Layers of soil (soil horizons) soil profile Surface litter – fallen leaves and partially decomposed organic matter Topsoil – organic matter, living organisms, and rock particles Zone of leaching - dissolved or suspending materials moving downward, minerals may leach quickly and deprive plants of nutrients Subsoil – larger rock particles with organic matter, and inorganic compounds Weathered parent material – rock that has undergone weathering Bedrock – solid rock layer

Topsoil is richer in organic matter than the other soil layers; without it plants cannot grow Particle size increases down

Soil Characteristics Color Texture Darker soils means richer in humus and nutrients Use as indicator of soil’s fertility Texture Based on particle size Clay, silt, and sand (smallest to largest) Loam – even mixture of the 3 particle sizes Influences workability because of how porous it is Finer the particle size, less space and harder for air and water to travel through Silty soil or loamy material is best for plant growth

Soil Characteristics (continued) Structure Arrangement of particles – “clumpiness” Clumpy soil has more humus and is more rich in nutrients Too clumpy may prevent plant roots from growing pH Plants die if soil is too acidic or too alkaline Acid precipitation and leaching can affect pH

Learning Target To understand ways to prevent soil degradation and why they will prevent soil degradation

Land degradation occurs when human activity or natural processes damage land so that it can no longer support plant growth or other ecosystem services

Erosion #1 cause of land degradation Can help create soil through deposition Takes away the topsoil Humans cause this through overgrazing, clearing forests on slopes, clear-cutting, and leaving soil bare after harvests

Farming Practices for Soil Conservation Plants slow wind and water roots hold soil in place and absorb water Intercropping Crop rotation Cover crops Shelterbelts Conservation tillage Terracing Contour farming soil conservation

Intercropping Planting crops in mixed arrangements More plant cover Less vulnerable to insects and disease

Crop rotation Alternate crops grown in a field Returns nutrients to soil Breaks disease and pest cycles Prevents erosion