eChapters

9.1 Introduction

After knowing when to irrigate and how much to irrigate, next important thing is how to irrigate the crop field. Methods of irrigation plays a very crucial role in deciding how to irrigate the crop fields since all the crops do not require same methods of irrigation. Depending on the sources of water available for irrigation, type of crop to be irrigated, quantity and quality of water to be applied and other economic considerations, methods of irrigation will vary. Irrigation water may be applied to the crops by flooding it on the field surfaces as surface irrigation, by applying it beneath the soil surface as sub irrigation, by spraying it under pressure as sprinkler or overhead irrigation or by applying it in drops around the root zone of the crop as trickle irrigation. The commonly used methods of irrigation are described in schematic diagram as follows

8.1 Introduction

After knowing when to irrigate and how much to irrigate, next important thing is how to irrigate the crop field. Methods of irrigation play a very crucial role in deciding how to irrigate the crop fields since all the crops do not require same methods of irrigation. Depending on the sources of water available for irrigation, type of crop to be irrigated, quantity and quality of water to be applied and other economic considerations, methods of irrigation will vary. Irrigation water may be applied to the crops by flooding it on the field surfaces as surface irrigation, by applying it beneath the soil surface as subirrigation, by spraying it under pressure as sprinkler or overhead irrigation or by applying it in drops around the root zone of the crop as trickle irrigation. The commonly used methods of irrigation are described in schematic diagram as follows:

Soil is the outer loose layer of earth consisting of layers of mineral material (regolith) whose properties differ from one another and these differences are largely due to the variation in biological activities. Soil micro-environment principally comprizes of inorganic particulates (sand, silt and clay) plus certain oxides and hydroxides, plant roots, organic matter, microbial biomass and aqueous and gaseous phases. The uneven distribution of these components provides a great variety of conditions from field to micropores. The interaction of physical and chemical factors contributes to the creation of varied soil habitat and hence determines the composition and activity of soil biota at a particular site and time. Over geological times, microorganisms have had great opportunity to become distributed worldwide. Such growth and development of microorganisms as well as species diversity is of considerable significance. The existing geographic distribution is reflective of long term adaptation of microorganisms to the various environmental conditions. The preferred environment of an organism is usually referred as ‘habitat’.

Microbial Based Formulations examines preparations produced through beneficial microorganisms, fermentation, and indigenous microbial resources. It covers Waste Decomposer, Effective Microorganisms, Fermented Plant Extract, EM-Bokashi, Indigenous Microorganisms, Fermented Plant Juice, Fermented Fruit Juice, Oriental Herbal Nutrient, and lactic acid bacteria. Water-soluble potassium, phosphoric acid, and calcium preparations, brown rice vinegar, loess powder, fermented seawater, and microorganism-enriched mixtures are also discussed. The chapter demonstrates how microbial activity and fermentation can transform locally available materials into agricultural inputs. Together, these formulations illustrate approaches for nutrient management, plant growth support, compost enrichment, and ecological farming using biologically mediated processes and farm-level resources. for preparation.

Soil microbial biomass is an important parameter linking the plants to soil. It comprises about 2-3% of the total organic carbon in the soil and recognized as an important source of nutrients to plants. It is also a dynamic component of the soil associated with several functional properties of the terrestrial ecosystem. It represents the fraction of the soil responsible for the energy and nutrient cycling and the regulation of organic matter transformation.

Microbial biomass is a small but labile and living component of soil organic matter that is involved in most bio-geo-chemical processes in the terrestrial ecosystem. It interacts with crop productivity by regulating nutrient availability as a source; determining soil carbon storage- sink; and contributing to the atmospheric CO₂ from respiration. Thus it is the main agent that controls the flow of carbon and cycling of nutrient elements.

There is a close relationship between soil microbial biomass, decomposition rate, and nitrogen mineralization. It is also positively correlated with grain yield in organic farming and also contributes to soil structure and stabilization. Thus, there is the immense importance of microbial biomass in soil fertility as well as in agriculture.

