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For the hundreds of thousands of years that we lived on earth,there were few rapid changes in the atmosphere. It is only in recent times, particularly since the Industrial Revolution, that our activities on earth began to modify our environment in a significant manner.  Industrial pollution has affected the water we drink, the air we breathe, and in general,the biosphere itself.Now noise has joined the bandwagon of pollutants.

Noise certainly comes within the scope of definition of a pollutant that “..... any undesirable change in the physical, chemical or biological characteristics of our air, land and water that may or will harmfully affect human life or that of any other desirable species or industrial process, living conditions or cultural assets, or that may or will waste or deteriorate our raw material resources.”

Pesticides are used to control plant growth (herbicides), insects (insecticides), worms  (vermicides), bacteria (bacteriocides), fungi (fungicides), and other organisms. Almost without exception, pesticides are used to benefit humans by the control of unwanted species of plants (e.g. weeds in a lawn), disease-causing bacteria (e.g., Pneumococcus, the causative agent of pneumonia), disease-carrying insects (e.g. malarial or yellow fever mosquitoes) or in controlling destruction of agricultural products by disease-causing organisms (e.g., corn-borers, the virus of anthurium blight). Although they are by and large mostly beneficial, pesticides used both properly and improperly are also “resources out of place”, that is pollutants, that are subject to normal ecological processes.

It is a well known fact that natural disasters strikes countries, both developed and developing, causing enormous destruction and creating human sufferings and producing negative impacts on national economies. Due to diverse geo-climatic conditions prevalent in different parts of the globe, different types of natural disasters like floods, droughts, earthquakes, cyclones, landslides, volcanoes, etc. strikes according to the vulnerability of the area. India is considered as the world’s most disaster prone country. It has witnessed devastating natural disasters in recent past like droughts, floods, cyclones, earthquakes, landslides, etc. 

The phenomenon we call tsunami is a series of large waves of extremely long wavelength and period usually generated by a violent, impulsive undersea disturbance or activity near the coast or in the ocean. A tsunami is a very long-wavelength wave of water that is generated by sudden displacement of the seafloor or disruption of any body of standing water.  Tsunami are sometimes called “seismic sea waves”, although, as we will see, they can be generated by mechanisms other than earthquakes.  Tsunami have also been called “tidal waves”, but this term should not be used because they are not in any way related to the tides of the Earth.  Because tsunami occur suddenly, often without warning, they are extremely dangerous to coastal communities.

Continental drift is the theory that continents move slowly about the earth’s surface, changing their positions relative to one another and to the poles of the earth. It includes the idea that former continents may have broken apart and that the fragments have recombined in different patterns (Fig. 15.1). Some authorities have considered that this happened only once, beginning within the past 200 million years; others believe that it has long been a continuous process, so that all existing continents are mosaics. Those who accept the theory believe that the rates of motion have been only a few inches a year. Earlier, it was considered that the continents moved like ships through a slightly plastic ocean floor. Today some consider that the continents are frozen into the earth’s surface like rafts in ice, and that the motions are the result of growth of the sea floor along certain midocean ridges and reabsorption of the sea floor elsewhere beneath deep ocean trenches and young mountains. The continents are carried passively about embedded in moving plates of the surface. Some authorities  now  agree  that  there  is  a  deformable  layer,  called  the asthenosphere, at depths of from about 50 to 400 kilometers within the earth. It is white hot, and slightly viscous, and many believe that the surface can break into plates which slide over it.

HUMAN POPULATION GROWTH

The evolution of man took place about one million years ago in response to changes in the physical environment. We learnt gradually to adapt different modes of life to varying environments and migrated different parts of the world. Human activities have had their impact on the environment, which was depending on the number of people living in  the area and  their level  of economic development. Per capita consumption of food, energy and other resources in developed countries is larger and its impact on the environment is much greater than equal number of persons living in developing countries in Africa or Asia. Therefore, the distribution of population needs to be examined in detail.

