May 2i, 1917 
Solubility of Certain Inorganic Soil Constituents 
267 
were used immediately for soil extraction. Two types of soil, a clay 
loam and a sandy loam, were used. 
In the four soil extractions these organic solvents removed from the 
soil from two to five times as much calcium as was added to the soil 
with the solvents. Iu most cases these solvents removed more magne¬ 
sium from the soil in the four extractions than was added with the 
solvents, the increase varying from a small fraction to about 80 per cent. 
The amount of iron and phosphoric acid removed from the soil by these 
organic solvents in the four soil extractions did not equal the total 
amount added to the soil with the solvents. However, the amount of 
iron dissolved from the soil by the organic solvents exceeded the amount 
dissolved by distilled water from 1 to 5.5 times. The amount of phos¬ 
phoric acid dissolved from the soil exceeded the amount dissolved by 
water from 1.7 to 5.4 times. These various organic solvents, whether 
derived from a leguminous or a nonleguminous crop, had about equal 
solvent action on the soil minerals. 
Organic solvents obtained from cow manure treated in a manner similar 
to the freshly decomposing green manures did not dissolve as much 
calcium from the soil as the solvents derived from the latter substance. 
They exerted about the same solvent action, however, on the other 
elements under investigation. 
The solvent action of these organic extracts on the soil minerals 
appeared to be due both to the inorganic salts present in the organic 
solvents and to the organic compounds. 
Green manures kept moist until thoroughly decomposed gave organic 
solvents which removed calcium from the soil in amounts several times 
that added with the organic solvents. These solvents also removed 
magnesium, phosphoric acid, and iron considerably in excess of the 
amount dissolved by water alone. 
The organic solvents showed no alkaline reaction with phenolphthalein 
nor acid reaction with methyl orange. 
Three per cent of green manures and stable manure mixed with soil 
and allowed to undergo partial decomposition increased the solubility of 
calcium and phosphoric acid in the soils from 30 to 100 per cent. 
Artificial humus solutions free from calcium, magnesium, iron, and 
phosphoric acid were prepared by hydrolyzing green manures and sugar 
with strong acid, washing them free from acid, and extracting with 
ammonia. These organic solvents, when freed from ammonia, increased 
the solubility of calcium in the soil, compared with its solubility in 
water, by amounts varying from a few parts to 240 parts per million of 
soil. They also increased the solubility of magnesium, phosphoric acid, 
and iron, but to a less extent. 
In brief, the solubility of calcium, magnesium, iron, and phosphoric 
acid in Citrus soils of the Riverside district is measurably increased by 
the addition of green manure, stable manure, or their extracts. This 
82982°—17 - 2 