The study of soil microorganisms involves various complicacies when compared with those of plants or animals aboveground. The complicated heterogeneous environment existing in soil and the varied growth behaviour of microbial populations in soil have necessitated the development of special techniques to study the microbes and their metabolic diversity, individually and holistically without disturbing their natural habitat. With the gradual improvement in microscopy since its discovery in 1667 and also with the greater understanding of the nature of soil microbes and their properties in relation to total ecosystem function, the concept of studying microbes in isolation has enormously changed. Microscopes have helped in magnifying these, otherwise invisible, minute creatures within the limits of naked eyes.

Soil microorganisms immobilize and mineralize various elements to satisfy their growth requirements. The subsequent turnover of microbial biomass also releases several mineral elements. The elements may be released as a result of organic matter decomposition (e.g. during the process of mineralization, ammonification, etc.) or through biological weathering. Other transformations may involve oxidation and reduction of various inorganic ions and compounds which are mostly catalyzed by chemoautotrophic bacteria during oxidation of ammonium, nitrite, sulphur, iron, etc. Such oxidations may also release energy for microbial growth.

Micronutrients are those elements essential for green plants but required in very small quantity for their growth and development. There are altogether eight micronutrient elements in soil consisting of iron, manganese, zinc, copper, boron, molybdenum and chlorine with the recent addition of nickel. These together with large number of other elements usually present in plants with small concentrations are formed as trace elements. Another element, cobalt is known to be required for microorganisms concerned mainly with nitrogen fixation in legumes affects indirectly the growth of many higher plants, thus, may be considered to be included in the list of essential micronutrient element. Similarly, Vanadium and sodium although present as beneficiary elements for plant growth may also have the possibilities to be enlisted into this group of elements.

Micronutrients are required in small quantities but are essential for normal plant growth and crop productivity. Their availability in irrigated soils can vary considerably because of changes in soil pH, moisture conditions, organic matter, texture and interactions with other nutrients. This chapter introduces the concepts of micronutrient deficiency and toxicity and discusses critical limits used for evaluating micronutrient status. Particular emphasis is placed on boron and zinc. Boron content, deficiency in Indian soils, availability and leaching are examined, together with the influence of soil texture, pH and moisture. Boron indicator plants, correction of deficiency, sources, crop response and frequency of application are also discussed. Interactions between boron and other nutrients receive attention. The chapter then considers zinc content and zinc deficiency in soils and examines the influence of pH, phosphate level, organic matter and adsorption by clay minerals on zinc availability. Methods, timing and rates of zinc application and crop responses are presented to support effective micronutrient management.

ZINC (Zn)

Chandler et al., (1932) deduced the requirement of zinc by plants while working solution for little leaf or “rosette” on peach. Zinc plays significant role in assimilation of NO₃ and for synthesis of tryptophan. Involved in biosynthesis of indole acetic acid which is responsible for f lowering and fruiting, it is an activator of several enzymes (triphosphate dehydrogenase and tryptophan synthetase), involved in photosynthesis and nitrogen metabolism.

Deficiency results in poor growth of the terminal bud. Decrease in stem length resulting in resetting and whorling of leaves. Zinc deficiency disorder in rice is called khaira. Common when zinc availability is < 0.7 ppm. White bud in maize and malformation of fruits, reduction in water uptake. Interveinal chlorosis often with necrosis and pigmentation and reduced leaf size in broad leaved crops known as little leaf and malformation of leaves.

