eChapters

Background and Technology Intervention

Owing to the subsequent monsoon failures and unavailability of water for irrigation, Tamil Nadu farmers have switched over to drip irrigation which is not only saving huge quantity of water for them, but also preventing irrigation run off and providing deep water percolation. In Tamil Nadu, usage of drip irrigation is prevalent among vegetable and fruit growers and organic farmers.

To relieve the plants from stress or strain of water logging and water scarcity, Tamil Nadu Horticulture Development Agency has played a key role by rightly intervening the farmers through drip irrigation technology and thereby improving water use efficiency.

Surface: border strip, furrow, basin and check basin
Sub-surface
Micro-irrigation: drip, sprinkler; Pichter and bottle
Definition of Irrigation Method
Application of irrigation water to cropped field by different types of layouts is called as irrigation methods. The methods of irrigation initially might have been started to check the over flow of water from one field to another. But today, it has become necessary to save the water by proper methods to arrest run-off loss, percolation loss, evaporation loss etc., and to optimize the crop water need. Hence, irrigation method can be defined as the way in which the water is applied to the cropped field without much application and other losses, with an objective of applying water effectively to facilitate better environment for crop growth.
Factors Influencing Irrigation Methods
Soil type: The soil physical properties such as texture, structure, porosity, infiltration rate, etc. influence the selection of irrigation methods. Heavy texture soil restricts water movement than light texture soil wherein water move freely to deeper sections due to high porosity. Single grain structure soil allows water freely to move downward compared to other structures
Soil depth: If soil is shallow which holds less water, leveling and forming bunds etc. to hold? Maximum water is to increase the irrigation interval. Similarly if the soil is deep, it holds more water and needs longer irrigation interval. Accordingly, the irrigation methods can be selected.
Topography of land: In undulating topography, it is very difficult to adopt normal methods of irrigation. The slope of the land also decides the methods to be adopted. If the land is more sloppy, basin method cannot be used. In this condition strip method can be used. For undulating topography instead of strip or basin method, sprinkler or drip methods can be used.

Background and Technology Intervention

Tanks are one of the oldest structures in India that has been serving as an important water harvesting device since time immemorial. The total number of irrigation tanks in India is estimated to be around 2, 08,000 of which, three states in South India viz., Andhra Pradesh, Tamil Nadu and Karnataka accounts for nearly 1, 27,000 tanks irrigating 1.8 million hectares of land (Gandhiraj, 2009, Siva Subramanian, 2006, Sakthivadivel et al. 2004, Vaidhyanathan, 2001). In Tamil Nadu for instance, there are more than 39,000 tanks at present many of which were constructed during 18th and 19th centuries by kings, zamindars and Britishers (Jagadeesan, M 2011; Palanisami and Easter 2000: 9). Similarly in Telangana region of Andhra Pradesh, tank irrigation developed extensively since ancient times. The district of Warangal and Karim Nagar have several old irrigation tank structures.

Analytical methods for study of soil microbes

The analytical techniques for study of soil microbes are grouped under the following heads :

• Determination of form and arrangement of microorganisms in soil
• Isolation and characterization of soil microorganisms
• Detection of microbial activity in soil
• Determination of microbial biomass.

For the above, the different analytical methods used are described below.

Soil organisms play vital role in agri-ecosystem processes such as nutrient cycling, soil detoxification and organic matter decomposition. They also influence water infiltration by improving soil porosity through production of polysaccharides. Rhizosphere microorganisms help plant to acquire macro and micronutrients, produce phytohormones for better crop establishment. Soil microbes process organic matter to provide a balance of minerals and nutrients which are utilized by plants to achieve healthy and vigorous growth. Microbes also colonize on plants parts and offers protection by excluding many plant pathogens. They are the basic indicators of soil fertility and are responsible for maintaining a hospitable environment for crop growth.

New techniques and approaches to groundwater studies are always in deep concern with the hydrogeomorphologists. The designing of new techniques or adapting existing techniques with better enhancement to solve practical problems in the study of groundwater are of central concern. One of the recent technical developments include the mathematical model of groundwater flow that has become the most widely used computer-based model in the groundwater industry. Techniques to identify and date recently recharged water that is useful in characterizing the susceptibility of hydrogeologic environments to contamination are utilized by various research groups all over the world.

Geophysical methods for determining the hydraulic properties of fractured rocks gained the importance in the hydrogeomorphic studies. Predicting the movement of water and contaminants through fractured rocks has been one of the most challenging problems in hydrogeomorphology. Besides conventional and above mentioned techniques the techniques discussed in this chapter are Remote Sensing, Geographical Informational system (GIS), Global Positioning System (GPS), Digital Elevation Model (DEM), Groundwater Information System (GWIS), Digital Surface Terrain Modelling (DSTM), Multicriteria evaluation (MCE) and Thermal Infra Red (TIR) Mapping and Microwave Data.