Energy, food production and various other natural resources are the limiting factors on this earth. The result of this bitter truth has been published in a book titled ‘The Limits to Growth’ in 1972. If the enormously growing population and the industrial process is not checked, then the earth’s civilization may come to an end within next hundred years.

By considering the space travel, we can very well understand about the Ecosystem. When we go away from the biosphere, it will be appropriate to develop unlimited environment through the energy accumulated from the sunlight in space. For the space travel for some days to moon and back to earth, we need not establish the entire ecological system as greater quantity of O₂ and food stuffs can be stored and CO₂ and other unwanted materials can be fixed for establishing space colonies, we have to build a special space ship with important abiotic components which can be recycled for use again and again. The vital processes of production, consumption and decomposition can be established and balanced through biotic components. In other words we are creating a complete mini human ecological machine. Before we established this system, we should be quite familiar about the space problems and its implications.

The Global Environmental Issues

 
Expansion of the scale of human activity in recent years has put so much strain on the natural environment of this planet that in some cases nature can no longer recover. The nature’s ability though recovers damage or harmful effects in one part of the world do not stop in the very area and keeps going beyond national borders and become environmental problems on a global scale, but in a limited manner.

Object: Preparation of solutions. 

Material required: Volumetric flask, measuring cylinder, beakers, pipettes, balance, distilled water and chemicals. 

Theory: The use of solution is common in experimental procedures of plant physiology. It is very important for a student to be familiar with their preparation. The substance dissolved in a solution is called solute and the medium in which it is dissolved is known as solvent. Solutions of two liquids (e.g. alcohol in water) and solid in liquid (e.g. NaCl in water) are most common. Solutions are thus a homogenous mixture of a solute in a solvent. 

Object: To demonstrate the phenomenon of osmosis using potato osmoscope. 

Material required: A potato tuber, sugar solution, beaker, water, petridish, knife, measuring cylinder, and stand.

Theory: Osmosis is a phenomenon in which water molecules diffuse through the semi permeable membrane from region of its higher concentration to the region of lower concentration.

Object: To demonstrate the phenomenon of endosmosis and exosmosis by using grapes and raisins.

Material required: Grapes, raisins, beaker or petridish, water and sugar solution.

Object: To demonstrate the process of diffusion.

Material required: Beakers, copper sulphate, distilled water and sugar solution.

Object: Methods of measurement of water status and water saturation deficit in plant parts. 

Material required: Leaf samples, leaf borer, water, petridishes, forceps, oven and blotting paper. 

Theory: Plant water status strongly influences plant growth and biomass production through its effects on leaf and root expansion and on photosynthesis. Therefore, measurement of plant water status is an important component of understanding plant processes and maximizing yield under different ecosystems. 

Method: Plant water status can be measured and computed by any one of the following methods

Object: Estimation of water potential of plant tissue by Chardakov’s method.

Material required: Test tubes, sucrose or polyethylene glycol (PEG) 6000, methylene blue and dropper.

Principle: Concentration of the solution in which a plant tissue is immersed changes. If the solution is hypertonic (with lesser yw) the tissue loses water and the solution becomes dilute. If the solution is hypotonic (with higher yW) the tissue absorbs water and the Solution becomes concentrated. If the solution is isotonic (with yw equal to the tissue sap) the tissue neither loses nor absorbs water and the solution concentration does not change. Thus the yw of this solution gives the yw of the tissue.

Objective: Estimation of photosynthetic pigment from plant leaves.

Material required: Plant leaves, test tube, test tube stand, spectrophotometer, balance, centrifuge machine, mortar and pestle, acetone and distilled water.

Theory: Photosynthetic pigments, namely, the chlorophylls are present in green leaves and shoots of plants. There are at least five types of chlorophylls in plants. Chl’a’ and ‘b’ occur in higher plants, ferns and mosses. Chl ‘c’,‘d’ and ‘e’ are found only in algae and in certain bacteria. Chlorophylls are extracted from plant leaves. The absorption peaks of chl ‘a’ at 663 nm and ‘b’ at 645 nm are characteristic measures from which amount of chlorophylls can be calculated.

