eChapters

There are over 100,000 different types of soil in the world, each with its own set of characteristics. If any soil is dug deep, one can see that it is made of layers, or horizons. The horizons together form a soil profile. Each profile tells a story about the life of a soil.

The development of soil profile is a constructive process where in disintegrated materials resulting from weathering of rocks and minerals get converted into a soil body. Soil Individual or Polypedon is a natural unit of soil that differs from its adjoining unit on the landscape in one or more properties. In modern soil taxonomy, polypedon is the unit of soil mapping. Apedon is the smallest volume recognizable in nature that can be called “a soil”.

Introduction

Intensive production of agricultural crops has contributed to decline in soil quality, leading to lower crop productivity and farm profitability. Major causes of this decline are soil compaction, surface crusting, low organic matter, increased pressure and damage from diseases, weeds, insects, and other pests, as well as a lower density and diversity of beneficial soil organisms. These constraints have increased the interest of farmers in assessing the health status of their soils and in implementing sustainable soil management practices. Soil health is critically important to sustainable agricultural productivity and environmental well being. Healthy soils provide a range of environmental services including water infiltration, habitat provision and profitable and sustainable agriculture.

 

Introduction
Soil quality is a critical concept in environmental science, agriculture, and land management. It refers to the ability of soil to perform its essential functions, which include supporting plant growth, regulating water flow, cycling nutrients, filtering pollutants, and providing habitat for microorganisms. Healthy, high-quality soil is fundamental for the productivity of ecosystems and the sustainability of agricultural practices. The quality of soil is influenced by a combination of physical, chemical, and biological factors. These include soil texture, structure, organic matter content, pH, nutrient availability, and the presence of beneficial organisms like bacteria and fungi. When these factors are balanced, soil can support healthy crops and ecosystems. However, soil degradation—caused by practices such as overuse of chemical fertilizers, deforestation, erosion, and pollution—can severely reduce its quality, leading to lower agricultural yields, water contamination, and loss of biodiversity. Assessing soil quality involves monitoring several key indicators, such as organic matter levels, soil texture, compaction, water infiltration rates, and the presence of key nutrients. Organic matter is especially important, as it helps to bind soil particles, retain moisture, and provide a food source for beneficial microorganisms. The chemical aspect of soil quality is equally vital, encompassing the availability of nutrients such as nitrogen, phosphorus, and potassium, as well as the presence of any harmful contaminants like heavy metals. The biological dimension of soil quality relates to the diversity and activity of organisms within the soil. A rich microbial community enhances nutrient cycling, helps decompose organic matter, and promotes plant health. Earthworms, for instance, play a critical role in aerating the soil and facilitating water infiltration. Soil quality is not a static property; it can change over time depending on land management practices. Sustainable practices such as crop rotation, conservation tillage, the use of organic amendments, and maintaining ground cover can improve and maintain soil quality. Conversely, unsustainable practices like excessive tillage, monoculture, and the overuse of agrochemicals can degrade soil, making it less productive and more prone to erosion. In

Soil quality is the capacity of the soil to function, within its natural or managed ecosystems, to sustain plant and animal productivity, maintain or enhance water and air quality, support human and animal health and habitation. This is not limited to agriculture, though most work and evaluation has occurred on agricultural lands.

Soil health refers to the condition of the soil and its potential to sustain biological functions, maintain environmental quality and promote plant and animal health. Healthy soils are the key to food security and sustainable future. They support sustainable food production, mitigate and adapt to climate changes, filter water, enhance resilience to floods and droughts and so much more.

Soil health

Soil health is defined as the continued capacity of soil to function as a vital living system, by recognizing that it contains biological elements that are keys to ecosystem function within land use-boundaries. These functions are able to sustain biological activity of soil, maintain the quality of air and water as well as promote plant, animal and human health.

The characteristics of a healthy soil depends on the physical, chemical and biological properties of soils which directly or indirectly influence crop production.

