eChapters

4.1. Introduction

Globally, rice is cultivated on about 165 million ha of land, which provides around 787 million tons of paddy annually (FAO, 2023). In Asia, 708 million tons of paddy is produced from nearly 143 million rice-cultivated areas. Rice crop is grown in a wide range of climates, varied soil types, and hydrological situations. Rice is the lone cereal crop that grows well in floods.

The rice habitat can be divided into four groups based on the hydrology of the rice field: irrigated lowland rice (79~80 million ha), rainfed lowland rice (54~55 million ha), upland rice (14~15 million ha), and flood-prone rice (11~12 million ha) (Table 4.1) (Bouman et al., 2006).

5.1. Introduction

Rice-fallows are a rainfed rice mono-crop production system, where only a single crop (rice) is grown and these lands remain without any crop for the rest of the period of the year (fallow). An estimate shows that rice-fallow areas extended over 22.3 M ha in South Asia, maximum in India ( 88.3%) followed by Bangladesh (8.7%), Nepal (1.4%), Sri Lanka (1.1%), Pakistan (0.5%), and Bhutan (0.02%) (Gumma et al., 2016). The eastern part of India accounts for ~ 84% (9.7 million ha) of the country’s total rice-fallow area (i.e. 11.7 million ha) (Ali et al., 2014; Singh et al., 2017), despite high rainfall during rainy / monsoon season. The reasons are that after the rainy season, irrigation facilities are lacking, very fast depletion of the soil residual moisture due to temperature rise, the poor economic condition of the farmers, and a lack of awareness or knowledge of available technologies. Additionally, delayed harvesting of long-duration rice (150-160 days) results in late sowing of winter crops, which, in turn, exacerbates the temperature and moisture stresses in winter crops (Kumar et al., 2018a; 2018b). Overall, the challenges of growing another crop in rice-fallow areas are the lack of irrigation facilities including declining groundwater levels, the dominance of the long-duration rice varieties cultivation, higher evaporative loss of the residual soil moisture, degradation of soil quality, and poor financial conditions of the farming community with diminishing profit. Recently, climate change with erratic rainfall and delayed monsoon arrival added more challenges for these areas in several places. Deficit soil moisture imposes stress on the crops and negatively affects the winter crops productivity in the rice-fallow system, and several times it results in complete crop failure (Singh et al., 2012; Ghosh et al., 2016).

Introduction

Crop production system includes the components like soil, climate and plant (genetic) material. Within a particular genetic make up of the crop, productivity of the system is limited either by climatic factors, that is, radiation, temperature and rainfall (water), or by inherent edaphic environment that govern the root development and consequent uptake of water and nutrients. Where soils are cultivated over long periods, the edaphic conditions reach at its low levels. When water, nutrients and CO2 are plentiful, yield is determined by radiation and temperature regimes during the growing season. However, under actual field situations, the yields are limited by factors other than climate, which is water and nutrients. These are not only limited in amounts but also are becoming costlier every year. It is, therefore, important that available fertilizers be used efficiently.

Summary
 
This chapter explores different approaches to manage water in rain-fed and irrigated agricultural systems. The first methods support the retention of water and reduce soil erosion. These methods include mulching – the application of a surface coating over the soil – which is usually organic mater. This reduces the damage to soil caused by rain and wind and reduces water loss to evaporation and helps with infiltration. The other methods explored are bunding and terracing.  These approaches are about stopping the flow of water across land to increase the amount of water infiltration into the soil and to reduce or prevent soil run off.  These approaches are labour intensive. A less labour -intensive approach is contour ploughing. This approach is about encouraging farmers and tractor drivers to plough across sloping fields not up and down them. The second group of technologies refers to the introduction of water through irrigation methods.

6.1 INTRODUCTION

Water in soils is essential to plant growth, being the medium through which inorganic nutrients are translocated to the root surface and carried through the plant. Most of the water in soils at or near field saturation can be considered as equivalent to bulk water, and only bulk properties need be considered in discussing its movement through soil interstices and its retention in soil capillaries; this is the field with which soil physics deals. But, in the first molecular layer in contact with soil particles, and perhaps for several molecular layers beyond, the behaviour of water molecules is very different from that in the bulk. Strong adsorptive forces can reduce the volatility of these molecules and restrict their mobility. Such an adsorbed layer of water competes with other polar molecules for adsorption sites, and so has an important role in determining the release and retention of fertilizers and pesticides. Such strongly adsorbed layers confer wettability on soils, but hydrophobic surfaces can also be present and these lead to non-wettable soils with serious consequences in run off and inefficient use of precipitation. This region of distinctive molecular interactions between water and soil particles falls within the field of soil chemistry.

