetic variation, stabilizing their evolutionary dynamics, and preventing dissemination of pathogen variants carrying new infectivity or resistance to pesticides (Zhan et al. 2014). As environmental and ecological issues continue to impact on agriculture, all the crop-specific and regional-specific, Good Agricultural Practices (GAP) to be developed for crop production, must be economically feasible, ecologically sound, environmentally safe and socially acceptable. Numerous non-chemical methods for management of crop diseases such as pathogen-free seeds, disease resistance, crop rotation, plant extracts, organic amendments and biological control agents are considered less harmful than chemical pesticides and therefore, offer great potential for application in modern agriculture (Marshal et al. 2008). No single method can provide satisfactory management of crop diseases. Integration of all the effective and eco-friendly measures in accordance with the dynamics of the agro-ecosystem management would be the best strategy for efficient plant disease management.

Introduction

Weeds are the most costly category of agricultural pests, causing more yield losses and added labor costs than either insect pests or crop disease. Weeds are a constant fact of life in annual row crops, vegetables, and other horticultural crops. In India, the manual method of weed control is quite popular and effective. The usage of herbicides in India and elsewhere in the world is increasing due to possible benefits to farmers. At the same time, the continuous use of herbicides of the same weed shift, herbicide resistance in weeds and environmental pollutions. Application of herbicides also kills species of bacteria, fungi and protozoa thereby upsetting the balance of pathogens and beneficial micro organisms. The complexity of these situations has resulted in a need to develop a holistic sustainable eco-friendly weed management programme throughout the farming period (Gnanavel and Natarajan, 2014). Sustainable development of agriculture is concerned about the conservation of land, water, plant and animal genetic resources, is environmentally non-degrading, technically appropriate, economically viable and socially acceptable. Sustainable weed management is the use of weed control methods that are socially acceptable, environmentally benign and cost-effective.

Introduction to sustainable livestock

Sustainable development has been defined by FAO as “the management and conservation of the natural resource base, and the orientation of technological and institutional change in such a manner as to ensure the attainment and continued satisfaction of human needs for present and future generations. In other words, the development that meets up the needs of the present without compromising the ability of future generations to meet their own needs. Such sustainable development (in the agriculture, forestry and fisheries sectors) conserves land, water, plant and animal genetic resources, is environmentally non-degrading, technically appropriate, economically viable and socially acceptable”. (FAO Council, 1989). Hence, sustainable livestock farming is “the efficient production of safe, high quality products, in a way that protects and improves the natural environment, the social and economic conditions of farmers, their employees and local communities, and safeguards the health and welfare of all farmed species”.

Introduction

With India’s population to catapult to a gigantic figure of 1.63 billion by 2050, it rests upon the shoulders of the country’s dwindling land resources to cater to the food demand to the surging human race with an eco-friendly manner. This requires a mammoth effort from the food producing machinery of the country-an effort which has to be inclusive of the technological innovation and extension in this field and to the fullest possible extent. Coping with the short-run challenges to food security posed by food price volatility is indeed a daunting task. But the serious concern is the long-term challenges of avoiding a perpetual food crisis under conditions of global warming. The decline of contributions of Indian Agriculture to the National GDP and an apparent stagnation of the growth rate in agriculture, non remunerative agricultural system, ever increasing population pressure, shrinking land resources, global warming and climate change, indiscriminate use of agricultural inputs, over exploitation of natural resource base and environmental quality have made the situation more vulnerable towards food security. In this backdrop, agricultural knowledge and technology accumulation, transfer, application, and diffusion are key to sustainable development and food security in an eco-friendly manner. The knowledge and technology revolution is critically different from the past industrial revolution in that it is based upon a shift of wealth creating assets from physical things to intangible resources based on knowledge and technologies. Thus, effective management and transfer of knowledge and technologies are believed to be the most critical capability of individuals, organizations, and nations in the globalized 21st knowledge society. Extension could play a pivotal role in fostering sustainability through its educational programs but there has been a growing realization that traditional extension models have not been sufficiently effective in promoting socialization of sustainable agricultural practices. Since sustainable agriculture is a knowledge-intensive system, it requires a new kind of knowledge, which differs from other forms on the basis of conventional agricultural practices. In fact, conventional extension system cannot accomplish sustainability in agriculture; because today’s agricultural extension must consider environmental implications, social issues, and overall economic growth within the agriculture sector. In such a situation, the present conceptual discussion shall be envisaging the dictum and destiny of evolving extension approaches by cherishing a clear focus on extension management perspectives towards sustainable development and environment protection and management so as to the well established extension approaches can be restructured and applied in the niche of extension management towards sustainability.

