About Lesson
Bulk Density:
- Soil bulk density is the mass per unit bulk volume of soil that has been dried to a constant weight at 105°C.
- e. Bulk density = Weight of dry soil (g)/ volume of dry soil (cm3)
- Bulk Density (Db) is the mass of dry soil per unit volume, including pore spaces.
- It influences soil compaction, porosity, root growth, and water movement.
Factors Affecting Bulk Density (Db)
- Texture:
- Fine-textured soils (e.g., silt loams, clays) have lower bulk density due to higher organic matter content and greater pore space.
- Sandy soils have higher bulk density because of minimal organic matter and closely packed particles.
- Organic Matter (OM) / Humus:
- Humus binds soil particles into aggregates, increasing pore space and reducing bulk density.
- Surface soils with high OM have lower Db
- Soil Depth:
- Surface soil has lower Db due to higher organic matter content and plant root activity.
- Subsoil has higher Db due to compaction, reduced organic matter, and fewer roots.
- Nature of Crops:
- Grasses reduce Db by binding soil particles with their roots and adding organic matter through dead roots.
- Cultivated crops (e.g., potatoes) increase Db due to excessive tillage, which destroys aggregates and accelerates OM decomposition.
- Animal Trampling & Heavy Machinery:
- Animal trampling, especially in wet conditions, increases soil compaction and Db by reducing pore spaces.
- Heavy machinery (e.g., tractors) also compacts soil, restricting water infiltration, root penetration, and aeration, hindering plant growth.