ABSTRACT

Remote Sensing and Geographical Information System play major role in the water planning of river basins. Varahanadhi is one of the 17 major river basins of Tamilnadu, bounded in North by Palar basin, East by Bay of Bengal and West & South by Ponnaiyar basin. It drains through Thiruvannamalai and Villupuram districts. There are three sub basins viz., Ongur, Nallavur and Varahanadhi sub basins. From Survey of India top sheets, Basin boundary, sub basin boundary maps were generated. Administrative map with district, block boundaries was prepared. GIS software - Arc view, was utilized for this purpose. By using ERDAS IMAGINE, Digital Image processing software, satellite image mosaic of Varahanadhi Basin, Geomorphology, Land use, Wasteland, Structural-Lineament maps were generated. IRS P 6 RESOURCESAT, LISS III and PAN data were used for the thematic map preparation. From the collateral data collected, the thematic maps on Geology, Soil, and annual north east, south west. summer, winter rainfall, irrigation system, pre monsoon and post monsoon groundwater levels, ground water quality were prepared using ARC GIS Software. Relief and Drainage map were also generated in GIS environment. The surface water potential was assessed by rainfall run off method for which geomorphology map interpreted by remote sensing and GIS was utilized. Based on geomorphology and land use maps, draft for irrigation was estimated. Geology, geomorphology, depth to bedrock, rainfall pattern, water level maps were used

to asses groundwater potential and draft. Sectoral demand on power, industry and domestic were made based on collected collateral data. Environmental Impact Assessment was assessed using land use maps and ground water quality maps interpreted from remote sensing data for years 1998 and 2004 were prepared and compared. Wasteland map was prepared to know the extent of wastelands and their types as per National Waste Land Board norms. Remedial measures to convert waste lands into productive lands were also suggested. By superimposing geomorphology and lineament maps upon the wastelands, sites suitable for groundwater development in the waste lands were identified. In the same way by using GIS overlay analysis developmental and action plan maps were also prepared with technical recommendations. By applying remote sensing and GIS techniques the basin water resources assessment, draft to meet out sectoral demands and balance of water available for future use can be decided. Varaganadhi basin is a surplus basin as per the study.

Introduction
Water is chemical substance which important for all living organism to survive on this planet. Water is necessary for all cell of the living organism’s body to performance any normal work. Water covers 71% of the Earth’s surface, most like in oceans and other more water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapors, clouds and precipitation. Some observation have estimated that by 2025 more than half of the world population will be facing water-based vulnerability, a situation which has been called a ‘water crisis’ by the United Nations. A recent report suggests that by 2030, in some developing regions of the world, water desire will be exceed supply by 50%. The total volume of water 1,385 million Km3 on the planet earth, 96.5% is salt water (oceans and seas), the fresh water is mostly ice (24 million Km3). The fresh water available as annual stream flow is 46,768 Km3, that is 0.00034% of the total global water. If there is no intake of water into the body, death can ensue in 7-10 days. Water is also essential to man for maintaining personal hygienic and freedom from disease. Today there are many cities worldwide facing actual shortage of water and nearly 40 percent of the world’s food supply is grown under irrigation and a wide variety of industrial processes depends on water. Water is the most vital element among the natural resources, and is critical for the survival of all living any organisms including human, food production, and economic development. The environment, economic growth and developments are highly affected by water is regional and seasonal availability and the quality of surface and groundwater. The quality of water is affected by any human activities and is declining due to the rise of urbanization, population growth, industrial production, climate change and other factors. The resulting water pollution is a serious surrounding to the well-being of both the Earth and its population. The pressures is increasing population, growth of industries, urbanization, energy intensive life style, loss of forest cover, lack of environmental awareness, lack of implements of environmental rule, regulations and environment improvement plans, untreated effluent discharge from industries and municipalities, use of non

Water is indispensable for our life. About 2/3 of earth is covered with water. No organism can survive without water. So keeping water free from any pollutant is very important. Water is said to be  “polluted” when it is hanged in its quality and composition directly or indirectly by man’s activity so that it becomes less suitable for drinking, domestic, agricultural or any other purpose. Polluted water transmits a large number of diseases in man. They are cholera, typhoid, dysentery, jaundice and other bacterial or viral diseases.  Water becomes polluted by the presence or addition on inorganic or organic substances or biological agents. Soil erosion, leaching of minerals from rocks, decaying of organic matter are natural sources of water pollution. There has been an alarming increase in the degradation of water quality in the recent past in the large cities and industrial areas.

Water pollution can be studied under the following heads—  (i) medium in which it occurs (surface water, ground water); (ii) habitat (lakes, estuaries and open seas); and (iii) type of pollutants (bacterial, metallic, thermal and radioactive).

Ours is a Living Planet because ours is a Water Planet. The health of the Living Planet depends on the health of its water resources. Ironically, the health of its water resources is at stake. And so of its life! The waters of the Earth are in the grips of pollution. Much of the water is already polluted and the rest is increasingly becoming polluted. Water pollution, indeed, is one of the worst problems life on Earth is faced with. Water pollution is halting human progress and is phenomenally affecting all walks of human civilization. Water pollution is even putting a question mark on our sustainable future. This chapter presents the causes, magnitude, and consequences of water pollution and also suggests ways and means to prevent and control water pollution and also attempts to manage water resources.

Introduction
In the global perspective, water contamination is a significant issue. Every day, it is the cause of almost 14,000 deaths. The most valuable natural resource on Earth is water, which makes up more than 70% of its surface.
Definitions
• The term “water pollution” refers to the contamination of water bodies by human activity, which can be detrimental to the plants and organisms that call thesem bodies of water home. It can be characterized as any alteration in the quality of water brought about by human activity that makes it less suitable for any of its positive uses, actual or potential. Excess of any substance or heat that could endanger people, animals, or aquatic lifeMan’s actions alter the quality or composition of water, either directly or indirectly, making it unfit for any purpose.
Sources of Water Pollution
• Point source pollution, which is defined as pollution having a distinct source and point of entry into the water, making it easy to identify. It describes impurities that find their way into a waterway by a covert channel, like a ditch or pipe. For instance, contaminants include metals and organics in municipal and industrial discharge pipelines.

