Soil Chemistry Lesson 8 2024 PDF

ENGINEERING FOR CHEMISTRY 1 SOIL CHEMISTRY FILL IN THE BLANKS M_NE___S O_GA_IC _ A T _ E_  S__L _HE_I_T_Y SOIL CHEMISTRY Soil chemistry is a branch of soil science that deals with the chemical composition, chemical reactions and chemical properties in soils. It involves the study of th...

ENGINEERING FOR CHEMISTRY 1 SOIL CHEMISTRY FILL IN THE BLANKS M_NE___S O_GA_IC _ A T _ E_  S__L _HE_I_T_Y SOIL CHEMISTRY Soil chemistry is a branch of soil science that deals with the chemical composition, chemical reactions and chemical properties in soils. It involves the study of the chemical characteristics of soil, focusing on the interactions between minerals, organic matter, water, and the atmosphere within the soil. It examines how chemical reactions in the soil affect plant growth, nutrient availability, soil structure, and environmental health.  SOIL CHEMISTRY HISTORY Jethro Tull Eighteenth-century British gentleman farmer Jethro Tull (1674– 1741) is popularly regarded as the inventor of the seed drill, widely cited by agricultural historians, soil scientists and school history textbooks alike. "The New Hourse-Houghing Husbandry" "ingesting proper pabulum" "lacteal mouth" of the roots SOIL COLLOIDS➡️ CLAY AND HUMUS ORGANIC COMPONENT OF SOIL ORGANIC 01 MATTER 02 WATER 03 AIR 04 MINERALS  01 ORGANIC MATTER Soil organic matter is the fraction of the soil that consists of plant or animal tissue in various stages of breakdown (decomposition). They not only stores nutrients in the soil, but is also a direct source of nutrients. This includes both micro and macro organisms that plays an important role in maintaining the soil’s nutrients. Example: Living organisms Remains of microorganisms Remains of plants and animals Organic compounds that has been decomposed in the soil. 02 WATER Soil water is particularly important in nutrient management. In addition to sustaining all life on Earth, soil water provides a pool of dissolved nutrients that are readily available for plant uptake. Therefore, it is important to maintain proper levels of soil moisture. Amount of water in the soil is dependent among these (2) factors: Soil water is intimately related to the climate, or the long term precipitation patterns, of an area. The amount of water in the soil depends upon how much water a soil may hold. WATER HOLDING CAPACITY Water is held within the pores of the soil, the water holding capacity depends on capillary action and the size of the pores that exist between soil particles. Large particles and large pores = Less ability to hold water, resulting to dry soil Small particles and small pores = Greater ability to hold water, greater moisture 02 AIR Soil aeration influences the availability of many nutrients. Particularly, soil air is needed by many of the microorganisms that release plant nutrients to the soil. An appropriate balance between soil air and soil water must be maintained since soil air is displaced by soil water. The network of pores within the soil aerates, or ventilates, the soil. Not only are both soil air and soil water very dynamic parts of soil, but both are often inversely related: The soil atmosphere is not uniform throughout the soil because there can be localized pockets of air. The relative humidity of soil air is close to 100%, unlike most atmospheric humidity. Air in the soil often contains several hundred times more carbon dioxide. Soil air is different from the above- ground atmosphere. Aside from it having more moisture, they also differ in the level of carbon dioxide. MINERAL COMPONENT OF SOIL The mineral component of soil is fundamental to soil chemistry, structure, and fertility. It comes from the weathering and breakdown of rocks and minerals over time. Types of Soil Minerals: Primary Minerals Secondary Minerals PRIMARY MINERALS: These are minerals that originate directly from the parent rock material and are generally resistant to weathering. They are usually found in sand and silt fractions of soil. PRIMARY MINERALS: Common primary minerals include: Quartz: Very resistant to weathering and contributes to the sand fraction of soil. Feldspars: Break down over time to release potassium, calcium, and sodium. Micas (e.g., biotite and muscovite): Provide potassium and other nutrients when weathered. SECONDARY MINERALS These minerals form from the weathering of primary minerals, usually under soil-forming processes. Found predominantly in the clay fraction, secondary minerals have high surface areas, which allow them to retain water and nutrients.  