eChapters

Soil fertility management refers to the practices and techniques used to maintain and improve the fertility of soil. Soil fertility is crucial for agriculture because it determines the soil's ability to provide essential nutrients to plants, support their growth, and sustain productivity over time. Effective soil fertility management aims to optimize soil health and productivity while minimizing environmental impacts.

3.1 Key Aspects of Soil Fertility Management Include

1. Nutrient Management: This involves supplying essential nutrients (nitrogen, phosphorus, potassium, etc.) to the soil through organic or synthetic fertilizers to meet the needs of crops.

2. Soil Amendments: Adding organic matter (such as compost or manure) or other amendments (like lime or gypsum) to improve soil structure, water retention, and nutrient availability.

3. Crop Rotation and Diversification: Rotating crops and diversifying plant species can help manage nutrient depletion and improve soil health by reducing pest and disease pressures.

4. Conservation Tillage: Minimizing soil disturbance through reduced tillage or no-till practices helps preserve soil structure, reduce erosion, and maintain organic matter content.

5. Cover Cropping: Planting cover crops during fallow periods or between main crops helps prevent soil erosion, improve nutrient cycling, and enhance soil fertility.

14.1. Soil fertility

Ability of the soil to supply essential plant nutrients during growth period of the plants

Crop producing capacity of the soil

Abstract

Understanding the impacts of organic or inorganic nutrient management on soil biology and biochemistry may help to develop more sustainable fertilization strategies. The results from comprehensive study made on a field experiment comparing the long-term (more than 100 years) effects of organic manures and inorganic chemical fertilizers on soil biological and biochemical properties are reviewed. The soils adopted with three nutrient managements viz., no fertilization (control), inorganic chemical fertilizers (IC) and organic amendments (OM) obtained from long-term fertilizer experiment were assessed for physical, chemical, microbiological and biochemical properties in three successive years. The response of most of the assessed soil variables to long-term organic nutrient management was significantly higher than those from inorganic fertilization and control (OM > IC = control).

Introduction

Ideal plant health and productivity of a cropping system depends on an adequate amount of plant nutrients. Fertility of the soil refers to its capacity to support the production of crops. A productive fertile soil can support optimal plant growth, seed germination to plant maturity by providing adequate soil volume for plant root development, essential plant nutrients to meet the nutritional requirements of the plants, and encourage for the consequent plant structure. These attributes of the soil can be distinguished as inherent or dynamic soil quality indicators.Optimum plant health and productivity of a cropping system depends on an adequate supply of plant nutrients. The quantity of nutrients required by plants varies depending on many interacting factors including:

• Agronomic effects

• Soil properties

• Climatic condition

• Management practices

Soil fertility is the resultant of several factors, not the least important of which is the soil itself. Theoretically, the soil only plays the part of a support and could be very easily dispensed with and replaced by sand and even that can be replaced by a wire framework to support the plant mechanically and it will grow quite well if the right amount of nutrient materials have been added to water. ‘Where does the soil come in?” you will ask. The importance of the soil is two-fold: (1) It provides vast reserves of plant food which is slowly made available. (2) It provides limiting factors which restrict plant growth; these limiting factors must be neutralized. We have already discussed these reserve food materials and limiting factors in Chapter II.

It has been shown that if we treat a soil with dilute acid exhaustively we can remove everything from it except the mineral framework. If we try to grow anything in this mineral framework nothing will grow. Yet it is not like sand, for whereas in sand by adding appropriate amounts of nutrient materials in water solution you could grow a crop, nothing will grow if you added the same solution of nutrient materials to the soil. This mineral framework, therefore, is not inert like sand, but it is active and can react with the nutrient salts in such a way that either they are rendered unavailable or something else which is toxic is produced by the interaction between the soil and the nutrient salts. This mineral framework is not acted upon by dilute acids, but it reacts with alkalies in such a way that the alkalies are neutralized. In this respect, therefore, the mineral frame work behaves like an acid. With alkalies it forms salts and different alkalies are required in equivalent amounts for the formation of these salts. Thus we can have salts of a number of bases and if we use sodium hydroxide for neutralizing we shall have sodium soil, similarly we can have a calcium, magnesium or potassium soil. Now in nature, all the various bases principally, calcium, magnesium, sodium, and potassium, are associated with it in different proportions. The nature and amount of these bases determines the physico-chemical properties of the soil affecting crop yield and leading to soil infertility. We have already indicated the method of bringing the soiil to the normal state when it suffers from any of the defects associated with the soil framework.