It is estimated that the world requires nearly 70 per cent increase in agriculture production to meet the demand for food by the year 2050 based on current trends in population growth it can be achieved either by increasing land under cultivation (which is not possible), increasing the availability of more water for agriculture and efficient utilisation of available land and water resources. The best available option is to increase in productivity of unit of land for unit water. However, the availability of water for agriculture production cannot be presumed to be same year after year as the major source of water is precipitation more known for its uncertainty due to change in weather patterns from season to season and year to year all over the world. The element of uncertainty is increasing since the beginning of the present century due to climate change under the present circumstance, the crop production is practiced -
• In Irrigated Areas
• In Rainfed Areas
• Under Conserved Moisture Condition Without Any Source Of Irrigation
For increasing crop production under irrigated condition, it is necessary to identify crops and varieties that can produce more yield per unit of water even when there is some decrease in availability of water through irrigation. Therefore, the concept of water production function is used for evaluation of water use efficiency of the crops.

The quality of irrigation water is a crucial factor for long-term soil productivity. Poor quality water if used for a long time can make the soil less productive or even barren, depending on the amount and type of constituents present in it and the texture of the soil in question. Low or marginally saline waters sometimes appear to stimulate crop growth because of the higher amounts of nutrient ions present.

Aquaculture is the cultivation of fish, molluscs, crustaceans (shell fish) and aquatic plants in controlled conditions, provides an increasingly significant proportion of food production globally. The sector has represented the greatest growth of all food production systems in the last two decades and an estimated 10% yearly increase in output is likely to bring productivity to a predicted 47 million tonnes in the year 2010 (Pedini and Shehadeh, 1997). Significantly, the greatest contribution to total production and the greatest rate of uptake of aquaculture activity is in the developing world. More than 82% of the total global yield in 1999 was produced by developing countries (GESAMP, 2000) and growth rates between 1984 and 1995 were six times higher than that from developed countries (Rana, 1997; Tacon, 1996).

2.1 Historical Development

We have seen in Chapter 1 that modeling is about establishing cause effect relationship. Perhaps one of the earliest attempts in this direction is made as early as 1848 in Germany where it was tried to establish a relation between purity and pollution to the occurrence of certain biological organism. But as far as water quality modeling is concerned the first major breakthrough in this direction is the effort of Streetor and Phelps (1925) in oxygen sag curve. They developed model for estimating DO and BOD in Ohio River. The work of O’Conner (1962) for bacteria models are major milestone in pre-computer era modeling.

With the advent of computer during 1960s complicated kinetics and time variable simulation came into being. Most of the workers presented their efforts in terms of linear programming based water management models concerning waste discharge. Thomann(1963) has formulated linear programming based models for dissolved oxygen in an estuary. So a stage is set for study of eutrophication through modeling, but the problem is determination of values of various parameters in these equations.

During 1970s models expanded in terms of complexities mainly because of enhanced computational facilities. Two dimensional and dynamic framework has started replacing one dimensional steady state configurations. In the same year, Di Toro presented an analysis of the steady state two dimensional concentration distribution that results in the horizontal plane from the continuous discharge of a non-conservative substances (DO and BOD) into an infinite body of water.

1.1. Status of irrigation in Tamil Nadu

Geographical area of 13 million hectares is ranked eleventh in size among the Indian states.

Net area sown is about 6 million hectares.

3 million hectares or 50% get irrigation facilities.

1.1 Introduction

Climate change is evident from the observation of increase in global average air and ocean temperatures, precipitation and extreme rainfall, widespread melting of ice, storms / storm surges flooding and rising global mean sea level, as recorded in the Fourth Assessment Report of IPCC. Eleven of the last twelve years (1995-2006) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850). 

1. Introduction to Water Resources in Agriculture

Water, the quintessential life force for agriculture, intricately intertwines its significance throughout the fabric of global farming practices.

1.1 Significance of Water in Agricultural Practices

1.1.1 Sustenance of Plant Life

• Beyond its role as a life sustainer, water emerges as the very essence that propels plant development. It acts as the vital catalyst for photosynthesis, the engine of plant growth. This intricate process is the heart of the plant’s ability to convert sunlight into energy, driving robust development from seed germination to harvest.

Introduction

Water is a precious natural resource vital, for sustaining all life on the earth. It is in a continuous circulatory movement - hydrologic cycle. It is not uniformly distributed in time and space. Due to its multiple benefits and the problems created by its excesses, shortages and quality deterioration, water as a resource requires special attention. On a global scale, total quantity of water available is about 1600 million cubic km. The hydrological cycle moves enormous quantities of water about the globe. However, much of the world’s water has little potential for human use because 97.5% of all water on earth is saline water. Out of remaining 2.5% fresh water, most of which lies deep and frozen in Antarctica and Greenland, only about 0.26% flows in rivers, lakes and in the soils and shallow aquifers which can be readily used. Sustainable water management in India is fast becoming a necessity, with the looming crisis over water resources in the country threatening the security and livelihood of the population and the environment over the coming decades. Managing water resources, river catchments, and coastal zones are outstanding challenges of today and tomorrow’s. Global changes ask for a comprehensive scientific approach, an international multi-disciplinary orientation and require a new mind-set towards water and coastal management problems.

