Soil The Rhizosphere Four distinct components of soil: Four distinct components of soil: inorganic mineral particles inorganic mineral particles water water air air organic matter organic matter Inorganic mineral particles Inorganic mineral particles sand, silt, and clay from weathered parent material (most of soil) sand, silt, and clay from weathered parent material (most of soil) Organic matter Organic matter remains of dead and decomposed organisms remains of dead and decomposed organisms Soil Layers Mite Nematode Root Protozoa Bacteria Fungus Parent material (bedrock) Subsoil Topsoil Surface litter Fig. 10-6, p. 204 Humus Soil Formation weathering processes weathering processes biological, chemical, physical biological, chemical, physical Parent material Humus Time sometimes thousands of years sometimes thousands of years Soil Texture affects drainage water holding capacity In a dry soil, a thin film of water is tightly bound to soil particles, and soil air occupies most of the pore space. Soil air Soil water Soil Nutrients affect plant growth MACRONUTRIENT MACRONUTRIENT An essential element that is required in a fairly large amount for normal plant growth An essential element that is required in a fairly large amount for normal plant growth MICRONUTRIENT MICRONUTRIENT An essential element that is required in very small amounts for normal plant growth An essential element that is required in very small amounts for normal plant growth Nutrient Cycles Soil Chemistry affects plants