Our production systems are at a pivotal stage in terms of meeting consumer demand for affordable food while improving sustainability. Current intensive crop production practices designed to maximize yield have created an unstable, fragile, and non-sustainable production system. Such systems are prone to reduced soil quality, frequent insect and disease resurgence, emergence of resistant weed species, reduced food quality, and detrimental effects on the health and well-being of our communities. With increasing awareness among consumers of produce quality, nutritional value, methods of crop production and effects of production techniques on the environment, there has been a strong move to improve the quality of our production systems. Grower response to this change has been supportive. Growers have shown interest in developing resilient and stable production systems through the adoption of production practices that enhance soil health, crop productivity, and improve long-term farm sustainability and profitability. Such practices emphasize the use of natural processes within farming systems, often called ‘ecologically sound’ practices which build resilience through synergies and complementarities within the field, the farm, and across our landscape and communities.

Sustainable horticulture is nothing but a contemporary approach to horticulture that emphasizes organic/natural approaches and allows an integrated meshing of ideas with synthesized chemicals used sparingly or relegated to the “last resort.” High Tech & Low Tech are encouraged to create a long-term viable result. Short-Term techniques that impact the environment negatively and thwart the biodynamic continuum are rejected.

Soil represents a medium or substrate in which numerous microorganisms live and bring about a great variety of processes that are responsible for the continuation of the cycle of life in nature. The numerous living forms which spend their life in the soil, ranging from submicroscopic forms to the lower animal forms. With the growing recognition of the numerous processes carried out by the microorganisms in the soil there gradually emerged a branch of microbiology, which came to known as soil microbiology. It is a branch of soil science concerned with soil-inhabiting microorganisms and their functions and activities.

Since soil microbiology concerns soil microorganisms and their processes it is closely associated with soil biochemistry. Medical bacteriologists are interested in the soil as a medium for the growth and survival of disease-producing organisms. Agricultural chemists are also interested in the soil processes that result from the activities of microorganisms. General bacteriologists, zoologists, botanists are interested in a certain special group of organisms found in the soil. Recently, soil microbiology has expanded to include the study of the role of soil microorganisms in genetic engineering, in the biological control of pests and diseases, the degradation of pollutants, production and destruction of radioactive gases and its transfer. Thus microbial participation in several important processes emphasizes that soil microbiology has become a global science.

History of Soil Microbiology

There is enough evidence in the literature to believe that microorganisms were the earliest of the living things that existed on this planet. Man depends on crop plants for his existence and crop plants in turn depend on soil and soil microorganisms for their nutrition. Scientists from the beginning studied the microorganisms from water, air, soil, etc. and recognized the role of microorganisms in natural processes and realized the importance of soil microorganisms in the growth and development of plants.Thus, microorganisms have been playing a significant role long before they were discovered by man. Today, the soil is considered to be the main source of scavenging the organic wastes through microbial action and is also a rich storehouse for industrial microflora of great economic importance.

Unlike soil science whose origin can be traced back to Roman and Aryan times, soil microbiology emerges as a distinct branch of soil science during the first half of the 19^th century. Some of the notable contributions made by several scientists in the field of soil microbiology are highlighted in the following paragraphs.

Anton Von Leeuwenhoek (1673) discovered and described microorganisms through his own made first simple microscope with a magnification of 200 to 300 times. He observed minute, moving objects which he called “animalcules” (small animals) which are now known as protozoa, fungi, and bacteria. He for the first time made the authentic drawings of microorganisms (protozoa, bacteria, fungi).