Object: Measurement of absorption spectrum of chloroplastic pigments.

Material required: Spectrophotometer, plant leaves, ethanol, electric balance, beaker, test tubes and water.

Object: To demonstrate chlorophyll fluorescence.

Material required: Spectrophotometer, fresh green spinach, mortar, pestle, acid washed sand, acetone, funnel, filter paper and test tubes.

Principle: Chlorophyll molecule absorbs light in the blue (450nm) and red (660nm) region and get into excited state and emits an electron. The electron drops back to the ground state within 10-9 seconds and some energy (which is not used in biochemical reaction) are given out as the observed fluorescent far red light.

Procedure and observation: Take some soft green spinach leaves. Grind these with a pestle -mortar in acetone adding a pinch of acid washed sand. Make a fine paste. Filter to get a clear solution in a test tube. Take the test tube in bright sun light.

Object: Measurement of leaf area by graph paper method.

Material required: leaves, graph paper and pencil or pen.

Object: Estimation of stomatal index and stomatal frequency with replica method.

Material required: Leaf sample, blue/red correction fluid, transparent finger nail polish, brush glass slide and microscope.

Principle: The number of stomata per unit area of the leaf is called as Stomatal Frequency. The stomatal index is defined as the percentage number of Stomata as compared to all the epidermal cells in a unit area of leaf i.e.

Object: Demonstration of leaf anatomy or structure of C₃ and C₄ Plants (demonstration by already prepared slides).

Material required: Already prepared slides of corn and wheat leaves and microscope.

Object: To demonstrate that water is lost from a living plant during transpiration. 

Material Required: A potted healthy plant, a bell jar, a rubber sheet or oil cloth, a glass sheet and grease.

Theory: Transpiration: Loss of water in the form of water vapour from the internal tissues of living plants through aerial parts of the plant is known as transpiration.

Object: To measure rate of transpiration of potted plant by gravimetric (Lysimeter) method. 

Material required: Potted plants, Polythene sheet, Platform and electric balance etc.

Method: Select same size and same type well watered potted intact plants. Seal the pots and the root system with a sheet of polythene so that the water loss to the atmosphere occurs only from the shoot system not from the soil (To check evaporation losses). Immediately record the weight of the potted plant and keep them in different environment such as (1) warm environment (2) cool environment (3) Calm environment.

Object: To measure the rate of transpiration by using Ganong’s potometer

Material required: Ganong’s potometer, beaker, wax or vaseline, stop watch and twig or a branch of a plant.

Theory: The amount of water absorbed is almost equal to the amount of water transpired. The difference between the two amounts is negligible. 

Method: Potometer consists of wide mouthed tube fitted with a hard cork in which a twig or branch of a plant is inserted. Other end of tube is dipped in beaker. One half of the tube is graduated. The apparatus is filled with water using the reservoir. An air bubble is inserted in the tube as shown in figure.

Object: To find out the relation between transpiration and absorption. 

Material Required: Wide mouthed glass bottle, with a narrow graduated side tube, split rubber cork, water and a plant with intact root system.

Theory: The loss in weight of plant indicates the amount of water transpired. And fall in water level of the side tube indicates the amount of water absorbed. This shows that amount of water transpired is normally equal to the amount of water absorbed by the plant roots.

Object: To demonstrate unequal transpiration by the two leaf surfaces from four leaf method. 

Material required: four leaves of china rose or any dorsiventral leaves, two stands, thread and grease or vaseline. 

Theory: Transpiration is a process in which loss of water occurs in the form of water vapour from the aerial parts of the living plant. 

Method: Take four leaves of equal size from a plant (e.g. China rose). Now apply or smear the vaseline on the four leaves as follows:

Object: To demonstrate that light and carbon dioxide are essential for photosynthesis (Moll’s half leaf experiment). 

