eChapters

The Renewable energy (also called green energy) is generally defined as energy that comes from resources which are naturally replenished on a human timescale. In other words, Renewable energy is energy derived from natural sources that are replenished at a higher rate than they are consumed. The most widely used renewable energy types are solar energy, wind energy,biomass energy, and hydroenergy.
India has made significant progress in the renewable energy sector, with renewable energy accounting for 43.12% of the country’s total installed power generation capacity. Globally, India ranks 4th in overall renewable energy capacity, 4th in wind power with 46.65 GW, and 5th in solar photovoltaic power with 85.47 GW. The country has surpassed 200 GW of non-fossil fuel energy capacity which includes 85.47 GW of solar power, 46.93 GW of large hydropower, 46.66 GW of wind power, 10.95 GW of biopower, 5.00 GW of small hydropower, and 0.60 GW of waste-to-energy capacity.
Presently India has set ambitious renewable energy targets. By 2030, the country aims to achieve 500 GW of non-fossil fuel energy capacity and meet at least 50% of its total energy requirements through renewable sources. These efforts position India as a global leader in the transition towards sustainable and clean energy.
In recent years, India’s renewable energy capacity has grown rapidly. As per the Ministry of New and Renewable Energy (MNRE, 2025), the country’s total installed renewable energy capacity (excluding large hydro) reached 220.10 GW by March 2025. When large hydro and nuclear power are included, the non-fossil fuel capacity has crossed 242.8 GW, representing over 50 percent of India’s total

Soil fertility -importance

From edaphological point of view soil is a medium for plant growth. It holds and nourishes the plants. Soil fertility refers to the ability of soil to supply plant nutrients. Soil fertility and fertilizers are very much closely related terms; and cannot be neglected one from the other in their function. Soil fertility acts as a ‘SINK’ where in plants can draw nutrients for maximum productivity, where as fertilizer, acts as a ‘SOURCE’ wherein we can apply continuously different nutrients. The importance of soil fertility and nutrient management is being increasingly recognized in all countries recently to meet the demand for food and other agricultural raw materials. Intensive use of fertilizer, intensive cropping and high yielding seeds have no doubt increased the food production and reduced the food shortage but it has also ushered in innumerable problems of soil fertility, soil and water pollution. On the other hand, fast depletion of nutrients due to over exploitation, a wide spread deficiency of N, P, K and S coupled with micronutrients deficiencies specially Zn, B and Mo is taking place. Further deforestation, shifting cultivation, burning of crop residues, trees, bushes, grasses and cow dung, soil erosion, nutrient losses and imbalanced nutrient application, leaching losses etc., have aggravated the depletion of soil fertility status. The productivity of Indian agriculture solely depends on scientific management of soil fertility along with judicious and efficient use of fertilizers integrated with organic sources.

1.1 Introduction to Sustainable Energy
The idea of sustainable energy has come to light in the twenty-first century as the globe struggles with rising energy demands, environmental degradation, and the menacing threat of climate change. It offers hope and a way forward for a more promising future. A major change in the production, distribution, and consumption of energy resources is what sustainable energy entails. It is a paradigm that includes a range of clean and renewable energy sources, technologies, and methods with the goal of supplying our energy demands with the least amount of harm to the environment (Andrews and Shabani, 2014). 1.2 Importance of Sustainable Energy Sources Sustainable energy is of paramount importance due to several interconnected reasons listed below and shown in Figure 1:
1.2.1 Environmental Concerns: For many years, conventional fossil fuelbased
energy sources like coal, oil, and natural gas have formed the foundation of our energy system. But as they burn, greenhouse gases (GHGs) mostly carbon dioxide (CO2) are released into the environment (Hosseini and Wahid, 2016). These greenhouse gases are the main causes of climate change, which raises global temperatures, brings on harsh weather, and raises sea levels. Conversely, sustainable energy sources are crucial for reducing climate change because they emit little or no greenhouse gases when in use.
1.2.2 Finite Nature of Fossil Fuels: Because fossil fuels are limited resources,
their stocks are running out quickly. The task that follows is to ensure that future generations have access to economical and dependable energy sources. Because they are renewable or endless, sustainable energy sources provide a solution to the problem of energy security (Su-Ungkavatin et al., 2023).
1.2.3 Economic Benefits: Making the switch to renewable energy can be
very profitable. It can improve national energy security and lessen trade deficits by fostering innovation, generating jobs, and lowering dependency on energy imports. Furthermore, because they frequently have lower operating and maintenance costs than fossil fuel-based systems, sustainable energy technologies can result in cost savings over time (Shafiei et al., 2015).

