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The soil microorganisms thrive on organic matter in soil by feeding readily on soluble substrates and rather slowly on insoluble substrates. Organisms derive carbon and energy during the process of organic matter decomposition and release organically-bound carbon, thereby decrease C :N ratio and utilize nutrients. Any decrease in organic matter content in soil is likely to affect the microbial biomass and their activities thereby influence the soil fertility and productivity. It is, therefore, imperative to recycle the organic matter in soil in whatsoever form it may be. The raw organic matter requires appropriate treatment to boost decomposition process.

Soil is inhabited by incredibly diverse living microorganisms that are significant to plant growth and development. Soil microorganisms produce a variety of metabolites, probably several thousands, which influence the plant growth either positively or negatively. Therefore, in such a complex situation, identification of any one metabolite or a compound as active phytohormone or phytotoxin is really an uphill task. Appropriate extraction procedure, knowledge about the proper site for its action, appropriate conducive physiological environment and the effective intensity or concentration is of prime importance. Compounds, in general, are inhibitory to growth at higher concentrations but usually stimulatory at lower concentrations. All growth regulators, irrespective of their provenance or structure, may be divided into two groups.

Soil is a living entity having dynamic physico-chemical and biological properties. Besides supporting the growth of various biological communities, it also serves as a medium on which the organic residues, in the form of dead plant and animal or their excretions, are degraded and decomposed. The biological properties to soil are endowed through the interactive activities of plant root, soil microbes and soil animals. The soil organisms live in a constant state of competition and have to struggle hard for their survival. In this struggle some species become dominant and some remain sub-dominant and others perish or remain in very low profile. So a sort of dynamic equilibrium is the net result of wide range of interactions occurring both at organism and population levels amongst different components of soil biota. Many interactions are short-lived and sporadic and others are more stable.

Mycorrhizae denote the symbiotic associations between plant roots and fungal mycelia. Literally it means fungal root. In 1840, Vittandini proposed that ‘tree rootlets are nourished by certain fungal mycelia which mantle them’. The first illustrations of mycorrhiza were published in the same year by Robert Hartig. However, in 1885 A.B. Frank coined the term “mykorrhizen” to the mutualistic symbiotic fungal association of roots (‘mykos’ fungus ‘rhizen’ roots). He characterized the sheath-forming fungi on tree as ‘ectotropisch’ (ectotrophic) and those without such compact sheath as ‘endotropisch’ (endotrophic). Fossil records reveal that mycorrhizae are as old as terrestrial plants.

Soil microorganisms immobilize and mineralize various elements to satisfy their growth requirements. The subsequent turnover of microbial biomass also releases several mineral elements. The elements may be released as a result of organic matter decomposition (e.g. during the process of mineralization, ammonification, etc.) or through biological weathering. Other transformations may involve oxidation and reduction of various inorganic ions and compounds which are mostly catalyzed by chemoautotrophic bacteria during oxidation of ammonium, nitrite, sulphur, iron, etc. Such oxidations may also release energy for microbial growth.

Sulphur in nature follows similar cycle as that of nitrogen and shares many common features with it. In soils, decomposition of organic matter releases major portion of nitrogen and sulphur bound in proteins, as cystine or methionine amino acids, or vitamins, etc. In proteins, on an average, for every 36 atoms of nitrogen one atom of sulphur is present. Mineralization supplies a large fraction of nitrogen and sulphur to the plants. Secondly, both nitrogen and sulphur have several chemical forms under different soil conditions (Table 8.1) and both are subject to microbial reduction. Thirdly, both can enter or leave soil in gaseous form and both are subject to some degree of leaching in the anionic form.

Phosphorus, an essential element, plays a central role in cell metabolism and reproduction. It is a structural component of energy transferring molecules (ATP, ADP and AMP), nucleic acids, coenzymes, phosphoproteins, phospholipids and sugar phosphates. In soils, the phosphorus does not occur as abundantly as nitrogen or potassium. The total phosphorus in an average arable soil is estimated to be about 0.05% (by weight) with an average of approximately 1100 kg P ha-1 (range 200-2000 kg P ha^-1). But only a meager proportion (only ~0.1-1.0%) of it is available for use by plants and microorganisms because phosphorus has poor solubility and gets fixed in soil. Not only the native inorganic phosphates but even the added soluble phosphates of fertilizers and manure readily combine with the cations present in soil solution to form low solubility products. Fixation reactions in soils allow only a small fraction (10-15%) of phosphorus fertilizer to be taken up by the plants in the year of its application.

