ZOOLOGY 260 Lecture Notes - Lecture 11: Soil Fertility, Pedogenesis, Volcanic Ash
2 Feb 2017
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Document Summary
Soil formation- rock weathering (wind, water, ice) Surface soils can be enriched from earth"s crust. Plant growth (from photosynthesis + atmospheric gases) above ground drops to soil surface and decomposes. Earthworms- turn over soil (tilling) by burrowing and digesting organic material; Break down large organic matter into smaller. Roots acidify the soil, promoting breakdown of inorganic nutrients from rocks. Soil is exposed to atmospheric oxygen (o2) & unprotected so weathering occurs. Plants protect themselves w/ antioxidants like vitamin c. More weathered soil is light brown/grey, less weathered is darker/richer. Chemical forces bond soil particles together to make small soil aggregates. Bacteria produce glue that sticks soil together. Biota creates water repellent in soil: water pockets contain nutrients, air pockets allow gas exchange, restricted diffusion when film is thinner than micro-organism or nutrients. Root nodules (nitrogen-fixing bacteria), mites, nematodes, roots, protozoa (fungus and bacteria) Surface litter, topsoil, subsoil, parent material (bedrock) Medium of prop production (plants/crops grow in soil)