1.1. Soil Resource Evaluation

Soil is the essence of life on the planet Earth. It has sustained humanity and human civilizations through five functions (Karlen et al. 1997) viz., i) sustaining biological activity, diversity and productivity; ii) regulating and partitioning water and solute flow; iii) filtering, buffering, degrading, immobilizing and detoxifying organic and inorganic materials, including industrial and municipal byproducts and atmospheric decomposition; iv) storing and cycling nutrients and other elements within the earth’s biosphere; and v) providing support to socioeconomic structures and protection for archaeological treasures associated with human habitation. Reeling under the pressure of increasing food, fodder, feed, fibre and fuel production, soil has been used as a medium of plant growth with considerable reliance on external supply of major nutrients, irrigation water, plant protection chemicals, etc. Although soil, a product of millions of years of weathering, has supported various forms of terrestrial life, its sustainable management holds the key for meeting the basic requirements of burgeoning population and development commitments. So intense has been the pressure of increasing food, fodder, feed, fibre and fuel production that the soil has been exploited often exceeding its carrying capacity. The soils are increasingly used for agricultural and non-agricultural uses, such as disposal of farm, urban and industrial wastes, ensuring environmental safety etc. This is possible by the judicious use of this resource.

A clear and intimate knowledge of the kinds of soils and their extent of distribution are essential prerequisites in developing rational land use plans for agriculture, forestry, irrigation, drainage, etc. soil resource inventory or mapping provides an insight about their potentials and limitations. It is therefore imperative to prepare an inventory of this resource for developing optimum land use plan and conservation plans.

This chapter presents a birds’ eye view of the soil to develop the interest among the readers to know more about the fundamental concepts of soil.

Soil is a major determinant of terrestrial ecosystems and helps in the distribution of land flora and fauna. Soils are sources, transformers and stores of plant nutrients. Soils are the recycling places of plant and animal residues and wastes. Soils are also the screen and filter of pollutants in many ways, forms and degrees. Soils are the main link and recharger of hydrological cycle. Soils influence radiant heat exchange, temperature change and land surface reflection characteristics. Soils are important sources and sinks of biogeochemical cycles of carbon dioxide, methane, nitrogen oxides and sulphur dioxide. Soil is used in buildings, roads, brick kiln, naturopathy etc. Soils are good record of past climatic conditions and human activities, as they have some stable features originated from the interactions of climate, organisms, relief, parent material and time. Soil provides nutrients, water, air, heat and mechanical support to arable plants to produce the food, fodder, fibre, fuel and other plant products for human and animals. Mainly the soil is studied as a natural body and as a medium for plant growth.

From the dawn of settled agriculture, the rhythm of seasons and the vagaries of weather have dictated the fortunes of human societies. The earliest farmers were keen observers of the skies, their very survival intricately linked to predicting rainfall, temperature fluctuations, and the onset of frost. This fundamental dependence fostered the nascent field of agricultural meteorology, an art and science passed down through generations, relying on empirical knowledge and local wisdom. Think of the ancient civilizations that timed their planting cycles with the flooding of rivers, or the traditional weather lore that guided farmers on when to sow and harvest. Even today, this fundamental understanding remains crucial, forming the bedrock upon which modern agricultural meteorology is built (Fig.1.1).  However, the 21st century presents agricultural systems with unprecedented complexities. The looming shadow of climate change manifests in increasingly erratic weather patterns: intensified heatwaves scorching crops, prolonged droughts decimating livestock, and more frequent and severe floods inundating arable land. These changes disrupt traditional agricultural practices, threaten yields, and exacerbate food insecurity, particularly in vulnerable regions. The comfortable predictability of the past is eroding, demanding a far more sophisticated and proactive approach than ever before.

