Soil Fertility and Nutrient Management

A Way to Sustainable Agriculture

A.S. Jadeja, D.V. Hirpara, L.C. Vekaria, H.L. Sakarvadia

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000429589
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Agriculture durable

The book entitled Soil Fertility and Nutrient Management is a compilation work and most of the information was farmed very critically covering all the main topics of plant nutrition. The book will be serve as useful reference to students, teachers, researchers scientists, policy makers and other interested in soil science, agronomy, crop science, environmental sciences and agriculture.

Note: T&F does not sell or distribute the Hardback in India, Pakistan, Nepal, Bhutan, Bangladesh and Sri Lanka.

CHAPTER 1

INTRODUCTION

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The relationship of soil, environment and society is intimate and depends on soil quality and its management. Soil is a naturally occurring thin layer of materials on the part of Earth’s surface (land) composed of mineral and organic solids, gases, liquids and living organism which can serve as medium for plant growth. Soil science is the branch of agriculture that deals with soil considered as a natural body and as an important medium for plant growth. Therefore, a fundamental knowledge of soil science is prerequisite to meeting the natural resource challenges that will face humanity in the 21^st century.

1.1 CONCEPT OF SOIL AND ITS DEFINITION

The term soil is derived from the Latin word “So/um” which means floor/ground. What a soil scientist calls soil - “a natural body on the earth’s surface, a geologist may call fragmented rock, an engineer may call earth and economist may call land.” There are two basic concepts of soil that have already evolved through two centuries of scientific study. The first one considered soil as a natural body, a biochemically weathered and synthesized product of nature and second one considers soil as a natural habitat for plants and other living organisms and justifies soil studies primarily on that basis.

The approaches of soil study: The two approaches: (i) pedological and (ii) edaphological approaches can be used in studying soils. In other words, there are two main branches of soil science are Pedology and Edaphology.

1. Pedological approach: The origin of the soil, its classification, and its description are examined in pedology (from the Greek word “pedon”, which means soil or earth). Pedology is the study of the soil as a natural body and does not focus primarily on the soil’s immediate practical use. A pedologist studies, examines, and classifies soils as they occur in their natural environment.
2. Edaphological approach: Edaphology (from the Greek word “Edaphos”, which means soil or ground) is the study of soil from the standpoint of higher plants (Study of the soil in relation to plant growth, nutrition and yield of crops). Edaphologists consider the various properties of soils in relation to plant production. They are practical and have the production of food and fiber as their ultimate goal. To achieve that goal, Edaphologists must be a scientist to determine the reasons for variation in the productivity of soils and find means of conserving and improving productivity.

Functions of the soil: Followings are the major ecological functions of the soil

• Soils serve as medium for growth of all kinds of plants.
• Soils provide the physical support to the plants.
• Soils provide (supplies) moisture and nutrients for plant growth.
• It serves as a home for a myriad of organisms.
• Soils act as a living filter to clean water before it moves into an aquifer.
• It acts as a recycling system for nutrients and organic waste.
• It is a store house of nutrients.
• Soils modify the atmosphere by emitting and absorbing gases (carbon dioxide, methane, water vapor, and the like) and dust.

Soil is a three phase system: Soil mass is generally a three phase system as it consists of: (i) Solid phase, it includes various sizes of mineral and organic particles and living organisms (ii) Liquid phase, it includes water and dissolved nutrients/salts (soil solution) and (iii) Gases phase, it consisted of various gases like CO₂, N₂, O₂ etc. All these three phases play a very vital role for plant life. Relative proportion of these phases in soil governs the properties of soils. These properties of soil often determine the nature (type) of vegetation.