2.1. Introduction

Water plays a pivotal role in this earth system. The withdrawal of water for irrigation is about 70% of the global freshwater. Water use efficiency is less than 50% in many countries. It has been forecasted by the Food and Agricultural Organization (FAO, 2015) that global water requirements will be increased by 50% by the year 2050 to meet the demands of agricultural water use. This is so because food demand will be higher for the growing human population. We have entered into an earth system where everything living has evolved and developed (Cosgrove and Loucks, 2015). There has been a new geological scenario, some say Anthropocene (Crutzen, 2002; Williams et al., 2011). Consequently, freshwater will increasingly be a scarce and the costliest resource in the future, which needs to be managed properly.

4.1. Water Use Efficiency (WUE)

An efficient irrigation system implies effective transfer of water from the source to the field with minimum possible loss.

To identify the nature of water loss and to decide the type of improvements in the system.

Evaluation of performance in terms of efficiency is prerequisite for proper use of irrigation water.

The presence of water in its various phases (gas, liquid, and solid) within the atmosphere plays a pivotal role in shaping our weather and climate. This chapter, “Moisture in the Atmosphere,” will delve into the crucial concept of atmospheric humidity – the amount of water vapor in the air. Water, unique in its ability to exist in all three states at Earth’s temperatures, undergoes phase changes that are fundamental to the formation of clouds, precipitation, and atmospheric stability. Understanding the sources of atmospheric moisture, the ways it is measured and expressed, and its influence on atmospheric processes is essential for comprehending a wide range of meteorological phenomena (Fig. 4.1). We will explore concepts such as evaporation, condensation, humidity indices, and the role of moisture in energy transfer within the Earthatmosphere system. Join us as we unravel the dynamics of this vital component of our atmospheric environment

The presence of water in its various phases (gas, liquid, and solid) within the atmosphere plays a pivotal role in shaping our weather and climate.This chapter, „Water Vapor in the Atmosphere,“ will delve into the crucial concept of atmospheric humidity – the amount of water vapor in the air. Water, unique in its ability to exist in all three states at Earth‘s temperatures, undergoes phase changes that are fundamental to the formation of clouds, precipitation, and atmospheric stability. Understanding the sources of atmospheric moisture, the ways it is measured and expressed, and its influence on atmospheric processes is essential for comprehending a wide range of meteorological phenomena. We will explore concepts such as evaporation, condensation, humidity indices, and the role of moisture in energy transfer within the Earth-atmosphere system. Join us as we unravel the dynamics of this vital component of our atmospheric environment.
8.1. Expressions Used for Water Vapor in the Atmosphere
The concepts of vapor pressure, saturated vapor pressure, vapor pressure deficit, and dew point has been discussed with detailed explanations:
8.1.1. Vapor Pressure (e)
Vapor pressure is the partial pressure exerted by water vapor molecules in ,the air. It represents the contribution of water vapor to the total atmospheric pressure. Imagine air as a mixture of gases; the vapor pressure is the „pressure“ exerted solely by the water vapor component of that mixture.

The presence of water in its various phases (gas, liquid, and solid) within the atmosphere plays a pivotal role in shaping our weather and climate.This chapter, „Water Vapor in the Atmosphere,“ will delve into the crucial concept of atmospheric humidity – the amount of water vapor in the air. Water, unique in its ability to exist in all three states at Earth‘s temperatures, undergoes phase changes that are fundamental to the formation of clouds, precipitation, and atmospheric stability. Understanding the sources of atmospheric moisture, the ways it is measured and expressed, and its influence on atmospheric processes is essential for comprehending a wide range of meteorological phenomena. We will explore concepts such as evaporation, condensation, humidity indices, and the role of moisture in energy transfer within the Earth-atmosphere system. Join us as we unravel the dynamics of this vital component of our atmospheric environment.
8.1. Expressions Used for Water Vapor in the Atmosphere
The concepts of vapor pressure, saturated vapor pressure, vapor pressure deficit, and dew point has been discussed with detailed explanations:
8.1.1. Vapor Pressure (e)
Vapor pressure is the partial pressure exerted by water vapor molecules in the air. It represents the contribution of water vapor to the total atmospheric pressure. Imagine air as a mixture of gases; the vapor pressure is the „pressure“ exerted solely by the water vapor component of that mixture.

Introduction
Waterlogging refers to the accumulation of excessive water in the root zone, leading to anaerobic conditions. This surplus water hampers the exchange of gases with the atmosphere, and biological processes deplete the oxygen supply in both soil and water, resulting in anaerobiosis, anoxia, or oxygen deficiency. In India, approximately 11.6 million hectares, constituting 8.3% of its net sown area, are affected by waterlogging (Planning Commission, 2011). According to Brundtland and Khalid (1987), available estimates indicate an annual global loss of 1.5 million hectares of irrigated land due to salinity and waterlogging. Regrettably, data regarding the occurrence and extent of these issues are inconsistent and incomplete. More recent estimates, provided by Datta and Joshi (1992), range from 5.5 million to 13 million hectares. After conducting a comprehensive global survey, it has been determined that submerged and waterlogged soils cover approximately 5 to 7% of the Earth’s land surface. The total area of waterlogged soil worldwide is estimated to be around 700 to 1000 million hectares. Tropical swamps, rice fields, and floodplains collectively represent nearly 14%, 12%, and 10% of the total waterlogged area, respectively. In India, Odisha, West Bengal, Bihar, and Uttar Pradesh have the highest concentration of waterlogged soil, with an estimated total area of one million hectares. The eastern region bears a significant portion of this burden, with over 20% of the affected land suffering from surface waterlogging, which severely diminishes productivity. Waterlogging is characterized by the soil becoming unproductive and infertile due to excess moisture, creating anaerobic conditions known as waterlogged soils. Waterlogged soil presents a significant challenge to agricultural productivity and soil health, characterized by excessive water saturation that restricts oxygen availability to plant roots. In this chapter, we delve into the multifaceted aspects of waterlogged soil, exploring its causes, defining characteristics, and far-reaching consequences. The serves as a comprehensive overview, underscoring the detrimental impact of waterlogging on agriculture, ecosystems, and human well-being. It identifies key factors contributing to