Nitrogen ranks fourth element in cell composition after C, H and O. It forms main components of amino acids, the building blocks of peptides and proteins. Besides, it is present in the genetic material of cell as well as in the chlorophyll and cell wall in the form of chitin and mucopeptides. Plant growth in soil is often limited by less supply of nitrogen, therefore a major nutrient limiting factor in crop production. About 26 x 10⁶ Mg N is globally applied to soil each year to enhance crop productivity.

Soil microorganisms in true sense are one of natural safety valves that regulate biogeochemical transformations in soil ecosystem. They act as natural agents for the disposal of organic matter. The various essential biological elements such as C, N, S and P, apart from H and O, form the primary building blocks of cells and their constituent elements are recycled through tiny microorganisms present in soil. More they are in quality and quantity, better recycling is expected by them. The organically bound materials are converted to simpler inorganic forms to complete biological cycle initiated during photosynthesis and other anabolic processes.

The study of soil microorganisms involves various complicacies when compared with those of plants or animals aboveground. The complicated heterogeneous environment existing in soil and the varied growth behaviour of microbial populations in soil have necessitated the development of special techniques to study the microbes and their metabolic diversity, individually and holistically without disturbing their natural habitat. With the gradual improvement in microscopy since its discovery in 1667 and also with the greater understanding of the nature of soil microbes and their properties in relation to total ecosystem function, the concept of studying microbes in isolation has enormously changed. Microscopes have helped in magnifying these, otherwise invisible, minute creatures within the limits of naked eyes.

Soil is the outer loose layer of earth consisting of layers of mineral material (regolith) whose properties differ from one another and these differences are largely due to the variation in biological activities. Soil micro-environment principally comprizes of inorganic particulates (sand, silt and clay) plus certain oxides and hydroxides, plant roots, organic matter, microbial biomass and aqueous and gaseous phases. The uneven distribution of these components provides a great variety of conditions from field to micropores. The interaction of physical and chemical factors contributes to the creation of varied soil habitat and hence determines the composition and activity of soil biota at a particular site and time. Over geological times, microorganisms have had great opportunity to become distributed worldwide. Such growth and development of microorganisms as well as species diversity is of considerable significance. The existing geographic distribution is reflective of long term adaptation of microorganisms to the various environmental conditions. The preferred environment of an organism is usually referred as ‘habitat’.

The plant roots, soil animals and microorganisms make up soil biological communities, accelerate biochemical activities through intra- and extra-cellular enzymes and interact in such a manner that biogeochemical cycling on this earth continues uninterrupted. Without intermeshing vital processes of soil microflora, microfauna and associated mesofauna, the soil would have become a repository of plant residues and animal remains with no facility for recycling the vital nutrients for plant growth, thus halting the whole process of geo-chemical recycling in nature. Though living component rarely makes up more than 4% of the total soil organic carbon, it plays vital role in geochemical recycling, soil development and ecosystem stability.

Definition : Soil microbiology is the study of microorganisms living in soil which complete whole or some part of their life cycle in soil. They include both beneficial as well as deleterious microorganisms but as a specialized branch main thrust is laid on their metabolic activities and the role they play in energy flow, cycling of nutrients associated with the primary productivity and soil ecosystem development. Besides, it focuses on environmental impact, whether favourable or unfavourable, on soil microorganisms and the various soil biochemical processes mediated by various microbes. A clear understanding of the interactions between soil microbial communities and elemental soil components is imperative to comprehend total ecosystem function. Atlas and Bartha have defined the soil microbiology as ‘the study of organisms that live in soil; their metabolic activity; their roles in energy flow; their roles in nutrient cycling’. As per Tate soil microbiology involves ‘the study of soil ecosystem which is the product of intricate interactions between physical and chemical matrix of highly variable composition and living communities of all form’.

Introduction

Spices hold a special place in world trade and were a catalyst in many historical events, discoveries, wars and inventions. It has even been cited as an important element in the spread of knowledge and culture. Spices are non-leafy parts of plants used as a flavoring or seasoning. Asia is known as ‘Land of Spices’ as it is the place of origin, production, consumption and export of most spices. Out of the world’s 70 plant species grown as spices, 13 are considered major spices produced in Asia. Spices had many uses, from adding flavour to food to medicinal properties, but only grew in a few places. In the last decade, the annual average growth in spice production was 4.3% and trade in spices grew at an average of 5.8% /year. More sophisticated consumers, health-conscious eating habits (but also the rise in the amount of processed foods that use herbs and spices as inputs), rising incomes, increased world trade and globalisation are driving this new era of profitability. Spices are ideal commodities for international trade. They are normally exported in raw or dried form and are usually easy to store and transport. Consequently they do not need expensive infrastructure such as cold chain management or advanced storage facilities and they are not particularly time sensitive. In addition, they are recognised as high value products that can be produced relatively easily on small farms and do not require investments in advanced technology and machinery.

