eChapters

Chemical oxygen demand (COD) is measurement of oxygen demand of waste in terms of the total quantity of oxygen required for oxidation of the waste to carbon dioxide and water. This test is based on the fact that all the organic compounds, with few exceptions, can be oxidized The test is based on the fact that all organic compounds, with a few exceptions, can be oxidized by the action of strong oxidizing agents under acid conditions. Organic matter + Oxidizing agent = CO2 + H2O. The major advantage of COD test is the short time required for evaluation. The determination can be made in about 3 hours rather than the 5-days required for the measurement of BOD
Principle
The oxidizing agents like potassium permanganate and potassium dichromate is usually used to determine COD. Potassium permanganate is selective in the reaction like it reacts with carbonaceous on the other hand it shows nonreactive with nitrogenous matter. Estimating of COD with any method, oxidizing agent must be present to ensure that organic matter is oxidized completely. The organic matter and oxidisable inorganic substances present in water or wastewater get oxidised completely by standard potassium dichromate (K2Cr2O7) in the presence of H2SO4 to produce CO2 + H2O.The excess K2Cr2O7 remaining after the reaction is titrated with ferrous ammonium sulphate [Fe(NH4)2 (SO4)2]. The dichromate consumed gives the 02 required for oxidation of the organic matter.

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

11.1. What is acid soil?

Acid soils refer to those soils that are characterized with the presence of higher concentration of H⁺ in soil solution and at exchangeable sites or characterized with its high proton donating capacity such as aluminium (Al³⁺) on hydrolysis gives rise to proton. Both H⁺ and Al³⁺ are responsible to contribute soil acidity. Al³⁺ causes soil acidity indirectly by generating H⁺ through its hydrolysis, while H⁺ contributes directly. Therefore, due to more abundance of H⁺, they exhibit low soil pH and low base saturation (Ca²⁺, Mg²⁺, Na⁺ and K⁺). Such soil is considered as problematic soil because plant growth is affected adversely under acidic conditions and they suffer root injuries when grown in acid soils. Besides, soil acidity interferes in the soil nutrients availability to plants, making them either deficient to plants (such as phosphorus, calcium, magnesium, molybdenum) or toxic to plants for their more availability. Under acidic condition, Al, Mn and Fe are found in more soluble form. Thus, they are taken up by the plant in such a higher level that they become toxic to plants. Phosphorus becomes immobile due to the formation of insoluble compounds with aluminium and iron under acidic conditions. Ca, Mg and Mo also become unavailable in acid soil and show their deficiency symptoms. Soil acidity also affects soil microbial growth and thus, in turn, affects the nutrient dynamics in soil. Soil acidification is induced heavily under intensive agricultural practices such as increasing leaching due to more irrigation practices, addition of fertilizers, build-up of soil organic matter and many other possible ways.

Soil  is an interface of inorganic and organic componentsof the planet earth, which combines carbon and nitrogen from the atmosphere with different mineral elements of the lithosphere through millions of microorganisms, intercepting energy from the sun and moisture from the hydrosphere and atmosphere. It is a source as well as sink to adsorb, desorb, fix or release mineral elements and gases, decompose organic residues, simultaneously and support the growth of plants. All these natural processes are accompanied by runoff, percolation and evapotranspiration processes of the hydrologic cycle. Thus, soil is a dynamic body that acquires properties in accordance with the forces, which act upon it. Many soil properties emanate from physical, chemical and biologically mediated reactions, where the factors like climate, vegetation, topography and time  influences the processes. Soil reaction is one of the most important chemical characteristics of the soil solution,which has both direct and indirect effects on plant nutrition.

12.1. Introduction

All soils invariably contain soluble salts. However, physico-chemical and biological soil properties start degrading when excessive amount of salts are accumulated in soil, particularly in rhizosphere, due to several anthropogenic activities and environmental conditions, and crop production is severely affected. Then we refer those soils as salt-affected soil.