Material Required: A potted plant, a wide mouthed bottle, caustic potash, splits of rubber Cork and vaseline etc. 

Object: To demonstrate that O₂ is evolved during photosynthesis. 
 

Material required: Hydrilla plant, beaker, test tube, funnel, pond water and pyrogallol. 
 

Theory: Oxygen is a byproduct of photosynthesis, which is evolved in presence of light and chlorophyll during photosynthesis.

Object: To demonstrate anaerobic respiration. 

Material required: Soaked pea or gram seeds, mercury, test tube stand, forceps and KOH pellets. 

Theory: Generally, plants at certain stage have the capacity to respire in absence of oxygen i.e. anaerobic respiration. In this process, oxidation of carbohydrate takes places, ethyl alcohol and CO2 being end products and only a little amount of energy is liberated-

Object: To demonstrate that oxygen is used up during respiration. 

Material required: A conical flask, some germinating seeds, glass tube having two bends at right angles, mercury, beaker, small tube and caustic potash (KOH).

Theory: Plants at some stage have a capacity to respire more rapidly in presence of oxygen i.e. aerobic respiration. In this process, oxidation of carbohydrate occurs resulting in conversion of carbohydrate into carbon dioxide (CO₂) and water with release of large amount of energy.

Object: To determine respiratory quotient of different types of respiratory substrates.

Object: To demonstrate the optimum conditions for seed germination. 

Material required: Beaker, glass slide, bean seeds, thread and water.

Theory: Germination is a process by which the embryo in the seed becomes activated and begins to grow into a new seedling under favorable conditions. Food is stored in the seeds in dry conditions but the developing embryo cannot utilize this dry food. Food can be utilized in liquid form only and seeds can utilize only dissolved oxygen. Excess water stop germination because once all the dissolves oxygen is utilized by the seed, further germination is not possible as the life supporting oxygen is lacking. Suitable temperature is necessary because low temperature retards the embryo activity and high temperature destroys the delicate embryo tissue. Seed usually germinate between 0oC to 50oC temperature and the optimum temperature is lies between 25 to 30oC. During germination rapid cell division takes place. Energy is required for cell division. This energy is obtained from oxidation. The oxygen is required for oxidation is supplied by the air.

Object: Breaking of seed dormancy to facilitate germination.

Material required: Seeds, water, sharp needle, sharp razor, sandpaper, acids, Potassium nitrate and gibberellic acid. 

Definition: Inability of a viable seed to respond the favorable environmental conditions for germination is known as dormancy.

Object: Determination of the viability of seeds by tetrazolium test. 

Material required: Healthy seeds, tetrazolium solutions, beakers, water and petridishes. 

Theory: Viability of seeds shows their potential towards germination.

Object: To demonstrate the measurement of growth in plants with the help of Arc auxanometer. 

Material required: Potted plant, Arc auxanometer, rope and weight.

Theory: Growth is a permanent change in plants with respect to its size, form, weight and volume.

Object: Growth analysis: Calculation of growth parameters. 

Material required: Primary data collected from individual plants or derived from whole canopies. 

Theory: The growth analysis study provides information on the growth of plants or of a plant community in a precise way with the available’ raw data. The study also provides precise information on the nature of plant and environment interaction in a particular habitat.

Object: Yield estimation of kharif crops.

Material required: Polythene bags, balance, gunny bags or baskets, pans and harvesting equipment like sickle, knife etc.

Theory: Yield is the ultimate objective of cultivating agricultural plants. Different plant parts constitute the economic yield in different crops, like grain in cereals, pulses and oil seeds, vegetative parts or fruits in record yield at the correct maturation stage. Do not allow excessive wilting or drying of the material. Estimate yield in a sufficiently large sample. Materials required only a representative crop to estimate yields. (Do not select plants of any particular type. Do not damage any plant part vegetable crops; bark or out growth in fiber crops (jute, cotton); and the entire plant in fodder crops. The yield per unit area (per M₂ or ha) is the product of yield per plant multiplied by the number of plants per unit area. It is, therefore, essential to know the yield components per plant as well as per unit area.