Soil quality and soil health are terms that are discussed in agricultural community. Both these terms encompass a complex, dynamic concept, different to define and hard to measure. The term soil quality and soil health are often used interchangeably in the scientific literature, with scientists in general preferring soil quality and producers preferring soil health. Soil health may be considered as the state of soil at a particular time equivalent to the dynamic properties in short term. In contrast, soil quality may be considered for a particular purpose over a longer time scale, equivalent to static soil quality. In a broader way soil quality may refer to both permanent and static soil properties. (Fig. 11.1).

A static soil property relates to natural characteristic of soil (texture) which are derived from pedogenic processes. These properties cannot be easily amended. The dynamic properties are readily related to management practices. The dynamic component is of most important for the growers because it allows the soil to come to its full potential.

Soil Reaction

Soil reaction is an indication of the acidity or basicity of the soil and is measured in pH units. The pH scale ranges from 0 to 14, with 7.0 as neutral point. From pH 7 to 0, soil is increasingly acidic. From pH 7 to 14, soil is increasingly alkaline.

Pure H₂O ionizes to a very small degree, though to a measurable extent, so that it has the following equilibrium: both H+ and OH^- are in concentrations of 10^-7 moles L^-1.

10.1. Determination of Soil pH

The soil pH value is the measure of hydrogen or hydroxyl ion activity in the soil solution and it indicates whether the soil is acidic, neutral or alkaline in reaction. The pH is the most important property of soil as it controls the availability of plant nutrients, microbial activity and physical condition of soil. Since crop growth is affected both under very low (strongly acidic) and very high (strongly alkaline) soil pH, reclamation of these soils are necessary. Soil pH in fact indicates the extent of active acidity (activity of hydrogen ion in soil solution) of soil. Depending upon the purpose of measurement and soil condition, soil pH is measured in several soil-water or soil-salt solution ratios. The saturated paste is used for identifying specific soil problems like degree of acidity or alkalinity. For making fertilizer recommendation, 1: 2 soil-water suspension is generally adopted. To mask the variability in salt content of the soil, the pH is measured in soil-CaCl₂ suspension (1:2 soil-0.1 M CaCl₂ solution). The soil pH value is independent of dilution over a wide range of soil-salt solution ratio, thus more reproducible than those obtained with soil-water suspension.

17.1 Determination of Soil pH

The soil pH value is the measure of hydrogen or hydroxyl ion activity in the soil solution and it indicates whether the soil is acidic, neutral or alkaline in reaction. The pH is the most important property of soil as it controls the availability of plant nutrients, microbial activity and physical condition of soil. Since crop growth is affected both under very low (strongly acidic) and very high (strongly alkaline) soil pH, reclamation of these soils are necessary. Soil pH in fact indicates the extent of active acidity (activity of hydrogen ion in soil solution) of soil. Depending upon the purpose of measurement and soil condition, soil pH is measured in several soil-water or soil-salt solution ratios. The saturated paste is used for identifying specific soil problems like degree of acidity or alkalinity. For making fertilizer recommendation, 1: 2 soil-water suspension is generally adopted. To mask the variability in salt content of the soil, the pH is measured in soil-CaCl₂ suspension (1:2 soil-0.1 M CaCl₂ solution). The soil pH value is independent of dilution over a wide range of soil-salt solution ratio, thus more reproducible than those obtained with soil-water suspension.

4.1. What is pH?

pH is used to classify substance as acidic, neutral and alkaline, based on the prevalence of free H⁺ ions. Water molecules on autoionization dissociate to produce H⁺ and OH^- in equal number, although degree of dissociation is very small because of its stability (about one molecule in 10 million is ionized at any one time). H⁺ ions later attached to un-ionized water molecule to give rise hydronium ions, (H₃O)⁺