The crops which are known to respond for zinc application are maize, rice, soyabean, castor, onion, barley, wheat, potato, sorghum and cotton

Iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), nickel (Ni), boron (B), molybdenum (Mo) and chloride (Cl) elements are known as micronutrients. The micronutrients are also called as trace elements or minor elements as they are required very small quantities by plants. The elements Fe, Zn, Cu, Mn and Ni are known as micronutrient cations and B, Mo and Cl are known as micronutrient anions and they behave accordingly in soils. Among these elements, Fe content in soil as well as plant is the highest and sometimes higher than phosphorus (P) and sulphur (S). In plant, the concentration of micronutrients often found up to 100 mg kg^-1, except that of Fe and Mn which may go up to 500 mg kg^-1 (dry weight basis). Another element, cobalt (Co) is also regarded to be essential for the growth of certain higher plants and animals, and likely to be included in the list of micronutrients. The importance of micronutrients has been realized during the past four decades when micronutrient deficiencies were observed in most of the soils in our country, where intensive agriculture is practiced.

18.1. Determination of Available Micronutrient Cations (Zn, Cu, Fe and Mn) in Soil

The available micronutrient cations (Zn, Cu, Fe and Mn) can be estimated in a single extraction with diethylene triamine pentaacetic acid (DTPA) as proposed by Lindsay and Norvell (1978). DTPA has the excellent property to combine with free metal ions in the solution forming soluble complexes. The stability constants of metal-DTPA complexes make DTPA as a most suitable extractant for simultaneous complex formation with Zn, Cu, Fe and Mn. In calcareous soil DTPA extractant may result overestimation due to excess dissolution of CaCO_3, thus releases occluded micronutrient cations which are not plant available. To avoid this excessive dissolution of CaCO₃, DTPA is buffered at pH 7.3 using triethanol amine (TEA). At this pH major part (3/4^th) of TEA is present as HTEA⁺ (protonation) and exchanges for Ca and Mg ion from the soil exchange site. This increases concentration of Ca and Mg in the solution phase and suppresses dissolution of CaCO₃. The DTPA has the capacity to complex each of the micronutrient cations 10 times of its atomic weight and it ranges from 550 to 650 ppm depending on the micronutrient cation.

The amount of cation in the extract is determined on an atomic absorption spectrophotometer (AAS). The experimental condition such as shaking time, DTPA concentration, pH and temperature during shaking influence the amount of Zn, Cu, Fe and Mn extracted. Increase in shaking time and temperature markedly influence the extractability of these cations.

There are nine essential micronutrients, namely, iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), chlorine (Cl), vanadium (V) and nickel (Ni). Out of these, Fe, Mn, Zn, Cu and Ni (Dominic et al., 1978) are taken up by plants in their ionic form X²⁺, Mo as MoO^2-, chlorine as Cl^– form and boron as boric acid (H₃BO₃) or as its ionic form B (OH)₄ ^–. The absorption of vanadium by plants has received only limited attention (Lepp et al., 1983); it may be absorbed as cation V or vanadyl (VO²⁺) and anion vanadate (VO₄ ^3–). Bulk of the information is available on Fe, Mn, Zn and Cu, because of the acceptability of the single DTPA (Diethylene triamine pentaacetic acid)–CaCl₂ extraction test of Lindsay and Norvell (1978) for availability of all these four nutrients followed by their estimation on Atomic Absorption Spectrometer (AAS). Available B is estimated by hot 0.15 M CaCl₂ extraction method (Saha and Singh, 1997). Molybdenum data base is poor, because its determination is dif?cult and Mo de?ciency in crops has not been much noticed in India. Chloride is available in plenty in irrigation water and soil in India and has not received much attention in India.

