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Ag science preswex
Soil theory. Ag science
| Term | Definition |
|---|---|
| ideal soil composition | 25% air, 25% water, 45% mineral, 5% organic |
| humus | decomposed plant/animal matter |
| pore space | space between soil particles |
| soil texture | measure of % sand, silt and clay |
| loam soil | soil with equal amounts of sand, silt and clay |
| features of a sandy soil | well drained, low fertility, prone to drought |
| features of a clay soil | poor drainage, high fertility, poor aeration |
| factors affecting structural development | freeze thaw, wetting and drying, plant root activity |
| soil air | essential for root respiration |
| saturation point | pores are full of gravitational water |
| field capacity | water in soil after gravitational water has drained away |
| permanent wilting point | point where no more water can be removed by roots. drought |
| available water capacity | field capacity - permanent wilting point |
| red soil colour | indicates presence of iron |
| chemical reactions doubled with | every 10°c increase in soil temp. |
| chemical properties of soil | cation exchange capacity, pH |
| soil colloid | tiny particle of soil, cations stick here |
| acid soil | ph 5, granite parent material |
| basic soil | pH 7.5, limestone parent material |
| optimum pH of soil | 6.5 to 7.5 |
| soil biomass | total mass of living things in soil |
| O horizon | contains most organic matter |
| podzol | acidic, highly leached, waterlogged soils |
| iron pan | accumulation of minerals in B horizon, impermeable |
| brown earth soils | fertile, no distinct horizons, no leaching, limestone parent material |
| Gley soil | waterlogged, anaerobic conditions, poor structure, grey/blue colour |
| factors of soil formation | parent material, climate, topography, time |
| raised bog | 8-12m deep, dome shaped, pH 4-6, located in lakes |
| blanket bog | 2-3 m deep, pH 5, located in mountains and lowland west coast |