The world is facing unprecedented challenges in ensuring global food security, and climate change is exacerbating these challenges. Rising temperatures, changing precipitation patterns, and increased frequency of extreme weather events are altering the dynamics of crop diseases, making them more unpredictable and difficult to manage. The consequences are dire: crop diseases can lead to significant yield losses, reduced food quality, and economic hardship for farmers. Therefore, it is imperative that we develop and implement effective strategies for managing crop diseases in the face of climate change. Weather wisdom is a critical component of these strategies. By understanding and interpreting weather patterns and their impact on crop diseases, farmers can make informed decisions about crop management, disease monitoring, and control. This approach is essential for climate-smart agriculture (CSA), which aims to promote agricultural practices that can help farmers adapt to climate change while improving agricultural productivity and sustainability. By leveraging weather wisdom, farmers can reduce crop losses, improve food quality, and enhance their resilience to climate change. This book, “Weather Wisdom for Crop Disease Management: A Requisite for Climate-Smart Agriculture,” provides a comprehensive overview of the role of weather wisdom in crop disease management. The book brings together the latest research and knowledge on the impact of weather patterns on crop diseases, as well as practical strategies for leveraging weather wisdom to manage crop diseases. The book is designed to serve as a resource for farmers, extension agents, researchers, and policymakers who are interested in promoting climate-resilient crop disease management practices.
1.1 Role of Weather in Disease Managemènt
Weather plays a crucial role in the occurrence and spread of crop diseases. The development and dissemination of plant pathogens are significantly influenced by weather conditions such as temperature, humidity, wind, and precipitation (Fig 1.1). A climate change may alter the life cycle, survival, virulence and even genetics of a plant pathogen. Favorable environmental conditions are always a prerequisite for a pathogen to establish pathogenicity. Temperature is a critical factor in the development of crop diseases. Optimal temperatures vary among different pathogens, and temperatures that are either

This chapter introduces soil testing as an essential component of scientific nutrient and land management. It traces the establishment and expansion of soil-testing laboratories in India and explains their role in assessing soil fertility, productivity and physical, chemical and biological conditions. Soil testing helps determine suitable fertilizer and amendment requirements while preventing the excessive or unbalanced application of nutrients. The chapter emphasizes that fertilizer recommendations must reflect differences among soils and fields. It also introduces representative soil sampling as the foundation of dependable laboratory results and outlines important precautions concerning equipment calibration, clean glassware, contamination prevention and safe laboratory practices.

Arsenic contamination is one of the serious concerns for public health throughout the world. During the weathering of rocks and minerals, which are followed by subsequent leaching and runoff, arsenic (As) is released into the soil and groundwater. Additionally, human sources can transfer it into the soil and groundwater. Depending on the geological settings, geochemistry, and geo-environmental conditions of an aquifer, different aquifers may have different adsorption and desorption processes, arsenic species, Eh, pH, solid phase dissolutions, and precipitations. Therefore, rigorous geochemical investigation for an adequate understanding of arsenic geochemistry under different hydrogeological and geo-environmental conditions of aquifers is essentially required for evolving sustainable solutions. All of the arsenic affected river plains have river routes originated from the Himalayan region. Arsenic in groundwater contamination has far-reaching consequences including its ingestion through the food chain, which are in the form of social disorders, health hazards and socioeconomic dissolution besides its sprawling movement, and exploitation of groundwater. Food crops produced with arsenic tainted water are marketed to other locations, including areas where people may eat the tainted food and be exposed to arsenic. The arsenic contamination of groundwater is a form of groundwater pollution which is due to naturally occurring high concentrations of arsenic in deeper levels of groundwater.

The Asia-Pacific region is highly vulnerable to climate change, with impacts such as more frequent natural disasters, sea-level rise, floods, droughts, and changing weather patterns. Rural areas, particularly those reliant on agriculture, are disproportionately and non-identically affected. The Asia-Pacific region, home to over 60% of the world's population, is among the most vulnerable to climate change due to its diverse geography, dense coastal populations, and socioeconomic disparities [IPCC, 2022a], Climate change is an emerging threat that affects all countries to varying degrees. The recently released IPCC Assessment Report identified agriculture as one of the critical sectors both susceptible to climate change and contributing to it through Greenhouse Gas (GHG) emissions. Countries in the Asia-Pacific region are investing significant resources to strengthen agriculture on various fronts. These investments focus on the research and development of new varieties and agro-technologies to adapt agriculture to emerging climatic threats and, simultaneously, mitigate GHG emissions from the agricultural and allied sectors. These initiatives are in their early stages, and there is a need to assess the current status of countries' vulnerability to climate change and the measures taken to address

Agriculture encounters a complex dynamic system of natural conditions. The meteorological factors among these natural conditions play a pivotal role so far as agriculture is concerned. The rate of growth and development of a bio-system is largely depending upon its ambient temperature and moisture. The plant productivity per unit area, total production, quality of the produce, operational efficiency as well as econometrics are solely governed by the meteorological parameters. Therefore, their through understanding including the computation and the measurement techniques is absolutely essential. It is no less important to have sufficient workable information on weather phenomena as well as climatic resources to determine realizable potential and an appropriate solution for a number of problems faced in agriculture.