SECONDARY MINERALS Clay Minerals: Such as kaolinite, montmorillonite, and illite, which can retain water and nutrients due to their fine particle size and surface charge. Iron and Aluminum Oxides: Form in highly weathered soils and contribute to soil color (e.g., red, yellow) and chemical reactivity. Carbonates: Including calcite and dolomite, which are found in alkaline soils and provide calcium and magnesium. Soil Particle Size and Texture -Soil minerals vary in particle size, and these sizes are classified into three main categories: Sand The proportions of sand, silt, and clay determine the soil texture, which influences water retention, drainage, and root Slit penetration. For example, clay- rich soils hold water well but may drain poorly, while sandy soils drain quickly but retain Clay fewer nutrients. Sand: Largest particles (0.05–2 mm) that improve drainage but have low nutrient-holding capacity. Silt: Medium-sized particles (0.002–0.05 mm) with moderate nutrient and water retention. Clay: Smallest particles ( 7). For home gardens, maintaining a soil pH in the range of 6 to 7 is generally recommended, as this supports a wide variety of plants and ensures optimal nutrient availability. If the soil pH is too low, you can raise it by adding lime (calcium carbonate). The amount of lime needed to achieve the desired pH is called the lime requirement.  IMPORTANCE NUTRIENT MICROBIAL SOIL MINERAL AVAILABILITY ACTIVITY SOLUBILITY Soil pH significantly affects the The activity of soil The solubility of minerals in the availability of essential microorganisms, which are soil is affected by pH levels. nutrients to plants. For crucial for nutrient cycling and This can influence the overall example, certain nutrients organic matter fertility of the soil and the become less available in decomposition, is influenced effectiveness of fertilizers. highly acidic or alkaline soils, by soil pH. A balanced pH which can lead to supports a healthy deficiencies and impact plant microbial community. health. SOIL PH TEST To determine soil pH, you can use various methods, including pH meters or test kits available at garden centers. It's important to take samples from different areas of your garden to get an accurate reading. Redox in Soil Redox (reduction-oxidation) involves the exchange of electrons. One substance is oxidized (loses electrons), and another is reduced (gains electrons). This process is driven by soil microorganisms that use these reactions for energy. Redox influences soil fertility, pollutant breakdown, and even greenhouse gas emissions. It determines the chemical forms of nutrients, minerals, and pollutants, affecting their mobility and bioavailability. Redox Conditions in Soil 1. Oxidative Conditions (Well-drained soils) Oxygen is abundant supporting oxidation reactions. Nutrients like nitrate (NO3​) remain stable and accessible to plants. 1. 2. Reducing Conditions (Waterlogged soils) Oxygen is scarce, creating an environment for reduction reactions. Electron acceptors like nitrate, iron ( ), manganese oxides ( ), or sulfate ( ​ ) are used instead. This shift impacts microbial activity and changes nutrient forms. Redox Potential (Eh) A measure of the soil’s tendency to gain or lose electrons. High Eh (oxidizing conditions): Oxygen is abundant, organic matter decomposes fully, and nutrients like nitrate are stable. Low Eh (reducing conditions): Oxygen is scarce, leading to processes like denitrification and the release of reduced metals (e.g., , ) Redox Reactions in Soil 1. Nitrogen Cycle (Denitrification): This process removes nitrogen from the soil but also releases nitrous oxide, a potent greenhouse gas. 1. 2. Iron and Manganese Reduction: (ferrous iron) Influences soil color and plant nutrient availability. Toxicity risks can arise if concentrations are too high. Redox Reactions in Soil 1. 2. 3. Sulfur Cycle: Common in flooded soils, producing a rotten egg smell. 1. 2. 3. 4. Carbon Cycle: Organic matter decomposition: Aerobic conditions produce ​, while anaerobic conditions produce methane (​ ). REFERENCE: Admin. (2024, July 2). Types Of Soil - Sandy Soil, Clay Soil, Silt Soil, And Loamy Soil. BYJUS. https://byjus.com/biology/types-of-soil/ Soil management. (n.d.). https://www.ctahr.hawaii.edu/mauisoil/a_comp02.aspx Queensland Government. (2013, September 24). Soil pH Levels https://www.qld.gov.au/environment/land/management /soil/soil-properties/ph. QUIZ TIME!