Although the application of fertilizer to even fairly fertile soils can give a great increase in crop yield, soil fertility is not simply a matter of nutrient content. It is dependent on a number of complex of issues:

Soil depth

The volume of soil from which the crop draws its nutrition varies according to the rooting depth of the crop. However hard or rocky layers can restrict natural root development; this is particularly the case with micro irrigation systems.

Soil structure

Particle size and soil aggregate size and distribution, effect the size and distribution of pores and therefore the availability of air and water to the roots.

Soil fertility is defined as the quality that enables the soil to provide proper nutrient compounds in proper amounts and in proper balance for the growth of specified plants. Soil fertility is also defined as the ability of soil to supply adequately the nutrients normally taken from the soil by plants.

1. White alkali soils also know as

a. Acid soil                  b. Saline soil

c. Saline sodic soil    d. Sodic soil

ACID-FORMING FERTILIZER: A term applied to commercial fertilizers which leave an acid residue in the soil. The amount of calcium carbonate required to neutralize the acid residue is referred to its equivalent acidity.

Introduction

Pedology:- Pedology word drive from Greek word pedon, means soil or earth and logos means to study. Pedology is concerned with origin of the soil, its classification, distribution and character (Physical, Chemical and Biological).

Definition:- Soils are natural bodies made from both mineral and organic materials and capable of supporting plants out-of-doors.

Composition of soil on volume basis (Soil components)

i. Mineral matter :- 45%

ii. Organic matter :- 5%

iii. Soil water :- 25%

iv. Soil air :- 25%

Soil formation is a long term process. It takes several million years to form a thin layer of soil. The soil is made up of broken down rock material of varying degree of fineness and changed in varying degrees from the parent rocks by the action of different agencies such that the growth of vegetation is made possible. As soil is a complex mixture of various components, its formation is also more complex. The Formation of a particular type of soil depends upon the physico-chemical properties of the parent rock, intensity and duration of weathering, climatic and other parameters.

Soil formation takes place in two consecutive stages:

1. The weathering of rocks into regolith

2. The formation of true soil from regolith

The evolution of true soil from regolith takes place by the combined action of soil forming factors and processes. The first step is accomplished by weathering (disintegration and decomposition) and the second is associated with the action of soil forming factors which are known as pedogenic factors.

The pedogenic processes are dynamic and extremely complex involving several chemical and biological reactions, usually operating simultaneously in a given area. One process may counteract another, or two different processes may work in tandem to achieve the same result. Different processes or combination of processes operate under varying natural environments. The combined interaction of various soil forming factors under different environmental conditions set a furtherance to certain recognized soil forming processes. Pedogenic processes include:

Rock

A rock may be defined as “an aggregate of one or more minerals”. An aggregate of single mineral calcite gives rise to crystalline limestone. Granite is a combination of several minerals. Most rocks are hard and compact as granite and basalt, but some are loose and feebly aggregated as sandstone. Rocks possess certain characteristics such as structure, colour, specific gravity, cleavage and mineralogical make-up by which we can identify the rocks and also distinguish one from the other.

2.1. Minerals

Primarily, minerals are usually inorganic substances possessing a definite chemical composition and a definite molecular arrangement which is usually expressed in geometric form. The mineral matter is made up of various elements, combined to form compounds. Usually, minerals consist of more than one constituent elements. Quartz contains two elements, silicon and oxygen. Other minerals may contain many elements, such as amphibole consists of several elements that include sodium, calcium, magnesium, iron, aluminium, silicon, and oxygen. Some elements exist as such without forming compounds. They contain exceptionally one element. Graphite (C), diamond (C), and Sulphur (S). Minerals are naturally occurring crystalline solid where the atoms are arranged in a regular three-dimensional array. A crystal is a solid, formed by a repeating three-dimensional pattern of atoms, ions, or molecules & possessing fixed distances between the different parts. Minerals that do not grow in these regular or crystalline patterns are called amorphous solids. When we talk about ‘naturally occurring’, we exclude the laboratory-synthesized crystalline solids. Glass and amber are also naturally occurring solid, but they are not crystalline and thus, they are not considered as minerals, rather they are referred as amorphous solids.

Soil genesis, or pedogenesis, is the combined effect of physical, chemical, biological and anthropogenic processes working on soil parent material (rocks & minerals). Soil is said to be formed when organic matter has accumulated and colloids are washed downward, leaving deposits of clay, humus, iron oxide, carbonate, and gypsum, producing a distinct layers. These constituents are moved from one level to another by water and animal activity.

