Soil Science 1: Principles of Soil Science PDF

Iloilo Science and Technology University Leon Campus Leon, Iloilo SOIL SCIENCE 1 PRINCIPLES OF SOIL SCIENCE Prepared by: Jertz Vlyn D. Escala, M.Sc.  Soil Sci 1 – Principles of Soil Science...

Iloilo Science and Technology University Leon Campus Leon, Iloilo SOIL SCIENCE 1 PRINCIPLES OF SOIL SCIENCE Prepared by: Jertz Vlyn D. Escala, M.Sc.  Soil Sci 1 – Principles of Soil Science SOIL: A NATURAL RESOURCE CHAPTER 1 At the end of this unit the students must have: a. demonstrated a unified view of the soil as a natural resource and an important medium for plant growth. b. defined soil, its functions, and boundaries c. discussed the composition of the soil, its importance, formation and development d. examined the common soil-forming minerals and rocks; and e. described a soil profile Lesson 1 – Soil Definition, Importance and Functions Components of the Global Ecosystem (Figure 1) Atmosphere: air surrounding the Earth Biosphere: environment in which living organisms are found, and with which they interact Hydrosphere: total body of water that exists on or close to the surface of the Earth. Lithosphere: upper (oceanic and continental) layer of the solid Earth. Pedosphere: the envelope of the Earth where soils occur and where soil-forming processes are active. It is the Earth’s living skin. - It is at the interface of the lithosphere, biosphere, Figure 1. Interaction of the different atmosphere and hydrosphere, hence it interacts with components of the Global Ecosystem these spheres. Definition of Soil Soil – is a living dynamic system which forms at the interface between the atmosphere and lithosphere in response to forces exerted by climate and living organisms acting on parent material as conditioned by topography/relief over a period of time. (Figure 2). Figure 2. Different soil profiles (Buol et al., 2011) *Note: the underlined words are the five factors of soil formation. Chapter 1: Soil: A Natural Resource |page 1  Soil Sci 1 – Principles of Soil Science Definition of the soil varies according to use for which it is put. To a Pedologist, soil is a natural body, both spatial and temporal, forms at the surface, is a result of complex biogeochemical and physical processes, capable of supporting life, and can be mapped at an appropriate scale. To an Engineers, soil is the unconsolidated material above the bedrock. It is overburden to be moved. Geologists define soil as the natural medium for the growth of plants on lands. Many a times acronym SOIL is expanded to Soul Of Infinite Life. Soil microbiologists rightly define soil as a polis (society or community) that is “governed” by soil organisms where fungi are the “governing” organisms in forest soils whereas other microbes are the “governors” or “soil managers” in other ecosystems. To a Home owner, soil is a place to put foundation and build memories. Significant financial investment To an Agriculturist, soil is a natural medium on the surface of the earth in which plants grow. According to the FAO, “Soil is a natural body consisting of layers (soil horizons) that are composed of weathered minerals, organic matter, air and water; it is a natural medium for the growth of plants”. Functions of the Soil (Figure 3) 1. Habitat for Food and Other Biomass Production/ Production Function – soil acts primarily as a medium for the growth of natural vegetation. Soil assures the supply of food, feeds, fiber and fuel. Soil provide nutrients, water and other necessary environment which nurture plants for survival. 2. Environmental Interaction/Ecological Regulator- soil acts as buffer, filter and transformer of various substances in or that are added to the soil 3. Biological Habitat and Gene Pool - soil is a habitat of a multitude of flora and fauna. The largest quantity of organisms on the earth is in the soil. Chapter 1: Soil: A Natural Resource |page 2  Soil Sci 1 – Principles of Soil Science Figure 3. Schematic presentation of soil function 4. Source of Raw Materials – soil is a source of several raw materials (i.e., for industry. 5. Physical and Cultural Heritage - Soil acts as a physical and cultural heritage of the natural and cultural history of the human society, because it reflects on the evolution of natural conditions in an agricultural region and some aspects of human evolution. 6. Platform for Man-made Structures, Buildings and Heritage/ Engineering Function - soil acts as a support for houses, industrial buildings, communication ways (road, highways, and airports), sports’ fields, and storage of household and industrial wastes. Soil Dimensions Classical Concept: Soil is a 3-dimensional body (length, width and depth) Modern concept: Soil is a space-time structure (length, width, depth and time dimension) Time Soil Boundaries 1. Upper boundary – generally considered as air or water 2. Lateral boundary – deep water or barren areas of rock, ice, salt, or shifting desert sand dunes. Sediments at depths greater than where emergent plants grow is not considered as soil. 3. Lower boundary – generally thought of as the rooting depth (shallow www.slideshare.net in deserts, deep in humid tropics) of the native perennial plant Figure 4. Pedon showing the soil dimensions. Chapter 1: Soil: A Natural Resource |page 3  Soil Sci 1 – Principles of Soil Science Importance of Studying Soils 1. To understand how soil chemical, biological, and physical properties affect various uses of soils. 2. To learn how to conserve and utilize soils properly. 3. To understand how soil properties can be modified to improve their quality for a particular use. Approaches in the study of Soil Science Two general approaches in the study of soil science: 1. Pedology – study of soil as a natural entity – origin, classification and description 2. Edaphology – study of soil from the standpoint of plant growth Areas of Study in Soil Science 1. Soil Genesis - The study of the origin of the soil with special reference to the processes responsible for its development from the unconsolidated parent material 2. Soil Survey and Classification - The systematic examination, description, classification, and mapping of soils in an area. 3. Soil Physics - The physical properties of the soil, with emphasis on the state and transport of matter (i.e. branch of soil science that deals specially with water) and energy in the soil. 4. Soil Microbiology - The branch of soil science concerned with soil-inhabiting microorganisms, their functions, and activities. 5. Soil Fertility - The branch of soil science concerned with the quality of a soil that enables it to provide nutrients in adequate amounts and in proper balance for the growth of specified plants or crops. 6. Soil Chemistry - The branch of soil science that deals with the chemical constitution, chemical properties, and chemical reactions of soils. 7. Soil Conservation - The branch of soil science concerned with the protection of the soil against physical loss by erosion or against chemical deterioration; that is, excessive loss of fertility by either natural or artificial means. Chapter 1: Soil: A Natural Resource |page 4