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Soils – Nebraska’s Envirothon William C. (Chuck) Markley Resource Soil Scientist – North Platte, NE.

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Presentation on theme: "Soils – Nebraska’s Envirothon William C. (Chuck) Markley Resource Soil Scientist – North Platte, NE."— Presentation transcript:

1 Soils – Nebraska’s Envirothon William C. (Chuck) Markley Resource Soil Scientist – North Platte, NE

2 Soil = Sand: That mineral part of a soil that you can feel as “gritty” Silt: That mineral part of a soil that is powdery when dry and slick when wet Clay: That mineral part of a soil too small to be seen without a microscope, but gives the soil a sticky feel— when wet; and to become brick hard when dry. + Organic Matter: The non-mineral part of a soil that gives it dark color, aggregate strength and fertility

3 Physical Properties Texture: Percent of sand, silt and clay. (see textural triangle to make a list of textures) Structure: The form or shape of the individual soil aggregates or “peds” –this property is directly related to the aging process within the profile Aggregation: Created by the weathering process, pedoturbation by roots, insects & freeze-thaw; & from coatings from organic matter decomposition Consistence: Resistance of aggregates to rupture from applied stress & degree of cohesion/ adhesion Bulk Density: How tightly the soil particles are packed together (Increased B.D. slows H2O percolation) Soil Color: Shades of tan, brown, black, white, gray, red, or blue(green) Available Water Capacity: Total field capacity (saturation) minus non-available high-tension water held by the soil particles (sands—least AWC; silt loams—greatest AWC)

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5 Structure

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7 Consistence Loose, blowing fine sand (lost during a single wind storm)

8 This was a germinated field of wheat! This guy lost some soil and some wheat because he didn’t understand soil consistence, but a neighbor’s field a few miles away caused a major crash on I-80 during this same storm: People died!

9 Soil Properties—Bulk Density Things that increase Soil Bulk Density: Tillage (disking/plowing): a dense pan forms underneath the coulters and shears after repeated tillage operations Wheel/hoof/pedestrian traffic: the weight of traffic over the soil can compress or completely crush the soil aggregates to a depth of as much as 24 inches (combines/grain carts) Natural Settling: following a disturbance (loss of excessive macro-pores) Liquid Compaction: used in building dams—can obtain up to 95% compaction in conjunction with mechanical compaction Any time soil is disturbed (whatever it is) when very moist or wet. (Dry soil is much less susceptible to compaction.)

10 Soil Properties—Color Tans: Normal color of fresh parent material in most Nebraska soils [exceptions: sandstones and shales] Dark browns: Surface color of grassland soils: (humic acids from decomposed O.M. cause the darkening of surface soils) Black: Wet soils, (usually high in O.M. like on floodplains) White: Washed Quartzitic sands; very high calcium carbonates and/or bicarbonate of soda coat soil peds with whitish coatings Gray: Wetness (also parent material color—shales); high calcium + wetness Red: Oxidized iron (rust stains) from intermittent reduction and saturation; (also parent material color—sandstones) Blue, Blue-green: Prolonged inundation/saturation—iron and other metals are reduced producing the blue or blue-green color

11 Soil Properties—Aggregation Crop Residues  Organic matter  humus  humic acids Coatings of exudates -- larger aggregates Fungal hyphae -- large weak aggregates Root massing -- large weak aggregates Humic acids -- electrically bonded to clay micelles – small, very strong aggregates

12 Soil Profile A Horizon: Surface horizon—every soil has an A horizon, which is usually darker than other horizons from additions of organic matter, (except fresh sediments on a floodplain or foot-slopes may be light colored). It has granular structure. B Horizon: This horizon forms in older soils where clay has illuviated (trickled down) into this horizon from above. It has sub-angular blocky and prismatic structure. C Horizon: This is the parent material. Little or no structural development has occurred (massive or single-grain). A 2C horizon occurs where there has been a lithological discontinuity (or depositional change). Every soil has a C horizon at some depth. CR or R Contact: This is the depth (w/in rooting zone) at which bedrock or sedimentary rock is contacted. Root penetration is stopped.

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14 Soil Landscapes Upland: Nebraska’s uplands may have formed in residuum (bedrock derived), glacial till, outwash, loess (wind-blown deposits) or very old alluvium Sandhills: These are wind-blown sediments that have dune and interdune topography. The sand was saltated (rolled, bounced) into place rather than carried aloft by wind. Tableland: This landscape differs from uplands primarily in its broad, relatively low relief across the entire interfluve (between river & stream valleys) River Valley: Caused by down-cutting of rivers and streams. Typically have a flood plain and terrace(s).

15 Southwest Nebraska Upland – Frontier County

16 Another Upland landscape in Frontier County

17 Sandhills landscape – McPherson County Overgrazed corner—Logan County

18 Tablelands landscape – Perkins County

19 Valley landscape – Lincoln, Co.

20 Valley landscape – Lincoln County Marsh –very poor drainage Wetland—very poor drainage Wet-Subirrigated – poorly drained Subirrigated – somewhat poorly drained Sandy lowland—mod. well drained

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22 Tablelands Uplands SandhillsTablelands Sandhills

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24 Public Land Survey

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26 Hydric Soils From ‘hydra’ – “water” or wet soils Are saturated, flooded or ponded (anaerobic conditions) within the surface 12 inches for significant periods during the growing season Have redoximorphic concentrations (rust spots [metals oxidized] within the matrix, on ped surfaces, or along root channels, or Are gleyed (gray, blue or bluegreen) [metals reduced] throughout the matrix Can support & favor the dominance of hydrophitic vegetation

27 Redoximorphic Concentrations Root Channel (end) Surface of “peds” Root Channel (side)

28 Erosion and Sedimentation Erosion: The loss of fertile, well aggregated surface soils by wind or water removal Sedimentation: The accumulation (deposition) of fertile and non-fertile sediments of structureless soil by wind or water agents

29 Sheet Rill Gully Erosion Sheet and Rill Rills

30 Erosion Sedimentation

31 2004 Dust Storm – Kansas (Wind Erosion)

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