eChapters

Liebig (1840) on the basis of soil and plant analysis deduced the phosphorus requirement of plants. J.B. Lawes conducted series of field experiments to improve the fertilizer value of common sources of phosphorus such as bone meal, apatite, rock phosphate. Lawes (1843) produced super phosphate by treating apatite mineral containing phosphorus with sulphuric acid. He also stated that the phosphorus present in bones of higher animals can be made available by treating with sulphuric acid.

Phosphorus is the second most deficient nutrient in the world. Annual application of phosphorus fertilizers to crops is 36 million tons of which

1.32 m tones are consumed in India. Most of the arable soils in tropical and subtropical regions are deficient in phoshphorus, but the response of crops to phosphorus is uncertain. Phosphorus concentration in plants ranges from 0.1 to 0.4 per cent.

1. Introduction
Water is the most essential resource for life, supporting the survival of allliving beings, including humans, and playing a crucial role in food productionand economic progress. Currently, many cities around theworld are facingsignificant water shortages. About 40 % of global food production dependson irrigation, and countless industrial operations rely heavily on water. Theavailability and quality of water, whether surface or groundwater, have amajor impact on environmental health, economic development, and societagrowth. Human activities like urban expansion, population increase, industrialoutput, and climate shifts are causing a decline in water quality. As nationsdevelop, industrial activities increasingly lead to the pollution of watersources, resulting in negative consequences such as widespread disease and
diminished beauty of water bodies. This pollution is a significant threat toboth the planet and its inhabitants. Higher temperatures are interfering with themetabolic processes of aquatic life, while changes in water pH create unstableconditions. Additionally, increased cloudiness in water reduces oxygen levels,affecting deep-water species and contributing to health issues for both animalsand humans. Polluted water also hinders growth and development in allliving organisms Haldar et al., 2015 and Arif et al., 2020. A study conductedby Halder et al. (2015) highlighted severe health challenges faced bylocalcommunities due to pollution in the Turag River, Dhaka, caused by thedischarge of untreated wastewater into the river. It was revealed that elevatedpH levels in the water, resulting from the use ofcaustic chemicals such assoda ash and caustic soda in industrial processes, were associated with skinirritation and sores. Dietary exposure to polluted crops and fish was found
to contribute to stomach ailments, including gastric ulcers. Concerns wereraised about potential groundwater contamination through the infiltration ofindustrial waste. Microbial contamination was identified as a likely cause ofdiarrhoea and dysentery. The use of river water for bathing and laundry wasobserved to facilitate the spread of waterborne diseases. Outbreaks of yellow
fever, cholera, dengue, malaria, and other epidemics were noted as prevalent inthe area. Respiratory problems and foul odours were attributed to air pollutioncaused by industrial discharge. Maternal and child health in riverbank slumsfound to be vulnerable, emphasizing the urgent need for interventions to addressthese public health concerns.Wastewater produced by industries, agriculture,and domestic activities contains high levels of nutrients, heavy metals, andchemicals, which harm the environment by polluting land, air, and water,

Abstract

Photosynthetic blooms of toxin producing marine algae are often referred to as “red tides”. Proliferations of freshwater toxin-producing cyanobacteria are simply called “cyanobacterial blooms” or “toxic algal blooms.” Biotoxins of cyanobacteria are water-soluble and heat stable and they are released upon aging or lysis of the cells. The primary types of cyanobacterial biotoxins involves three types of toxins: hepatotoxins (microcystin; cylindrospermopsin and nodularin), which are taken up by the liver and cause weakness and anorexia (loss of appetite); neurotoxins (usually anatoxin and saxitoxin), which effect the nervous system and dermatotoxins (aplysiatoxin and lyngbyatoxin, LPS), which cause skin and mucous irritations upon contact. Unlike freshwater toxic algal blooms, marine algal toxins become a problem primarily because they may concentrate in shellfish and fish that are subsequently eaten by humans, causing syndromes known as paralytic shellfish poisoning/PSP (paralysis due to saxitoxin and gonyaulatoxins), diarrhetic shellfish poisoning/DSP (diarrhea due to okadaic acid) , amnesic shellfish poisoning /ASP(memory disturbances due to domoic acid), neurotoxic shellfish poisoning/NSP (paresthesia due to brevetoxin; also bronchial spasms). Coral reef fishes are the vectors of another algal poisoning, the ciguatera fish poisoning/CFP (paresthesia, warm-cold sense inversion etc., due to ciguatoxins and maitotoxin).

