What is Organic Matter?
Soil organic matter encompasses all non-mineral solids in soil, arising from biological tissues, byproducts, and wastes. Soil organic matter includes a range of chemical constituents, from simple sugars to complex molecules and partially decomposed particles. Organic matter imparts a variety of chemical and physical benefits on soil and it is the foundation of the soil food web. Soil organic matter is an important indicator of soil health.
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Title | Source | Resource type and Date | Short Summary / Preview |
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Soil Organic Matter Does Matter | University of Minnesota and North Dakota State University | Extension Webpage
2018 |
Explanation of the nature and formation of soil organic matter and overview of soil management influences on soil organic matter pools. |
Advanced Soil Organic Matter Management | Michigan State University | Extension Publication
Feb 2011 |
This bulletin describes the agronomic practices you can use to build soil organic matter and the science behind the practices. |
Soil Organic Carbon Cycle | Michigan State University | Extension Fact Sheet
Aug 2018 |
Fact sheet about soil organic carbon and a handout. |
Using Manure to Improve Soil Health | Livestock and Poultry Environmental Learning Community | Extension Webinar
Mar 2019 |
This webinar looks at current practical research in South Dakota and Michigan related to manure use as it relates to soil health. |
Soil organic matter | North Dakota State University | Extension Webpage
2014 |
Soil organic matter makes up between 1 and 5% of most soils. This small fraction in the soil alters many soil health parameters and benefits plant productivity. |
Particulate Organic Matter | Soilquality.org – NRCS & others | Webpage
Sep 2011 |
POM is biologically and chemically active and is part of the labile (easily decomposable) pool of soil organic matter (SOM). |
Soil Quality Indicators: Biological Indicators and Soil Functions | USDA | NRCS Fact Sheet
Feb 2015 |
Soil biological indicators provide insight into the living component of the soil. Similar to physical and chemical indicators, biological indicators have a relationship to soil functions and can evaluate soil functions to assess |
Soil Quality Indicators: Particulate Organic Matter | USDA | NRCS Fact Sheet
Apr 2011 |
Particulate organic matter (POM) fraction referred to in this document comprises all soil organic matter (SOM) particles less than 2 mm and greater than 0.053 mm in size. |
Amount of Organic Matter in Soils | SARE | Fact Sheet
2012 |
Anything that adds large amounts of organic residues to a soil may increase organic matter. On the other hand, anything that causes soil organic matter to decompose. |
Organic Matter: What It Is and Why It’s So Important | SARE | Fact Sheet
2012 |
The living part of soil organic matter includes a wide variety of microorganisms, such as bacteria, viruses, fungi, protozoa, and algae. It even includes plant roots and the insects, earthworms, and larger animals, such as moles, woodchucks, and rabbits that spend some of their time in the soil. The living portion represents about 15% of the total soil organic matter. |
Photos on crop residue | SARE | Image
Not Dated |
Photos on crop residue from SARE Library. |
Manure’s Impact on Yield, Nitrogen, and Carbon | Soil Health NEXUS | Research Summary
May 2018 |
Manure is often viewed by many as an environmental liability. However, if manure is applied at rates equal to or less than the nitrogen (N) requirement of a crop, can manure produce environmental benefits over commercial fertilizer? |
Soil Health – Guides for Educators – Soil Organic Matter | USDA | NRCS Educator Guide
May 2014 |
Soil organic matter (SOM) is necessary for all soil functions, and it is the most important indicator of soil health. |
Title | Source | Resource type and date | Short Summary |
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What Does Organic Matter Do In Soil? | Noble Research Institute | Blog post from an independent research institute
Aug 2001 |
Soil organic matter is a small, but critical component of the soil. This article demonstrates the value of enhancing soil organic matter for increasing the functionality of soils. |
Soil Quality Information | Penn State | Extension Publication
Aug 2012 |
Healthy soils yield healthy crops, But what is healthy soil and how do we achieve it? |
Soil Organic Matter: The Living, the Dead, and the Very Dead | University of Vermont | Extension Publication
Not Dated |
Extension guide about Soil Organic Matter (SOM). SOM makes up only a few percent of most soils, but it has a great deal of influence on soil properties, and in turn, agricultural productivity. |
Building Healthy Soils | University of Tennessee | Extension Publication
Sep 2012 |
Organic matter refers to the portion of soil comprised of living organisms, decaying plant residues, and humus. |
Soil pH and Organic Matter | Montana State University | Extension Publication
2017 |
After reading this module, the reader should: (1) Know what soil pH is and how it relates to soil acidity, (2) Understand how soil pH affects nutrient availability in the soil, (3) Learn techniques for managing soil pH, (4) Know the soil organic matter cycle, and (5) Understand the role of soil organic matter in nutrient and soil organic carbon management. |