Any perturbation and chaos in ecological setting and its functioning will lead to serious disruptions disruption in both resilience and livelihood. This is exactly what is being confronted by Indian Agriculture upfront. Our soils are brutally extorted to accept the harsh reality that close to 70 per cent of our cultivable land is starving of organic carbon. The ground water depletion in the name of modern agriculture has been another testimony of our ruthlessly prodigal agriculture amounting to serious water crisis. Every five seconds equivalent to a football ground, the golden acres, are vanishing with fertile soil from the chest of the planet. Thus, soil erosion amounting to almost 15 tons per hectare per year in Indian agriculture is not only alarming but also humongous. The losses of biodiversities including floral and faunal counts are adding blistering blistering barrier for our food production system. In the name of green revolution, we turned wrongly illusioned with the ability of so called high yielding varieties and have driven out our valuable landraces to invite gene myopia and gene erosion. This has got a catastrophic consequence. The stagnation of production and productivity in food sector is going to be the bleak indicator of our fragile and frail ecological resilience in the entire production system. But the down to earth reality is that apart from experts, most of our farmers are not aware of this threat, sensitized either. The book has assimilated the data in a delving manner, and real time fact of ground reality that reveals an interesting interpretation of farmers' perception on the rhetoric’s of ecological resilience in India.

A model is something that mimics the behavior of some real system of interest. Our interest here will be in water quality models, which are usually equations, and which predict some result based on factors that influence that result. A water quality model is a representation of a real system. The essence of a good water quality model is that it is simple in design and exhibits the basic properties of the real system that we are attempting to understand. The model should be testable against empirical data. The comparisons of the model to the real system should ideally lead to improved mathematical models. The model may suggest improved experiments to highlight a particular aspect of the problem, which in turn may improve the collection of data. Thus, modeling itself is an evolutionary process, which continues toward learning more about certain processes rather than finding an absolute reality.

Water pollution is a large set of adverse effects upon water bodies such as lakes, rivers, oceans, groundwater caused by human activities. Although natural phenomena such as volcanoes, storms, earthquakes etc. also cause major changes in water quality and the ecological status of water while these are not deemed to be pollution. Water pollution has many causes and characteristics. Increases in nutrient loading may lead to eutrophication. Organic wastes such as domestic sewage and farm waste impose high oxygen demands on the receiving water leading to oxygen depletion with potentially severe impacts on the whole ecosystem. Industrial discharge a variety of pollutants in their wastewater including heavy metals, organic toxins, oils, nutrients, and solids. Discharges can also have thermal effects, especially those from thermal and nuclear power stations, and these too reduce the available oxygen. Siltbearing runoff from many activities including construction sites, forestry and farms can inhibit the penetration of sunlight through the water column restricting photosynthesis and causing blanketing of the lake or river bed which in turns damages the ecosystems the process is called as eutrophication.

Pollutants in water include a wide spectrum of chemicals, pathogens, and physical chemistry or sensory changes. Many of the chemical substances are toxic or even carcinogenic. Pathogens can obviously produce waterborne diseases in either human or animal hosts. Alteration of water’s physical chemistry include acidity, conductivity, temperature, and excessive nutrient loading. Even many of the municipal water supplies in developing countries can present health risks leads to many diseases.

1.1. Meteorology and Climatology
Atmospheric science encompasses the main subfields of meteorology and climatology that are similar in the scientific principles and phenomena being examined, but usually differ by approach, time scale, and application. Meteorology is the scientific study of the atmosphere and weather including weather forecasting. It is an interdisciplinary science that involves observing, understanding and predicting weather conditions likely to prevail well in advance (Fig.1.1). The study of meteorology has been around thousands of years, but significant progress did not begin until the 18th century. Climatology is an atmospheric science that focuses on the processes that create weather patterns and variability. Climatology was developed as a science that is based on weather data recorded at multiple locations for comparatively longer periods, usually for 30 years or more. The study of climatology based on the physical processes is influenced by the geographical features, topography and interaction between land and oceans.
1.2. Agricultural Production
Life demands food. The production of food depends upon 4 major factors that are soil, genetic material, management practices and weather. Over a period of time, formers have evolved the cropping strategies based on their local knowledge and experience on the changes in weather within a cropping season. With rapid advances in agricultural sciences, several new varieties of crops were developed, appropriate soil and water management practices were evolved and suitable measures for reducing abiotic and biotic stresses on crops were identified. However, the recent threats of climate change due to increased atmospheric