Now-a-days, a watershed management or watershed development has been fully recognized as a unit for over all development of rainfed areas (Gupta, 2006a and b). Hydrological problems such as excessive runoff, large scale soil erosion, inadequate or faulty drainage and occurrence of droughts are the most significant problems in almost all the rainfed areas. These problems, however, can be alleviated through running watershed based development programmes that recognize the natural topography and water movement patterns of the land.

1.1. Watershed development

Refers to the conservation, regeneration and judicious utilization of all the resources viz., land, water, vegetation, animal and human within a particular watershed in integrated manner.

Water drainage area on earth’s surface from which runoff, due to precipitation, flows into a single to a larger stream, a river, a lake or the ocean.

1.2. Concept of watershed management

Planning and design of soil and water conservation structures such as bunds, waterways, overflow structures, water harvesting structure.

A watershed is an area that provides pathway to the surface or sub surface water flow to a given drainage system. The watershed is a hydrological unit. The area of watershed may vary from few hectares to thousands of square kilometres. The watershed development involves effective management of land and vegetation in order to conserve and improve the quantity of water. The watershed development is a comprehensive and sustainable solution to water conservation (Fig.13.1).
The watershed development has several advantages. It helps in
• Conservation, upgradation and utilization of natural resources particularly land, water and vegetation
• Minimise the inequalities between rainfed and irrigated areas
• Promoting cost effective adoptable simple technologies
• Supply water for domestic ,agricultural and industrial use
• Poverty alleviation and employment generation
• Reducing chemical pollution
• Adopting flood control measures by constructing water storage or impounding structures

Agriculture is world’s single largest employer and probably the most weather dependent of all human activities.  Climate and its variability have been and continue to be, the principal source of fluctuations in global food production. Throughout history, extreames of heat and cold, droughts and floods, and various form of violent weather have wretched havoc on the global agricultural production. With the unprecedented increase in population over past few decades, clearly the mankind faces undertaking task to ensure food and nutritional security for all, considering reduced per capita land, reduced availability of water, depleting biodiversity and need to preserve ecology and environment. In India, of the total geographical area of 328 m ha, about 175 m ha (53 % of total) are categorized as degraded land, of which 150 m ha are subjected to serious water and wind erosion (Singh et al. 1981). Crops are sown in about 180 m ha annually. Since it seems very much impossible to bring more area under cultivation we need to achieve greater efficiency in the natural resources use while conserving the environment by placing greater emphasis on understanding and exploiting climatic resources for the benefits of agriculture.

Technical Term                            Definition

Geomorphological Analysis       Geomorphological analysis is the systematic description of watershedís geometry and its stream channel system to measure

                                                   the liner aspects of drainage network, aerial aspects of drainage basin and relief aspects of channel network.

Watershed

A watershed is the area of land where all of the water that is under it or drains off of it goes into the same place. John Wesley Powell, scientist geographer, put it best when he said that a watershed is: “that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community.”

Watershed is defined as a hydro-geological unit of area from which the rainwater drains through a single outlet. Watershed development refers to the conservation, regeneration and judicious use of all the natural resources (like land, water, plants, animals) by human beings. Watershed Management brings about the best possible balance between natural resources on the one side and human beings on the other. Human beings and the ecology are interdependent. The changes in the environment directly affect the lives of the people depending on it. A degraded environment means a degraded quality of life of the people. This degradation can be tackled effectively through the holistic development of the watershed. A watershed provides a natural geo-hydrological unit for planning any developmental initiative. The approach would be treatment from “ridge to valley”.

A watershed, also called a drainage basin or catchment area, is defined as an area in which all water flowing into it goes to a common outlet. People and livestock are the integral part of watershed and their activities affect the productive status of watersheds and vice versa. From the hydrological point of view, the different phases of hydrological cycle in a watershed are dependent on the various natural features and human activities. Watershed is not simply the hydrological unit but also socio-political-ecological entity which plays crucial role in determining food, social, and economical security and provides life support services to rural people.

Management of watershed in India

It involves management of water, land, energy and greenery, integrating all the relevant scientific approaches appropriate to socio-economic background for a pragmatic development of a watershed. In practice, it means allowing load free rainfall run off from the watershed. Clear outflow imply management of effective soil and water conservation and generating a lush green carpet in whole of the area. In other worlds, it is greening of a watershed through proper management of land, water and energy sources. The comprehensive development of watershed seems to make productive use of all its natural resources and also protect them is termed as watershed management.