Soil is a bioorganic - mineral complex of the loose surface layer of the earth’s crust. Soil microbiology is the science that deals with the millions of microscopic forms of life found in the soil. It is stated that one hectare - foot (one hectare to a depth of 30cm) contains 2 to 10 metric tons of living microorganisms. Soil microorganisms are in a constant struggle for existence and are believed to be in a state of dynamic equilibrium. Without microorganisms, the soil would be an inactive geological mass incapable of supporting plant life and without plant life, animal life would not be possible. This soil population consists mainly of bacteria, fungi, actinobacteria, algae, and protozoa. The soil ecosystem includes these microbial groups as well as the inorganic and organic constituents of a given site. The collections of cells represented in the community are considered as distinct populations. All the inhabitants of the particular locality make up the community.

Types of Microorganisms in Soil

Living organisms both plants and animals, constitute an important component of soil. The pioneering investigations of several early microbiologists showed for the first time that the soil was not an inert static material but a medium pulsating with life. The soil is now believed to be a dynamic or rather a living system, containing a dynamic population of organisms/microorganisms. Cultivated soil has relatively more population of microorganisms than the fallow land, and the soils rich in organic matter contain much more population than sandy and eroded soils. Microbes in the soil are important to us in maintaining soil fertility and productivity, cycling of nutrient elements in the biosphere, and sources of industrial products such as enzymes, antibiotics, vitamins, hormones, organic acids, etc. At the same time certain soil microbes are the causal agents of human and plant diseases.

Several environmental conditions affect the density and composition of the microflora and frequently alter their activities in soil. Primary factors include soil moisture, aeration, temperature, pH, organic matter and inorganic fertilizers. Lesser variables are the secondary factors, which include crop rotation, season, soil depth, cultivation practices etc.

I. Primary Factors

Soil moisture

Soil moisture is one of the important factors influencing the microbial population. Water is the major component of protoplasm; an adequate supply must be available for vegetative development of organisms. But, when it becomes excessive, proliferation is suppressed due to limitation in gaseous exchange and lowers the availability of O₂ supply creating an anaerobic environment. Most of the organisms prefer a moisture percentage between 20 and 60 per cent. Many bacteria and fungi can adjust themselves to different moisture conditions. Under dry conditions, the bacteria may form spores that can resist the drought conditions. The fungi may sporulate or form chlamydospores to tide over adverse conditions. The protozoans also may form cysts and can survive under dry conditions. Actinobacteria are the chief group of organisms that prefer dry conditions. It is believed that the concentration of nutrients is diluted and also the aeration is very much limited at moisture and hence only the anaerobic and microaerophilic organisms can develop better.

Soil microorganisms (Flora & Fauna) are just like higher plants depends entirely on soil for their nutrition, growth and activity. The major soil factors which influence the microbial population, distribution and their activity in the soil

Soil microbial biomass is an important parameter linking the plants to soil. It comprises about 2-3% of the total organic carbon in the soil and recognized as an important source of nutrients to plants. It is also a dynamic component of the soil associated with several functional properties of the terrestrial ecosystem. It represents the fraction of the soil responsible for the energy and nutrient cycling and the regulation of organic matter transformation.

Microbial biomass is a small but labile and living component of soil organic matter that is involved in most bio-geo-chemical processes in the terrestrial ecosystem. It interacts with crop productivity by regulating nutrient availability as a source; determining soil carbon storage- sink; and contributing to the atmospheric CO₂ from respiration. Thus it is the main agent that controls the flow of carbon and cycling of nutrient elements.

There is a close relationship between soil microbial biomass, decomposition rate, and nitrogen mineralization. It is also positively correlated with grain yield in organic farming and also contributes to soil structure and stabilization. Thus, there is the immense importance of microbial biomass in soil fertility as well as in agriculture.