Introduction

Soil health and fertility are pivotal to the success and sustainability of agricultural systems. The condition of soil directly influences plant growth, crop yield, and overall farm productivity. A focus on soil health encompasses not just the physical and chemical properties of soil but also its biological vitality, which includes the diverse community of microorganisms, fungi, and fauna that interact within the soil ecosystem. Biodynamic farming, founded by Rudolf Steiner in the early 20th century, offers a distinctive approach to soil health and fertility, integrating organic principles with a holistic view of agriculture that encompasses cosmic and spiritual dimensions. Biodynamic farming is an agricultural philosophy that extends beyond conventional organic practices. It views the farm as a living organism, where soil, plants, animals, and cosmic forces are interconnected and interdependent. This perspective emphasizes that the health of the soil is intrinsically linked to the broader ecological and cosmic environment. According to biodynamic principles, soil fertility is not merely a function of nutrient inputs but a reflection of the overall balance and vitality of the farm ecosystem.

Soil health and management are fundamental to sustainable agriculture, impacting crop productivity, environmental quality, and agricultural resilience. This article explores the various aspects of soil health, including its physical, chemical, and biological properties, and discusses management practices that enhance soil fertility and sustainability. The importance of organic matter, soil biodiversity, and nutrient cycling is highlighted, along with the challenges posed by soil degradation, erosion, and climate change. Through a detailed examination of traditional and innovative soil management strategies, such as crop rotation, cover cropping, conservation tillage, and soil amendments, the article provides comprehensive insights into maintaining and improving soil health. By understanding and implementing these practices, farmers and stakeholders can ensure long-term agricultural productivity and environmental stewardship.

Summary

Soil fertility is the ability of the soil to support plant growth. The productive capacity of the soil depends on complex interactions between biological, chemical and physical properties of the soil. In essence, soil fertility does not refer only to plant nutrients but also soil organic matter, structure and maintenance of thriving soil organisms. Good farm practices aim at managing the various factors that make up each of these three properties to optimize yields of crops in an environmentally friendly manner. The debate on soil fertility is often erroneously limited to issues relating to plant nutrients.

Introduction

Agriculture is the mainstay of the Indian population and contributes about 30 per cent to the gross domestic product of India. The government has laid great emphasis onimproving productivity, quality of produce and welfare of farmers through awareness campaign and enhanced agri-knowledge for the farming community to double the farmer’s income by 2022 and make the farmers realise their significant contribution to the nation building. Doubling the farmer’s income can only be possible, with proper diversification of crops, developing the existing irrigation system in proper utilization of available water on plant requirement basis, conservation of soil fertility through adding organic manures to the field, best utilization of human excreta from the storage tanks of individual toilets after proper decomposition through bacterial degradation, fulfilling the nutrient requirement of crops on the basis of soil test values, proper financial support from the Government to the farmers in managing stress due to natural calamities etc. The governmentbelieves that farmers’ welfare will improve if there is increase in net income from the farms. With this end in view, the approach is to reduce cost of cultivation, enable higher yield per unit area and realize remunerative prices of farm produce. To achieve this goal, action on three pillars needs to be taken.

Introduction

The sustainable agriculture begins with ideal soil health with minerals and organic matters. The sustainable farming practices enhance and protect soil health, water quality and water quantity, biodiversity, manage insect pests, disease and weeds. The Indian council of Agricultural Research (ICAR) set up an All India Soil Survey Committee in 1953 which divided the Indian soils into eight major groups. (i) Alluvial soils (ii) Black (or Regur soil) (iii) Red and Yellow soils (iv) Laterite soils (v) Arid and desert soils (vi) Saline and alkaline soils (vii) Peaty and marshy soils and (viii) Forest and mountain soils.

Natural farming is about keeping the long-term health of the soil in mind. Soil health is an active state or condition in which soil functions as a vital living ecosystem, enhancing plant, animal, and human health. Healthy soil has a good balance of minerals, organic matter, and moisture. With life processes occurring constantly, it has many complementary internal resources that allow it to be less reliant on external inputs. Natural farming helps to build this soil health, so that many years down the line, soil is in good health without being weakened by prolonged input redundancy. Regular tillage, which turns the soil over and breaks up the mycorrhizal fungi that connect the plants, is unnecessary in natural farming. We do not till. When we encourage life in the soil, it produces better soil heading towards fertility. Feeding the soil is the goal of natural farming. Ensuring robust health in the soil will, in turn, produce healthy plants, and by extension, a nutritious offering of produce. Soil health is a critical factor for natural farming. In every action we take to improve the health of the soil, we are addressing a component of healthy farming and being kind to the land. Soil health is the foundation of natural farming. The following sections detail the importance of organic matter, the role of microorganisms, water conservation, and preparation of natural inputs. By understanding these facts, we can truly understand soil health. Commercial inputs like pesticides, herbicides, and chemical fertilizers cost money. Natural farming aims to avoid the profit-zapping reliance on these costly inputs. Healthy soil produces hardy crops; strong plants do not get sick. Kept at their peak of health, strong, lifefilled soils have a congress of life in their root zones, providing steady food and balance to crops. There are no external inputs constantly taxing the health of these crops. By tending to the farm as a living system, soils and plants are helped to be as healthy as possible, of their own accord.