Abstract

The tectonic and the geomorphic features observed along the west coast of the area between Mangalore and Cape Comorin show that the NNW-SSE trending west coast has been carved out by the Western Ghats orogeny and the related NNW-SSE trending release fractures. The sinuosity of the otherwise straight coast line is due to Quaternary cymatogenic arching caused by the thrust related to the northerly movement of the Indian plate. The coast line has further attained peaks, projections and serrations due to the ENE-WSW trending series of Precambrian extension fractures which were reactivated gaining the northeasterly directed forces from the rising Carlsberg ridge. Overall, the west coast is being tectonically evolved even today due to the rise of Carlsberg ridge and the Indian plate movement.

Abstract

The analysis of IRS - 1A satellite imagery has indicated the existence of two NE - SW trending sub parallel faults along which the coast is undergoing land subsidence as revealed by the concavity in the shore line, preferential migration of the river systems and the drainage congestion, absence of beach ridges, occurrence of off shore shoal etc. The study has further indicated chains of tectonically induced environmental problems such as ground water logging, coastal zone flooding, storm surges, harbour sedimentation etc.

Abstract

The present study has revealed that the NE-SW and WNW-ESE trending sinistral faults are very active along the Tamil Nadu coast and the same have caused considerable slope modifications along the Coleroon and Karungalar rivers which are well-manifested in the land, water and mudflat distribution pattern. Similarly, the progradation of the land in Vedaranniam nose is due to the rise of Pattukottai-Mannargudi area and the time transgressive modifications of the Vedaranniam backwater indicates the opening up of the N-S trending Pleistocene-Holocene faults.

3.1 INTRODUCTION

The complete soil organic fraction is made up of live organisms, and their undecomposed, partly decomposed and completely transformed remains. Soil organic matter is the term used to refer more specifically to the non-living components which are a heterogeneous mixture composed largely of products resulting from microbial and chemical transformations of organic debris. These transformations, known collectively as the humification process, give rise to humus, a mixture of substances which have a degree of resistance to further microbial attack.

The scientific community has long relied on the expertise of trained researchers and professionals to advance our understanding of the world. However, with the increasing complexity of global challenges, such as climate change, biodiversity loss, environmental degradation, and public health concerns, it has become clear that a new approach is needed. The traditional model of scientific research, where experts work in isolation to collect and analyze data, is no longer sufficient to address the scale and urgency of these challenges. Citizen Science, which involves the active participation of the public in scientific research, has emerged as a powerful tool for addressing these challenges. By leveraging the collective efforts of citizens, researchers can tap into a vast pool of knowledge, skills, and perspectives, ultimately leading to more inclusive, equitable, and effective scientific inquiry. From monitoring water quality and tracking climate patterns to identifying species and analyzing satellite imagery, citizens are making meaningful contributions to scientific research (Fig. 3.1).
The benefits of Citizen Science are numerous. It provides opportunities for citizens to engage with scientific research, promoting a deeper understanding of the scientific process and its applications. It also enables researchers to collect data on a larger scale and in more diverse locations, leading to more comprehensive and accurate findings. Furthermore, Citizen Science has the potential to increase public trust in science, promote community engagement, and foster a sense of ownership and responsibility among citizens for environmental and societal issues.

4.1 Defining erosivity and erodibility

Rainfall erosion is the interaction of two items - the rain and the soil. The amount of erosion which occurs in any given circumstances will be influenced by both, and our study of the processes of soil erosion is simplified by considering the two aspects separately.

We know from observation that one storm can cause more erosion than another on the same land, and we also know that the same storm will cause more erosion on one field than on another. The effect of the rain is called erosivity and the effect of the soil is called erodibility. The way they differ is best explained by examples.

Let us imagine an experiment station which has over its whole area exactly the same soil type and slope. Assume also that the whole of the station is covered by a completely uniform crop. If the amount of erosion taking place during each storm were measured, the amount would be influenced only by the nature of the rain. Comparing the effect of one storm with that of another storm would provide a relative measure of the power of each storm to cause erosion, and that is what is meant by erosivity. This will enable us to say that on this imaginary experiment station, storm A caused a soil loss of X kilograms per hectare and storm B caused a soil loss of Y kilograms per hectare. If Y is half of X, then the erosivity of storm B is half of the erosivity of storm A.

10.1 INTRODUCTION

The fate of plant nutrients in fertilizers added to soils is to be: (1) taken up by crops; (2) retained by the soil; (3) removed in solution in drainage water; (4) lost as a gas; or (5) removed by erosion. These five processes are discussed in this chapter. The purpose of using fertilizers is to increase crop growth and they fail in this unless they are taken up by plants. Table 10.1 gives FAO (1972) data which show that large fertilizer use is restricted to the developed countries which use 65 times the amount used per hectare in developing countries. Within the group of ‘developed’ countries most of North-West Europe uses much fertilizer; outside of Europe large use per hectare is confined to a few countries such as Japan and USA. It is in the developed countries where much fertilizer is applied that efficient uptake of plant nutrients is already important to national economies, and where nutrients lost from agriculture cause eutrophication of natural waters and are regarded as pollutants.