Soil fertility depends on the physical, chemical, and biological properties of the soil. Among the biological properties, soil enzymes are used as an index of soil fertility. Soil enzymes respond to changes in soil management faster in comparison to other soil variables, and also catalyze the reactions necessary for the life processes of microorganisms in soils. The biochemical reactions are brought about by the catalytic action of enzymes. Soil enzymes include amylase, phosphatase, urease, cellulase, protease, glycosidase, and arylsulfatase. They play a role in organic material decomposition, the transformation of organic matter, nutrient cycling, nitrogen fixation, detoxification of pesticides, xenobiotics, etc., and thus regulate the ecosystem.

Depending on their location, enzymes can be extracellular or intracellular. Intracellular enzymes are found in the cell’s cytoplasm or bound to the cell walls of living and metabolically active cells. Extracellular enzymes released into the soil and are “permanently” immobilized on clay and humic colloids via ionic interactions, covalent bonds, hydrogen bonding, entrapment, and other mechanisms. There are two kinds of soil enzymes.

All organisms require the six elements CHNOPS in sizable quantities, and that these minerals may occur in different forms. Depending on whether the local environment is aerobic or anaerobic, the exact chemical form of any of these elements may change quickly and drastically. Example: : If the soil becomes waterlogged and anaerobic, sulfate will be converted into hydrogen sulfide and nitrate into nitrogen gas or ammonia (via anaerobic respiration). As the water recedes and the soil becomes aerobic again, the ammonia is oxidized back to nitrate in stages. All of this (and many other processes) occur largely because of the activities of soil microbes. Without these microbes, life as we know it would not occur because necessary elements would remain tied up in unusable chemical forms and gradually be removed by sedimentation. To maintain the level of these components it is essential that they undergo a regular process of recycling. Different microorganisms bring about this process of recycling through various transformations.

Carbon Cycle

The most important element in the biological realm and substance that serve as the cornerstone of the cell structure is carbon. It constituents about 40-50% of all living organisms, yet the ultimate source is the CO₂ that exists in a perennially short supply, only 0.03% of the earth’s atmosphere, which undergoes a cyclic change from an oxidized to reduced state. The concentration of carbon in living matter (18%) is almost 100 times greater than its concentration in the earth (0.19%). Hence, living things extract carbon from their non-living environment. For life to continue, this carbon must be recycled. Carbon exists in the nonliving environment as carbon dioxide (CO₂) in the atmosphere and dissolved in water (forming HCO₃") carbonate rocks (limestone and coral = CaCO₃) deposits of coal, petroleum, and natural gas derived from once-living things dead organic matter, e.g., humus in the soil. Carbon enters the biotic world through the action of autotrophs: primarily photoautotrophs, like plants and algae, that use the energy of light to convert carbon dioxide to organic matter through photosynthesis and to a small extent, chemoautotrophs - bacteria and Archaeans that do the same but use the energy derived from the oxidation of molecules in their substrate.

Soil Organic Matter

Soil organic matter plays an important role in the maintenance and improvement of soil properties. It is a dynamic material and is one of the major sources of nutrient elements for plants. Soil organic matter is derived to a large extent from residues and remains of the plants together with the small quantities of animal remains excreta, and microbial tissues. Soil organic matter is composed of three major components i.e. plant residues, animal remains and dead remains of microorganisms. Soil organic matter comprises residues of plants and animals and these compounds occur in soil in close combination with inorganic substances. Animals and plant residues are made up of complex carbohydrates, simple sugars, starch, cellulose, hemicellulose, pectins, gums, mucilage, proteins fats, oils, waxes, resins, alcohols, aldehydes, ketones, organic acids, lignin, phenols, tannins, hydrocarbons, alkaloids, pigments, etc.

The organic matter subjected to microbial decay in the soil comes from several sources like plant remains, forest litter, incorporation of plant tissues, animal tissues, and excretory products. The chemistry of organic matter is very complex, and investigations of the transformations and the responsible organisms have therefore been extremely interesting. The organic constituents of the plants are commonly divided into six categories.

Soil microorganisms are the most important agents in the cycling or transformation of various elements (N, P, K, S, Fe etc.) in the biosphere; where the essential elements undergo cyclic alterations between the inorganic state as free elements in nature and the combined state in living organisms. Life on earth is dependent on the cycling of nutrient elements from their elemental states to inorganic compounds to organic compounds and back into their elemental states.

