Do total soil organic matter content, nutrients contained in soil organic matter, and mineralized annually appear to be too high or too low? Why or why not? Glossary Active organic matter.—Organic protected inside soil aggregates or it is compounds used as food by chemically too complex to be used by most and associated with high organisms. Humus is important in binding biological activity. Active soil organic matter soil aggregates and improves the water and breaks down faster than other components nutrient-holding capacity of soils. of soil organic matter and responds more Mineralization.—Organic matter quickly to changes in management. decomposition that releases nutrients in a Fresh residue.—Plant residue, dead form available for plants (e.g., phosphorus, animals, and other organic substances that nitrogen, and sulfur). have recently been added to the soil and Soil micro-organisms (small living exhibit minimal decay. organisms).—Bacteria, fungi, nematodes, Humus (stable organic matter).—Complex protozoa, and arthropods, etc. organic compounds that remain after Soil organic matter (SOM)–Organic organisms have used and transformed the component of soil, consisting of plant original organic material. Humus is not residue (fresh), living organisms, readily decomposed either because it is decomposing organic matter (active), and physically stable organic matter (humus).
Do total soil organic matter content, nutrients contained in soil organic matter, and mineralized annually appear to be too high or too low? Why or why not? Glossary Active organic matter.—Organic compounds used as food by and associated with high biological activity. Active soil organic matter breaks down faster than other components of soil organic matter and responds more quickly to changes in management. Fresh residue.—Plant residue, dead animals, and other organic substances that have recently been added to the soil and exhibit minimal decay. Humus (stable organic matter).—Complex organic compounds that remain after organisms have used and transformed the original organic material. Humus is not readily decomposed either because it is physically protected inside soil aggregates or it is chemically too complex to be used by most organisms. Humus is important in binding soil aggregates and improves the water and nutrient-holding capacity of soils. Mineralization.—Organic matter decomposition that releases nutrients in a form available for plants (e.g., phosphorus, nitrogen, and sulfur). Soil micro-organisms (small living organisms).—Bacteria, fungi, nematodes, protozoa, and arthropods, etc. Soil organic matter (SOM)–Organic component of soil, consisting of plant residue (fresh), living organisms, decomposing organic matter (active), and stable organic matter (humus).
USDA_NRCS_OM_guide.docx