eChapters

This chapter introduces plant analysis as a means of determining crop nutrient status and diagnosing nutritional deficiencies. It explains the selection of representative plant tissues at suitable stages of growth, followed by washing, drying, grinding, digestion and elemental estimation. Recommended tissues and sampling stages are provided for cereals, pulses, oilseeds, fibre crops, vegetables, ornamentals and fruit crops. Procedures are included for estimating nitrogen, phosphorus, potassium, sulphur, boron, zinc, iron, copper and manganese in plant samples. The chapter stresses that reliable interpretation depends on correct tissue selection, careful sampling and freedom from contamination. It thereby connects laboratory measurements with crop nutrition and fertilizer management.

This chapter describes methods for evaluating soil reaction, salinity, organic matter and plant-available nutrients. It begins with soil pH and electrical conductivity, explaining their importance in nutrient availability and the identification of acidic, saline or alkaline conditions. Procedures are then provided for estimating organic carbon, available nitrogen, phosphorus, potassium and sulphur. The chapter also covers calcium, magnesium and micronutrients, including zinc, iron, copper, manganese, boron and molybdenum. Every method identifies the necessary apparatus and reagents and explains extraction, colour development, instrumental measurement, calculation and interpretation. Particular attention is given to calibration, sample preparation, reagent quality, contamination control and laboratory safe

This chapter presents laboratory procedures for measuring the major physical properties that regulate soil behaviour, water availability, aeration and root development. It begins with particle-density determination using a pycnometer and proceeds to bulk density, soil texture, moisture content, total pore space, porosity and water-holding capacity. Each practical exercise provides the underlying principle, required apparatus, procedural steps, calculations and relevant precautions. The hydrometer method is introduced for estimating the proportions of sand, silt and clay. Methods for evaluating moisture retention and pore relationships are also described. Collectively, these measurements help characterize soil structure, compaction, drainage, water storage and its suitability for crop production.

This chapter explains how representative soil samples should be collected, labelled, transported and prepared for analysis. It identifies essential sampling equipment, including spades, khurpis, augers, trays, sampling bags, markers and polythene sheets. The recommended procedure involves dividing land into uniform sampling units, collecting soil from several well-distributed locations and combining these portions into a composite sample. The chapter describes V-shaped sampling cuts, suitable sampling depths and sample reduction through quartering. It also lists the field information that should accompany each sample. Procedures for air-drying, grinding, sieving and mixing samples are presented, together with precautions for avoiding unusual areas and contamination.

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.

Climate change is one of the most pressing issues of our time, with far-reaching consequences for the environment, human health, and the economy. One of the most significant impacts of climate change is on the world’s water resources. Rising temperatures, changing precipitation patterns, and increased frequency of extreme weather events are all taking a toll on the availability, quality, and management of water resources. Water is essential for human survival, and its availability and quality are crucial for human health, food security, and economic development. However, climate change is altering the hydrological cycle, leading to changes in precipitation patterns, increased evaporation, and altered water flows. These changes have significant implications on demand for water resources, including reduced water availability, decreased water quality, and increased risk of waterrelated disasters which will ultimately impact agricultural production and food security.
15.1. Changes in Precipitation Patterns
One of the most significant impacts of climate change on water resources is the alteration of precipitation patterns and projected per cent changes in average annual precipitation over 1850-1900 period at 2.00C increase in temperature are depicted here (Fig.15.1).

Hydrometeorology forecasting is limited to forecasting of occurrence of rainfall to a greater extent. Although several countries all over the world have developed and established hydrometorological forecasting with focus on occurrence of floods and droughts, still there is very limited success. Floods are associated with occurrence of continuous heavy rainfall due to movement of low-pressure systems like cyclones and depression overflow into rivers, reservoirs and breaching of bunds. In countries like India, the floods occur on the average in 70 lakh hectors of area and the economic loss due to floods and expenditure on relief operations mounting year after year besides loss of life. Foods occur at all of a sudden leaving little time for planning mitigation or rescue operation. Flood forecasting in based on impact assessment of heavy rainfall assessments to identify the exact area that is likely to be affected. It requires more intensive research. Forecasting of droughts is still an area of serious concern. There is need to strengthen regional capabilities to develop forecasting techniques for occurrence of flood and droughts through proper analysis of historical data in conjunction with meteorological forecasts and remote sensing data. Though flood alerts are issued, the identification of exact area and the extent to which flood impacts are not very clear most of the times heavy rainfall warnings are not just sufficient until and unless the vulnerable areas can be clearly specified. The medium range forecasting will be extremely useful for issuing flood alerts.
14.1. Forecasting Droughts
Long range forecasting of seasonal rainfall can indicate the possibility of receiving excess or deficit rainfall over larger regions. In India, there is considerable progress in development of long range forecast of Southwest monsoon rainfall. This forecast also indicating the regions which may get surplus or deficit rainfall and for indifferent parts of a given region as well. However, there is serious dearth of local expertise to further analyse and interpret the long-range forecast for a given area on the basis of local climate data. The advantages of reliable long-range forecast are still unexpected. Almost one fifth of the area in India gets affected by draught most of the years. The drought affects are more severe in arid and semi arid regions. Prediction of occurrence of drought and its intensity, period of occurrence and the areas to be affected by drought is very important. During recent years, there is considerable increase in the occurrence of droughts due to climate change which is attributed mainly to atmospheric pollution. The physics of the pollution is consistent and not the policies support in handling hydrometerological disasters. There are instances where in flood and droughts occurred in the same