Soil health management plays a pivotal role in sustainable agriculture and directly influencing plant growth, crop productivity and environmental quality. Healthy soils are essential for nutrient cycling, water retention and supporting a diverse array of microorganisms that contribute to plant resilience. However, modern agricultural practices, including the excessive use of chemical fertilizers, monoculture cropping and improper irrigation, have degraded soil health, leading to nutrient imbalances, reduced organic matter and soil erosion. This has sparked a growing awareness of the need for effective soil health management strategies that not only maintain but enhance soil quality. Innovative tools for soil health management are reshaping plant protection strategies by promoting holistic approaches that focus on maintaining and improving the biological, chemical and physical properties of the soil. These tools range from organic amendments and biofertilizers to advanced diagnostic technologies such as soil microbial profiling, remote sensing, and precision agriculture techniques. Together, they offer a comprehensive framework for addressing soil-related constraints and enhancing plant resistance to pests and diseases.

Soil health determines agricultural productivity, resource efficiency and long-term sustainability. Conventional laboratory and field-assessment methods provide valuable information but can be time-consuming and difficult to scale. This chapter presents a computational approach combining soil sensors, remote sensing and historical agronomic records. Indicators such as moisture, nutrients, pH and organic matter are processed using data-cleaning and feature-extraction techniques. Random Forest, Support Vector Machine and neural-network models estimate soil-quality parameters and identify degradation patterns. Explainable artificial intelligence improves the transparency and usefulness of predictions. Integration with edge computing enables real-time soil evaluation and supports targeted fertilization, efficient irrigation and sustainable soil-management decisions.

Introduction Soil ecosystems are the foundation of human life support systems. Soil erosion, loss of soil organic matter and nutrient depletion are among the leading contributors to impaired soil health, reduced crop yields and poverty. Realizing the significant role that soils play in food and environmental security and in abating climate change, the United Nations declared 2015 as the Year of Soils. The International Union of Soil Sciences (IUSS), in 2002, proposed to observe the 5th December as “World Soil Day” [WSD] to create awareness among all stakeholders on the importance of soil as a critical component of the natural system and as a vital contributor to human commonwealth through its contribution to food, water and energy security and as a mitigation of biodiversity loss and climate change. These occasions remind all stakeholders associated with agriculture all over the world to put in all efforts to promote scientific management of soil resources for soil protection, conservation and sustainable productivity.

Soil is a dynamic, vital living natural resource. Soil health is the condition of the soil and its potential to sustain biological functions, maintain environmental quality, and promote plant and animal health. It is qualitative trait of soil. Healthy soil is the foundation for profitable, productive, and environment friendly agricultural systems.

SOIL WATER

Soil water and oxygen share the pore space in soil and generally the oxygen content is determined by the water content, which is added by irrigation or rains and then keeps on changing due to evapotranspiration. Water is the vehicle by which most nutrients move from the soil to root surface. But for the lowland rice, nutrients are most available to plants at ?eld capacity moisture (about 0.3 atmosphere soil water tension) and the availability decreases as the moisture content decreases to wilting point (about 15 atmosphere tension). That is why rainwater or irrigation increases nutrient availability, while extremely dry condition decreases it. There is thus a signi?cant interaction between water and nutrient availability in soil (Singh et al., 2014). In a study in India (Singh et al., 1980) the yield of wheat was signi?cantly affected by irrigation water and nitrogen treatments; maximum yield was obtained with irrigation at 50% available soil water in 60 cm soil depth and 120 kg ha ^–1 nitrogen addition. A study on wheat at Delhi (Kumar et al., 2015) very well shows the effect of irrigation water on yield and uptake of nutrients (NPK) (Table 5.1).

Genesis of Soil

World’s geography is very widely diversified in relief showing various features like mountains and hills covered with snow and trees, glaciers, higher altitudes to plain to lowest valleys, forests to barren lands, fertile fields to waste lands, plateaus, deltas, swamps, lowlands, deserts etc. Temperature varies from arctic cold to scorching hot of equator, Rainfall from aridity to per humidity. All these situations and conditions under different sets of combinations generate and develop numerous types of soil from a single type of parent material. Therefore, many types of soils may develop at a smaller area.