11.1 INTRODUCTION

The heavy metals which, by definition, are elements having a density greater than five in their elemental form, comprise some 38 elements. However, the term usually, and here, refers to twelve metals that are used and discharged by industry, i.e. Cd, Cr, Co, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sn, Zn. Most of the present discussion will centre on those metals that may represent potential hazards to plants or animals; these are Cd, Cu, Hg, Ni, Pb, and Zn.

The heavy metals are widely distributed in the environment, in soils, in plants and animals and in most of their tissues. The concentrations of individual metals in living tissue are ordinarily very low and must be maintained within narrow limits to permit the optimum biological performance of most organisms. Some heavy metals are essential in trace amounts, namely Co, Cu, Fe, Mn, Mo, Zn for plants and, in addition, Cr, Ni, Sn for animals; Cd, Hg, and Pb, have not been shown to be essential for either plants or animals. Deficiencies of the essential metals have been frequently reported and substantial benefits have arisen from correcting these by addition to the soil and subsequent transfer from soil to plant is for most increasing concern about the entry into soil of some heavy metals and the possible adverse effects that they might have on plants and animals and, in turn, on human health. The main sources of these heavy metals are: (i) urban industrial aerosols, created by combustion of fuels, metal ore refining and other industrial processes; (ii) liquid and solid wastes from animals and man; (iii) mining wastes; or (iv) industrial and agricultural chemicals. Although in some circumstances there are direct atmospheric inputs to plants, addition to the soil and subsequent transfer from soil to plant is for most heavy metals the major route of entry into the living tissues of plants, animals, and man. The fate of heavy metals added to soils, including their mobility and reactions in the soil and their subsequent uptake and distribution in plants, is therefore of critical importance in relation to man’s health.

9.1 INTRODUCTION

The annual production of organic carbon by photosynthesis on land is about 6x 10¹⁰ tonnes (Table 9.1), most of which eventually decomposes on or in the top 50 cm of the soil. This organic matter can be in lumps as big as a mature oak tree (say 0.5xl0²m³) or as small as a bacterium (0.5 x 10~¹⁸m³). It can be in material as resistant to decay as oil palm nuts, which persist for years in soil in the humid tropics, or as transient as mammalian protein. Yet in the long run, no fraction of the organic matter in plants and animals can withstand decomposition to carbon dioxide and water. If this were not so, any completely resistant fraction would by now cover the surface of the earth. Although under normal conditions organic matter does not accumulate indefinitely in soil, exceptions can occur, as, for example, when a soil becomes permanently waterlogged. When a geologically stable surface has been under the same vegetation for a long time, the soil approaches steady state conditions, with the annual losses of organic matter balancing the annual input. Thereafter the organic matter content of the soil remains constant, until the next vegetational change or geological catastrophe. This process, in which losses and gains proceed simultaneously, is described as turnover and may be defined (for carbon) as ‘the flux of carbon through the organic carbon in a given sample of soil’. Turnover time is then the amount of carbon in the soil system (or part of that system) divided by the annual input of carbon into the system (or part of that system). Turnover and turnover time will be discussed more fully in Section 9.2.5.

2.1 Geological and accelerated erosion

Erosion has always taken place, and always will. The surface of the earth is constantly changing, with mountains rising, valleys being cut deeper and wider, the coast line receding here and advancing there. The physical pattern of the surface of the earth which we see today is not the result of some single cataclysmic sculpturing but the result of changes so infinitely slow that only after centuries is the effect noticeable. Erosion is simply one of the aspects of the constant process of change. It is fundamental to the formation of alluvial soils and sedimentary rocks. Man’s activities seldom slow down or halt the process but frequently speed it up. We usually refer to geological erosion or normal erosion, or natural erosion when we mean that which results only from the forces of nature, and to accelerated erosion when the process is influenced by man.

When trying to predict the probable severity of man-made erosion it helps to consider the rate of geological erosion. If the conditions of climate and topography are such that geological erosion is quicker than usual, then these sameronditions will also lead to particularly severe accelerated erosion. Extreme examples of both kinds of erosion are shown in plates 2.1 and 2.2.

