Dolomitization in Semi-arid Hawaiian Soils 1 
G. Donald Sherman, Yoshinori Kanehiro, and 
Charles K. Fujimoto 2 
INTRODUCTION 
Soils developed under a limited rainfall 
usually show the influence of salinization by 
calcium or sodium salts. In the presence of 
appreciable quantities of sodium salts, soil 
carbonates are converted to sodium carbonate 
and give rise to a condition known as black 
alkali. Recently workers have found soils in 
which the salinization had been caused by 
magnesium salts. Ellis and Caldwell (1935) 
found a magnesium clay "solonetz” in cer¬ 
tain Manitoba soils in which 80 to 90 per 
cent of the adsorbed cations were calcium 
and magnesium. In addition, the calcium-to- 
magnesium ratio in these soils varied from 
1.6 to 1.0. Alicante (1933) reported a 
Philippine soil which contained twice as 
much magnesium as calcium in a soluble 
form. Kudrin and Rozanov (1938), work¬ 
ing with "sierozem” soils, found a high con¬ 
tent of adsorbed magnesium especially in the 
"solonchaks.” Rost and Chang (1941) di¬ 
vided the solonchaks of the Red River Val¬ 
ley of Minnesota into two groups: those 
having 20 to 50 per cent of their exchange¬ 
able cations as magnesium and those having 
more than 85 per cent of their exchangeable 
cations as calcium. In addition, they found 
a direct relation between exchangeable mag¬ 
nesium and gypsum in the soil. Thus, there 
is evidence that magnesium salts may play 
an important role in the salinization pro¬ 
cesses in soil. 
Salinization of a soil with magnesium salts 
1 Published by permission of the Director of 
the University of Hawaii Agricultural Experiment 
Station as Technical Paper 137. 
2 University of Hawaii Agricultural Experiment 
Station, Honolulu, Hawaii. 
would be expected to give rise to the forma¬ 
tion of magnesium carbonate, a very insolu¬ 
ble compound of magnesium. However, if 
a magnesium sulfate salinization occurred in 
a soil rich in calcium carbonate, then dolo¬ 
mitization might occur in the soil with the 
formation of two relatively insoluble com¬ 
pounds, dolomite (double carbonate of cal¬ 
cium and magnesium) and gypsum. The re¬ 
sults of some recent studies suggest that this 
process does occur in soils. Alway and Zet- 
terberg (1935) found that the molecular 
ratio of calcium carbonate to magnesium car¬ 
bonate varied from 1.51 to 4.80 in calcareous 
Minnesota soils. Later work on Minnesota 
soils (Sherman, 1937) showed the occur¬ 
rence of dolomitization in soils which have 
a high water table of waters rich in magne¬ 
sium sulfate. In some of these soils the 
molecular ratio of calcium carbonate to mag¬ 
nesium carbonate approached 1.0. The car¬ 
bonates in the dolomitized area did not vis¬ 
ibly effervesce when treated with cold dilute 
hydrochloric acid even though the soils con¬ 
tained as much as 40 per cent carbonates. 
When pure dolomite is treated with cold 
dilute hydrochloric acid, the ensuing effer¬ 
vescence is barely perceptible. This relative 
inaction of a carbonate to cold hydrochloric 
acid is characteristic of dolomite. The car¬ 
bonates from the area rich in magnesium 
were identified as dolomite and distinguished 
from calcite and other carbonates by a stain 
technique (Sherman and Thiel, 1939). Pel¬ 
lets containing gypsum and long needle-like 
crystals of gypsum were found imbedded in 
the clay below the dolomitized layer of soil. 
The nature of the occurrence of gypsum in. 
these forms suggested their secondary origin. 
38 
