Soil Physical Properties ESRM 311 SEFS 507

Transcription

1 Soil Physical Properties ESRM 311 SEFS 507

2 How are soils formed??? c/notes/chap4.wc/soils/how.soil.is.made.jpg 2

3 Weathering s Physical Influence on Soil Directly Texture - sand, silt, clay Structure Porosity Consistency Aeration Temperature Moisture Indirectly Bulk density Color 3

4 Horizons Color Texture Structure Consistence Bulk Density Soil Physical Properties

5 Weathering s Visual Influence on Soil: Soil Layers/Horizons 5

6 Soil Color Depicts OM brown or black, moisture moist is darker, and parent material eg, if Fe: salts - lighter,?? Affects temperatures aerobic = red, or anaerobic = gray/blue Indirectly, if OM, it affects nutrients, moisture, etc??? 6

7 Soil Color 7

8 Texture Soil texture refers to the proportion of the soil separates that make up the mineral component of soil (fine earth fraction < 2mm). These separates are called sand, silt, and clay. These soil separates have the following size ranges: Sand = <2 to 0.05 mm Silt = 0.05 to mm Clay = <0.002 mm % sand, silt and clay 8

9 Texture 9

10 10 Soil Structure The soil separates can become aggregated together into discrete structural units called peds. These peds are organized into a repeating pattern that is referred to as soil structure. Between the peds are cracks called pores through which soil air and water are conducted. Soil structure is most commonly described in terms of the shape of the individual peds that occur within a soil horizon.

11 Soil Structure 11

12 12 Soil Structure Aggregate: Soil particles glued together with organics and/or clays and oxides.

13 Soil Structure 13

14 Soil Structure 14

15 Soil Structure 15

16 Soil Structure aggregates 16

17 Soil Consistence Soil consistence refers to the ease with which an individual ped can be crushed by the fingers. Soil consistence, and its description, depends on soil moisture content.

18 Soil Consistence Terms commonly used to describe consistence are: Moist soil: loose noncoherent when dry or moist; does not hold together in a mass friable when moist, crushed easily under gentle pressure between thumb and forefinger and can be pressed together into a lump firm when moist crushed under moderate pressure between thumb and forefinger, but resistance is distinctly noticeable Wet soil: plastic when wet, readily deformed by moderate pressure but can be pressed into a lump; will form a wire when rolled between thumb and forefinger sticky when wet, adheres to other material and tends to stretch somewhat and pull apart rather than to pull free from other material Dry Soil: soft when dry, breaks into powder or individual grains under very slight pressure hard when dry, moderately resistant to pressure; can be broken with difficulty between thumb and forefinger

19 Soil Bulk Density Bulk density is the proportion of the weight of a soil relative to its volume. It is expressed as a unit of weight per volume, and is commonly measured in units of grams per cubic centimeters (g/cc) or tons per cubic meter (Mg/m 3 ). Bulk density is an indicator of the amount of pore space available within individual soil horizons as well as compaction.

20 Soil Bulk Density The average particle density of mineral soil material is 2.65 g/cc

21 Root structure belowground

22 Many counties in the U.S. have a Soil Survey produced by Natural Resources Conservation Service (NRCS) Soil Surveys Maps Profile descriptions Tables on soil properties: physical, chemical, engineering, land capabilities, plant growth 22

23 ALDERWOOD SERIES The Alderwood series consists of moderately deep to a cemented pan, moderately well drained soils formed in glacial till. Alderwood soils are on glacially modified foothills and valleys and have slopes of 0 to 65 percent. The average annual precipitation is about 40 inches, and the mean annual temperature is about 50 degrees F. TYPICAL PEDON: Ap--0 to 7 inches; very dark grayish brown; gravelly ashy sandy loam; moderate fine granular structure; slightly acid (ph 6.2). (3 to 7 inches thick). Roots? Bs1--7 to 21 inches; dark yellowish brown; very gravelly ashy sandy loam; weak medium subangular blocky structure; slightly acid (ph 6.2). Bs2--21 to 30 inches; dark brown; very gravelly ashy sandy loam; weak medium subangular blocky structure; slightly acid (ph 6.2). (Combined Bs1 and Bs2 horizons are 15 to 30 inches thick) 2Bs3--30 to 35 inches; 50% olive/yellowish brown and 50% dark greyish brown; very gravelly sandy loam, some cemented fragments, massive; moderately acid (ph 6.0). (0 to 15 inches thick) 2Bsm--35 to 43 inches; dark grayish brown cemented layer that crushes to very gravelly sandy loam; massive; 40 percent pebbles; moderately acid (ph 6.0). (5 to 20 inches thick) 2Cd--43 to 60 inches; grayish brown compact glacial till that breaks to very gravelly sandy loam; massive; extremely hard; 40 percent pebbles; moderately acid (ph 6.0).

24 Soil Survey Maps What are the site conditions? You have never been there What would you expect Soil survey mapping Paper Digital

25 About the Surveys Soil Survey Geographic (SSURGO) Data Base consists of 1:12,000 to 1:63,360 scale detailed local soils data Entire country over 3,000 individual surveys County area or sub-area Soil Attributes Unit description: parent material, horizons and textural properties Engineering properties, farming attributes, erosion many different attributes captured

26 How to get the Data Find the paper copy of the survey Online resources Web Soil Survey (WSS) Individual Soil Surveys NRCS Geospatial Data Gateway Bulk Download UC Davis smartphone app Your location Download data into: GIS

27 Example Bridle Trails State Park (Kirkland) Imagine: capstone project about Douglas Fir Need to know about soils, no GIS software? Use Web Soil Survey

28 Soil Mapping Major Soil Units Alderwood sandy loam Soil texture

29 Dive In Additional soils information Unique soil properties Overview Many ways to get soil surveys Useful information Cover more on this resource next week