soil physics with hydrus: chapter 1

Soil Physics with HYDRUS: Chapter 1

Equations, Tables, and Figures

1.1 – 1.5

v v v vg l s

1 avvs

avvg

vvl

a

1.6 – 1.10

m m m mg l s

ss

s

mv

bsmv

1 b

s

2( )18

s w d gV

1.11 – 1.13

gdhtws

2)(18

s

s

ma

s

sCEC

TABLE 1.1Approximate charge characteristics of soil colloids (Brady and Weil, 2008)

Colloid Type CEC AECcmolc kg-1 cmolc kg-1

Organic matter 200 0Smectite 100 0Vermiculite 150 0Fine-grained micas 30 0Chlorite 30 0Kaolinite 8 2Aluminum oxide 4 5Iron oxide 4 5Allophane 30 15

TABLE 1.2Specific surface area range for selected colloids (Skopp, 2000)

Colloid sm2 g-1

Kaolinite 15-20Illite 80-100Bentonite 115-260Montmorillonite 280-500Crystalline iron oxides 116-184Amorphous iron oxides 305-412Organic matter 560-800

TABLE 1.3Specific surface area for bulk soils (Skopp, 2000)

Soil Textural Class sm2 g-1

Sands <10loams and silt loams 5-20Clay loams 15-40Clays >25

TABLE 1.4Size classes of soil structure (Soil Survey Manual, 2008)

Size Class Platy† Prismatic or Columnar

Blocky Granular

Mm Mm Mm mmVery fine <1 <10 <5 <1Fine 1-2 10-20 5-10 1-2Medium 2-5 20-50 10-20 2-5Coarse 5-10 50-100 20-50 5-10Very Coarse >10 >100 >50 >10

TABLE 1.5

Cecil soil series description (plot 4 from Bruce et al., 1983)

Horizon Depth Textural Class Structure Colorcm

Ap 0-21 Loamy sand Weak, medium granular

Brown

BA 21-26 Clay loam Weak, medium,

subangular blocky

Red

Bt1 26-102 Clay Strong, medium,

subangular blocky

Red with few strong brown mottles

Bt2 102-131 Clay Strong, medium,

subangular blocky

Red

BC 131-160 Clay loam Weak, medium,

subangular blocky

Red

C 251+ Sandy clay loam Massive Red with light red and weak red mottles

Figure 1.1 The United States Department of Agriculture (USDA) and International Soil Science

Society (ISSS) classification systems for soil particle size fractions (Hillel, 2004).

Figure1.2 Textural triangle, showing the percentages of clay (< 0.002 mm), silt (0.002-0.05 mm), and

sand (0.05-2.0 mm) in the conventional soil textural classes (Hillel, 2004)

Figure 1.3 Particle size distribution of a clay, loam, well-graded sand, and poorly-graded sand (Hillel,

2004).

Figure 1.4 A soil aggregate broken open along a failure zone.

Figure 1.5 Strong, thin, platy structure (Soil Survey Division Staff, 1993).

Figure 1.6 Strong, medium, prismatic structure (Soil Survey Division Staff, 1993).

Figure 1.7 Strong, medium, coarse angular blocky structure (Soil Survey Division Staff, 1993).

Figure 1.8 Strong, fine, medium granular structure (Soil Survey Division Staff, 1993).

Figure 1.9 Nashville silt loam soil profile (Soil Survey Division Staff, 1993).