Soil Organic Matter Unit: Soil Science Lesson 3

Objectives• Define: soil organic matter• Explain the role of inherent factors affecting soil organic

matter• Explain the five soil organic matter management practices• Explain how soil organic matter relates to soil function• Estimate organic material needed to increase soil organic

matter• Measure soil organic matter

Soil Organic Matter • Is the organic component of soil, consisting of three parts:• Plant residues and small living soil organisms• Actively decomposing matter• Humus: Stable organic matter

Role of Inherent Factors Affecting Soil Organic Matter• Climate• Organic matter decomposes more quickly in warm and humid

climates that cool dry climates• Soil Texture• Soil aeration: more oxygen in the soil speeds up the

decomposition process • Vegetation• Prairie soils have more organic material added to the soil than

forest soils because of vegetation.

Soil Organic Matter Management• Use of cropping systems• Reducing or eliminating tillage• Reduce erosion • Soil-test and fertilize properly• Use of perennial forages

Benefits of Soil Organic Matter• Nutrient Supply• Water-Holding Capacity• Soil Aggregation• Erosion Prevention