The need of intensive agriculture to keep pace with the increasing world population for their food requirement necessitates to bring more agricultural land area under irrigation. However, irrigation system without taking enough drainage provision and poor water quality and its poor management may make the situation worst due to the development of salt-affected soils that ensue unproductive soil and low crop yield. Crops grown on salt-affected soils suffer from high osmotic stress, nutritional disorders due to nutrient (N, Ca, K, P, Fe, Zn) deficiency, specific ion toxicities, poor soil physical conditions and as a consequence, a reduced crop productivity.

Although it is considered that the rocks and minerals on weathering lead to salt accumulation in the soil, but the salt-affected soils are not truly originated from the accumulation of such salts in situ. On the contrary, occurrence of salt-affected soils is due to receiving salts that come from other locations with water. Sea water inundation in coastal belt, irrigation with poor quality water including saline groundwater, poor drainage system, irrigation adopting unscientific ways leading to waterlogging, shallow water table etc. contribute heavily toward development of salt-affected soils. Salt-affected soils may occur under almost all climatic conditions. Their distribution, however, is relatively more extensive in the arid and semi-arid regions compared to the humid regions because of poor precipitation to leach soluble salt adequately. Since evapotranspiration greatly exceeds precipitation in these climatic conditions, the soluble salts move upward with water due to capillary action and are left behind on the surface soil and the rhizosphere, once water is evaporated. The commanding ions of accumulated salts in affected soil are sodium, potassium, magnesium, calcium, chlorides, sulphates, carbonates and bicarbonates. The nature and properties of salt-affected soils are so diverse that they require specific approaches for their reclamation and management. Therefore, it is necessary to know their origin, formation, nature, chemistry and properties in detail to classify them into groups for their proper management to maintain sustainable agriculture.

13.1. Introduction

Water is chemically benign. However, its interference in free gas exchange in soil becomes detrimental to crop growth when soils are subjected to waterlogging or plants are submerged with water.Waterlogging of soil refers to a soil condition when the soil attains a moisture regime to such an extent that oxygen is not available in the pore space in enough quantity for plant roots to respire adequately. On the contrary, detrimental gases such as carbon dioxide, methane, hydrogen sulphide, ethylene etc. accumulate in the root zone and adversely influence the growth of plants. Thus, anaerobic condition prevails in waterlogged soil causing depletion of oxygen and increase of CO₂ in root zone, which severely affects aerobic micro-organisms while harmful organisms proliferate and restrict the plant growth. Waterlogging leads to nutrient deficiencies or nutrient toxicities, root tip decomposition and eventually, reduced growth or death of the plant. Physical, chemical and biological activities in the soil are also disturbed due to low temperature. However, this is important to note that plants differ among themselves in their demand for oxygen. Even oxygen demand for same plants differs with its growth stage. Therefore, it is well understood that there is no universal level of soil oxygen that can identify waterlogged conditions for all plants. Mostly waterlogging prevails in the land due to non-permeability of the soil material, the presence of an impervious layer in soil horizon, or a high-water table.

If the reader has endeavoured to follow the basic chemistry in the first chapter, he would be in a positions to follow up the various reactions that take place in soils and which hitherto had baffled him. Soils contain particles of various sizes ; some so fine that they would remain suspended in water for a long time; others so coarse that they would be sieved out by even a coarse sieve. Soils contain some salts that can be washed out by leaching with water; they contain some water which can be readily evaporated away by exposing to hot sun or by heating slightly. They also con-tain a little organic matter which can be burnt away or dissolved in alkali. When all the extraneous substances have been completely removed we are left with what we might call soil framework. This framework gives mechanical support to the roots of the plants. Without this framework the plant would not stand up even if it could be supplied with all the food material.

Let us suppose a soil freed from all the extraneous matter by continuous leaching with water or a dilute acid. In the former case the removal of all the extraneous matter is extremely slow, whereas by leaching with dilute acid everything except the soil framework is removed in a short time.

When soils from different localities are subjected to leaching with dilute acid we find that the soil framework in every case, behaves in a similar manner. No matter from what part of the world the soil has been obtained, the properties of its mineral framework only differ in quantity but not in kind.