The microbes through the process of biochemical reactions convert / breakdown complex organic compounds into simple inorganic compounds and finally into their constituent elements. This process is known as “Mineralization”.

Mineralization of organic carbon, nitrogen, phosphorus, sulphur, and iron by soil microorganisms makes these elements available for reuse by plants. In the following paragraphs the cycling or transformations of some of the important elements are discussed.

Fixation of elemental nitrogen in the atmosphere by the microorganisms through a reductive process into ammonia is called biological nitrogen fixation (BNF). Molecular nitrogen (N₂) is the major component (approximately 80%) of the earth’s atmosphere. The element nitrogen is an essential part of many of the chemical compounds, such as proteins and nucleic acids, which are the basis of all life forms. However, N₂ cannot be used directly by biological systems to build the chemicals required for growth and reproduction. Before its incorporation into a living system, N₂ must first be combined with the element hydrogen. This process of reduction of N₂ commonly referred to as nitrogen fixation (N-fixation).

N₂is transformed into reactive N via lightning discharge (5 teragrams (Tg) N / year; 1 Tg equals 1012 g) and by biological N fixation (100 -140 Tg N /year ). Conversion of dinitrogen to ammonia in the industrial process requires temperatures of 400 - 500^o C and high pressures (Haber-Bosch process). Biological nitrogen fixation is much more important as it contributes to more than 70 % of the input in to the world’s soil and water nitrogen. It has been estimated that 100 to 175 million tones of nitrogen are fixed annually by the process of biological nitrogen fixation.

The process of N₂ fixation is mediated by the enzyme, called nitrogenase (which reduces N₂ to ammonia). The overall reaction is as follows.

Phosphorus is only second to nitrogen as an inorganic nutrient required by both plants and microorganisms. It stimulates growth of young plants, giving them a good and vigorous start. Phosphorus management and nutrition has both economic and environmental implications. Phosphate constitutes nearly 0.1% of the earth’s crust. They occur in soil in inorganic and organic forms. The organic phosphorus containing compounds are derived from plants and microorganisms and are composed of nucleic acids, phospholipids, lecithin, phytin and related compounds. In soil, 15-85 % of the total P is organic and soils rich in organic matter contain abundant organic P. The inorganic forms are derived from parent rocks or through fertilizers application and manuring with bone meal. They are soluble in water when present as phosphates of Na, K, Ca, Mg etc. Phosphorus exists mainly as apatites, with the basic formula M₁₀ (PO₄) ₆ X₂. Commonly the mineral (M) is Ca, less often Al or Fe. The anion (X) is either F^-, Cl^-, OH^- or CO^2- ₃. Diverse combinations of M and X results in 200 forms of P.

It is a major constituent of nucleic acids in all living systems essential in the accumulation and release of energy during cellular metabolism. This element is added to the soil in the form of chemical fertilizers, or in the form of organic phosphates present in plant and animal residues. In cultivated soils it is present in abundance (i.e. 1100 kg/ha), but most of which is not available to plants, only 15 % of total soil phosphorus is in available form. Both inorganic and organic phosphates exist in soil and occupy a critical position both in plant growth and in the biology of soil.

Microbial transformations of sulfur (S) are even more complex than those of nitrogen because of the large number of oxidation states of S and the fact that several transformations of S also occur abiotically. Although a number of oxidation states of S are possible, only three are significant in nature, 2 (sulfhydryl, R–SH, and sulfide, HS-), 0 (elemental sulfur, S0), and 6 (sulfate, SO₄ 2-). The bulk of S Earth’s S is in sediments and rocks in the form of sulfate minerals, primarily gypsum (CaSO₄) and sulfide minerals (pyrite, FeS2), but the oceans constitute the most significant reservoir of SO₄ ^2- in the biosphere. A significant amount of S, in particular sulfur dioxide (SO₂), enters the S cycle from human activities, primarily the burning of fossil fuels.