Introduction

Over the past few decades, soil resources have witnessed many changes driven by demographic pressure and climate change. It is necessary to have up to date soil information to monitor the state of soils health with time. Soil resource inventory provides information about the potentialities and limitation of soils for its proper utilization. Soil survey offers an accurate and scientific inventory of different soils, their properties and extent. An in-depth knowledge of the type of soils and their spatial distribution is a prerequisite for developing rational land use planning. Remote sensing is the science of obtaining information about the earth’s surface without actually being in contact with it. On the other hand, proximal sensing refers to remotely sensed measurements that are taken at the field or laboratory level. Both these processes involve an interaction between incident radiation and the targets of interest. Fundamentally, remote sensing data products are a representation of the functional response of objects to energy sources. These are typically spectra, which are acquired as a discrete series of reflectance measurements taken at different wavelength intervals, or bands. In the shorter wavelengths of the electromagnetic spectrum (visible part), features can be detected by virtue of reflected solar energy, while in the longer wavelengths (microwave, thermal parts), sensing of emitted energy works. Conventional soil sampling, and subsequent laboratory analysis are generally time consuming and costly. In this context, remote sensing plays a crucial role for studying soil resources. The term remote sensing is generally used for airborne and space borne acquisitions, whereas proximal sensing refers to ground-based laboratory and field measurements. Advances in the quantitative disciplines like remote sensing and proximal sensing have laid the foundations for a spatial exploration of soil-system dynamics within a landscape context (Pennock and Veldkamp 2006).

Introduction

The life support systems of a country and socioeconomic development of its people largely depend on soils. The soils are the most valuable natural resources for the society. It caters the basic needs of mankind by producing food, fibre and timber. It is therefore essential to know the distribution and extent of different soils and their qualities, potentialities and constraints for sustainable utilization of this valuable natural resource (Shyampura and Sehgal 1995). Information on distribution, potential and constraints of major forest soils are essential to design most appropriate soil management systems in order to increase productivity of forests as forests also offer excellent potential for poverty reduction and rural economic growth in India. However, unlike agriculture lands forest soils usually draw less attention and are ignored in spite of the fact that they nourish the lungs of the Earth. Soil quality is the most important factor in forest management decisions. Soils will determine productivity of a particular forest and management strategy. Knowing about forest soils can serve as a basis for forest management decisions, including land acquisition, species selection for planting, site preparation requirements, watershed development, fertilization prescriptions, stand density/ composition, and harvest timing, as well as decisions affecting land ownership and use.

Soil respiration is a good estimator of overall biological activity and thus is often used for describing soil quality. Soil respiration is estimated as the flux of CO₂ emitted from the soil surface. It represents the sum of CO₂ produced by root respiration and by heterotrophic decomposition. This procedure is a laboratory method where soil is incubated for a given period of days and the released CO is trapped by sodiumhydroxide (NaoH). This is also known as alkali trap method.

Introduction to Soil Restoration and Management

One of the most crucial elements for human survival is the availability of arable land. Desertification caused by land degradation has emerged as a serious global environmental threat to human well-being and sustainable development in recent years because of both climatic shifts and an increase in human activities that have direct impacts on soil. It has been widely alarmed by the United Nations Convention to combat desertification and has shown considerable interest in this issue (UNCCD, 2015). Soil degradation is used to describe the transformation of arable land into unproductive land because of natural processes, typically accelerated by human activity (Lal, 1993).

Introduction

 Salinity is a form of salt that occurs naturally within soils or water. When soil

becoming salty form that is called salinization, it can be caused by mineral

weathering called as natural process but it can be caused by irrigation called

as artificial process. Saline or salty soil have a high salt content like sodium

chloride (NaCl also called table salt). Salinity is like- abiotic stress for plants

and reduced the plant growth but not for all because some of them crops are

survive in better way for growth and development such as barley, sugerbeet,

cotton and mustard etc. Basically, stress are two types-biotic and abiotic

stress. Abiotic stress are also called nonliving stress like- drought, salinity,

submergence, heat, cold and temperature that are affect to plant life cycle so

that are called as abiotic stress. Natural water and all types of soil both contain

soluble salts. Amount of salt affected to weather of soil, when excessive salt

present in soil and it adversely affects to crop growth and developments. Salt

affected soils exist under arid and semi-arid climates. Major constitutions of

soluble salt in soil are the cations and anions. Cations are containing sodium,

calcium, magnesium and anions are contains chloride, sulphate, carbonate and

bicarbonate. Saline soil have <8.5 pH, >4EC (dS/m) and <15 ESP. where EC

is eclectical conductivity that is measure of soil salinity and ESP stand for

Exchangeable sodium percentage.

