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Principles of Soils
Soil Water
| Term/Question | Definition/Answer |
|---|---|
| What are two ways water moves in soils? | Infiltration and Percolation |
| Infiltration | water movement into soil from the surface |
| Percolation Process | Downward movement of water through the soil; Permeability/speed |
| Permeability = | speed of movement |
| Field Cap | Maximum amount of water soil can store; AKA: full |
| What are the different types of water quantities in the soil? | Saturation; Field Capacity; Permanent Wilting point; Gravitational Water; Available Water Capacity |
| Saturation | soil water content when all pores are filled with water |
| Field Capacity | soil water content when plants extracted all water they can |
| Gravitational Water | amount of water held by the soil betwix saturation and field cap |
| Available Water Capacity | Amount of water held betwix field cap and wilting point; All water available to plants - last 50% extracted after stress |
| Cohesion | 1 water molecule interacting with another water molecule |
| Adhesion | 1 water molecule interacting with soil |
| Course Texture | mostly gravitational water |
| Fine texture | mostly unavailable water |
| Capillary Action | ability of soil pores to hold, and move water against gravity |
| What is capillary movement important for? | subsurface irrigaiton |
| Wetting Front | downward movement of water |
| What irrigation practices is capillary movement important for? | Drip and Furrow; The skip-row technique |
| Skipped row serves as a moisture bank | crop roots reach area later in season |
| Positive Results for milo and corn | lateral spreading roots (broad leaf, taproot) |
| Total plant population = | doesn't change |
| Must have and must be able to... | must have residue and be able to effectively control weeds |
| According to UNLs research on tillage and moisture, what is the water loss for every tilled pass compared no-till? | Tillage: 1/2 to 1 inch; No-till vs. 2 pass till saves: 3-4 inches of water |
| What are some long term no-till benefits on soil water? | Increase infiltration rates; Increase water holding capacity |
| What are two things residue and soil water improved? | Improved water capture - reduced run-off and improved water infiltration; Improved water storage - residue cover reduces evaporation losses |
| Improved soil quality (OM) = | greater water holding capacity |
| Why do soil crusts reduce water infiltration and increase runoff? | Soil not protected by cover of growing plants, residue/other materials and aggregates weak, energy cause crust to form; Individual soil particles fill pore space near surface and prevent water from entering (infiltrating) soil |
| How much can wet soil crusts reduce oxygen diffusion into the soil and what can it impact? | 50% and seed germination |
| How do soil crusts reduce surface water evaporation? | Crusts = Reflectance; Reflectance = less absorption of energy from sun; cooler surface and lower rate of evaporation |
| What soils have erosion risks when in the presence of soil crusts? | wind erosion = SAND |
| What are 3 reasons crusts form? | Bare soils surface, poorly aggregated soils - raindrop impact; Needs moisture - Freeze/Thaw Process |
| Prevention management stratagies | Plant cover; Residue cover; Improve soil aggregates: increase organic matter |
| Removal management strategies | Rotary Hoe; Pivot Irrigation |
| Erosion concerns | removing topsoil degrades soil structure |
| Removed topsoil | Looses nutrients (OM); Soil less favorable for plant growth; Can decrease root growth; Can decrease water holding capacity |
| Blowing Dust | Can effect human health and cause public safety problems; Also damage and cover small crop plants |
| Eroded soils accumulate and cause problems | Obstruct roadways; Fill drainage channels; Damage fish habitat |
| Silt = | MOST ERODIBLE |
| Eroded Nutrients accumulate in surface water bodies | Cause algal blooms; Cause late eutrophication |
| Water Erosion Causes | Exposed soil surface - soil texture (silt most susceptible); Long Steep Slopes; Long and intense rainfall/irrigation events; Low water infiltration; Low soil aggregation |
| Wind Erosion Causes | Exposed soil surface - low soil aggregation/soil temperature; High wind speeds; Long, unsettled, smooth soil surface; Little to no moisture in soil surface |
| Mechanical Erosion | Removal of soil by harvesting root crops (attached to equipment) |
| Erosion Management | No-Till: keep residue cover; Terraces: steep slopes=narrow spaces; Strip Cropping: crops grown @ different times of year; Contour Cropping; Windbreaks: permanent shelterbelts, herbaceous windbarriers; Cover Crops: living plants, +soil aggregates |
| Drainage Problem | High water table; Low spots; Poor Infiltration |
| Objective of Subsurface Drainage | Lower water table below root zone |
| Tile Drainage Field Design | Depth of line: 30-40 inches; Spacing of tile lines: 20-80 feet |
| What does tile drainage field design do? | the design connects the outlet to the drainage ditch |
| What are some concerns of the tile drainage? | Loss of wetland habitat; Increase of chemicals in rivers/streams (Nitrogen) |
Created by:
horktera
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