Principle
Chloride ion is determined by Mohr’s method, titration with standard silver nitrate solution in which silver chloride is precipitated first. The end of titration is indicated by formation of red silver chromate from excess AgNO3 and potassium chromate used as an indicator in neutral to slightly alkaline solution.
AgNO3 +Cl- ? AgCl+NO3
2AgNO3+ K2CrO4 ? Ag2CrO4+2KNO3 (Reddish Brown)
Reagents
1. Standard Silver nitrate 0.0141N : Take 1.189 g and dissolved it in 500 ml distilled water.
2. Sodium chloride 0.014N: Dissolve 0.28 g sodium chloride in 500 ml of distilled water.
3. Potassium Chromate indicator
Procedure
1. Take 50 ml sample in a 100 ml conical flask
2. Adjust its pH in between 7.0 and 8.0 either with alkali or acid solution. Otherwise, AgOH is formed at high pH level or CrO4 -2 at low pH level.
3. Add 1 ml of potassium chromate (K2CrO4) colour turn to light yellow.
4. Titrate with standard silver nitrate (AgNO3) solution till colour change from light yellow to brick red colour.
5. Note the volume of AgNO3 added (A)
6. For better accuracy, titrate distilled water in the same manner
7. Note the volume of silver nitrate added for distilled water (B)

This chapter describes about the review of relevant researches related to the present study. This also helps in developing conceptual framework and selecting proper methodology for the study. Although studies have been conducted on different aspects of conservation agriculture in past, but a few reviews were available on social ecology and perceptional change of the farmers in managing critical inputs to agriculture like water, nutrient and soil organic carbon, and ecosystem as a whole. So, reviews having a little indirect bearings are also included in this section. In accordance with the subject of the proposed study, the review of literature has been presented under the following sub-heads:

Citizen science has emerged as a powerful tool for monitoring and managing pests and diseases in agriculture. The concept of citizen science involves the active participation of citizens in scientific research, often through collaborative efforts with professional scientists. In the context of agriculture, citizen science offers a unique opportunity for farmers, gardeners, and other stakeholders to contribute to the monitoring and management of pests and diseases. Traditionally, pest and disease monitoring and management in agriculture have relied heavily on professional scientists and extension agents. While these experts play a critical role in providing guidance and support to farmers, they often face limitations in terms of resources, capacity, and geographical reach. Citizen science offers a way to bridge these gaps by leveraging the collective knowledge, expertise, and observational power of citizens (Fig.9.1).
In agriculture, citizen science can be applied in various ways to support pest and disease monitoring and management. For example, farmers and gardeners can be trained to recognize and report pests and diseases, providing valuable data on the distribution, prevalence, and impact of these organisms. This information can be used to inform management decisions, such as the application of pesticides or other control measures. Citizen science can also be used to support the development of integrated pest management (IPM) strategies, which aim to minimize the use of chemical pesticides and other harmful practices. By engaging citizens in the

The world of agriculture is undergoing a significant transformation, driven by advances in technology, data analytics, and citizen science. Smart farming, also known as precision agriculture, has emerged as a key driver of this transformation, enabling farmers to optimize crop yields, reduce waste, and promote sustainable agricultural practices. However, the full potential of smart farming can only be realized by integrating it with citizen science and agrometeorological advisories. Citizen science, which involves the participation of citizens in scientific research, has the potential to revolutionize the way we approach agriculture. By engaging citizens in the collection and analysis of data on weather conditions, soil health, and crop health, we can create a more inclusive and effective agricultural system. Agrometeorological advisories, which provide weather-based agricultural advice to farmers, can also be enhanced through the integration of citizen science data (Fig.10.1).
This book chapter explores the potential of bridging the gap between citizen science, smart farming, and agrometeorological advisories. We examine the current state of these fields, highlighting the opportunities and challenges associated with their integration. We also discuss the role of technology, including mobile apps and online platforms, in facilitating this integration and enhancing the effectiveness

Droughts are intricate and multifaceted phenomena that can have far-reaching impacts on the environment, economy, and society. The complexity of droughts arises from the interplay of various factors, including climate variability, water availability, land use, and human activities. Given the varying characteristics and consequences of droughts, classification becomes a crucial step in understanding and managing these events. By categorizing droughts based on their severity, duration, and impact, researchers and policymakers can better grasp the intricacies of drought dynamics and develop targeted strategies for mitigation and adaptation. The classification of droughts is necessary for several reasons