Object: Effect of ethylene on regulation of stomata.

Material required: Plant leaves, ethaphon, ACC, double distilled water, measuring cylinder, beaker and electric balance.

Theory: Ethylene is a plant hormone that regulates many aspects of growth and development. Despite the well-known association between ethylene and stress signalling, its effects on stomatal movements are largely unexplored. Here, genetic and physiological data are provided that position ethylene into the Arabidopsis guard cell signalling network, and demonstrate a functional link between ethylene and hydrogen peroxide (H₂O₂). In wild-type leaves, ethylene induces stomatal closure that is dependent on H₂O₂ production in guard cells, generated by the nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase AtrbohF. 

Introduction

Agriculture is the most important sector in India accounting for 13.7 per cent of the country’s GDP and employs more than 60 per cent of the labour force. Our country has recorded the highest food grain production of 257 million tonnes during 2012-13, under favourable weather conditions those prevailed throughout the year. The mission of increasing food grain production, though realized to a commendable extent at present, but under risk due to climatic aberrations and reduced availability of land, water, nutrients along with poor and continuous degradation of the resources to cope up with the demands of increasing population. Although the country had attained self sufficiency in food grain production through intensification of agriculture with high–yielding varieties, fertilizer application and chemical pest control during the green revolution, productivity is still low and is stagnating.

Introduction

Cycling of plant material is required for any production system for biological activity, humus formation and thereby formation of a dark colored top soil. Incorporation of biomass results in production and proliferation of soil biota. But under annual crops compared to forest, production is much less, the biomass is largely removed, the soil is tilled several times each year. Consequently, less food and moisture are available for earthworms, insects, micro-flora and fauna; and their habitats are repeatedly disturbed or destroyed. Therefore, the primary need of our agricultural activities is to feed soil organisms (bacteria, fungi, earthworms etc.) and to regulate their living conditions while protecting them from chemical and mechanical impacts.

Introduction

Climate change and climatic variability are expected to reduce agricultural productivity and threaten food security of the world, particularly in developing countries. Producing enough food for the increasing population in a background of decreasing resources and a changing climate scenario, is a challenging task. Agriculture, forestry and land use change account for about 30% of greenhouse gases (GHGs) emissions. Therefore, mitigation of GHGs emission while enhancing production is another challenge in agriculture.
 
Conservation agriculture (CA), with the three core inter-linked principles of minimizing mechanical soil disturbance, enhancing organic matter cover on soil and diversification of crops, is a viable option for sustainable agriculture with an effective solution to climate change adaptation and mitigation. The principles can be integrated and applied into most of the rainfed and irrigated production systems including horticulture, agro-forestry, organic farming, rotational farming and integrated crop-livestock systems to strengthen ecological sustainability. Worldwide about 105 Mha land is under CA and the area is increasing. However countries like USA, Brazil, Argentina, Canada and Australia occupy about 90% of the area under CA. The CA, which is advocated as an alternative to the conventional production system for improving productivity and sustainability, is now adopted by many countries and agencies as a lead model for sustainable agricultural intensification.

Issues of conservation have assumed great importance in view of widespread resource degradation and the need to reduce production costs, increase profitability and make agriculture more competitive. The growing concerns for sustainable agriculture have been seen as a positive response to limits of both low-input, traditional agriculture and intensive modern agriculture relying on high levels of inputs for crop production. Sustainable agriculture relies on practices that help to maintain ecological equilibrium and encourage natural regenerative processes such as nitrogen fixation, nutrient cycling, soil regeneration, and protection of natural enemies of pest and diseases as well as the targeted use of inputs. Agricultural systems relying on such approaches are not only able to support high productivity, but also preserve biodiversity and safeguard the environment. Thus, Conservation agriculture has come up as a new paradigm to achieve goal of sustained agricultural production. It is a major step toward transition to sustainable agriculture. 