Physical, chemical and biological weathering processes disintegrate and decompose various rocks and minerals to make asymmetrical soil parent material. This parent material is converted in to the soil profile by soil forming processes in the presence of soil forming factors. Soil genesis is defined as mode of formation of the soil from the parent material due to the action of soil forming factors and processes. Parent material, Factors of soil formation and Processes of soil formation, are three main part of soil genesis. These are described here:

1. Parent Material,

2. Classification of parent material,

3. Factors of soil formation,

4. Processes of soil formation,

5. Types of soil forming processes.

Soil is a biologically active porous medium that has developed in the uppermost layer of the earth’s crust which serves as a natural medium for the growth of plants. It is one of the principal substrata of life on earth, serving as a reservoir of water and nutrients, and as a participant in the cycling of carbon and other elements through the global ecosystem.

Introduction

Soil management refers to a set of practices and strategies employed by farmers and land managers to maintain, improve, and sustain the health, fertility, and productivity of soil in agricultural systems. It encompasses a range of activities aimed at optimizing soil conditions for crop growth while minimizing environmental degradation. Soil management practices include soil testing to assess nutrient levels and pH, the application of fertilizers and soil amendments to correct deficiencies, erosion control measures to prevent soil loss, and conservation practices to enhance soil structure and health. Additionally, soil management involves the integration of organic matter, such as compost and crop residues, to enhance soil fertility and microbial activity. The overarching goal of soil management is to ensure the long-term sustainability of agricultural systems by preserving soil health, supporting crop productivity, and minimizing environmental impacts.

Method of Soil Management 1

. Soil Testing and Analysis: Soil testing and analysis play a pivotal role in soil management for agricultural crops, providing farmers with critical information about soil health, fertility, and nutrient status. By understanding the composition of their soil, farmers can make informed decisions about fertilization, soil amendments, and crop selection to optimize yields and minimize environmental impacts. For example, soil testing can reveal deficiencies or excesses of essential nutrients such as nitrogen, phosphorus, and potassium, enabling farmers to tailor their fertilizer applications accordingly. If a soil test indicates low levels of phosphorus, for instance, farmers can apply phosphorus-rich fertilizers to replenish the nutrient and support healthy crop growth. Conversely, if soil pH is too high or too low, amendments such as lime or sulphur can be applied to adjust pH levels and create optimal growing conditions for crops.

Introduction Soil management in horticultural crops refers to the deliberate and systematic approach of caring for soil to optimize its health, fertility, structure, and overall quality to support the growth and development of horticultural plants. It involves a range of practices aimed at preserving and enhancing soil resources, including soil testing, nutrient management, irrigation scheduling, erosion control, and organic matter addition. The goal of soil management in horticultural crops is to create and maintain an environment in which plants can thrive, maximizing crop yields, quality, and sustainability while minimizing environmental impacts such as soil erosion, nutrient runoff, and soil degradation. By implementing effective soil management strategies, horticultural growers can ensure the long-term productivity and viability of their farming operations, while also promoting soil health and resilience in agricultural ecosystems.

Current Soil Conditions

A study conducted in 2016 over 75 fields revealed that soil compaction was present in 70% of annual crops and 60% of perennial crops. Most of the soils used for both annual and perennial cropping were in a moderate condition. However, the soil condition for established crops was improved by performing cultivations before planting. Nevertheless, some soil formations exhibited instability, especially on soils with a lighter texture and a low content of organic matter. The majority of soil cultivations successfully alleviated compaction, however some cultivations had little impact or even exacerbated compaction due to spreading, puddling, or compression when performed in damp or wet field conditions. Tillage pans may greatly diminish productivity and overall efficiency of production by impeding drainage and root development. Approximately 60% of fields cultivating annual crops and 50% of areas cultivating perennial crops had a well-established tillage pan. Approximately 10% of fields underwent deep cultivation without any evidence of soil compaction, indicating a lack of consideration for soil conditions and the need for subsoiling. The abundance of earthworms in the topsoil may serve as a valuable measure of soil health, and is primarily influenced by the intensity of farming practices and the presence, nutritional value, and consistency of earthworm food sources. Earthworm populations exhibited a general scarcity in both annual and perennial crops, while they were relatively more plentiful in areas with ample crop waste and apple orchards. The regular tilling of the soil is believed to be a significant contributing factor to the very low population of earthworms found in places where crops are grown every year. Fields that had a mustard cover crop reported the greatest populations of earthworms.