Introduction

Drought occurs when a region experiences below average precipitation, resulting in prolonged shortages in its water supply, which can have a significant impact on agriculture and the ecosystem. To reduce the effect of drought on farm production and stabilize farm income, farmers must take systematic measures called drought coping mechanisms. These measures can be categorized into two broad categories: Ex-ante coping mechanisms, which are taken before the occurrence of drought, and Ex-post coping mechanisms, which are taken after the occurrence of drought. Ex-ante coping mechanisms include activities such as crop, spatial, and varietal diversification, income diversification, and the use of savings. Ex-post coping mechanisms include changing consumption patterns, borrowing money, liquidating assets, seeking government drought relief funds, and migration. Drought can have a significant impact on crop and livestock production, causing farmers to adopt drought coping mechanisms to stabilize their farm income. This study goals to identify the factors that determine the adoption of such coping mechanisms, to mitigate the effects of drought on the livelihoods of farmers.

Extensive studies have shown that much of the humified material in soil is finely bound to colloidal clay. However, it is uncertain to what proportion of the clay surface in any given soil is coated by organic substances as this will depend on the organic matter content and the type and amount of clay.

The ways in which organic substances are retained in soil are as follows:

1. As insoluble polymeric complexes of humic and fulvic acids.
2. As polymeric complexes of humic and fulvic acids bound together by di- and trivalent cations such as Ca²+, Fe³+ and Al³+.

Organic matter is of immense importance in forming good aggregates in a wide range of soil types, particularly those representing Mollisols, Alfisols, Ultisols and Inceptisols. Organic matter is somewhat less important in the Oxisols where hydrous oxides may play apredominant role. These relationships are depicted in Fig. 13.

Fig. 13.1: Relationship between OM and the formation of soil aggregates

Aggregates do not directly influence plant growth, but they alter the physical and chemical environments in which plant roots grow through their effects on porosity, aeration, moisture retention, etc., when well-irrigated, even fine- textured soils permit adequate exchange of gases with the atmosphere. The polysaccharides of soil have received the greatest attention in producing stable aggregates, but other organic substances bonded to clay through association with Fe or Al may also be involved.

Summary

Water security can be defined as reliable availability of water in sufficient quantity and quality to sustain human health, livelihoods, food (agriculture, fisheries and aquaculture) and the environment (biodiversity and ecosystems). Discharge of chemical and biological pollutants (from agriculture, industry and domestic uses) into rivers and development of engineering infrastructure such as dams and weirs over rivers have modified river ecosystems threatening the global water security, water quality and water dependent biodiversity. Climate change (increase in the intensity and frequency of floods, droughts, bushfire and sea-level rise, ocean acidification, etc.) is an additional stress on water security. There is a need to reduce climate change impacts on water security which can be done via adaptations to climate change. Adaptation is adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities. In other words, the adaptation can be considered as, tackling the effects of climate change. Adaptation to climate change in terms of sustainable use of water may include increasing water availability by developing hydro-basins and transferring water from areas in which it is abundant to areas in which there is scarcity, the reduction of water losses, increasing storage capacity by building reservoirs and dams, rainwater harvesting, improvement of water use efficiency, desalination of seawater, water savings (leakage management, metering, retrofitting existing homes with water efficient products in toilets, showers, baths, using energy efficient dishwashers and washing machines), mandatory rainwater tanks in new and old buildings (for toilet flushing, washing clothes, gardens, car washing), use of recycled or reclaimed water for landscape irrigation or to recharge groundwater aquifers, and to meet commercial and industrial water needs.