Managing Soil Health: Concepts and Practices | Penn State | Extension Publication
Jul 2017 |
Information for farmers and gardeners who want to understand the physical, chemical, and biological components of healthy soil and how to manage them. |
Managing Soils | Penn State | Extension Publication
Aug 2012 |
The goal of good soil management is to meet essential plant needs for water, nutrients, oxygen, and a medium to hold their roots with as little management as possible. |
Soil Health | University of California | University Webpage
Not Dated |
Soil health is the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans. Oftentimes, the features of healthy soil are related to the organic matter content. |
Title | Source | Resource type and Date | Short Summary |
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Measuring Dissolved and Particulate Organic Carbon (DOC and POC) | Science Education Resource Center at Carlton College | Blog Post
Not Dated |
Dissolved organic carbon (DOC) is defined as the organic matter that is able to pass through a filter (filters generally range in size between 0.7 and 0.22 um). Conversely, particulate organic carbon (POC) is that carbon that is too large and is filtered out of a sample. |
Glossary of Soil Science Terms | Soil Science Society of America | Definitions
Not Dated |
Soil Organic Matter: The organic fraction of the soil exclusive of undecayed plant and animal residues. See also humus. |
Soil biology and soil organic matter; What do recent discoveries mean for soil management? | Washington State University | Extension Blog Post
Jun 2019 |
This blog post describes various recent advances in our understanding of soil organic matter cycling and storage, and management principles to incorporate these advances are suggested. |
The importance of soil organic matter | Food and Agriculture Organization of the United Nations (FAO) | Bulletin
2005 |
This soils bulletin concentrates on the organic matter dynamics of cropping soils. In brief, it discusses circumstances that deplete organic matter and the negative outcomes of this. The bulletin then moves on to more proactive solutions. It reviews a “basket” of practices in order to show how they can increase organic matter content and discusses the land and cropping benefits that then accrue. |
Soil Community Structure, Function, and Spatial Variation in an Organic Agroecosystem | SARE | Guide Sheet
2008 |
Farmers are becoming increasingly interested in their soil’s biological status. Nitrogen mineralization, aggregate formation, and pathogen control, along with other soil biological processes, affect farm productivity, and profitability. |
Global meta-analysis of the relationship between soil organic matter and crop yields | Soil | Peer-Reviewed Publication
Jan 2019 |
Developed a quantitative model exploring how SOM relates to crop yield potential of maize and wheat in light of co-varying factors of management, soil type, and climate. We found that yields of these two crops are on average greater with higher concentrations of SOC (soil organic carbon). However, yield increases level off at ∼2 % SOC. |
The Sanborn Field Experiment: Implications for Long-Term Soil Organic Carbon Levels | American Society of Agronomy | Peer-Reviewed Publication
Jan 2011 |
It appears that an equilibrium level of SOC for some cropping systems takes about 30 to 40 yr to develop. Initial active carbon (AC) content assessment as a proxy for soil quality shows greater AC with manure and higher input management systems. The AC had a wide seasonal flux within a growing season as a function of temperature and moisture fluxes on microbial activity. |
Texture, Climate, and Cultivation Effects on Soil Organic Matter Content in U.S. Grassland Soils | American Society of Agronomy | Peer-Reviewed Publication
May 1989 |
The purpose of this study was to evaluate the major controls over soil organic carbon content and to predict regional patterns of carbon in range and cultivated soils. Organic C increased with precipitation and clay content and decreased with temperature. |
Developments in Agricultural Soil Quality and Health: Reflections by the Research Committee on Soil Organic Matter Management | North Central Education and Research Activity Committee (NCERA-59) | Peer-Reviewed Publication
Jul 2019 |
Article comments on the science supporting soil quality and associated soil health assessment for agricultural lands with the goal of hastening progress in this important field. |
Soil Organic Carbon and Nitrogen Feedbacks on Crop Yields under Climate Change | Agricultural & Environmental Letters | Peer-Reviewed Publication
Aug 2018 |
A critical omission from climate change impact studies on crop yield is the interaction between soil organic carbon (SOC), nitrogen (N) availability, and carbon dioxide (CO2). We used a multimodel ensemble to predict the effects of SOC and N under different scenarios of temperatures and CO2 concentrations. |
Evaluating the impact of soil conservation measures on soil organic carbon at the farm scale | Computers and Electronics in Agriculture | Peer-Reviewed Publication
Apr 2017 |
The study compares the CO2 emission and sequestration patterns of agricultural soils. |
Last reviewed February 29, 2020