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Soil Science Ch4
| Question | Answer |
|---|---|
| iron in it's reduced vs. oxidized state | greyish=reduced, reddish/yellow=oxidized |
| accumulation of salts and carbonates | whiteish color |
| hue | dominant spectral color of the rainbow |
| value | darkness or lightness of a color |
| chroma | relative saturation or strength of a color |
| aerenchyma | tubes that deliver oxygen down to the roots of the plant from the entire body of the plant |
| surface area is important | water retention, absorption of dissolved substances, mineral weathering rates, promotes soil aggregation, habitat for microbial growth |
| Sand: water holding, aeration, compactability | low, good, low |
| Silt: water holding, aeration, compactability | medium |
| Clay: water holding, aeration, compactability | high, poor, high |
| loam | equally balanced properties of sand silt and clay, not necessarily equal percentages |
| Disadvantage of fine textured soil as compared to crumb/granular | fine textured soil has fine pores filled with water, air not easily distributed. |
| clay/granular soil | large pores in between individual aggregates or peds |
| soil shapes | spheroidal (A)= granular/crumb. crumb is smallest. plate-like(E horizons) block like= angular or subangular (B horizons)prism-like (B)= columnar (sodium influence on clay) or prismatic (no sodium influence on clay) |
| organic matter promotes good aggregation by: | soil humus creation by microbes, binds soil together, soil organisms activity simulated, improve structure (fungi tie w fibers), protects from raindrop impact, soil does not fall apart as easily |
| glomalin | accounts for carbon in soils, holds particles together, critical for soil structure. "glue" |
| how do bacteria help with aggregation? | produce slime, polysaccharide material on outside of cells that helps hold particles together |
| relationship between cultivation/plowing and soil stability | the more plowing, the less stable the soil will be and the less organic matter and decreased infiltration rates. |
| surface crusting | after raindrop impact dries at the surface of the soil. less pores/holes in the soil. |
| bulk density | dry weight of soil per unit volume of soil |
| particle density | weight per unit volume of solid rock |
| core method of determining bulk density | sampler removes an intact cylinder of soil |
| root penetration inhibited | when bulk density ranges from 1.4 to 1.7 |
| bulk density vs. pore space (cultivated soil?) | inverse relationship. cultivated soils have high bulk density |
| Moldboard Plow | lifts the upper 20 cm of soil but compacts the next lower layer causing a plowpan to develop that roots cannot penetrate |
| Alleviate subsoil compaction: 2 methods | 1) forage radish (root has enough strength to break through so just plant these radishes) 2) heavy chisel plow, subsoiler, ripper |
| Reduce subsoil compaction | large wheels to distribute weight, walking on a board |
| No till agriculture | reccomended because maintains soil structure, organic layer on top of the soil. pizza knife slits and drop seeds in. however, must use herbicides but overall less energy useage |
| soil porosity | aggregation promotes good porosity for finer textured soils |
| aggregation helps soil porosity by... | increasing macropore space. microp pores are waterfilled and restrict aeration bc it is difficult for oxygen to diffuse through them |
| macro/micropores in relation to aggregates | macropores are between aggregates while micropores are within aggregates |
| macropores | so big that they cannot hold water against force of gravity, provide aeration |
| well aggregated vs compacted soil | well aggregated= equal amounts of micro/macropores compacted= macropore space between the aggregates becomes micropore space, much less macropore space |
| tilling is bad because... | dramatically decreases macropores in soil. decreases amount of organic matter because it breaks things up creating more surface area etc. |
| Soil types likely to be poorly aerated | poorly drained, high clay content after rainfall, deep subsoils in clayey soils (when wet), highly compacted fine textured soils, massive unstructured deep clay |
| PAM | polyacrylamide can stabalize soil aggregates |
| soil tilth | the physical condition of a soil in relation to plant growth: incorporates aggregate formation/stability, bulk density, soil moisture, aeration, water inflitration rate, drainage |
| ways to make soil good, have good soil tilth | adding organic mattter to make more humus, minimize tillage, sod crops w more fibrous root systems to support structure, manure/cover crops (to later form humus) |
Created by:
mlux
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