Brent Rouppet, Ph.D., Soil  Scientist / Agronomist

Legend of Chemical Symbols


CaSO4·2H2O              gypsum (as it exists in nature)

Ca2+                            calcium ion (the form of calcium that plants use)

CaCO3                         free (or pure) lime (or limestone)

HCO3                         bicarbonate (the most toxic anion for plants)

Cl                               chloride ion

H+ (acid)                    the generic chemical symbol for any acid

OH–                                            hydroxyl ion

CO2                             carbon dioxide (an atmospheric gas)

S                                                   elemental sulfur (as it exists in nature)

SO42-                           sulfate ion (the form of sulfur that plants use)

K+                                                potassium ion

Na+                             sodium ion (very toxic to plants and harmful to soil structure)

Mg2+                                         magnesium ion (harmful to soil structure when insufficient calcium is present)

soil                             a soil particle that has a net negative electrical charge (attracts positively charged ions; e.g., sodium, magnesium, calcium, etc.)

Na2SO4                       sodium sulfate.  A non-electrically charged salt that can be leached through the soil with irrigation water

Common Soil and Water Chemical Reactions

2HCO3(bicarbonate) + Ca2+ (calcium ion)     →     CaCO3 (free lime)     + H2O    +     CO2

HCO3 (bicarbonate) + H+ (acid)     →     H2O   +     CO2

2S (elemental sulfur) +      3H2O     +     3O2    →       H2SO4 (sulfuric acid)

H2SO4 (sulfuric acid) +     CaCO3 (free lime)     →     Ca2+ (calcium ion)    + SO42- (sulfate ion)     +     CO2      +     H2O

2 H+ (acid) + CaCO3 (free lime)     →     Ca2+ (calcium ion)    +     CO2      + H2O

CaSO42H2O (gypsum) +     H2O     →    Ca2+ (calcium ion)     +     SO42- (sulfate ion)

Na+/Mg2+(sodium/magnesium ions)- [on soil] +     CaSO42H2O (gypsum)     →      Ca2+/Mg2+ (calcium/magnesium ions) – [on soil]     +       Na2SO4            (sodium sulfate)  [now leachable]