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Principles of Soils
Physical Properties of Soils
| Term/Question | Definition/Answer |
|---|---|
| Soil Health | physical properties (visual, feel, strength), Chemical Properties, biological properties |
| Soil Depth | Depth of A/B horizons deeper soils more productive Can affect road/home construction |
| productivity of deeper soils | roots won't grow through bedrock, more important during stress conditions |
| affects of road/home construction | blasting bedrock is expensive |
| Soil Texture | size of mineral particles |
| What are some influences on soil texture? | water holding ability, water penetration(infiltration), root growth, nutrient holding ability, and aeration |
| sand | 2.0-.05 mm |
| silt | .05-.002 |
| clay | .002>less than |
| What are the names of soil textures based on? | soil texture triangle; combinations of sand, silt, clay, and loam |
| What does the soil texture triangle show? | the % sand silt and clay |
| What are some properties of loamy soils? | exhibits properties of sand, silt, and clay equally; though clay percentage is less since clay properties strongly expressed |
| Pros of Sandy soils | more oxygen levels, better aeration, less compactable, better water infiltration |
| Cons of Sandy soils | doesn't hold water, doesn't hold nutrients well, erosion challenges |
| Pros of Silt | Highest plant available water, good aeration/nutrient holding capacity |
| Cons of Silt | most erodible |
| Pros of Clay | holds water, holds nutrients, low erosion |
| Cons of Clay | low water infiltration, runoff, poor drainage, poor aeration |
| Soil Structure | arrangement of soil particles into larger units, called aggregates that are naturally occurring (not clods), and may or may not be visible |
| What is the importance of soil structure? | improves water infiltration, water holding capacity, reduces erosion potential, improves pore space for aeration and roots |
| SS: Blocky | .5-2" aggregates; Primarily B Horizons |
| SS: Granular | size like bread crumbs/cottage cheese; best for plant growth; A Horizons, what you want to see in A Horizon |
| SS: Platy | surface/E Horizon; large, visible, horizontal plates |
| SS: Prismatic/columnar | most common in "B" Horizon; about 2" diameter, 8-15" long |
| Structureless: Single Grain | common in very sandy soils |
| Structureless: Massive | single soil mass; high clay soils w/ little to no OM dry soils = cracks |
| Destroyed Soil Structure | Puddled, soils high in clay; trampled/plowed when wet; similar to massive |
| Soil Structure Formation: What are some natural substances that cause particles to stick together? | Organic Matter (most important), clay particles, chemical charges in soil (+-); little bit of clay helps stick together |
| What are some soil structure formation processes? | freezing/thawing, wetting/drying, insects, microbes/root growth |
| Destruction of soil structure | tillage is the number 1 destroyer; heavy rains can expose soils |
| Porosity | fraction of soil volume consisting of pore space; available for water or air |
| Bulk Density | weight of soils solids per unit volume of soil; inversely related to porosity |
| Tillage vs. Bulk Density | tillage destroys soils structure/OM and causes loss of pore space |
| What causes soil compaction? | tillage/heavy equipment |
| What are some of the damages caused by soil compaction? | soil structure, increased bulk density, decreased available water, restricts roots/nutrient deficiencies; reduces soil aeration, reduces water infiltration, increases erosion, increases surface runoff |
| What are 5 ways to manage soil compaction? | Reduce wheel traffic (drive in same tracks) reduce tillage; no-till deep ripping - temporary solution Increase crop diversity/intensity; cover crops/more days with roots stay off wet soils |
| What four things relate to soil color? | organic matter content mineral content soil drainage climate |
| Organic Matter content | dark brown/black topsoil high fertility |
| Poor Drainage | Blueish Gray (blotches of different color) |
| Leached layers/salts | white to light gray |
| What three color factors is the Munsel system based on? | Hue - color wavelength Chroma - color purity Value - color lightness/darkness |
| Soil temp | more buffered than air temp; most important for seed germination, crop emergence, and root growth |
| What are some factors that affect the warming of soils? | soil organic matter content soil water content soil color soil texture soil residue cover plant shading |
| What are some factors that cause the cooling of soils? | heat lost through radiation - sun sets, soil loses the heat which soils will lose heat fastest - tilled/bare soils |
| no microbial activity below | 32 degrees Fahrenheit |
| activity slows significantly at | 50 degreed Fahrenheit |
| seeds may rot if | soil moisture too high/too cool of soils |
| slow emergence may be caused by | soil temps below optimum temperature; more opportunity for disease/death |
| as the temp decreases the | root growth also decreases; can affect seedlings from getting nutrients; use of starter fertilizers recommended |
Created by:
horktera
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