Soil as a medium for plant growth: In any ecosystem, soils play six key roles in relation to plant growth. These are as follows:

1. Provide physical support: Soils provide the physical support, anchoring the root systems so that the plant does not fall over or below away.
2. Soil act as a ventilator: To obtain energy, plant roots depend on the respiration process. In the respiration process, plant root consumes O₂ and release the CO₂. Soil pores allowing CO₂ to escape form root zones to atmosphere and fresh O₂ to enter the root zone.
3. Provide water: For growth, plant takes water from the soil through roots. Soil absorbs rain/irrigation water and holds it against the force of gravity in micro pores. Part of this water is used by plants.
4. Act as temperature moderation: The soil also moderates temperature fluctuations. The insulating properties of soil protect the deeper root system from extremes of hot and cold that often occur at the soil surface.
5. Soil protects plant from toxins: Several toxins (harmful substances) are produced in the soil as a result of microbial activity, root exudation, chemical reactions etc. or may result from human activity (pollution). Healthy soil will protect the plant from toxic concentration of such substances by ventilating gases, by decomposing or adsorbing organic toxins or by suppressing toxic producing organisms.
6. Soil provides essential nutrients: Seventeen elements have been shown to be essential elements (also called as essential nutrients), meaning that plants cannot grow and complete their life cycles without them. Soil provides most of essential nutrients to growing plants, without nutrients, plants life is not possible.

Soil properties and plant growth: Soil being a living organism exhibits all the three properties of any living being on the earth. These three properties are: physical properties, chemical properties and biological properties. All these three properties of the soils play an important role in determining its suitability for crop production. For example, water logged clay soil is suitable for rice cultivation whereas, remaining cultivated crops requires well drained soils. Citrus plants requires alight acidic to neutral soil reaction for optimum productivity. Moreover, one property of soil may also directly or indirectly affect other properties of soil. For example, neutral soil pH is ideal for soil fertility. Extreme acidic or alkaline pH adversely affects the soil fertility and ultimately crop productivity. Sandy soil has a poor CEC as well as fertility than the clay soils. Addition of Soil Organic Matter (SOM) improves the all physical, chemical and biological properties of soil.

1.2 SOIL FERTILITY AND PRODUCTIVITY

The interactions of various physical, chemical and biological properties in soil controls soil fertility (Plant nutrient availability). Therefore, understanding the soil properties and processes and how they are influenced by environmental conditions during growing season enables us to optimize nutrient availability and plant productivity.

Soil fertility: Soil fertility is the inherent capacity of soil to provide the essential plant nutrients in adequate amounts and in proper proportions for the plant growth. It represents the available nutrients status of the soil. The availability of nutrients to the plants is greatly influenced by physical (soil texture, soil structure, soil porosity etc.), chemical (pH, ESP, CEC etc.) and biological properties of soil. Therefore, knowledge of soil fertility along with other properties of soil that affects the plant growth is essential to optimize the soil productivity.

Soil fertility and plant nutrition are two closely related subjects that emphasize the forms and availability of nutrients in soils, their movement in the soil and their uptake by roots. Soil fertility also can be readily altered by the application of soil amendments and nutrients etc. Knowledge of soil fertility is important for the development of soil management systems that produce profitable crop yields while maintaining soil sustainability and environmental quality.

Soil productivity: Soil productivity encompasses (involve) soil fertility plus all other factors affecting plant growth, including soil management practices. Therefore, Soil productivity is defined as the ability/capacity of the soil to produce crops yield with specific systems of management. OR soil productivity is the ability of the soil to produce the crop yield under specified management practices. It should be expressed in terms of yield (kg/ha. etc.).

Obtaining the maximum production potential of a particular crop in a region depends on the climatic condition, soil properties and biotic factors along with management practices. Thus, soil fertility is one of the several factors that affect soil productivity. All productive soils are fertile, but all fertile soils may or may not be productive due to some problems like water logging, alkalinity, salinity and adverse weather condition etc.

“All the productive soils are fertile but all the fertile soils may not be productive”

History of development of soil fertility

• Francis Bacon (1591- 1624) suggested that the principle nourishment of plants was water and the main purpose of the soil was to keep plants erect and to protect from heat and cold.
• Jan...