Introduction

In India out of the total 142 million ha of arable land around 67 per cent of them are affected by some form of land degradation due to development of salinity/sodicity or acidification, erosion by water or wind or chemical contamination. Frequent use of tillage operation under conventional cultivation system particularly in rolling terrain is one of the major causes of land degradation through accelerated water and wind erosion. The basic purpose of primary tillage operations are to control weeds, increase the availability of nutrient to plant through accelerated mineralization of organic matter, and to keep the field clean and pulverized for ease of sowing of the next crop. However the bare and pulverized top soil made them vulnerable to accelerated soil loss through runoff and also to erosion loss of soil by wind in drier agro-climatic regions. Besides soil loss, conventional tillage operation breaks the soil aggregates and exposes the soil organic carbon locked inside the aggregates to accelerated microbial degradation and thus results in net loss of organic carbon from the arable ecosystem.

The productivity of agricultural ecosystems depends on the interactions and interdependence of numerous species, such as other plant species, micro-organisms, pollinators, predators of agricultural pests and livestock. Agricultural ecosystems serve as an important habitat for many plant and animal species. Wild species are sometimes used to provide valuable genetic resources, for instance for certain plant breeding. When preserved, these can help to meet future food and livestock production challenges, including adaptation to climate change. Conservation agriculture provides an ample opportunity for the maintenance of agricultural biodiversity. This paper discusses the agricultural development phases, their consequence on the environment and cropping system diversification opportunities in conservation agriculture.

Introduction

The basic principle of conservation agriculture is to minimize soil disturbance in order to stabilize the soil structure, increase the fertility and balance the eco-system. Applied together, conservation agriculture practices – no tillage, permanent soil cover, use of crop cover and crop rotation, residue management- have complementary positive outcomes; no tillage maintains soil structure and biological activity; a permanent soil cover protects the soil surface from erosion and creates a stable and favourable micro-climate; cover crops and residue management provides organic matter, reduce soil erosion and improves soil fertility. Management of the soil water balance should be considered as a positive for cover crops and improvement of soil water infiltration, reduction in soil water evaporation, and decreasing water extraction from the soil would impact subsequent plant growth.

Introduction

“Conservation agriculture (CA) is a concept for resource-saving agricultural crop production that strives to achieve acceptable profits together with high and sustained production levels while concurrently conserving the environment” (FAO, 2007). Aspects of conservation that we normally deal are the management of soil, water, crop diversity, animals, storage of produce (seed, fertilizer, etc.), and maintenance of tools, implements, machinery, etc. Some of the important key principles of conservation agriculture are illustrated as (i) Tillage: practice of minimum mechanical soil disturbance which is essential to maintaining minerals within the soil, stopping erosion, and preventing water loss from occurring within the soil. (ii) Crop residues/Mulch: Managing the top soil to create a permanent organic soil cover for growth of organisms within the soil structure. (iii) Crop rotation: The practice of crop rotation with more than two crop species (iv) Economics: Secure farm level economic viability and stability. To achieve this will involve the development of innovation systems focused on the needs of farmers and will include multiple agents who will use their comparative advantages to adapt the principles of CA to the farmers’ various biophysical and socioeconomic conditions. Crop diversification could also be proved as remunerative.  (v) Environment protection:  The CA has a role to conserve the environment in terms of climate resilient agriculture and emission of green house gases (GHG).

Conservation agriculture (CA) refers to a set of agricultural practices involving three basic principles of proven scientific soundness. These include continuous minimum mechanical soil disturbance; permanent organic soil cover with crop residues or cover crops; and diversified, efficient, economically viable, appropriate spatial and temporal crop sequences providing opportunities for saving on inputs (labor, fuel, machinery etc.), improving resource use efficiency (water, nutrient, energy etc.) and mitigating GHGs emission with climate change adaptation. Recently research efforts have been made to refine the crop management technologies which are more resource efficient, improve production and income, and reduce GHGs emission compared to the conventional practices. Resource conserving technologies (RCTs) are increasingly being adopted by farmers in the rice-wheat belt of the Indo-Gangetic Plains because of advantages of saving on labor, water, fuel and cost along with timeliness in operations particularly early planting of wheat.