The magnitude and trajectory of changes in ecosystem services and functioning have been as conspicuous as has never been until before 1980’s in this subcontinent. Both the services and resilience of agro-ecosystem, the pivotal for agricultural production and security have been disrupted in the name of modernization of agriculture as well as commercialization.
The impact of green revolution in India, that look place during 1960’s and 1970’s have started eroding very fast and as the consequence of this green revolution, the ground water depletion has gone to the worst, it is contaminated either. 40 % of ground water in Punjab has been moderately or severely contaminated leaving agriculture a coercive proposition both from economic and ecological perspective. 10-15 tonnes of top soil are being eroded per hectare per year in its wrong welcoming to farm mechanization process. Most of the highly yielding varieties which did the ‘magic revolution’ now has been fatigued or segregated either. The social-ecological impacts on agriculture perhaps have been both disruptive and deleterious. Due to unabated fragmentation of holding which again is tiny in size, has initiated another problem of resource and energy wastage, bad enough to add to an ecological disruptions.
With a non-denial to the gleaming success of green revolution, which ensured us with much awaited food security and self-reliance, has its intrinsic weakness and coercion as well.

1.1. Background

Once this beautiful planet conceived human civilization with the glory of motherhood, the birds kept on twittering in an ecstasy of joy and freedom; the ripples of pristine rivers, blue and giggling, offered shelter to silvery fishes and pink Amazon Lilies! But human greed has defeated its own needs. So, what had been a means to survive now has turned into tools to triumph, rather, a weapon to destroy her own creation. By this time, we have transformed fertile lands into a barren Arizona, deep forests into a nasty slums and blue rivers into a filthy stream, called Yamuna.

The advent of the Anthropocene, implies that an unprecedented era of human impact on the natural environment, is now so large that the Earth has entered a new geological epoch; it is leaving the Holocene, the environment within which human societies themselves have developed (Gornish and dos Santos, 2016; Reynolds, 2021). Climate change is a prominent sign of human- driven changes to the global environment. There is every reason to be alarmed about anthropogenic climate change, pollution, and biodiversity loss, all of which have been accelerating in recent decades and do pose “existential crisis” (Díaz et al., 2020; Abhilash et al., 2021). Sixth Assessment Report of Intergovernmental Panel on Climate Change (IPCC) released on February 28, 2022, paints a troubling picture as limiting global warming to 1.5oC (a global target in the Paris Climate Agreement) is not safe for all. If warming exceeds 1.5oC, even temporarily, much more severe, often irreversible effects of climate change will occur, land and ocean temperature change, sea level rise and ocean acidification, loss of Arctic Sea ice and ice sheets, stronger storms, longer heatwaves and droughts, abrupt precipitation mainly intensity and seasonal distribution, thawing permafrost and more (IPCC, 2013). On the basis of the Sixth Assessment UN Secretary-General António Guterres said “The alarm bells are deafening, and the evidence is irrefutable: greenhouse gas emissions from fossil fuel burning and deforestation are choking our planet and putting billions of people at immediate risk.” According to the United Nations (2015), there are still 836 million people in the world living in extreme poverty (less than USD,1.25/ day). And according to the International Fund for Agricultural Development (IFAD), at least 70% of the very poor live in rural areas, most of them depending partly or completely on agriculture for their livelihoods. It is estimated that 500 million smallholder farms in the developing world are supporting almost 2 billion people, and in Asia and sub-Saharan Africa these small farms produce about 80 percent of the food consumed (IFAD, 2011). The rural poor often depend partly on forests for their livelihoods (World Bank, 2002). It is estimated that between 660 and 820 million people (workers and their families) depend totally or partly on fisheries, aquaculture and related industries as a source of income and support (HLPE, 2014).