Hydrogen Sulfide and Sulfate Reduction

A major volatile S gas is hydrogen sulfide (H₂S). Hydrogen sulfide is produced from bacterial sulfate reduction or is emitted from sulfide springs and volcanoes. Although H₂S is volatile, different forms exist depending on pH: H₂S predominates below pH 7 and the nonvolatile HS- and S^2- predominate above pH 7. Collectively,H₂S, HS, and S₂ are referred to as “sulfide.” Sulfate-reducing bacteria are a large and highly diverse group and are widespread in nature. However, in anoxic habitats such as freshwater sediments and many soils, sulfate reduction is SO₄ ^2- limited. Moreover, because organic electron donors (or H₂, which is a product of the fermentation of organic compounds) are needed to support sulfate reduction, it only occurs where significant amounts of organic material are present.

Potassium (K) is among the most important essential macronutrients for plant growth. About 98% of the potassium in the earth’s crust exists in insoluble forms as rocks and silicate minerals, resulting in very low concentrations of soluble potassium in the soil for plant growth and development. Potassium is never incorporated in any organic compound and even in the plant system it remains as K⁺ ion. It does not form any gas that could be lost to the atmosphere. It does not cause eutrophication. When left in the ecosystem as such, it is not at all toxic.Potassium activates enzymes, maintains cell turgor, enhances photosynthesis, reduces respiration, helps in transport of sugars and starches, and is essential for protein synthesis. In addition to plant metabolism, potassium improves crop quality because it helps in grain filling and kernel weight, strengthens straw, increases disease resistance and helps the plant better to withstand stress.

Potassium in Soils

Soils usually contain potassium in larger amounts than any other nutrients. Total K content in soil is 30,000- 50,000 kg/ha in top layer of the soil. Nearly 98 % of K bound in the mineral form and 2 % is in soil solution. Generally, potassium in soils exist in four forms (often called fractions), their availability to crop roots is considerably different.

Zinc is found in earth’s crust to the tune of 0.008%. However about 50% of Indian soils exhibit deficiency of zinc with a content much below the critical level of 1.5 ppm. Soil contains both available and unavailable form of zinc. Water soluble, exchangeable, organically complexed and armorphous iron oxide bound forms are considered available zinc and crystalline iron oxide bound and residual zinc are considered as unavailable. The available fraction constitutes around 8% of the total zinc which is too low for utilization by crops in zinc deficient soils.

Zinc is required by crops in microquantities for its growth. The use of high analysis fertilizer due to cultivation of high yielding varieties, enhanced cropping intensity and the decline in the use of organic manures result in the deficiency of trace elements particularly zinc. With the liberal application of nitrogen the demand for zinc increases producing deficiency symptoms. The critical limit of zinc in dry matter for different crops and levels less than 20 ppm suggests the probability of zinc deficiency and less than 15 ppm indicate sure deficiency.

Zinc is a limiting factor in crop production and application of ZnSO₄ is preferred because of its water soluble nature. The zinc sulphate, when applied soil, gets transformed into different forms like Zn (OH), zinc carbonate in calcium rich alkali soils ; zinc phosphate in near neutral to alkali soils of high phosphorus application; and zinc sulphide under reduced conditions.

Bioconversion refers to the recycling and reprocessing of organic waste materials using the system of biological decomposition or biodegradation into value added products. Composting is one way of conversion of organic waste into manures. It is defined as a method of solid waste management whereby the organic component of the solid waste stream is biologically decomposed under controlled conditions to a state in which it can be handled, stored or applied to the land without adversely affecting the environment.

Composting provides a partial solution to an issue of great concern in many communities. All around the world, landfills are filling up, garbage incineration is becoming increasingly unpopular, and other waste disposal options are becoming ever harder to find. Composting provides a way not only of reducing the amount of waste that needs to be disposed of, but also of converting it into a product that is useful for agriculture. Composting reduces waste, makes us less dependent on landfills, and decreases greenhouse gas emissions. Composting recycles essential nutrients back into the soil and promotes a prolific soil ecosystem.