Introduction

Indian agriculture is entering in a new phase. The major research and development efforts in the Green revolution era focused on enhancing production and productivity of selected food grains crops and only in Indo-Gangetic plains. The new challenges demand that issues of resource and input use efficiency receive high priority to ensure past gains can be sustained and further enhanced to meet the emerging needs. Issues of conservation have assumed importance in view of widespread resource degradation and the need to reduce production costs, increase profitability and make agriculture more competitive. The conventional mode of agriculture through intensive agricultural practices was successful in achieving goals of production, but simultaneously led to degradation of natural resources. The growing concerns for sustainable agriculture have been seen as a positive response to limit both low-input, traditional agriculture and intensive modern agriculture (relying on high levels of inputs for crop production). Sustainable agriculture relies on practices that help to maintain ecological equilibrium and encourage natural regenerative processes. Agricultural systems relying on such approaches are not only able to support high productivity, but also preserve biodiversity and safeguard the environment. Conservation agriculture has come up as a new paradigm to achieve goal of sustained agricultural production. It is a major step toward transition to sustainable agriculture.

Introduction

The subject of conservation agriculture CA has emerged as a need given the declining productivity of land and increasing costs of input that is putting tremendous pressure on the farming community. Higher yield expectation from land given also brings pressure to the subject of food security. Considering the markets with the globalisation influence is beyond a farmer’s means of influence and price realisation is not a point of control, the situation has deteriorated to their disadvantage. Climate change and soil degradation on the other hand is a reality and agriculture is both a sufferer and contributor, and cannot ignore this reality. Good physical management of soils is one of the key factors to maintain or improve agricultural productivity, in tropical and subtropical regions, and to reduce soil and environmental degradation (Lal, 2000). Tropical soils often have a stable structure and are well aggregated but management practices like intensive ploughing or avoiding the use of cover crops can lead to rapid deterioration (Madari et al., 2005).

Introduction

The hills and mountains are one of the most important agro-ecosystems that supports life of half of the mankind either directly or indirectly. In India, hills are rich source of bio-diversity and possess enormous potential for sustaining agriculture, including horticulture and animal husbandry. The ecological fragility and vulnerability of the Himalayas to climatic aberrations, increasing demand for land to grow more food have been issues of concern for quite some time. Nearly 59% of the total work force in the Himalayas is engaged in subsistence agriculture which is barely enough to feed the growing population for 5-6 months in a year (Raizada et al., 2009). The North-West Himalayas (NWH) consisting of Jammu & Kashmir, Himachal Pradesh and Uttarakhand spreads to 33 million ha, habited by 25 million humans and 19 million livestock. Though, the whole economy of the region is based on agriculture, the total cultivable land is only 3.2 million ha of the total geographical area of the region (Srivastva et al., 2009).

Introduction

The Indo-Gangetic plain (IGP) is of great importance for the food security of India. It extends over 1,600 km with a width of 320 km, including the arid and semi arid environments in Rajasthan and Punjab and the humid and per humid deltaic plains in west Bengal (Shankaranarayana, 1982). During the green revolution period in the early 1960s, production increased through area expansion and intensification of the rice –wheat system. Driving forces included suitable thermal regimes for rice and wheat cultivation, development of short- duration, nitrogen responsive cultivars, expansion of irrigation and an ever increasing demand for food from the rising population. The rice –wheat system, covering an area of around 10 million hectares (mha), is the major cropping system in the IGP. These two crops together contribute more than 70 % of total cereals production in India from an area of around 25 mha under wheat and about 40 mha under rice. The small states of Punjab and Haryana contribute 20 % of the total national grain production and 50 % and 85 % of the government procurement of rice and wheat, respectively (Singh, 2000).