Aggregate: Particles of soil grouped together to form structure units e.g. platy, blocky, prismatic.
Air-dried Soil: Soil exposed to the air to allow its moisture content to be approximately the same as the atmosphere.
Available Water: The part of the soil water that can be absorbed by plants.
Biotic: Pertaining to life; biological.
Cover crop: A crop used to cover the surface of the soil; mainly used to prevent soil erosion and leaching.
Furrows: Narrow trenches left in the ground after ploughing.
Horizon: Layers of soil often clearly visible in a soil profile; no two horizons have teh same characteristics.
Leaching: The process in which soluble salts are washed from the surface soil to the subsoil by means of percolation.
Oxidation: Any chemical change which involves the addition of oxygen or its chemical equivalent. May adversely affect agricultural products.
Pan: A compact, hardened, subsurface layer in a soil profile.
Percolation: The downward movements of water through the soil because of gravity.
Plant Medium: Soil material, e.g. sand, peat, moss, vermiculite in which plants are grown or cuttings rooted.
Porosity: The percentage of the volume of soil not occupied by soil particles.
Root zone: The normal depth of root penetration in the soil.
Sod: The top 3-7 cm of soil held together with grass.
Tilth: The physical state of the soil that determines its suitability for plant growth based on texture, structure, consistency and pore space.
Unavailable Water: Water that is present in the soil but that cannot be taken up by the plant roots because it is strongly absorbed onto the surface of particles.
Grade 9 SCCP Curriculum Guide