| A | B |
|---|
| Soil | a complex plant-supporting system made up of minerals, organic matter, air, and water. |
| parent material | the base geologic material in a particular location. It can be lava or volcanic ash; rock or sediment deposited by glaciers; sand dunes; sediments deposited by rivers, in lakes, or in the ocean; or bedrock. |
| bedrock | the continuous mass of solid rock that makes up Earth’s crust. |
| Weathering | Physical and chemical breaking of rocks and minerals into smaller pieces |
| Physical weathering | the natural break up of rock without chemical change. |
| Chemical weathering | when water and other substances chemically break down parent material and rocks, transforming them into different material. |
| Decomposition | Breakdown of waste, organisms, and organic material into simple molecules that are added to the soil. |
| Leaf litter | leaves dropped by deciduous trees are broken down by decomposers and detritivores. The nutrients become part of the soil. |
| O horizon | the litter layer |
| topsoil | consists of mostly mineral particles such as weathered parent material mixed with organic matter and humus from the O horizon |
| Leaching | the process whereby solid particles suspended or dissolved in liquid are transported to another location. |
| Clay | particles less than 0.002 millimeter in diameter |
| Silt | particles 0.002-0.05 millimeters in diameter |
| Sand | particles 0.05-2 millimeters in diameter |
| Loam | soil with a relatively even mixture of sand, silt, and clay |
| Structure | describes the arrangement of soil particles; “clumpiness” |
| pH | a soil’s acidity or alkalinity affects its ability to support plant growth. |
| Soil degradation | the deterioration of the soil characteristics needed for plant growth or other ecosystem services |
| Erosion | the process by which material, such as topsoil, is moved from one place to another |
| Intercropping | Different crops mixed together; provides more plant cover than a single crop; reduces a field’s vulnerability to insects and diseases; |
| Crop rotation | Crops are alternated; returns nutrients to the soil; breaks pest and diseases cycles |
| Cover crops | planted after a field has been harvested; helps prevent erosion and restore fertility. |
| Shelterbelts | Tall trees or perennials are planted along the edge of a field to block wind. |
| No-till | tractor pulls a drill that cuts a furrow through weeds and crop remains and topsoil; seeds are fertilizer are dropped into furrows and they are closed. |
| Reduced-tillage | disturbs the soil slightly more than no-till |
| Terracing | Steep slopes turned into “steps”; labor intensive but the only way to farm mountains |
| Contour farming | Planting perpendicular to hill’s slope; plowed furrows follow contours of the land and the downhill side of each furrow acts as a dam that catches soil before it is carried away |
| Ranching | the raising and grazing of livestock. |
| Desertification | Loss of more than 10% of soil productivity |
| salinization | buildup of salts in upper soil horizons. |
