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Soil!
Enviro Sci Quiz on Soil
| Question | Answer |
|---|---|
| soil | uppermost layer of Earth's crust that supports plants, animals, and microbes. |
| soil composition | 1. mineral particles 45% 2. organic material %5 3. water 25% 4. air 25% |
| mineral particles | 45%, sometimes called 'parent material,' made of weathered rock. |
| methods of rock breakdown | biological chemical physical |
| organic material | 5%, leaf litter, animal dung, dead remains of plants and animals. After much decomposition what remains is called humus. |
| pore space | air and water |
| soil air | increases aeration |
| soil water | -water to roots -from precipitation, moves down from groundwater, rises up |
| If water is not bound to soil particles or absorbed by roots, what happens? | leaches |
| leaches | it percolates carrying dissolved minerals with it |
| illuviation | some compounds (iron, etc.) humus, clay, will be deposited in lower layers of soil |
| If substances are small enough, | they completely leach out of the soil and can end up in groundwater |
| soil horizons | soils are organized into clear horizontal layers |
| u-horizon | surface layer, rich in organic material, decaying plants and animals |
| a-horizon | the 'topsoil,' dark color, rich in organic matter and humus, somewhat nutrient mineral (magnesium, iron, phosphorous etc.) poor due to leaching. |
| e-horizon | some soils have this layer, heavily leached |
| b-horizon | lighter color than a, rich in iron, aluminum, and clay. it's where leached things accumulate. |
| c-horizon | weathered pieces of rock (geyond the extent of most roots) |
| soil texture | affects soil properties |
| soil texture | relative proportion of inorganic mineral particles of: sand, silt, and clay Sand: 2mm--0.05mm Silt: 0.05mm--0.002mm Clay: <0.002mm |
| coarse textured soil (sandy) | excellent drainage, but doesn't hold minerals |
| clay soils | poor drainage, low oxygen levels in soil particles hold K+, Mg+ mineral ions for plant use. |
| soil acidity | measured with pH, usually ranges from 4 to 8, affects solubility of certain plant nutrients, optimum soil ph is 6-7 because easier to absorb nutrients. |
| five major soil groups | spodosols, alfisols, mollisols, aridosols, oxisols |
| soil separates into --- orders | 12 |
| soil subdivides into more than ----- soil series | 19,000 |
| spodosols | acidic, nutrient poor (bc leaching), usually under coniferous forests, not good farmland |
| alfisols | -brown to grey brown a-horizon -if forest is cleared fertilizer must be added to maintain fertility -temperate deciduous forest |
| mollisols | -found in temperate semi-arid grassland -very fertile soil -rich in humus -low rainfall keeps nutrient minerals in upper horizon |
| aridosols | -found in arid regions of all continents -low precipitation prevents leaching and growth of lush vegetation -a salt layer is possible |
| oxisols | -tropical and subtropical areas with high precipitation -super fast decay rate on surface -b-horizon is highly leached and nutrient poor |
| Soil erosion | soil can be removed faster than natural processes can replace it wind, water |
| why is soil erosion a problem? | causes a loss in soil fertility. More fertilizers must be used to replace nutrients lost to erosion. Accelerated by poor soil management practices |
| why and how does soil lose its fertility if used extensively for agriculture? forests don't lose their soil fertility, why? | ecosystem must be balanced |
| soil problems | often in arid and semi-arid areas salt concentrations get to levels toxic to plants (result of using groundwater) |
| desertification | degradation of once-fertile rangeland, agricultural land, or tropical dry forest into nonproductive desert |
| what causes desertification? | overgrazing, forest removal, overconsumption of water by local population, slash and burn agriculture practices, draught can contribute (but is not considered a cause and desertification can actually intensify drought) |
| conservation tillage | -residues from previous year's crops are left in place to prevent soil erosion -cut narrow furrow for seeds--leave rest of soil undisturbed -40% of Us cropland is farmed this way |
| crop rotation | planting a series of different crops in the same field over a period of years corn and soybeans (legumes) |
| contour plowing | plowing around hills, instead of up and down them |
| strip cropping | alternating strips of different crops along natural contours terracing--prevent erosion |
| organic fertilizers | animal manure, crop residue, bone meal and compost releases nutrients slowly increases water-holding capacity |
| inorganic fertilizers | -manufactured from chemical compounds -soluble -fast acting, short lasting -mobile: easily leach and pollute groundwater |
| soil reclamation | 1. stabilize land to prevent further erosion 2. restoring soil to former fertility |
| best way to pursue soil reclamation | plant a shelterbelt |
| shelterbelt | a protective layer of trees |
| soil conservation act 1935 | formed soil conservation service (now natural resource conservation service NRCS) |
| food security act (farm bill) 1985 | farmers with highly erodible soil had to hange their farming practices -institute conservation reserve program |
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st10693
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