1. Introduction
The amount of water present in the soil is called as soil moisture. The soil moisture availability is an important topic to study as it affects plant growth, agricultural outputs and the water resource management as well. The amount of soil moisture present in a place and in a time depends on the factors like soil type, Land use, vegetation cover of the place and evaporation taking place in that area at that time. The amount of water hold by the pores in the soil determines the soil moisture. This water holding by the soil depends on various factors like temperature, moisture levels, organic matters and the soil living organisms (Rasheed et al., 2022). Essential Climate variable (ECV) is very important to our planet which can be recognized by GCOS (Global Climate Observing System). Important sustainable development issues say drought, flood management, food security, ecological health and water resources are being impacted by the soil moisture. Soil moisture changes have also a role in evapotranspiration, rainfall, and the runoff distribution and intensities. (Zeng et al., 2023).
Soil moisture content (SMC) have a huge impact in shaping the water, carbon cycles of earth and energy balance in different scales of time and space. It is an important factor for the effective water management due to its influence on the precipitation, surface temperature and evaporation which will be affecting the processes say river runoff, vegetation health, and irrigation practices. The highcost traditional methods make to overlook for SMC in environmental modelling (Edokossi et al., 2020). The atmospheric and the land surface process are blinked by the key facto of SMC as said by Robinson et al. (2008). For gaining the knowledge on water, carbon cycles and energy as well as for studying extreme weather conditions, understanding soil moisture is very much needed. (Vereecken et al., 2014; Li et al., 2007; Seneviratne et al., 2010; Robock & Li, 2006).
Due to the soil moisture’s impact on the factors say when to plant, when to blossom and when to harvest the crop, soil moisture should be considered as the important factor as it is in improving the water resources and boost the agricultural output. Remote sensing methods like microwave remote sensing plays vital role in creating maps depicting the distribution of soil moisture spatially and temporally high resolutions. These maps help in effective crop planning, in-season drought assessment, irrigation and soil managements. The traditional methods like TDR probe, Soil moisture utilizing neutron probe and gravimetric methods are inefficient in studying the soil moisture with high spatial and temporal resolutions due to factors like Variations in terrain, soil type and land use pattern. We can overcome these and enhance our ability to map soil moisture in different scales through the recent advancements of microwave remote sensing (active and passive microwave remote sensing) which are having advantages like clear, accurate and timely measurements of soil moisture content.
Irrigation water sources are controlled through the soil moisture studies by executing the sustainable water management plans and by monitoring high yields despite the environmental changes, increasing water demands and climate changes. To predict the agricultural output, irrigation management, drought early warning, creating vegetation indices, soil moisture study with high temporal and spatial resolutions will be a key factor as it improves the crop stress reduction also which are the major driving forces of yield reduction (Doraiswamy et al., 2004). So, the soil moisture has a direct impact on the crop yield which are studied using variable rate technology say selective application of pesticides which can improve farmers financially as well as environmentally (Harris et al.,1964).

The living organisms in the terrestrial ecosystem have unique characteristics of taking up the substances from atmosphere and soil for the synthesis of their own cellular component or as a source of energy. The supply and absorption of chemical compounds required for the growth and metabolism of the organisms may be defined as nutrition and the compounds required by them are called nutrients. The process by which the nutrients are converted to cellular material is known as the metabolism. Out of 118 chemical elements so far detected in the modern periodic table, 92 elements from hydrogen to uranium are naturally occurring, a large portion (more than sixty) of such have been detected in the plant tissues. But, the elements which take part in the nutritional requirement and metabolic processes of the plant are said to be essential elements, others which do not participate in such processes are considered non-essential.

Introduction

The inevitability of detrimental effects of climate change is looming large not only on the sustenance of agriculture, but also on the survival and progress of mankind. Estimates by the Organization for Economic Cooperation and Development (OECD) reveal that the atmospheric concentration of GHG would exceed 680 parts per million (ppm) CO₂-equivalents by 2050, which is about 50% higher than baseline year 2010 (OECD, 2012). Additionally, global temperature is predicted to increase by 2°C within this period, resulting in meansea level rise and erraticweather conditions. Consequently, the catastrophic effects on food consumption pattern by the end of 2050 will create malnutrition in at least 290 million people. Agricultural crops provide 63% of the human protein, and additionally supply almost 100% protein to the livestock, which are the second major sources of protein in human diet. Altogether, the detrimental effect of climate change on agriculture would make about 300 million additional people malnourished. Add to that a 2.7 billion increase in human population by 2050, coupled with shortage of water availability that would affect 3.9 billion people by 2050, and one can easily perceive the grim scenario for our kind in not so distant future.