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

A disaster is sudden event that causes significant damage to the people, environment and the economy. Disasters are serious disruptions to the functioning of a community that exceed its capacity to cope up using its own resources. The disasters that result either due to excess water or severe water deficit are floods and droughts.
12.1. Floods
The flood is an overflowing of water onto land that is normally dry. Floods may occur due to
• Heavy rainfall
• Ocean waves
• Snow melting
The economic losses due to floods will be very high and nearly 68 per cent of the economic losses are attributed to floods only. During the year 2018, India suffered a loss of nearly 90,000 crores due to floods alone. There are several causes for occurrence of floods in India. The major causes are
• Severe cyclonic storms in coastal areas which produce continuous heavy rainfall for 3 to 4 days in succession
• Encroachment of flood plains with residential structures
• Inadequate strength of river banks when there is high flows of water in the rivers
• Unplanned growth of urban areas
• Silting of water storage structures due to increased soil erosion thereby decreasing the storage capacity of reservoirs
• Simultaneous flooding of rivers and tributaries due to excessive water flows

Agriculture sector alone uses nearly seventy per cent of fresh water in the world. Therefore, water use economy in the agriculture sector is becoming a necessity. Increasing flood production is possible reducing water used for irrigation if we can adopt precision irrigation (Fig.11.1).
The precision irrigation has to be practiced by providing water to the crop plants in its root zone to meet the water requirements. The precise irrigation can result in-
• Water saving
• Avoid weed control
• Preventing loss of water due to infiltration
• Preventing loss of water due to surface evaporation from the soil
• Minimise salinity problems
• Improving water use efficiency of crops
Traditionally farmers were practicing flood irrigation. It is a method of watering crops delivering to a field and allowing it to flow over the ground among the crops. It is a simple and inexpensive technique followed in less developed areas. Flood irrigation is not very efficient way as nearly 50 per cent of the water applied in the field will be lost through run-off, soil evaporation and other factors. Flood irrigation is only suitable in wet climates and not effective in sandy soils. It leads to water logging in clay soils. There are several types of flood irrigation such as basin, border, furrow and contour irrigation. Although flood irrigation is not very efficient, the water wastage can be avoided to some extent using some techniques

The purpose of irrigation scheduling is to decide upon the amount of water to be applied for irrigation and timing of irrigation in order to avoid wastage of precious water. The irrigation scheduling is also used to determine the number of irrigations required for a crop during its growth cycle and judicious use of water depending upon the weather forecasts issued from time to time. The irrigation scheduling has to be planned for either full irrigation or supplementary irrigation depending upon the availability of water resources and the season during which crops are grown. Crops grown during the dry season requires full irrigation and crops grown during the rainy season require supplementary irrigation. The third category of irrigation is protective irrigation which is practiced in dryland areas. The protective irrigation is given when the crops are experiencing severe moisture stress due to prolonged dry spells wherever the farmers has access to small ponds and tanks developed within his own field as water harvesting structures.
10.1. Full Irrigation
Under full irrigation, the crops are provided with irrigation right from land preparation till the crop is getting ready for harvest maturity. The full irrigation will be usually planned for maximum yields of the crop (Fig.10.1).

Remote sensing involves measurement of the physical properties of a body without actual contact with it. It is based on the reflectance when the electromagnetic radiation is incident upon a body or surface. The spectral characteristics of the reflected radiation vary depending upon the nature and condition of the surface. In case of vegetation, it absorbs light and can reflect light in the visible range. The leaf pigments dominate the reflectance properties (Fig.9.1). The radiation bands within which the reflectance of electromagnetic radiation takes place are classified as follows-
Spectrum Wave Length (nm)
Visible 400-700
Near Infrared 701-1300
Middle infrared 1301-2500
Far infrared >3000

9.1. Vegetation Indices
The vegetation index is a mathematical expression that uses spectral imaging data to characterize the health and growth of the vegetation indices are calculated using data collected by remote sensors like Satellites. The vegetation indices have wide range of applications in agriculture and hydrology including
• Classification of vegetation
• Apex health of vegetation
• Changes in land cover
• Drought monitoring
• Estimation of soil moisture
• Evaluate crop growth, vigour, biomass and chlorophyll content
• Irrigation scheduling