Carbon is found in all living organisms and is the major building block for life on earth. It exists in many forms, predominantly as plant biomass, soil organic matter, and as the gas CO₂ in the atmosphere and dissolved in sea water. Carbon cycles globally among five distinct pools among which the largest oceanic poolis estimated at 38000 Pg (Pg= petagram =1x10¹⁵g=billion tonnes) and is increasingat the rate of 2.3 Pg C yr^-1 (Fig. 1). The geological C pool, comprising fossil fuels, is estimated at 4130 Pg, pedologic, estimated at 2500 Pg to 1m depth, atmospheric pool comprising 760 Pg of C with nearly all of it as CO₂, and the smallest among theglobal C pools is the biotic pool estimated at 560 Pg. The pedologic and biotic C pools together are called the terrestrial C pool estimated at approximately 2860 Pg.

1. Introduction
As climate change advances, risk of managing soil and atmosphere with regard to emission and pollution is going out of hand. Many researches and reports say that currently the global warming is 1.1°C more than the pre-industrial levels, which is not far behind the target of 1.5°C which was agreed by nations under the Paris agreement in 2015 (Janki M, 2023). Achieving that will likely involve removing carbon dioxide from the atmosphere, according to the Intergovernmental Panel on Climate Change. But strategies like capturing and storing the carbon emissions from biofuel-burning power plants, or planting new forests to absorb carbon, can create their own problems. Recently UN security general said we are shifting to the “Era of global boiling” from global warming. Globally countries are witnessing unbearable heat waves, forest fires, irregular rainfall, flashfloods, coral bleaching and unpredictable weather patterns which often resulting in devastating effects on the coastal and hilly regions of the country. Around nine tipping points have been identified so far globally. Climate tipping points are threshold that when crossed leads to irreversible changes in the climate system and will have a severe impact on the living organisms on the earth. All these variations in climate are driving by increasing greenhouse gas (GHG) emissions and global warming. We cannot change the state of atmosphere to as existed thousands or millions of years ago. Only option left with us is to reduce emissions and prevention of further global warming and climate change. As we are already existing in some level of changed climate, responding to climate change involves a two-pronged approach, reducing emissions of and stabilizing the levels of heat-trapping greenhouse gases in the atmosphere through mitigation and secondly, adapting to the climate change. Because climate change is irreversible process.

Is it possible to feed a world population projected to reach 8.5 billion by 2030, 9.7 billion by 2050 and exceed 11 billion in 2100? India expected to surpass China as the most populous country in the world within seven years (UN report July 2015). Besides that there is an immense decline in yield and quality over the past three decades may be at the point of diminishing returns (Bouis 1993; Cassman et al. 1995; Flinn and De Datta 1984). Furthermore, the soil is partially under tremendous pressure to sustain yield and production. The excessive and exhaustive agriculture practices have not only declined the soil quality but it’s also reported for different human and animal health issues. Thus, keeping pace with population growth and health safety appropriate soil management practices must be addressed. Now burgeoning population load, declining yield, soil health diminution, and effect on human and animal health arises the opportunity for sustainable soil management to cater the problem at the right time. Figure 1 clearly indicates the tremendous load on soil and subsequent results. Burgeoning increase in population and a load of food production intensification, sustainable soil management will become increasingly important in future. Soil being the powerhouse of the mineral nutrients also retains most living organisms within it. The appropriate soil management practices ensure the critical level of mineral elements which finally come into the human body.

7.1 Introduction

Soil is an essential component of ecosystem sustaining all living vegetation, microorganisms, herbivores and carnivores. It is the outermost layer of the earth. It varies greatly in its physical and chemical properties which depend on its age and on the conditions (parent material, climate, topography and vegetation) under which it was formed. Processes such as leaching, weathering and microbial activity combine to make a whole range of different soil types, each of which has particular strengths and weaknesses for agricultural/ horticultural production.

The materials present in the soil are mostly in three states, i.e., solid, liquid and gaseous. They differ in their percentage from soil to soil. A good soil should have 5% organic matter, 45% mineral matter, 25% air and 25% water. So, while establishing an orchard, whole soil profile should be taken into consideration. Digging a pit shows the different layers of soil profile. Usually these are same and not distinct in many areas. Inorganic materials are the major component of most soils. They consist largely of mineral particles with specific physical and chemical properties which vary depending on the parent material and conditions under which the soil was formed. It is the inorganic fraction of soils which determines soil physical properties such as texture and has a large effect on structure, density, water retention and aeration. Air and water percentage in soil vary significantly with soil texture and weather conditions. The soil texture is a property which is determined largely by the relative proportions of sand, silt and clay particles content in it. The classification of soil based on particle size is termed as textural classification of soil. As per USDA classifications, clay particle size is less than 0.002 mm, silt size varies in between 0.002 to 0.05 mm and sand size in between 0.05 to 2.0 mm. On the basis of percentage of these particles present in a soil, the type of soil can be easily determined.

