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In agricultural practices pesticide application is an inevitable factor for maintaining high crop productivity and is currently an integral part of modern farming. Pests (insects, microbes and weeds) cause approximately 20-30% loss in crop production so making pesticide use indispensable for crop protection.
 
Pesticide : A pesticide may be defined as ‘any agent or chemical or a mixture of chemicals/ substances intended to prevent, destroy, repel or irritate one or more pest populations causing economic loss in crop production’. Worldwide more than 450 active pesticide chemicals formulated into more than 10,000 commercial products are currently used by farmers. The most worrying aspect is that about two-third of the 800 chemicals tested so far have been found involved in causing or promoting tumor in rodents. Yet more than 50,000 synthetic chemicals/formulations remain untested so far.

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’.

22.1 Introduction

Nanotechnology has proved to have infinite potential in increasing the quality of life of the human population. There is however, a growing realization regarding the potential health and safety risks of associated with development, production and application of these nanoparticles. Nanoscale particles are produced from a variety of different processes. Nanoparticles are the end product of a wide variety of physical, chemical and biological processes, some of which are novel and radically different, others of which are quite commonplace. Nanometer sized particles are also found in the atmosphere where they originate from combustion sources (traffic, forest fires), volcanic activity, and from atmospheric gas to particle conversion processes such as photochemically driven nucleation. A large quantity of nanoscale particles are also produced during the various human activities, Welding can generate large quantities of nanoparticles usually in the form of a well defined plume of aggregated nanoparticles.

21.1 Introduction

Nanotechnology is an emerging field of science which is being highly exploited in the sphere of medicine where “nano” plays a vital role in delivery of drugs or chemical molecules to the point it is required in précised quantities in right proportions. Nanoscience infuses intelligence to the truck load of chemical constituents that are to be delivered at appropriate locations and cleave from the site after the task is complete. Such process will likely to reduce the cost besides ensuring environmental safety. Nanoscale devices with its unique properties make the agricultural system more smart and effective; such devices are capable of responding to different situations by themselves, thus taking appropriate remedial action with the need of external directions from humans. In short, these devices act as a detectors and if need arises serve as a solution/remedy for the particular issue. These smart delivery systems of chemicals in controlled and targeted manner can be considered synonymous to the proposed nano-drug delivery system in human (Patolsky et al., 2006). 

20.1 Introduction
  
Fertilizers play an important role in improving soil fertility and productivity of crops regardless of nature of cropping sequence or environmental conditions. It has been unequivocally demonstrated that one third of crop productivity is dictated by fertilizers besides influencing use efficiencies of other agri-inputs. In the past four decades, nutrient use efficiency (NUE) of crops had hardly exceeded 35-50%, 18-20% and 30-35 % for N, P and K, respectively, despite our relentless efforts. The remaining nutrients stay in soil or enter into the aquatic environment causing eutrophication. In addition to the low nutrient efficiencies, Indian agriculture is facing a problem of low organic matter, imbalanced fertilization and low fertilizer response that eventually caused crop yield stagnation (Biswas and sharma, 2008).The fertilizer response ratio in the irrigated areas of the country  has dcreased from 13.4 kg grain / kg nutrient applied in 1970’s to just 3.7 kg in 2005. In other words, more amounts of fertilizers is required to produce the same quantity of grain output. For instance, 27 kg NPK ha-1 was required to produce one tonne of grain in 1970 while the same level of production can be achieved by 109 kg NPK ha-1 in 2008. 

19.1 Introduction

Nano technology or Nano Science is a new branch of research though nano materials or Nano Structures are not new. In nature nano particles or nano materials are abundant .The idea of manipulation, production, controlling size and physico - chemical properties and application as well as making devices out of these nano materials is the subject of Nano Science & Nano Technology. As the name suggests, the domain of Nano starts from 10-9 m but especially the effect of nano structures exists mostly in the 1-100 nm regime where quantum - mechanical behiviour is prevalent. Molecules with more than 10 atoms fall into the nanometer range  and scientists were not able to visualize individual molecules and nano scale objects until the invention of some very powerful microscopes. Working in Nano domain requires two basic facilities -

18.1 Introduction

Nano – Science & Technology is design, fabrication and application of nanostructures or nanomaterials, and the fundamental understanding of the relationships between physical properties or phenomena and material dimensions at nano meter scales.

17.1 Introduction

In industrialized nations the air is filled with numerous pollutants caused by human activity or industrial processes, such as carbon monoxide (CO), chlorofluorocarbons (CFC), heavy metals (arsenic, chromium, lead, cadmium, mercury, zinc), hydrocarbons, nitrogen oxides, organic chemicals (volatile organic compounds, known as VOCs, and dioxins), sulphur and other particulates. The presence of nitrogen and sulphur oxide in the air generates acid rain that infiltrates and contaminates the soil. The high levels of nitrogen and sulphur oxide in the atmosphere are mainly due to human activities, particularly burning of oil, coal and gas. Only a small portion comes from natural processes such as volcanic action and decay of soil bacteria. Water pollution is caused by numerous factors, including sewage, oil spills, leaking of fertilisers, herbicides and pesticides from land, by-products from manufacturing and extracted or burned fossil fuels.