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Soil Science Formulas

This document defines 10 key formulas used in soil science: 1) Formula for calculating soil texture using the hydrometer method. 2) Formula for correcting hydrometer readings based on temperature differences. 3) Formula for calculating bulk density based on dry soil mass and total volume. 4) Formula for calculating particle density based on solid mass and volume.

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1K views2 pages

Soil Science Formulas

This document defines 10 key formulas used in soil science: 1) Formula for calculating soil texture using the hydrometer method. 2) Formula for correcting hydrometer readings based on temperature differences. 3) Formula for calculating bulk density based on dry soil mass and total volume. 4) Formula for calculating particle density based on solid mass and volume.

Uploaded by

gljae479
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Topic or Computing Meaning of Each

Formula
for… Legend
V = velocity of settling
1. Soil Texture(basis of 2 K = constant to correct for the
V =KD
hydrometer method) effect of temperature
D = diameter of soil particle
CF = correction factor
2. Correction Factor OHRb = observed hydrometer
reading of blank solution
(only used if Ts ≠ Tb;
CF=OHRb +0.36 (T s−T b ) Ts = temperature of soil
temperature should suspension
be in °C) Tb = temperature of blank
solution
CHRs = corrected hydrometer
reading of soil suspension
3. Corrected
CF = correction factor
hydrometer reading CHR s=OHR s−CF
OHRs = observed hydrometer
for soil suspension reading of soil suspension

Ms Ρb = bulk density, g/cm3


4. Bulk density ρb = Ms = oven dry mass of soil, g
Vt Vt = total volume of soil, cm3
Ms Ρs = particle density, g/cm3
5. Particle density ρ s= Ms = mass of solids, g
Vs Vt = volume of solids, cm3
ρb Ρb = bulk density, g/cm3
6. Percent pore space or
%E=(1− )×100 Ρs = particle density, g/cm3
porosity ρs %E = porosity
Hw = height of water
θv = moisture content by
volume
Ht = height/depth of soil
7. Depth of water; H w =θ v × H t
GW = groundwater
Available GW =Sat−FC Sat = saturation
water/moisture AW=FC −PWP FC = field capacity of soil
AW = available water
PWP = permanent wilting point
of soil
Mw %θm = percent moisture content
% θ m= ×100 by mass
8. Moisture content as Ms
Mw = mass of water
percent by mass(%θm) (M t −M s ) Ms = oven dry mass of soil solids
% θ m= ×10 0
Ms Mt = mass of fresh soil sample
9. Moisture content as %θv = percent moisture content
percent by ρb by volume
% θ v =% θm × %θm = percent moisture content
volume(%θv) ρw
by mass
Ρb = bulk density of the soil
Ρw = density of water
10. Cation exchange Summation of all adsorbed
capacity(CEC) cations
Σ Bases
11. Base saturation %BS= ×100
CEC

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