The Banave terraces in Indonesia and those in Nepal, Mediterranean are examples of integration of human elements into a system of land management, which is an early achievement in watershed management. Watershed management is not merely anti-erosional and anti-run off approach but also a comprehensive integrated approach of land and water resources management. The approach is preventive, progressive, corrective as well as curative. Here wasted land resources could be fruit fully harvested into a productive face for rural development.

Watershed is defined as a natural hydrological unit that covers a specific land surface area from which runoff passes through a common outlet or area with common drainage or outlet. In simple terms, it implies a catchments or drainage basin from which water drains towards a single channel. It may extend over a few acres only or may cover thousands of acres.

Watershed management is the integration of technology within the natural boundaries of a drainage area for optimum development of land, water and plant resources to meet the basic minimum needs of the people in a sustained manner.

It is also defined as the development and management of watershed resources in such a manner as to achieve optimum production without deterioration of resources base or disturbing the ecological balance. It is also termed as “Resource centered technology” since it helps in assessment, augmentation and optimal utilization of all natural resources viz., land, water and vegetation, it prevents deterioration of resources and at the same time ensures sustained productivity of land to meet basic needs of people.

The adjustment and maintenance of soil pH at a value suitable for optimal crop production is the first step in soil management, because soil pH affects soil properties, nutrient availability and plant nutrition. In India, about 30M ha cultivated  land  suffer from high soil acidity (pH < 5.5). These soils are critically degraded and are of poor health producing crop yields, which are often less than 50% of that in normal soils. Due to this, farmers use much less fertilizers for crops (50 to 80 kg NPK ha^-1), since this is not profitable.

As we conclude this comprehensive review of the complex relationships between weather, crop diseases, and disease management, it is essential to reflect on the current state of knowledge and identify areas that require further research and attention. The preceding chapters have highlighted the significant impacts of weather factors on crop diseases, emphasizing the need for a deeper understanding of these relationships to develop effective disease management strategies. Significant work particularly on effects of different weather combinations on pathogen population and disease severity needs to be addressed well in time. Despite significant advances in our understanding of the weather-crop disease nexus, there remain substantial knowledge gaps that hinder our ability to predict and manage disease outbreaks effectively. For instance, the complex interactions between weather factors, crop physiology, and disease development are not yet fully understood, making it challenging to develop accurate predictive models. Furthermore, the impacts of climate change on weather patterns and crop diseases are still being researched, and more work is needed to understand these relationships fully. To address these knowledge gaps and improve our understanding of the weather-crop disease nexus, several action plans are required. Firstly, continued research is needed to elucidate the complex relationships between weather factors, crop physiology, and disease development. This research should focus on developing a deeper understanding of the underlying mechanisms driving these relationships, as well as identifying key weather thresholds that trigger disease outbreaks. Secondly, the development of accurate predictive models that can forecast disease outbreaks based on weather data is critical. These models should be able to account for the complex interactions between weather factors, crop physiology, and disease development, as well as incorporate data from multiple sources, including weather stations, satellite imagery, and field observations. Thirdly, there is a need for more effective communication and collaboration between researchers, policymakers, and farmers to ensure that research findings are translated into practical disease management strategies. This will require the development of user-friendly decision support tools that can provide farmers with timely and accurate advice on disease management, based on weather forecasts and other relevant data. Finally, addressing the impacts of climate change on weather patterns and crop diseases will require a coordinated effort from researchers, policymakers, and

In the present system of curriculum changes, participation of all the stakeholders are not actively involved in developing curriculum over the years.

The march of weather factors during crop period is never smooth and regular. Agriculture, because of its dependance on climate is inevitably subjected to unpredictable long and short term fluctuation characteristic of atmosphere conditions. Climate introduces an element of risk in farming which makes it particularly hazardous occupation.

A Weather hazard in this context can be defined as any type of extreme weather condition that can damage the crops and animals leading to abnormal decrease in production and income. The extent to which these hazards create risk depends on the time of occurrence, intensity and duration of the hazard besides the age, stage of development and inherent resistance of the crop or livestock involved. Major abnormalities affecting the crop production are:

Agriculture, the cultivation of life that sustains human civilization, is profoundly intertwined with the rhythms of the natural world. Of all the environmental factors that influence farming, weather reigns supreme, orchestrating a complex symphony of elements that dictate the success or failure of crops. This chapter delves into the intricate relationship between weather and agriculture, exploring how temperature, precipitation, sunlight, and other atmospheric conditions shape every facet of agricultural production.
Weather’s influence begins with the very first stage of a plant’s life. Temperature governs seed germination and seedling development, while sunlight provides the energy for photosynthesis, the process by which plants convert light energy into chemical energy. The availability of water, dictated by rainfall patterns, is crucial for plant growth and nutrient absorption. Wind patterns can aid in pollination but also cause damage to crops.
Throughout the growing season, weather continues to play a critical role. Optimal temperatures are essential for each stage of plant development, from flowering to fruit production. Adequate rainfall, or irrigation to supplement it, ensures healthy growth and abundant yields.
Extreme weather events, such as droughts, floods, heatwaves, and frosts, can have devastating consequences for agriculture. These events can destroy crops, reduce yields, and disrupt food production, leading to economic losses and food insecurity (Fig. 18.1).