Abstract

Satellite photographs depict exciting evidence on the migratory melodrama of river systems. A study has been conduced in parts of Tamil Nadu using IRS-IA Satellite pictures, archaeology and Tamil literature, which reveals that from Pleistocene to 2700 years B.P.(Before Present) the river Cauvery flowed in a northeasterly direction from the Stanley reservoir via Chinnar, Palakkodu, Mattur, Tiruppathur (Tiruppattur), Gudiyatham (Gudiyattam), Vellore and Walajapet to meet the sea at Madras. From 2700 to 2300 years B.P., it flowed via Uttangarai and Tirukkovilur to meet the bay of Bengal near Pondicherry, over which the present-day Ponnaiyar is a misfit stream . From 2300 to 1300 year B.P. it has flowed via Erode, Tirukkampuliyur, Alagarai , Tiruchy, Kiranur and Pudukkottai meeting the sea in the region where the present-day Agniar and Ambuliar meet the sea. Subsequently, between 1600 and 1300 years B.P., the Cauvery flowed along the present-day tracts of the Vennar and Vettar, after which it seems to have flowed as the Kodamurutti, Arasalar and PalanCauvery from 1300 to 1000 years B.P. From about 900 years B.P. it flowed via Tirupurampayam (Tirupurambiyam), Achalpuram till around 750 years B.P. and then it is stabilised as the Colleroon (Kollidam). Such periods and phases of river migration as well as their implications in the search for archaeological remains are discussed in this paper.

3.1 Physical characteristics

There is obviously an association between the amount of rainfall and the amount of soil erosion, i.e. more rain goes with more erosion, and less rain with less erosion, but in statistical terms the correlation between the two is poor. The same total quantity of rain can on different occasions result in widely differing amounts of erosion, and so other more specific measures are required to describe the ability of rainfall to cause erosion. In this chapter we shall establish the known facts about the main physical properties of rainfall, and then in chapter 4 show how these properties are related to the erosive power of rainfall.

3.1.1 Quantity of rainfall

Any measure of rainfall amount is a sample, and so associated with the inevitable problems of sampling, namely, ⁴is the sample representative of the whole?’ and ‘is the sample measured accurately?’ On both counts the data of rainfall which are usually available are of very doubtful reliability. Considering firstly the size of the sample measured, a very intensive network of rain gauges such as that established in an experimental catchment might be as dense as one gauge per 25 hectares, but this corresponds (with a 125 mm diameter gauge) to a sample of about one in 20 million, which would for any other scientific measurement be considered totally inadequate. The density of gauges in a country which considers itself very well provided might be one gauge per 25 square kilometres - a sample of one in 2 000 million, and in an undeveloped country the density of one gauge per 2 500 square kilometres is a sample of 1 in 200 000 000 000! Secondly, the siting of this remarkably small number of gauges is usually arranged primarily on convenience, eg where they can be easily read and contained, with little or no consideration of whether the site is representative of the whole. Thirdly, the accuracy of the measurement is usually unknown and studies have shown that variations in the shape and size of the instrument, and in the height at which it is mounted, and the way it is shielded from the wind, can seriously affect the recorded amount of rainfall. Clearly, even the apparently straightforward question of how much rain falls is not answered as precisely as might be imagined from a survey of rainfall tables and maps.

2.1 INTRODUCTION

Textural assessment has long been used to indicate quality in agricultural soil and although it contains an element of subjective judgement, a skilled surveyor can differentiate many grades of texture. Soil texture correlates with the distribution of particle size in the soil, though this is not the only component in texture. Although particle size distribution is an objective attribute of soils and can, in principle, be measured with accuracy, the determination is in practice quite difficult and certainly laborious, so that it is customary in soil mechanical analysis to divide the soil into several broad fractions: sand, silt and clay are the principal categories. The clay fraction, which comprises the smallest particles in the soil, is generally defined as the fraction smaller than a nominal diameter of 2 jam. The practical division is, however, based on the velocity of fall of soil particles through a fluid, calculating the diameter of the particles from the equation of Stokes

8.1 INTRODUCTION

The development of a soil profile involves the mobilization of major and minor elements and their subsequent deposition elsewhere in the profile or removal in the drainage water. For a full understanding of these processes we need to know what are the forms and reactivities of the soil constituents, the nature and mode of action of the mobilizing agents, the forms in which the mobilized material is transported—whether colloidal or in true solution, whether in ionic or complex form, whether alone or in association with other soil constituents—as well as its stability towards oxidation and reduction, microbial action, pH, and sorption and coprecipitation. The availability of micronutrients to plants is presumably governed by factors such as these. The current concern with problems of soil contamination has brought to the attention of soil chemists numerous toxic metals that were previously regarded as essentially the province of the geochemist.

It is probably true to say that no one of the factors listed above can be considered in isolation, but so far as any one factor is of dominant importance, this is nature of the mobilizing species; this determines the form in which the metal is transported, and its ultimate fate in the soil or in the drainage water.

This chapter is an attempt to summarize our present knowledge of the processes responsible for the mobilization and immobilization of metals in soils.