Soil mechanics as a distinct branch of soil science is comparatively of recent growth. Its need arose from the fact that the requirements of the engineer are very often quite different from those of the agriculturist. Whereas the former would as a rule require hard, compact, impervious soil, the latter would have no use for it for the growth of his plants which require soft, friable and porous soil. The agriculturist generally has to look up to nature to help him out of his difficulties, the engineer has to depend on his scientific skill to modify the soil to suit his requirements. In this chapter an attempt will be made to explain in a simple language the requirements of the building, road, and irrigation engineer for particular types of soils and how they are met by modifying the soil if the required properties already do not exist.

Q. 1 Hygrophilic soils are those
(A) Which attract water       (B) Which do not attract water
(C) Which transmit water    (D) Which produce water

Soil is the largest terrestrial ecosystem where a wide variety of relationships exists between different types of soil organisms. The associations existing between different soil microorganisms, whether of a symbiotic or antagonistic nature, influence the activities of microorganisms in the soil. Microflora composition of any habitat is governed by the biological equilibrium created by the associations and interactions of all individuals found in the community. In soil, many microorganisms live in close proximity and interact among them-selves in a different ways. Some of the interactions or associations are mutually beneficial, or mutually detrimental or neutral.

Introduction

Soil is a complex system consisting of physical, chemical and biological components. These components dynamically interact making it functional to sustain life. All life forms rely on soil microbial processes for their survival. Microbial diversity in the soil is greater than the diversity of any other group of organisms existing in the earth. Microbes as inhabitant of soil are responsible for diverse metabolic functions that affect soil and plant health (Table 1).

Abstract

The traditional forage production systems and grazing lands are under extreme pressure due to the population growth of both human and livestock, decreasing area and inputs. In the central India, especially the Bundelkhand region, the soil is highly weathered, degraded and have low inherent nutrient, which was further worsened due to use of chemical fertilizers and pesticides, for enhancing crop production to meet the escalating demand of the population.

Introduction

Microorganisms generally present in all the environments are the most abundant and diverse living organisms present on earth. Microorganisms have great impact on the biosphere due to their inbuilt ability to transform the key elements of life into forms usable by other organisms and plants. Because of heterogeneity in nature of soils from variations in physical, chemical and biological properties the various natural habitat are microbially most diverse environments on the earth maintaining the stability between complex microbial communities and their function (Daniel 2005). One gram of soil contains about 10 billion microorganisms of possibly thousands of different species but microbial diversity in general, and particularly in extreme environments, and its role in ecology is poorly understood (Rossello-Mora and Amann 2001).

Deserts present a unique environment with very little precipitation and large variations in day and night temperatures, making it inhospitable environment for living organisms. Still a number of microbial species do survive in those harsh environments. The populations of aerobic bacteria in deserts across the world are reported to vary from < 10 in Atacama desert to 1.6 × 10⁷ cfu g^–1 in soils of Nevada (Skujnis 1984), and India is not exception to that with the bacterial population in the range of 1.0 × 10³ to 8.35 × 10⁶ cfu g^–1 sediment or ml^–1 water in the samples collected from cold deserts of north western Himalayas (Yadav et al. 2015).

Soil is a living entity having dynamic physico-chemical and biological properties. Besides supporting the growth of various biological communities, it also serves as a medium on which the organic residues, in the form of dead plant and animal or their excretions, are degraded and decomposed. The biological properties to soil are endowed through the interactive activities of plant root, soil microbes and soil animals. The soil organisms live in a constant state of competition and have to struggle hard for their survival. In this struggle some species become dominant and some remain sub-dominant and others perish or remain in very low profile. So a sort of dynamic equilibrium is the net result of wide range of interactions occurring both at organism and population levels amongst different components of soil biota. Many interactions are short-lived and sporadic and others are more stable.

