7234508
| Question | Answer |
| Microbial symbiont with grasses | Arbuscular mycorrhizae |
| Microbial symbiont with Azolla | Anabaena |
| Microbial symbiont with pine trees | Ectomycorrhizae |
| Microbial symbiont with Lichen | blue-green alga |
| Microbial symbiont with actinorhizal plants | Frankia |
| Microbial symbiont with leguminous plants | Rhizobium |
| Ochric | Pale, thin, low in organic C |
| Natric | accumulation of silicate clays and <15% of exchangeable Na |
| Umbric | similar to mollic but has a lower base cation saturation |
| Histic | organic material (20-60cm) overlying mineral soil |
| Spodic | accumulation of illuvial humus and aluminum oxides |
| Kandic | accumulation of Fe and Al oxides and kaolinite |
| Oxic | highly weathered, high in Fe and Al oxides and kaolinite, humid tropical regions |
| Albic | light colored eluvial horizon, Fe and Al oxides have been removed |
| Xeric | Cool, moist winters and warm dry summers with drought conditions. “Mediterranean” climate |
| Aridic | Soil dry for at least half the growing season and moist for <90 consecutive days. |
| Ustic | Soil moisture intermediate between Udic and Aridic. Some plant available water during growing season but drought may occur. |
| Udic | Soil moisture is sufficient for plant needs year-round |
| Aquic | Soil is saturated with water and anaerobic for long enough to show soil indicators of poor aeration |
| subordinate horizon designation "p" | plowed |
| subordinate horizon designation "t" | accumulation of clay |
| subordinate horizon designation "h" | concentration of humus |
| subordinate horizon designation "k" | accumulation of carbonates |
| subordinate horizon designation "g" | gleyed -prolonged wetness |
| Histosol | • Layered organic materials •Cool, wet environments at high latitudes or in wetlands • Histic epipedon* • No permafrost |
| Entisol | • Little or no horizon development • Characteristics reflect varied parent materials • Very dry or cool climates, unstable landscape positions, or resistant parent material |
| Andisol | • Form in recent (5,000 – 10,000 yrs) volcanic ejecta •Generally high in natural fertility • Easily wind eroded |
| Inceptisol | • Beginning horizon development • Often found in mountainous areas |
| Aridisol | • Arid climates • Ochric A • Often CaCO3 or Na salt accumulations • May have Bt formed during wet climate |
| Vertisol | • High content of shrinking/swelling clays • Ca and Mg rich parent materials • Contain ‘slickenslides’ - smooth surfaces created as the subsoil masses move past each other and smear the clay. • Fertile; high CEC; high OM |
| Mollisol | • Highly fertile soils of grasslands • Mollic A • Bt (argillic) • Often calcic (Ck) horizons |
| Alfisol | • Form mainly under deciduous forests • Ochric A horizon • Often E horizon • Argillic horizon (Bt) |
| Ultisol | • Form on old stable land surfaces • Usually tropical forest vegetation • Warm humid climate • Umbric or ochric A; Bt; often E |
| Spodosol | • Form in sandy materials under coniferous forests • Usually in wet, cool climates • Albic and spodic horizons |
| Oxisol | • Most highly weathered soils • Form in hot, humid climates • Oxic B • Low natural fertility and high soil acidity |
| Immobilization | ammonium-N and nitrate-N are incorporated into living tissue |
| Mineralization | releases soluble nitrogen as the result of the breakdown of nitrogen-rich organic compounds |
| Nitrification | NH4 is changed to NO3 by bacteria |
| Volatilization | loss of N by the conversion of NH4 to N gas |
| Denitrification | reduction of NO3 to nitrogen gas by microorganisms occurring under anaerobic conditions |
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