Introduction to Nano-materials

Nano-sized materials are naturally present from forest fires and volcanoes, but are also generated unintentionally from anthropogenic sources as a by-product of combustion and deliberately as manufactured nanomaterials. Nanoparticles have been used for centuries. The coloured glass that we see in many old cathedrals from the middle age was made of gold nanosized clusters that created different colour depending on the size of the nanoparticles. The most prominent example of engineered nanoparticulate material is carbon black which has been around us for decades in applications like printing inks, toners, coatings, plastics, paper, tires and building products.
 
Two of the major factors why nanoparticles have different properties (optical, electrical, magnetic, chemical and mechanical) than bulk material are because in this size-range, the quantum effects start to predominate and the surface area to volume ratio is increased.

10.1 Different practices for different purposes

There are so many different practices used in erosion control that to describe them needs some form of grouping. For a long time mechanical protection was used to describe all the methods which involved earth moving, such as digging drains, building banks, levelling sloping land, and so on. Anything else was lumped together under biological methods for want of a better title.

This is appropriate for large mechanized farms where the approach is to use machines to do the earth-moving and follow up with improved farming methods. But this division does not suit the concept of erosion control through better land husbandry supported by mechanical protection, and the division is artificial when we start talking about progressive terracing using grass strips or live hedges.

An approach more suited to today’s thinking is to group methods and techniques according to their main objective. All have an element of saving soil loss, but an important difference is the handling of surface runoff. This chapter identifies three kinds of water management objective and two types of soil management on sloping land.

5.1 Introduction
Since the early days of human interaction with the environment, particularly in industrial settings, humans have continually been “shaped” to meet the demands of their surroundings. Historically, people have often endured significant discomfort and limitations without much complaint. In metaphorical terms, individuals have adapted by extending their reach to operate controls that were difficult to access, pushing their perceptual abilities to detect faint sounds or invisible signals, and compressing their bodies to fit into cramped workspaces. Cognitive abilities have also been stretched to accommodate monotonous or tedious tasks. However, as both work environments and machines have grown more complex, these challenges have become increasingly significant. A poor “fit” between the human operator and their environment has led to countless accidents, decreased productivity, and errors in many industries. The primary goal of ergonomics is to assess human capabilities and design the environment to align with these capabilities. Instead of attempting to adapt humans to jobs, ergonomics strives to “fit the job to the person.” This approach aims to optimize safety, efficiency, and comfort by aligning machine requirements with the operator’s abilities. By establishing a connection between humans and machines, ergonomics ensures that machines communicate information to the operator through their sensory systems, prompting a response that may alter the machine’s state. Key environmental factors such as temperature, humidity, lighting, sound, and visual conditions have a direct impact on both human well-being and the quality of production. The design of both the human workspace and the equipment used can be highly effective if the environment is conducive to the operator’s needs. Therefore, it is essential to study each environmental factor from an ergonomic perspective to ensure a comfortable and productive environment for workers. This includes designing jobs, equipment, and considering human anthropometric measurements in the design process.
5.2 Heat
Heat stress occurs as a result of the combined effects of environmental conditions, physical exertion, and clothing. The key environmental factors influencing heat stress include air temperature, humidity, radiant heat, and air movement, all of which can significantly affect work performance. Heat strain refers to the

Three fundamental processes that are responsible for inducing changes in weather are transfer of heat, energy and mass. The Sun, whose inter-surface temperature is estimated to be around 6000°C emits heat energy in the form of solar radiation which is received at the earth’s surface after it is partly depleted in the atmosphere. Therefore, it is essential to understand the processes that govern the transfer of heat in the earth-atmosphere system.

