290 likes | 1.36k Views
Physical Properties of Soils. Introduction to Agriculture. Soil Texture. Minerals in the soil come in many sizes and are generally classified as: Coarse particles - anything in the soil larger than 2 mm Fine particles - less than 2 mm SAND 2.0-0.05 mm SILT 0.05-0.002 mm
E N D
Physical Properties of Soils Introduction to Agriculture
Soil Texture • Minerals in the soil come in many sizes and are generally classified as: • Coarse particles - anything in the soil larger than 2 mm • Fine particles - less than 2 mm • SAND 2.0-0.05 mm • SILT 0.05-0.002 mm • CLAY Less than 0.002 mm
Textural Classes • Soil texture is the percentage of sand, silt and clay in the soil • Sandy Soils – 70% sand or more • Silty Soils – 80% silt or more • Clay Soils – 40% clay or more • Loam Soils – perfect mix of sand, silt and clay, most desirable for growing crops
Soil Triangle • A soil triangle is a chart that shows the soil texture class based on the percentage of sand, silt and clay • How to read a soil triangle: • Must know % of at least two particle sizes • Read along lines to where two % meet • CLAY (across) → • SILT (down) ↓ • SAND (up) ↑
Soil Color Black-Brown Yellow-Red White-Light Grey Bluish-Grey
Soil Structure • Soil structure is the arrangement of particles in the soil • Structure affects aeration, water movement, heat transfer, and root growth • Granular is ideal for agriculture, allows for maximum pore space
prismatic granular columnar blocky platy single grained massive
Soil Tilth • Soil tilth is the workability of the soil based on texture, structure and some other factors • Soil moisture and compaction play a role • Often due to over-working the soil and preventing root penetration
Review Questions • Name the 3 soil texture particles. Which is the largest? Which is the smallest? • What is soil texture? • What affects does soil structure have? • Define soil tilth. Why is good soil tilth important?
Review Questions • Which soil type (particle) has the best drainage and density? Why? • A soil that is 20% sand, 30% silt, and 50% clay has what texture? • A soil that is 10% sand, 55% silt, and 35% clay has what texture? • A soil that is 60% sand, 10% silt, and 30% clay has what texture?