Agriculture, the cultivation of life that sustains human civilization, is profoundly intertwined with the rhythms of the natural world. Of all the environmental factors that influence farming, weather reigns supreme, orchestrating a complex symphony of elements that dictate the success or failure of crops. This chapter delves into the intricate relationship between weather and agriculture, exploring how temperature, precipitation, sunlight, and other atmospheric conditions shape every facet of agricultural production.
Weather’s influence begins with the very first stage of a plant’s life. Temperature governs seed germination and seedling development, while sunlight provides the energy for photosynthesis, the process by which plants convert light energy into chemical energy. The availability of water, dictated by rainfall patterns, is crucial for plant growth and nutrient absorption. Wind patterns can aid in pollination but also cause damage to crops.
Throughout the growing season, weather continues to play a critical role. Optimal temperatures are essential for each stage of plant development, from flowering to fruit production. Adequate rainfall, or irrigation to supplement it, ensures healthy growth and abundant yields.

Weather and climate have great influence on farm animal production. The environment in which an animal lives is referred to as its habitat. A habitat includes both biotic (living) and abiotic (nonliving) components of the animals’ environment. Abiotic components of an animal’s environment include temperature, humidity, oxygen, wind, soil composition, day length and elevation. Knowledge of how potential environmental stressors (ambient temperature, humidity, thermal radiation, air speed, etc.) can directly and adversely affect animal performance, health and wellbeing is also required for a successful animal farming. The indirect consequences of weather include their impact on feed quality and availability.

Birds and mammals are warmblooded (endotherms or homeotherms), possessing a thermoregulatory system that maintains a stable body temperature and uniform internal environment (homeostasis) by converting food energy into heat. All metabolic processes generate substantial heat and much of this is retained within the body of homeotherms by insulating layers of fat, feathers or fur. Dairy cattle, like other warmblooded animals, function most efficiently in environments where they can maintain their body temperature at around 38° C. Tissue and cellular metabolism and the underlying biochemical reactions that sustain life and productive functions need body temperature to be maintained within very narrow limits. Relatively small increases in body temperature result in the breakdown of body protein and a significant depression in production.

Climate change, particularly global warming has complex impacts on domestic animal production system affecting feed supply, challenging thermoregulatory mechanism resulting thermal stress, emerging new diseases due to change in epidemiology of diseases and causing many other indirect impacts. So, climate change will have farreaching consequences for dairy and meat production, especially in vulnerable parts of the world where it is vital for nutrition and livelihoods. Due to poor availability of good quality feed and fodders in India, animals are generally maintained on poor quality grasses available in the pastures or are stallfed, mainly on crop residues. India is already deficit in feed and fodder. These shortages would be further aggravated by the adverse effects of global warming on fodder crop production.

Bacterial diseases are a significant threat to human health, agriculture, and the environment. These diseases are caused by pathogenic bacteria that can infect various hosts, including humans, animals, and plants. The severity and spread of bacterial diseases are influenced by various factors, including weather parameters. Weather conditions, such as temperature, humidity, wind, and precipitation, play a crucial role in the development, dissemination, and survival of bacterial pathogens (Fig. 8.1). Fig. 8.1. Bacterial infection on soybean leaves Temperature, for instance, affects the growth and reproduction of bacteria, with optimal temperatures varying among different species. High temperatures can accelerate the growth of some bacteria, while low temperatures can slow it down or even kill them, however every pathogenic bacterium have its own weather window. For example, a daytime temperature of 35°C and nighttime temperatures of 27°C are most favorable for Xanthomonas oryzae infecting rice. Similarly, humidity influences the survival and dissemination of bacteria, with high humidity favoring the growth and spread of many bacterial pathogens. For example, lower soil moisture decreases the chances of infection of Ralstonia solanacearum in tomato plants. Wind and precipitation also impact the spread of bacterial diseases. Wind can disperse bacterial spores and cells, allowing them to reach new areas and infect new hosts. Precipitation, on the other hand, can influence the availability of moisture, which is essential for the growth and survival of many bacterial

Agriculture is the backbone of human civilization, providing food, fiber, and livelihoods for billions of people around the world. Crop yields, which are a critical component of agricultural productivity, are influenced by a complex array of factors, including genetics, soil quality, water availability, and management practices. However, among these factors, weather and climate stand out as two of the most significant drivers of crop yields.
Weather and climate are intimately linked, with weather referring to short-term atmospheric conditions, such as temperature, precipitation, and wind, and climate describing the long-term average atmospheric conditions in a particular region. Together, they form a dynamic duo that shapes the fate of crops, influencing their growth, development, and productivity.
The impact of weather and climate on crop yields is multifaceted. Weather events, such as droughts, floods, and heat waves, can have devastating effects on crops, leading to reduced yields, lower quality produce, and even complete crop failures. Climate, on the other hand, influences the overall growing conditions, determining the suitability of a region for specific crops and the timing of planting, growth, and harvest.
Understanding the complex interplay between weather, climate, and crop yields is crucial for ensuring food security, improving agricultural productivity, and promoting sustainable farming practices. This chapter aims to explore the intricate relationships between weather, climate, and crop yields, examining the ways in which these factors interact and influence each other. By delving into the latest research and findings, this chapter will provide insights into the following key topics:
The impact of weather events, such as extreme temperatures, precipitation, and wind, on crop yields
• The influence of climate on crop growth, development, and productivity
• The role of climate change in altering weather patterns and crop yields
• Strategies for mitigating the negative impacts of weather and climate on crop yields, such as climate-smart agriculture and weather-based crop insurance

In climatology, terms “Weather” and “Climate” have different connotations. Weather refers to the state of atmosphere at any given time denoting the short- term variations of atmosphere in terms of temperature, pressure, wind, moisture, cloudiness, precipitation and visibility. Weather is highly variable. It is constantly changing, sometimes from hour to hour and at other times from day to day. The aforementioned properties of the atmosphere are subject to constant change and their state at any time determines the state of the weather. However, weather elements are not separate rather they are closely related with each other.