3.1 Conduction

The transfer of heat from one point to another point within the material medium without the actual movement of the particles in the medium is called conduction i.e. the heat energy transfer is conducted by the particles in the medium from hot end to cold end. If a metal rod is heated at one end, the other end of rod becomes hot gradually due to transfer of heat by conduction. In the earth atmosphere system, conduction of heat is observed at the ground surface only. The amount of heat energy transferred due to conduction (Q) is

2.1. Soil structure

Important physical properties of soils

Soil texture

Soil structure

Surface area

Soil density

The major components of soil consisting with mineral and organic matter, water and air produces a three phase systems of solid, liquid and gas. Many of the soil properties influencing crop growth and other uses depend mostly on the relative proportions of these components as well as the size, shape and arrangements of the solid matters. The physical properties of soil have strong significance in sustaining agricultural productivity. Fertiliser alone or in conjunction with suitable crop varieties and plant protection measures cannot be sufficient towards improving crop productivity unless the soil physical properties are maintained at satisfactory level. Improvement and restoration of physical properties in soil are necessary for protection of soil resources against degradation. The physical properties of soil discussed in this chapter includes soil densities, texture, structure, porosity and consistency of soils and colour of the soil.

Introduction

India is having very rich sources of inland water bodies in the form of river, lakes and reservoirs. The reservoirs are constructed by impounding the river system. The reservoirs are constructed for effective utilisation of water for irrigation, power generation and flood control. Reservoir fishery in India is also important from socio-economic point of view as it has the potential of providing employment to about two million people, Kaushal and Sharma (2001). Total area under the reservoirs in India is 3:1 million ha and it is expected to double by 2020. This includes 19,000 small reservoirs with a total water surface area of 14,85,557 ha and about 180 medium and 56 large reservoirs of 5,27,541 and 11,40, 268 ha area respectively.

The Maharashtra is endowed with an area of 1,79,430 ha under reservoir and the Maharashtra produces 516 tonnes of fish through reservoirs. The state fisheries corporation was operating in 6,272 ha of reservoirs and marketing the catches.

Soil texture and mechanical analysis: The chemistry of the mineral framework was explained in Chapter II. Its physical properties are quite as important- When all the extraneous matter is removed from the soil we are left with a collection of particles of various sizes. These particles are not spherical in shape, but most of them are nearly so. At any rate the discussion is very much simplified if we suppose that they are spherical and the arguments advanced are equally applicable if the shape deviates from the spherical.

Introduction

Drought is the most important abiotic factor that adversely affect growth and crop production. Drought stress can altered the normal physiological processes that influence one or a combination of biological factors for yield and yield attributing traits (Ashraf, 2010). The abnormal metabolism due to stress may reduce plant growth (Claves et al., 2002). Production is limited by environmental stresses, according to different scholar estimates, only 10 per cent of the world’s arable land is free from stress, in general, a major factor in the difference between yield and potential performance, environmental stresses. Drought is one of the most common environmental stresses that almost 25 per cent of agricultural lands for agricultural farm products in the world are limited (Loresto, 1976; Chaves, 2002). Drought occurrence in India is also very frequent. Drought occurred in past 1967, 1968, 1969, 1972, 1974, 1979, 1987, 2002, 2009 and had considerable impact on food grain production. For example, the drought of 1966-67 reduced overall food grains production by 19%. The drought of 1972-73 reduced the food grains production from 108.95 million tonnes to 95 million tonnes, causing a loss of about $ 400 million $. The 1987 drought in India damaged 58.6 million ha of cropped area affecting 285 million people (Ray et al., 2015). Drought in 2002 has reduced food grains production to 174 million tonnes from 212 million tonnes resulting in decline of 3.2% GDP (Rathore et al., 2009; Ray et al., 2015).