Introduction

Plantation crops are high value industrial crops with great economic importance and play vital role in trade. It contributes to environment protection and sustains a large number of agrobased industries. It has great potential for utilization of waste lands in varied agro-ecosystems like rainfed, dryland, hilly, arid and coastal, providing higher employment opportunities, nutritional security, eco-friendly, high potential for foreign exchange earnings and above all providing livelihood security to people. They contribute 25% of AGDP. Major plantation crops grown in India are coconut,cardamom,cinchona, arecanut, oilpalm, cashew, palmyra, rubber, cocoa, tea and coffee. These crops grown between 20° N and 20° S of equator occupy nearly 3.2 million ha with a production of 9.8 million tonnes. All these crops are perennial in nature and demand  labour round the year. All plantation crops enter international trade and all of them have a long juvenile period. Coconut, arecanut and cashew are cultivated by individual land  owners who are not organized to the same extent as  planters of tea, coffee and rubber.

Introduction

India has a long history in the cultivation of vegetable crops and it sustains the livelihood of a large section of population directly or indirectly. Vegetable crops offer high returns,  have a potential to alleviate the poverty of people, provide nutritional security and essential raw materials for agro industries. These crops also offer greater rural employment opportunity and have high potential for foreign exchange earning. India bestowed with varied soil and high climatic conditions has excellent potential for growing both tropical and temperate vegetables. India is the second largest producer of vegetables in the world after China. The total area under vegetables is estimated 5.9 million ha which contributes more than 2.5% of total cropped area. The production is estimated  90.83 milion tonnes. China having a production of about 278.59 million tonnes  is the largest producer of vegetable crops in the world. The annual growth rate in vegetables is of the order of 2.6%. Potato, brinjal, tomato, chilli, cabbage, onion, cauliflower,okra and peas are grown on commercial scale. West Bengal, Uttar Predesh, Bihar, Orissa and Karnataka are the leading vegetable producing states. Maharashtra, Gujarat, Karnataka, Uttar Pradesh and Andra Pradesh are the leading states in onion production where as West Bengal, Uttar Predesh and Bihar are the leading potato producing states. Bengal, Orissa, Bihar and Assam are the leading brinjal producing states.

Stress is described as the cumulative detrimental effect of a variety of factors on the health and performance of living beings (Rosales, 1994). Heat stress arises when there is an imbalance between heat production within the body and its dissipation. Homeotherms can maintain their body temperature within a relatively narrow range and both physiological and behavioural responses help in thermoregulation. Stress occurs when an animal suddenly faces a change in its environment. Heat stress during summer and post summer months in tropical countries is a problem of great concern among farmers and livestock producers as it costs both production and reproduction of animals.

India has vast animal genetic resources with a wide variety of indigenous farm animal breeds. These breeds have evolved over generations to adapt to specific agro-climatic and socio-economic needs of the people. Many number of these breeds are now subjected to fast genetic degradation and dilution because of unplanned and indiscriminate breeding and introduction of exotic germplasm.

Domestic animal diversity in developing countries is embedded in traditional farming and pastoral communities who manage their livestock according to their Indigenous Technological Knowledge (ITK) and in tune with local ecological constraints.

Livestock sector may be considered as a driving force for nutritional security and an important component of sustainable agriculture in India. Livestock sector besides providing milk and meat also provides a diverse range of output for agriculture (manure, draught power and transport) and for manufacturing sector (fiber and leather). According to estimates of the Central Statistics Office (CSO), the value of output from livestock sector at current prices was about 4,59,051 crore during 2011-12 which is about 24.8% of the value of output from total agricultural and allied sector at current price and 25.6% at constant prices (2004-05). The value of output of milk is 3,05,484 crore in 2011-12, which is higher than the value of output of paddy and wheat. The value of output from eggs and wool group is 17,803 crore and 318 crore respectively for 2011-12. Livestock agriculture is the only way to produce food in many of the world’s harshest environments. Locally adapted breeds enable these vast areas to be used in a sustainable manner.

Biodiversity, coined by W. G. Rosen in 1985, is the variety of life on Earth. It is the occurrence of different kinds of organisms and the complete range of varieties adapted to different climates, environments and areas being constituents of food chains and food web of biotic interrelationship. Biodiversity refers to totality of genes species and ecosystems of a region. Biodiversity differs from place to place. Biodiversity is the biological wealth of world.

There is continuous depletion of biodiversity due to increasing population resources consumption, urbanization and pollution. The basic reason for concern is that biodiversity is being lost even before it attains its size. Loss of biodiversity would check evolutionary capability of biota to cope up with environmental loss.