Soil is inhabited by incredibly diverse living microorganisms that are significant to plant growth and development. Soil microorganisms produce a variety of metabolites, probably several thousands, which influence the plant growth either positively or negatively. Therefore, in such a complex situation, identification of any one metabolite or a compound as active phytohormone or phytotoxin is really an uphill task. Appropriate extraction procedure, knowledge about the proper site for its action, appropriate conducive physiological environment and the effective intensity or concentration is of prime importance. Compounds, in general, are inhibitory to growth at higher concentrations but usually stimulatory at lower concentrations. All growth regulators, irrespective of their provenance or structure, may be divided into two groups.

Definition : Soil microbiology is the study of microorganisms living in soil which complete whole or some part of their life cycle in soil. They include both beneficial as well as deleterious microorganisms but as a specialized branch main thrust is laid on their metabolic activities and the role they play in energy flow, cycling of nutrients associated with the primary productivity and soil ecosystem development. Besides, it focuses on environmental impact, whether favourable or unfavourable, on soil microorganisms and the various soil biochemical processes mediated by various microbes. A clear understanding of the interactions between soil microbial communities and elemental soil components is imperative to comprehend total ecosystem function. Atlas and Bartha have defined the soil microbiology as ‘the study of organisms that live in soil; their metabolic activity; their roles in energy flow; their roles in nutrient cycling’. As per Tate soil microbiology involves ‘the study of soil ecosystem which is the product of intricate interactions between physical and chemical matrix of highly variable composition and living communities of all form’.

1. Amoeba are unicellular organisms that feed on

a. Bacteria and algae     b. Bacteria and fungi

c. Fungi and algae        d. Nematode and fungi

Microorganisms being minute and microscopic are ubiquitous. Besides supporting the growth of various biological systems, soil and soil microbes serve as a best medium for plant growth. Soil fauna & flora convert complex organic nutrients into simpler inorganic forms which are readily absorbed by plants.

Soil microbes as nitogen fixers-Symbiotic (Associative): The organisms involved are Rhizobium, Bradyrhizobium in legumes(aerobic): Azospirillum, Azotobacter (grasses), Actinonycetes- Frantkia (with Casuarinas, Alder).

Soil microbes as biocontrol agents: Several ecofriendly bioformulations of microbial origin are used in agriculture for the effective management of plant diseases, insect pests, weeds etc. eg: Trichoderma sp and Gleocladium sp are used for biological control of seed and soil borne diseases. Fungal genera Entomophthora, Beauveria, Metarrhizium and protozoa- Maltesia grandis. Malameba locustiae etc.- are used in the management of insect pests. Nuclear polyhydrosis virus (NPV) is used for the control of Heliothis/American boll worm. Bacteria like Bacillus thuringiensis, Pseudomonas are used in cotton against Angular leaf spot and bollworms.

Degradation of pesticides in soil: Soil receives different toxic chemicals in various forms and causes adverse effects on beneficial soil micro flora / micro fauna, plants, animals and human beings. Various microbes present in soil act as the scavengers of these harmful chemicals in soil. The pesticides/chemicals reaching the soil are acted upon by several physical, chemical and biological forces exerted by microbes in the soil and they are degraded into non-toxic substances and thereby minimize the damage caused by the pesticides to the ecosystem. For example, bacterial genera like Pseudomonas, Clostridium, Bacillus, Thiobacillus, Achromobacter etc. and fungal genera like Trichoderma, Penicillium, Aspergillus, Rhizopus, and Fusarium play important role in the degradation of the toxic chemicals / pesticides in soil.

Biodegradation of hydrocarbons: Natural hydrocarbons in soil like waxes, paraffins, oils etc are degraded by fungi, bacteria and actinomycetes. E.g. ethane (C2 H6) is metabolized and degraded by Mycobacteria, Nocardia, Streptomyces Pseudomonas, Flavobacterium and several fungi.

4.1. Role of soil microorganisms

Soil N utilization by plants.

Dead organic matters decomposed.

Nutrient transformation.

Physical and chemical properties of soil.

CO₂ content.

Soil formation.

Soil minerals are naturally formed inorganic compounds with definite chemical composition and characteristic geometric (crystalline) form. They are classified as primary and secondary minerals, silicates and non-silicates minerals, and crystalline and non-crystalline minerals. Primary minerals have not been significantly altered chemically since deposition or crystallization from molten magma and are usually found in the sand and coarse silt fractions. Secondary minerals form as a result of the alteration of primary minerals by weathering and are found in the clay and fine silt fractions.

ALLIC: soil family class term used in Oxisols as a calcareous and reaction class category. Soils placed in the allic class are acid and have low CEC with high amounts of KCl-extractable aluminum in a layer at least 30 cm thick within the control section. If used for agriculture, these Oxisols require large inputs of lime to displace the aluminum and raise pH.