Pesticides are the chemical substances that kill pests and herbicides are the chemicals that kill weeds. In the context of soil, pests are fungi, bacteria, insects, worms, and nematodes etc. that cause damage to field crops. Thus, in broad sense pesticides are insecticides, fungicides, bactericides, herbicides and nematicides that are used to control or inhibit plant diseases and insect pests. Although wide-scale application of pesticides and herbicides is an essential part of augmenting crop yields; excessive use of these chemicals leads to the microbial imbalance, environmental pollution and health hazards. An ideal pesticide should have the ability to destroy target pest quickly and should be able to degrade nontoxic substances as quickly as possible.

The ultimate “sink” of the pesticides applied in agriculture is soil. Soil being the storehouse of multitudes of microbes, in quantity and quality, receives the chemicals in various forms and acts as a scavenger of harmful substances. The efficiency and the competence to handle the chemicals vary with the soil and its physical, chemical and biological characteristics.

Rhizosphere

The term Rhizosphere was introduced by the German scientist, Hiltner in 1904. It is region of the soil, which is subjected to the influence of plant roots. It is the unique environment under the influence of plant roots. The roots of plants are not only involved in the uptake of mineral nutrients and water for plant growth, but they also release a wide range of organic compounds in the surrounding soil.

The spermosphere represents a short-lived, rapidly changing, and microbiologically dynamic zone of soil surrounding a germinating seed. It is analogous to the rhizosphere, being established largely by the carbon compounds released into the soil once the seed begins to hydrate. These seed exudations drive the microbial activities that take place in the spermosphere, many of which can have long-lasting impacts on plant growth and development as well as on plant health.

Microbes that live inside plant tissues without causing disease are termed as endophytes. Endophytes have been found in all parts of plant viz., seeds, roots, stems, leaves, fruits etc. Within these organs, there is evidence of endophytes living in apoplastic intercellular space within parenchyma tissues and xylem vessel apoplast. Endophytic bacteria have been isolated from both monocotyledonous and dicotyledonous plants, ranging from woody tree species to herbaceous crop plants. Further, a single plant may be a host for several different bacterial species. They are consistently present in the root, stem, leaf, fruit and tuber tissues of a wide range of agricultural, horticultural and forest species. All plants in nature harbor a diverse community of endophytic bacteria which can positively affect host plant growth.

The potential of endophytic bacteria to fix nitrogen, promote plant growth and suppress plant diseases has renewed interest in such associations. It is advantageous to have the endophytic plant growth promoting organisms safely inside the plant, which could supply substantial amounts of nitrogen and other nutrients, growth hormones and other beneficial effects to the crop plants without the interference of the rhizosphere soil environment. Furthermore, plant growth promotion is often greater when it is induced by endophytes rather than by rhizosphere bacteria.

Plant Growth Promoting Rhizobacteria (PGPR) are root-colonizing bacteria that form symbiotic relationships with many plants. The name comes from the Greek rhiza, meaning root. Though parasitic varieties of rhizobacteria exist, the term usually refers to bacteria that form a relationship beneficial for both parties (mutualism). They are an important group of microorganisms used in biofertilizer. Biofertilization accounts for about 65% of the nitrogen supply to crops worldwide. The term PGPRs was first used by W. Kloepper in the late 1970s and has become commonly used in scientific literatures. PGPRs have different relationships with different species of host plants. The two major classes of relationships are rhizospheric and endophytic. Rhizospheric relationships consist of the PGPRs that colonize the surface of the root, or superficial intercellular spaces of the host plant, often forming root nodules. Endophytic relationships involve the PGPRs residing and growing within the host plant in the apoplastic space.Some common examples of PGPR genera exhibiting plant growth promoting activity are: Pseudomonas, Azospirillum, Azotobacter, Bacillus, Burkholdaria, Enterobacter, Rhizobium, Erwinia, Mycobacterium, Mesorhizobium, Flavobacterium, etc.An ideal PGPR should possess high rhizosphere competence, enhance plant growth capabilities, have a broad spectrum of action, be safe for the environment, be compatible with other rhizobacteria, and be tolerant to heat, UV radiation, and oxidizing agent.