David I. Blumenstock, an eminent climatologist has defined the weather in more restrictive sense. According to him, weather is the behaviour of the lower atmosphere with particular emphasis on the atmospheric behaviour which affect the lands and oceans and have a marked influence on the organisms that live upon the lands, within the waters of the earth or in the lower air. For the geographer, this definition of weather is more satisfactory. Since, he is interested more in the working of the lower atmosphere which affects the life of man as well as natural environment directly. Thus, we come across a great many varieties of weather covering a wide range of conditions.

INTRODUCTION

Integrated Pest Management (IPM) has been defined as a “system that, in the context of the environment and the population dynamics of the pest species, utilizes all suitable techniques and methods in as compatible manner as possible that maintain the pest populations at levels below those causing economic injury” (Glass 1975). The Inter society Consortium for Plant Protection (ICPP) has defined integrated pest management as “the use of multiple tactics in a compatible manner to maintain pest population at levels below those causing economic injury while providing protection against hazards to humans, domestic animals, plants and the environment”. The term ’integrated’ means it is a broad interdisciplinary approach taken using scientific principles of plant protection of variety of management strategies and tactics to fuse into a single system. The terms ‘pest’ means all biotic agents which adversely affect plant production. This includes insects, mites, nematodes, weeds, bacteria, fungi, viruses, parasitic seed plants and vertebrates. The term ‘management’ indicates to keep the pest population below some level based on economic criteria. It does not mean complete eradication of entire pest population.

Many diseases, nematodes, insects and weeds affect crop production, causing severe yield loss. Weather is the most important factor that determines the geographical distribution of these crop pests. The local weather patterns have a significant impact on the abundance of diseases and insect pests in the crops. The severity of disease and pest development depends on the combination of weather conditions during the growing season and is variable from season to season. The weather conditions include temperature (both the maximum and the minimum), light, rain, humidity, dew, cloudiness, sunshine, wind, air currents, evaporation, snow and atmospheric pressure. However, among these weather parameters, temperature and humidity play the major roles in infection of crops due to insect pests and diseases.

Fungal diseases are a significant threat to crop health and productivity worldwide, causing substantial economic losses and compromising food security. The development and spread of fungal diseases are influenced by a complex array of factors, including crop susceptibility, pathogen virulence, and environmental conditions. Among these environmental factors, weather plays a critical role in determining the severity and impact of fungal diseases on crops. Weather conditions, such as temperature, humidity, precipitation, and wind, can significantly affect the life cycle of fungal pathogens, including spore production, dispersal, and infection. For example, high temperatures and dry conditions can inhibit the growth and development of some fungal pathogens, while cool and wet conditions can favor their development and spread. Similarly, wind and precipitation can facilitate the dispersal of fungal spores, leading to the rapid spread of disease (Fig. 7.1). Understanding the impact of weather on fungal diseases is essential for developing effective disease management strategies. By recognizing the weather conditions that favor or inhibit the development of fungal diseases, farmers and crop managers can take proactive measures to prevent or mitigate disease outbreaks. This may involve adjusting planting dates, irrigation schedules, and fungicide applications to minimize the risk of disease. Furthermore, knowledge of the weather effects on fungal diseases can also inform the development of more accurate and reliable disease forecasting systems.

Weather parameters, such as temperature, humidity, rainfall, and wind, play a significant role in the epidemiology of viral diseases in crops. Viral diseases, caused by viruses that infect plants, can have devastating effects on crop yields and quality, leading to significant economic losses for farmers and the agricultural industry. The impact of weather parameters on viral diseases is complex and multifaceted. Weather conditions can influence the spread of viruses, the survival and multiplication of virus vectors, and the susceptibility of plants to virus infection (Fig. 9.1). Understanding the relationships between weather parameters and viral diseases is essential for developing effective disease management strategies and mitigating the impacts of viral diseases on crop productivity. Fig. 9.1. Yellow Leaf Curl Viral disease of Tomato Temperature, for example, can affect the replication and transmission of viruses, with optimal temperatures varying depending on the specific virus, its vector and host plant. Humidity and rainfall can influence the spread of viruses by affecting the movement and behavior of virus vectors, such as insects and nematodes. Wind can also play a role in the spread of viruses by dispersing virusinfected pollen and insects. This chapter will explore the effects of weather parameters on viral diseases in crops, with a focus on the relationships between temperature, humidity, rainfall, wind, and viral disease epidemiology. By examining the complex interactions between weather parameters and viral diseases, we can gain a deeper understanding of the factors that contribute to the spread and impact of viral diseases in crops, and develop more effective strategies for managing these diseases.

Abstract

Under Ministry of Earth Sciences, India Meteorological Department has launched District level Agro-meteorological Advisory Services in June 2008. The agro-advisory bulletins containing the forecast on rainfall cloud cover, wind direction and speed aid minimum and maximum temperature with their likely impact on crops are in use twice in a week.