| Symbol | 
description | 
Units | 
| C | 
concentration | 
kg m-3 | 
| Cv | 
soil heat storage capacity | 
J m-3 °C-1 | 
| d | 
diameter | 
m or cm | 
| D | 
diffusivity (or diffusion coefficient) | 
m2 s-1 | 
| Ds | 
diffusion coefficient, of solutes | 
m2 s-1 | 
| f | 
porosity or total porosity | 
m3 m-3   or cm3 cm-3   or % | 
| fa | 
porosity, air-filled | 
m3 m-3   or cm3 cm-3   or % | 
| fw | 
porosity, water-filled | 
m3 m-3   or cm3 cm-3   or % | 
| H | 
soil water potential, total | 
KPa or m of water | 
| hg | 
soil water potential, gravimetric | 
KPa or m of water | 
| hm | 
soil water potential, matric | 
KPa or m of water | 
| ho | 
soil water potential, osmotic | 
KPa or m of water | 
| hp | 
soil water potential, pressure | 
KPa or m of water | 
| J | 
diffusion flux (Fick’s law) | 
mg m-2 s-1 | 
| K | 
hydraulic conductivity | 
m s-1 | 
| Ks | 
hydraulic conductivity, saturated | 
m s-1 | 
| M | 
mass | 
kg or g | 
| Mg | 
mass of gas | 
negligible | 
| Ml | 
mass of liquid | 
kg or g | 
| Ms | 
mass of solid | 
kg or g | 
| Mt | 
mass, total | 
kg or g | 
| q | 
flux density | 
 | 
| qs | 
flux, solutes | 
kg m-2 s-1 | 
| qw | 
flux density, soil water | 
m s-1 | 
| R | 
radius | 
m or cm | 
| T | 
temperature | 
°C | 
| t | 
time | 
s | 
| V | 
volume | 
m3  or cm3 | 
| Vt | 
volume, total | 
m3  or cm3 | 
| Vs | 
volume of solids | 
m3  or cm3 | 
| Vl | 
volume of liquid | 
m3  or cm3 | 
| Vg | 
volume of gas | 
m3  or cm3 | 
| x | 
distance | 
m or cm | 
| z | 
depth | 
m or cm | 
| ρ | 
density | 
kg m-3 | 
| ρb | 
dry bulk density | 
kg m-3  or g cm-3 | 
| ρp | 
particle density | 
kg m-3  or g cm-3 | 
| ρl | 
density of liquid (soil water) | 
kg m-3  or g cm-3 | 
| θ | 
soil water content | 
% | 
| θw | 
gravimetric soil water content | 
kg kg-1  or g g-1 | 
| θv | 
volumetric soil water content | 
m3 m-3   or  cm3 cm-3 | 
| λ | 
thermal conductivity | 
J m-1 s-1 °C– |