Stress is force per unit area. When matter is subjected to stress; it may undergo changes in size, shape and displacement. Plants are grown in open environment and are likely to experience stress due to environmental conditions or when subjected to pests and diseases. The stress experienced by plants due to environmental conditions is called abiotic stresses. These include stresses caused by weather factors and climatic conditions and include moisture stress and thermal stress. The plants may also experience stress due to strong winds, dryness and as well as humid conditions (Fig.8.1).
The plants are generally classified into three types depending upon the ability to cope up with moisture stress as exhibited by-
• Drought resistance
• Drought tolerance
• Drought adaptations
The moisture stress may be to shortage of Water Compared to its requirements for evapotranspiration and metabolic activities. The plants may also suffer moisture

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 movement of water from soil to the crop canopy and leaves to provide water for transpiration and the effect of weather factors on transpiration is most important area of study. When the crop is just sown, there will be an only evaporation of water from the soil. After germination of seeds there will be emergence of seedlings. After the emergence of seedlings there will be formation of leaves. The small leaves start intercepting the incoming solar radiation and absorb some portion of solar energy, get heated and there will be evaporation turn off water from the stomata of the leaf. When water vapour escapes into the atmosphere through the stomata of leaf, the plant absorbs carbon dioxide which results in photosynthetic activity. During night time, there will not be any photosynthesis due to absence of sunlight. The plants use parts of the photosynthetic accumulate for its metabolic activity and the process is called maintenance respiration. The balance of the photosynthetic accumulate contributes to the expansion of leaves and increased dry matter accumulation in crop plans. The process of dry matter accumulation in plants is called crop growth. When the seedlings start growing, there will be formation of tillers or branches. When the leaves grow it reaches a stage when the crop will be completely shading the ground and the soil evaporation will be minimum and maximum amount of water is lost only through evapotranspiration (Fig.6.1).

The plants draw water from the soil for growth and development. The soil acts a reservoir for soil moisture (Fig.5.1). The basic aim of a soil water balance model is to quantify the manner in which the water supplied to the soil either through precipitation and irrigation is disposed off. In the process, the soil water balance models were found to be extremely useful to determine the amount of water utilized by the crop for evapotranspiration.
The concept of water balance was originally developed by Thornthwaite, an American geographer and it formed the basis for development of more scientifi c advances due to its wide range of applicability including
• Choice of crops/ cropping systems based on water availability
• Irrigation scheduling
• Optimisation of limited water resources for higher productivity
• Characterization of droughts and agricultural droughts
• Assessment of crop yield and pre harvest forecasting of crop yields
• Designing irrigation projects
• Development of water storage structures
There are quite a large number of water balance models available in literature nowadays. Several of these models may be applicable for regions where there are developed. There were considerable efforts to develop water balance models can be used by the crop on daily basis in case of different crops as well. The choice of a water balance model to a large extent depends on the availability of data required for running the model. It may not be possible to cover all models available in

The soil consists of many solid particles of different sizes and is capable of absorbing and retaining water in the soil within certain limits when water is received through either from precipitation or by irrigation. The water that is held in the soil is called soil water (Fig.4.1). It can exist also in the form of water vapour as well. The crop production depends upon the soil water. All the water that is present in the soil may not be available for plants.
The water availability to the plants from the soil depends upon some physical properties of the soil as well as on the physical processes that govern the existence of water in the soil. Therefore, it is necessary to understand about the relationships that govern the water availability in the soil as explained in the following text-
4.1. Energy Concept of Soil Water
Soil water energy concept is all about potential energy, gravitational potential, osmatic potential, pressure potential energies.
4.1.1. Soil Water Energy: The total energy state of soil water is defined by its
equivalent potential energy as determined by various forces acting on the water per unit quantity. Different energies are involved including kinetic and potential energy.

The major source of water supply on the earth is precipitation. The water received at the earth’s surface from the atmosphere either in solid or liquid form is called precipitation. The water received in solid form may be snow or hail. The precipitation is seasonal in character in many parts of the world. The precipitation may occur due to –
• Conventional physical process
• Orographic effect and
• Convergence of air masses
3.1. Conventional Physical Process
It occurs when the air on the surface of the earth and few metres above the surface of the earth is heated by absorbing long wave radiation emitted by the earth’s surface. As the air is heated, it becomes lighter. The water vapour formed due to evaporation from the soil surface or water bodies will mix with the air and the air will be moist. When the moist air gets heated it becomes lighter and rises vertically upwards. After reaching certain height, the air gets cooled enough to get saturated with water vapour. The moisture in the saturated air will condense on small solid particles to form tiny drops. These solid particles may be dust or smoke or solid particles suspended in the atmosphere and are called aerosols.