Organic matter in soil refers to the fraction of the soil that consists of plant or animal tissue in various stages of breakdown or decomposition. It is made up of living, dead, and decomposing plants, small animals, and microorganisms. Organic matter includes different components that can be grouped into three major types: active, intermediate, and stable. The humus fraction is the final product of decomposition and has less influence on soil fertility, but it contributes to soil structure, soil tilth, and cation exchange capacity. Organic matter plays a crucial role in soil productivity and contributes to soil health in many different ways. Here are some of the benefits of organic matter in soil:

• Provides essential nutrients for plants as it is decomposed by microbes.
• Feeds and provides habitats for diverse soil organisms, including those that help fight plant pests and diseases.
• Makes it easier for plant roots to thread through the soil to find water, air, and nutrients.
• Improves soil structure and tilth, which can increase water infiltration and reduce erosion.
• Increases the soils ability to hold onto nutrients and water, reducing the need for fertilizers and irrigation.
• Helps buffer soil pH, which can affect nutrient availability and uptake.

Soil organic matter is measured by weight, not volume, and most soil testing labs include the organic matter test in their basic soil test. Most garden and landscape plants perform best when the soil organic matter level is at least 2%, and the goal for vegetable and flower beds should be 5%-10%. Organic matter can be added to soil through the use of soil amendments such as compost, manure, and other organic materials.