The water deficit reduces crop yield due to decrease in photosynthetic area, decreased radiation use efficiency and harvest index (Earl and Davis, 2003). Drought stress affect the water balance and plant metabolisms. Plants under drought conditions use various changes to tolerate stress conditions and increase drought tolerance which includes changes in whole plant, tissue, at physiological and molecular levels. Appearance of a single or a combination of inherent changes determines the ability of the plant to stand under aridity conditions. Tolerant plant adjusts its water balance by osmotic adjustment, deep root systems and by transient leaf rolling.

The seed yield, along with the rate of application and uptake of nutrients, is used to determine the following parameters for nitrogen or other nutrients:

Partial Factor Productivity (PFP) (kg seed/kg N applied): Partial Factor Productivity (PFP) is a measure used in agriculture to assess the efficiency of nutrient use, particularly nitrogen or other essential nutrients, in crop production. It is calculated as the ratio of the seed yield to the rate of nutrient application. The formula for PFP is:

*A higher PFP value indicates greater efficiency, meaning that more crop yield is produced per unit of nutrient applied. This is desirable as it implies that the nutrient is being used more effectively by the crop.

Agronomic Efficiency (AE) (kg seed/kg N applied): Agronomic Efficiency is a measure used to evaluate the effectiveness of nutrient application in increasing crop yield. It specifically assesses the yield gain per unit of nutrient applied. The formula for AE is:

Plants are frequently subjected to environmental stresses such as water deficit, freezing, heat and salt stress. Soil salinity is a major problem in arid and semi- arid regions, where rainfall is insufficient to leach salt and excess of sodium ion down and out of root zone. In Asia, around 21.5 million ha of cultivable land was affected by salinity. India had 8.6 million ha of salinity affected cultivable land. It is observed that the area of salinity has been increasing in India. In Tamil Nadu, the area affected by salinity is around 6 lakh ha. Salinity affected areas are Chengalpattu, Salem, Thanjavur, Trichy, Tirunelveli, Dharmapuri and Ramanathapuram. Salinity is the most serious threats to the agriculture especially in the arid and semi-arid region. The presence of salts in the soil and their effects on the plant physiological mechanisms was major restrictive factor for agricultural productivity. Investigations on such soils have revealed that they were charged with high and abnormal soluble salt concentrations that lowered agricultural yield, limited crop distribution and even lead to extinction of certain species.

Salinity adversely affects plant growth and development, hindering seed germination, seedling growth, enzyme activity, DNA, RNA, protein synthesis and mitosis. There has been a variation in the response of plants to salinity with its growth stages according to quantity and period of exposure to salt. Salinity by competing in nutrition element absorption causes growth reduction. Primary salt injuries include metabolic disturbance and inhibition of growth and development. Secondary salt effects include nutrient deficiency and osmotic dehydration. Excessive amounts of salts, especially sodium chloride (NaCl), in the soil induce osmotic effects, leading to changes in plant metabolism. General symptoms of damage by salt stress are growth inhibition, accelerated development and senescence and death during prolonged exposure. Salt stress causes the reduction of rice yield and severe salt stress may even threaten survival.

Abstract

Nitrate uptake from the soil is the first step in nitrate acquisition and utilization by plants. Nitrate uptake and its release into cells is mediated by nitrate transporter(s) located into the plasma membrane of the root. Three transporters have been identified by kinetic measurements in plant roots. These are constitutive high affinity nitrate transporter (cHATS), inducible high affinity nitrate transporter (iHATS) and low affinity nitrate transporter (LATS). Two of these display saturable kinetics; a low capacity constitutive system and a high capacity inducible system. In addition, a non-saturating low affinity, high capacity system becomes apparent only at higher external NO^-₃ concentration. Genes that encode representatives of each class of transport system have been identified and fall into two families: NRT1 and NRT2. Members of these families are induced in response to nitrate in the environment and are regulated by internal signals including nitrogen metabolites and shoot demand for nitrogen. This chapter deals with the physiology and molecular biology of nitrate transporters in higher plants.