Introduction

The objective of soil sampling is to obtain reliable information about a particular soil. The value of laboratory data in soil studies largely depends on effective sampling. Soil sampling is one of the most important aspects in the determination of the properties of the soil. Care in preparation and analysis can overcome the damages of careless or inappropriate sampling in the field (Bates, 1993). Errors arising from sampling are mainly related to spatial variability of the soil. While keeping in mind financial constraints, sampling procedures should be adopted properly to minimize the influence of spatial variability and to maximize the accuracy of mean plot values for the measured soil variables. The obtained soil data should be representative for the whole observation plot, taking into consideration the spatial variability of the soil within the plot.

Importance of soil sampling

Soil sampling and testing are done to provide an estimate of the capacity of the soil to supply adequate amount of nutrients to meet the needs of growing crops and information to its nature and problem. Traditionally, the goal of soil sampling is to develop a representative estimate of a field. A few grams of soil are actually used for the laboratory analysis. That small amount must represent the entire area for which the recommendation is to be made. The samples should be collected in such a way that it would represent the area for which recommendation is to be made.

1.The fine earth covering land surface acts as a reservoir of nutrients and water Soil.
2.The word ‘Soil’ is derived from Latin.
3. Study of origin, classification, morphology of soil is known as Pedology.
4. The study of soils in relation to crop growth Edaphology.
5. The father of Soil Science Dokuchalev.

Soil

Soil is a natural body of mineral and organic constituents differentiated into horizons usually unconsolidated, of variable depth which differs among themselves as well as from the underlying parent material in morphology, physical makeup, chemical properties and composition and biological characteristics (Whitney, 1982; Hilgard, 1892; Dokuchaiev, 1900 and Joffe, 1936).

According to Soil Science Society of America (SSSA, 1970) soil is the unconsolidated mineral matter on the surface of the earth that has been subjected to and influenced by genetic and environmental factors of parent material, climate (including moisture and temperature effects), macro and microorganisms and topography, all affecting over a period of time and producing a product, that is “SOIL” that differs from the material from which it is derived in physical, chemical, biological and morphological properties and characteristics. The unconsolidated mineral material on the immediate surface of the earth, that serves as a natural medium for the growth of plants.

Approaches of Soil Study

Pedological Approach : The origin of the soil, its classification and description are examined in Pedology. (From Greek word pedon means soil or earth). It is the study of soil as a natural body and does not focus on the soil’s immediate practical use.

Edaphological Approach: Edaphology (from Greek word edaphos means soil or ground) is the study of soil from the stand point of higher plants. Edaphologists consider the various properties of soil in relation to plant production.

Soil Science : The science dealing with soil as a natural resource on the surface of the earth, including pedology (soil genesis, classification and mapping) and the physical, chemical and biological and fertility properties of soil and these properties in relation to their management for crop production.

Vegetables have got an important place in agriculture development, human diet and economy of the country. All the developed and developing countries realized the importance of vegetables an essential diet due to medicinal and nutritional value for human health. There is a steady upward trend in vegetable production. China is ranking first in the world and currently produces 237 million tonne of vegetables. India has made a quantum jump in vegetable production securing the second position in the world. The total production of vegetable is more than 91 million tonne in the country. Diseases and pests are the most important factors for low vegetable production. Various fungi, bacteria, viruses, phytoplasmas, nematodes and weeds are responsible for causing diseases in vegetables resulting heavy reduction in yield and quality.

Soil structure is highly important for maintaining favourable conditions for water movement, aeration, root development and crop production. In irrigated agriculture, inappropriate management practices can cause structural degradation through compression, puddling, compaction and crust formation. This chapter examines the major processes responsible for deterioration of soil structure and their effects on soil physical properties and crop performance. Soil compaction is discussed in relation to agricultural machinery, pressure distribution, formation of compacted layers and restrictions to root growth and water movement. The chapter also explains soil crusting, its mechanisms, effects on seedling emergence and methods for evaluating crust strength. Slow-permeable soils, including Regur soils, highly permeable soils and soils with shallow water tables are considered from a management perspective. Appropriate management practices are emphasized to restore permeability, improve soil structure and maintain favourable soil-water relationships. The chapter provides an integrated understanding of structural degradation and its management for sustainable irrigated agricultur