Meteorology is derived from the Greek word meteoro which means above the earth’s surface; i.e., the atmosphere. The state of the atmosphere experienced at a given time, in any location on the surface of the earth is known as weather. Thus meteorology is the scientific study of the atmosphere or the weather. It is a branch of physics dealing with atmosphere and it is often quoted as the ‘physics of the lower atmosphere’. The main focus of meteorology is to understand the weather processes and forecast the weather. Solar radiation, the air mass and moisture are the three key ingredients that make up weather. The exchange of heat, moisture and momentum between the earth’s surface and the atmosphere determines the characteristic of weather. The observable weather events are known as meteorological phenomena and are defined by a set of variables called weather elements. Atmospheric temperature, atmospheric pressure, humidity, precipitation, cloudiness, wind and visibility, etc. are examples of such weather elements. The weather elements are not separate entities. They are closely related with each other and are highly variable in nature. Meteorology explains and analyses the changes of these weather elements.

METEOROLOGY

The major subdivisions of meteorology are dynamic meteorology (or atmospheric dynamics) and physical meteorology (or atmospheric physics). The dynamic meteorology is concerned with the analysis and interpretation of the three-dimensional, time-varying, macro scale motions and energy transformations in the atmosphere. The science of dynamic meteorology is meant to develop models based on the hydrodynamic and thermodynamic equations. The physical meteorology is concerned with the processes that alter the physical properties and the chemical composition of air parcels as they move through the atmosphere.

1.1 Weather Forecasting
Farmers have always been at the mercy of the weather, and accurate forecasting has become an essential tool for their decision-making process. Weather forecasts play a critical role in supporting farmers’ decision-making processes, from crop planning and management to harvest planning and economic decision-making. Crop planning and management is one of the key areas where weather forecasts are crucial. Farmers use weather forecasts to determine the best time to plant seeds, taking into account temperature, moisture, and sunlight requirements. This enables them to choose crops that are suitable for the predicted weather conditions. Additionally, forecasts help farmers optimize irrigation, reducing water waste and ensuring crops receive adequate moisture (Fig.1.1).
Weather forecasts also help farmers mitigate weather-related risks. Extreme weather events like floods, droughts, heat waves, and storms can have devastating effects on crops. Accurate forecasts enable farmers to prepare for and respond to these events, reducing crop damage and loss. For instance, forecasts help farmers take measures to protect crops from frost and freeze damage, which can be catastrophic for certain crops.

“Hydrology is the science that treats the waters of the earth, their occurrence, circulation and distribution, their chemical and physical properties, and their reaction with their environment, including their relation with living things. The domain of hydrology embraces the full life history of water on the earth.” (Federal Council for Science and Technology, “Scientific Hydrology”, Washington, 1962)

This definition puts in a nutshell what is most often inadequately done before undertaking exploitation of water resources. In short, it is the scientific inputs that are likely to be missed while planning water resources management projects. It is the “full life history of water” part of the above definition that is of specific relevance to the theme of this book, Isotope Hydrology.

Conventional hydrology is strong on measurement and quantification of different parts of the hydrological cycle (Fig.1.1), be it precipitation, run-off, evaporation, transpiration, infiltration, groundwater dynamics etc. Through chemistry and isotopes, we try to understand the processes themselves in order to delineate the history of that part of the hydrological cycle that is being studied. For example, if we are measuring river flow, we would like to know the contribution of different components; base flow, rainfall run-off and snow melt, if any.

Let’s see what we know and what do not know in the conventional hydrological practice. We know surface waters evaporate, form into clouds and precipitation occurs under favourable weather conditions. What we often do not know is the source of moisture, oceanic or inland.

Crop production broadly depends on the fertility of the soil where a crop is raised. There are several factors like the kind and quality of seed, climate, water supply, and plant protection measures etc. that affect the crop production. Among these factors, the fertility status of the soil largely determines the ultimate yield even if all these factors are optimum for crop production. A clear distinction should be made between soil fertility and soil productivity. Soil fertility deals with the inherent capacity of soil to provide nutrients in adequate amounts and in proper balance, for the growth of specified plants when other growth factors such as light, water and temperature, and the physical condition of the soil are favourable. Soil productivity is concerned with the capability of soil to produce a specified plant or plant parts or a sequence of plants under well defined and specified systems of management inputs and environmental conditions, viz. climatic conditions. It does not mean that a fertile soil is always productive. A fertile soil, under a bad management system, may be unproductive for a crop. In this book, plant nutrient elements and their available forms, functions and deficiency symptoms are briefly described for the better understanding of soil testing and fertilizer recommendation.