Introduction

Climate variability can have significant impacts on agricultural production, affecting both the demand and supply sides of farming. As climate change continues to negatively impact our ecosystem, food production, and human livelihood, this topic has gained widespread attention from researchers and academics worldwide. Given that agriculture is highly dependent on factors such as precipitation and temperature, it is considered one of the most climate sensitive sectors (Sagar et al., 2022).

Climatic data is complex and nonlinear, with significant fluctuation across time components, resulting in greater volatility. This means that stochastic climatic variables, including rainfall, temperature, relative humidity, and other weather parameters, often exhibit conditional heteroscedasticity, leading to irregular residual mean and variance across time series.

4.1 Introduction

The developed or commercially available models can be applied for any water bodies such as fresh water lakes, ponds, rivers, estuaries and marine ecosystems. The predicted results can be compared with proved with field data and existing approved models and applies to the other such ecosystems. In this chapter, we can discuss about modeling of water bodies, water quality model, spatial discretizafion, modeling pollutants and toxicants, concentration modeling, hydrodynamic mixing zone analysis.

4.2 Modeling of Water bodies

The need for predictive water quality modeling has arisen largely as a result of increased eutrophication of lakes throughout the world (Forsberg, 1987; Canfield and Hoyer, 1988). The most common modelling approach is exemplified by the development and application of steady state, input-output models. Generally, nutrient concentrations are calculated from net inputs and chlorophyll a concentration is predicted by correlation with the limiting nutrient, most often phosphorus (Dillon and Rigler, 1975; Canfield and Bachmann, 1981; OECD, 1982).

Factors that can also influence phytoplankton biomass, such as light, climate, biological interactions and internal loading of nutrients, are not considered. Further more, the assumption that a lake is a continuously mixed system is very restrictive and only applicable at discrete times of the year. As a result, the shortcomings of such approaches include an inability to make predictions in the face of varying physical and biological conditions, and a failure to offer insights into the determinants of changing water quality.

7.1 Introduction

The coast is one of the most important boundaries in the world. It separates the marine part of the world from the continents. It separates the salt-water communities from fresh water communities; it separates land life from water borne life but amphibians living both environments (Fig. 7.1).

Some of the marine organisms move towards estuary for reproduction with less water salinity. The coastline as such is not a stable. It fluctuates in place over considerable distances due to erosion and sedimentation, but also due to the relative change of sea level with respect to land. The coastal zone is thus a very mobile part of the earth from a geographical point of view. Due to its specific geophysical properties, the coast is also a very important area for the development of flora and fauna. There is hardly any other part of the world that houses such a variety of species, both in flora and fauna.

The abundance of opportunities along the coast has also attracted a lot of human activities. The coastal zone has become an indispensable resource for mankind. It provides excellent opportunities for fisheries, housing, recreation, transport, defense purpose, industrial activities and many others. The influx of man with their social and economic activities, their needs for safe housing, food, drinking water, and with the tremendous quantities of waste they are producing poses at the same time a serious threat to the unique features of the coastal zone. It is therefore necessary to study this valuable region so as to prevent that competing activities are gradually causing depletion of the resources in the coastline. The following figures (Fig. 7.1and 7.2) show the typical coastal area of rocky coast and sandy coast.

8.1 Introduction

A lake is a body of water or other liquid of considerable size surrounded entirely by land (Fig. 8.1). A vast majority of lakes on Earth are fresh water, and most lie in the Northern Hemisphere at higher latitudes. In ecology, the environment of a lake is referred to as lacustrine.

Fig 8.1 A Typical Lakes

Large lakes are occasionally referred to as “inland seas” and small seas are occasionally referred to as lakes. Smaller lakes tend to put the word “lake” after the name, as in Green Lake, while larger lakes often invert the word order, as in Lake Ontario, at least in North America. The term lake is also used to describe a feature such as Lake Dal, which is a wet basin most of the time but may become filled under seasonal conditions of heavy rainfall and snowfall. Many lakes are artificial and are constructed for hydro electric power supply, recreational purposes, industrial use, agricultural use, or domestic water supply.