The specter of climate change looms large over our planet, its influence permeating every aspect of the Earth’s systems. Among the most concerning manifestations of this global shift is the increasing frequency and severity of extreme weather events, and atmospheric droughts are emerging as a particularly insidious threat. The present chapter shines a spotlight on this critical intersection, meticulously dissecting how the profound alterations in our climate are fundamentally reshaping the dynamics of atmospheric moisture Going beyond traditional notions of drought rooted in soil dryness, this chapter will illuminate the concept of atmospheric drought – a state where the air itself becomes exceptionally parched, characterized by low relative humidity and a voracious atmospheric demand for moisture. We will unravel the intricate ways in which climate change acts as a catalyst for these conditions. Rising global temperatures amplify evaporation rates, while shifts in large-scale atmospheric circulation patterns can steer moisture-laden air away from v

Climate change refers to long-term shifts in temperatures and weather patterns. These shifts may be natural, such as through variations in the solar cycle. But since the 1800s, human activities have been the main driver of climate change, primarily due to burning fossil fuels like coal, oil and gas. (https://www.un.org/ en/climatechange/what-is-climate-change) While it is possible to achieve enhanced food production to meet the demands of growing populations, the prevailing negative environmental trends, if continued, might cause crises in many parts of the world (Molden, 2007). The effects of climate change on agriculture can take place through changes in average temperatures, rainfall, and climate extremes (e.g., heat waves); changes in pests and diseases; changes in atmospheric carbon dioxide and ground-level ozone concentrations; changes in the nutritional quality of some foods; and changes in sea level. (Anonymous, 2014A)

Summary

The main greenhouse gases (GHGs) that have caused the global climate change or global warming are carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O). CO₂ is the principal anthropogenic GHG that affects the earth’s radiative balance. It is the reference gas against which other GHGs are measured and therefore has a Global Warming Potential (GWP) of 1. CH₄ and N₂O have a GWP of 21 and 310, respectively. CO₂ is responsible for most of the enhanced greenhouse effect of more than 50%, CH₄ for about 10-15% and N₂O for about 8%. The global atmospheric concentrations of CO₂, CH₄ and N₂O have increased since 1750. While CO₂ increased from a pre-industrial value of 280 ppm to 379 ppm in 2005, CH₄ increased from 715 ppb to 1774 ppb and N₂O increased from 270 ppb to 319 ppb during the same period. Rich countries and large developing countries account for most of global CO₂ emissions (China 23.5%, USA 18.27%, India 5.83%, Russia 5.72%, Japan 4.04% and European Union 13.98%). A new climate agreement called ‘Warsaw International mechanisms (November 2013) on loss and damage’ agreed to help the poor countries to cope with loss and damage from heatwaves, droughts, floods, typhoons, desertification and rising sea levels. The Warsaw agreement also includes a set of decisions to help developing countries to reduce GHG emissions from deforestation and degradation of forests which is backed by pledges of US$280 million financing by the United States, Norway and the United Kingdom. Projections for global average temperature rise is in the range of 1.1-6.4°C; a doubling of CO₂ (from pre-industrial 280 ppm) and average sea level rise is in the range of 0.18-0.59 m (Meehel et al. 2007) and 0.5–2.4 m (Brown et al. 2013). Hot extremes, heat waves and heavy precipitation events will continue to become more frequent. Projected data show that there is an increasing global trend in the rise of average temperature in all countries, regions or sub-zones; a decreasing trend in average precipitation in most sub-tropical areas and an increasing trend of precipitation in most of the tropical and high latitudes.

Introduction

Water and food security are the key challenges under climate change as both are highly vulnerable to continuously changing climatic patterns. Climate change has resulted in increases in globally averaged mean annual air temperature and variations in regional precipitation and these changes are expected to continue and intensify in the future. The projected changes in climate patterns over India include increase in surface temperature, variations in rainfall, increasing occurrence of extreme weather events like floods and droughts, rise in sea levels and impact on the Himalayan glaciers. Sectors of the Indian economy are most likely to be impacted by such changes in climate are those dependent on natural resources, namely agriculture, water and forestry. The likely impacts such as reduction in food production, water scarcity, loss of forest biomass Climate change is expected to bring more intense and more frequent extreme weather events including droughts and floods in India. The global atmospheric concentration of carbon di-oxide CO₂ for increased from preindustrial value of about 280 ppm to about 410 ppm at the present (2021). The global increase in CO₂ concentration is primarily due to fossil fuel use and land use change. Atmospheric methane was 1803 ppb in 2011, this is 150% greater than before 1750. Atmospheric nitrous oxide (N₂O) was 324 ppb in 2011, this is 150% greater than before 1750 (Table 1). These increase in GHGs have resulted in warming of the climate system by 0.74°C between 1906 and 2005.