"Consisting of plant and animal detritus at various stages of decomposition, cells and tissues of soil microbes, and substances that soil microbes synthesize."
The amount and type of organic material in soil, which affects soil structure, water retention, nutrient cycling, and carbon sequestration.
Introduction to Soil Organic Matter: This topic covers the fundamental aspects of Soil Organic Matter (SOM) including its definition, composition, functions, and characteristics.
Soil Organic Carbon: This refers to the amount of organic carbon present in soil, which is considered an essential component of SOM. This topic covers the factors that influence the concentration of carbon in soils, the forms of organic carbon, and the role of this important element in soil fertility.
Soil Microorganisms: This topic delves into the microorganisms that inhabit the soil including bacteria, fungi, protozoa, nematodes, and other species. These organisms play a critical role in the decomposition of organic matter and the release of nutrients for plant growth.
Soil Organic Matter Dynamics: This topic covers the processes that cause SOM to cycle in and out of the soil including decomposition, mineralization, immobilization, and organic matter storage.
Soil Organic Matter Management: This topic focuses on the practices that can be implemented to restore and maintain soil organic matter, including conservation tillage, cover crops, crop rotation, organic amendments, and composting.
Soil Carbon Sequestration: This topic covers the techniques that can be used to increase the amount of carbon that soils store, including afforestation, agroforestry, no-till farming, and other land use changes.
Soil Organic Matter and Climate Change: This topic examines the impact of climate change on SOM and the role of SOM in mitigating climate change by helping to sequester carbon.
Soil Structure and Aggregation: This topic covers how SOM affects soil structure and aggregation, which in turn, impacts soil water-holding capacity, soil strength, and soil fertility.
Soil pH: Soil pH is an important determinant of SOM decomposition rates as well as nutrient availability. This topic covers the factors that influence soil pH and how to manage pH to support Soil Organic Matter status.
Soil Organic Matter Testing: This topic examines the various methods used to quantify the content and properties of SOM, including wet chemical methods, spectroscopic techniques, and others.
Soil Organic Matter and Plant Nutrition: This topic explores the role of SOM in supplying nutrients that are essential for plant growth, including nitrogen (N), phosphorus (P), potassium (K), and micronutrients.
Soil Amendments and Soil Organic Matter: This topic covers the use of organic and inorganic amendments to enhance SOM levels in soils, including compost, manure, biochar, and other materials.
Soil Organic Matter and Water Quality: This topic explains how SOM can influence water quality by reducing soil erosion and promoting the retention of nutrients and pollutants within the soil.
Land-Use Management and Soil Organic Matter: This topic examines the impact of different land-use practices on SOM levels, including agriculture, forestry, urban development, and transportation.
Factors Affecting Soil Organic Matter: This topic covers the various factors that control SOM concentration and quality, including climate, land use, soil type, soil texture, and soil management.
Humus: Dark, amorphous organic matter that is formed from the decomposition of dead plant and animal tissues. It is essential for soil fertility maintenance, provides nutrient retention and soil structure.
Residue: Plant materials and other organic residues that fall onto the soil surface such as fallen leaves, stems, and roots. Residues decompose through microbial activity.
Compost: Decomposed organic waste that is added to soil as a soil amendment to improve soil structure and fertility.
Glomalin: A sticky, glycoprotein found in association with mycorrhizal fungi that binds soil particles together and increases water retention.
Charcoal: Carbon-rich material resulting from incomplete combustion of organic matter. Charcoal can improve soil fertility, increase water-holding capacity, and provide a habitat for beneficial microorganisms.
Biochar: A type of charcoal that is intentionally produced and used as a soil amendment to improve fertility, water retention, and soil structure.
Roots: Plant roots contribute organic matter through the production of root exudates, sloughed off root tissue, and root turnover.
Living Organisms: Soil microorganisms, earthworms, and other soil-dwelling animals contribute to SOM through their excretions, dead bodies, and other by-products of their metabolism.
Labile: Fresh organic matter that rapidly decomposes and is available as a food source for soil microbes. It serves as a source of nutrients for plants.
Recalcitrant: Organic matter that resists decomposition for extended periods of time such as tar, lignin, and some waxes. It helps protect the soil surface from wind and water erosion.
Particulate: Rough textured organic matter composed of larger plant and animal residues. It helps bind soil particles together, improves soil structure and water retention.
Dissolved: Organic compounds that are in a dissolved state in the soil solution. These compounds are readily available for uptake by plant roots.
"The benefits of SOM result in improvement of soil structure, aggregation, water retention, soil biodiversity, absorption and retention of pollutants, buffering capacity, and the cycling and storage of plant nutrients."
"SOM increases soil fertility by providing cation exchange sites and being a reserve of plant nutrients, especially nitrogen (N), phosphorus (P), and sulfur (S), along with micronutrients, which the mineralization of SOM slowly releases."
"SOM is especially critical for soil functions and quality."
"The amount of SOM and soil fertility are significantly correlated."
"SOM also acts as a major sink and source of soil carbon (C)."
"Ordinarily estimated to contain 58% C."
"Soil represents one of the largest C sinks on Earth and is significant in the global carbon cycle and therefore for climate change mitigation."
"The capacity of soils to provide the ecosystem service of carbon sequestration through SOM management has received considerable attention recently."
"The concentration of SOM in soils generally ranges from 1% to 6% of the total mass of topsoil for most upland soils."
"Soils whose upper horizons consist of less than 1% of organic matter are mostly limited to deserts."
"Soils in low lying, wet areas can have a SOM content as great as 90%."
"Soils containing 12% to 18% SOC are generally classified as organic soils."
"It can be divided into 3 genera: the living biomass of microbes, fresh and partially decomposed detritus, and humus."
"Surface plant litter, i.e., fresh vegetal detritus, is generally excluded from SOM."
"SOM contributes to the improvement of soil structure."
"SOM contributes to the improvement of water retention in soil."
"SOM contributes to the improvement of soil biodiversity."
"SOM contributes to the absorption and retention of pollutants in soil."
"SOM contributes to the cycling and storage of plant nutrients in soil."