Through green revolution, we have developed high yielding varieties albeit with high nutrient requirements putting much more reliance on chemical fertilizers. The major challenge facing plant biology right now is to improve crop production and to feed an expanding world population. This is against a background of pressure on agricultural land use and climate change having negative impacts on growing conditions. The adverse effects of agriculture, and specifically fertilizer use, include damage to the environment, a large carbon footprint for the manufacture and use of agrochemicals, and the utilization of non-renewable resources. One solution is to increase the area of land for agriculture, as well as increasing production while maintaining the current rate of inputs; however, this is predicted to have substantial negative impacts on the environment (Tilman et al., 2002), is unsustainable in terms of phosphate use, and would have a huge economic footprint in terms of energy demands for nitrogenous fertilizer production. The challenge is to increase yield, decrease inputs, and improve resistance to abiotic and biotic stresses. Improving crop nutrient use efficiency ideally requires an understanding of the whole system, from the macro (agro-ecosystem) to the molecular level.

4.1. Physiological disorders in field crops

Identification of physiological disorders in agricultural crops

Introduction

The physiological disorder of a mineral nutrient is entirely contingent upon its function within the plant body. Inadequate or excessive supply of any essential element can result in metabolic disruptions, influencing the activities of enzymes, rates of metabolic reactions, and concentrations of metabolites. Alongside alterations in metabolic patterns, severe deficiencies of specific essential elements also give rise to distinctive effects in leaves, stems, roots, blossoms, and fruits.

A. Nitrogen

Functions: Nitrogen is essential for plants, playing crucial roles in protein synthesis, nucleic acid formation, and chlorophyll synthesis. It is a key component of enzymes, contributing to various metabolic processes. Nitrogen also supports root development, cell structure, and the synthesis of secondary metabolites. Striking a balance in nitrogen levels is vital for maintaining plant health and ensuring optimal growth and productivity. Effective nitrogen management is essential for sustainable agriculture and overall ecosystem well-being.

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

Introduction: N metabolism

Nitrogen is one of the three essential macronutrients for plant growth and yield (Su et al., 2005) and most crucial elements for root growth also (Fageria, 2014). Most macromolecules and a variety of secondary and signalling substances, such as proteins, nucleic acids, cell wall components, hormones, and vitamins, contain nitrogen (N), an important element. In order to assimilate nitrogen, nitrate must be reduced to ammonium, and then ammonium must be converted into amino acids. Perez et al. (1973) pointed out that the rice genotype with high protein yield translocated N from leaf blade to the developing grains more efficiently than the low protein genotype. This was reported due to a high concentration of free amino acids in the sap translocated to the developing grains rather than to differences in translocation rates. Therefore, proper understanding of N metabolism and amino acid translocation are prerequisite to comprehend higher grain protein in high yielding rice genotypes. Use of N by plants involves several steps including uptake, assimilation, translocation and remobilization; and recycling and remobilization when the plant is ageing (Fig. 1). The enzyme nitrate reductase (NR) assimilates nitrate, the main form of nitrogen available to agricultural plants in the field. This enzyme and the nitrogen status of various higher plant systems have a strong positive link, and growth, yield, or protein content can occasionally be connected to this enzyme’s level in seeds or leaves. Nitrate intake occurs at the root level, and it has been demonstrated that plants have two nitrate transport systems that work together to cohabit, absorb, and distribute nitrate from the soil solution throughout the entire plant. (Srivastava 1980) Following NO3- uptake by NO3- transporters and reduction of NO3- to NO2- by nitrate reductase (NR) in the cytoplasm, the process of NO3- assimilation commences (Lea and Miflin, 1974).