804 
Journal of Agricultural Research 
Vol. XXIII, No. 10 
been cited suggest that the influence of the aluminum salts may be harm¬ 
ful in the leaves and that, while the stalks which are diseased seem to have 
large quantities accumulated in the nodal tissues, these accumulations 
may indicate only the relative quantities which have been carried on to 
the leaf tissues to concentrate there and become toxic when in sufficient 
quantity. The problem of chlorophyll disturbances is a most complicated 
one, and the influence of these metals as catalysts upon the production of 
chlorophyll and as harmful agents upon the functioning of the chlor¬ 
ophyll tissues is little understood. The metals affect the chlorophyll 
tissues differently according to the amounts of alkaline bases present in 
AVAILABLE ALUMINUM SALTS IN SOILS 
Much has been written of late relative to available aluminum and iron 
salts in the soil and their relation to soil acidity. Extracts from some 
acid soils have yielded quantities of aluminum salts in toxic concentra¬ 
tions. One of the explanations of the phenomenon of acidity in the soil 
is that it arises from the hydrolysis of salts of iron and aluminum. 
In 1913, Abbott, Conner and Smalley (r) reported the results of their 
investigations upon an unproductive acid soil in northern Indiana. They 
found aluminum nitrate present in the soil extracts and attributed the 
acidity of the soil to the hydrolysis of the aluminum nitrate. Daikuhara 
(< 8 ) believes that salts of iron and aluminum are absorbed by the humic 
acids and other colloids of the soil and are set free again on treatment 
with neutral salt solutions. He infers that such compounds must exer¬ 
cise considerable influence not only on the acidity of purely mineral soils 
but also on that of soils containing humus. The injury to vegetation 
is thought to occur when the compounds of iron and aluminum absorbed 
by the soil colloids are liberated as soluble acid salts of iron and 
aluminum upon the application of mineral fertilizers. 
In 1916, Conner (5) stated that much of the harmful acidity of acid 
soils is due to the presence of toxic acid salts of aluminum and iron and 
that the reduction of soil acidity by acid phosphate probably is due prin¬ 
cipally to a combination of the soluble phosphoric acid with the acid 
salts of aluminum and the consequent formation of insoluble nonacid 
compounds. 
Spurway (22) attributes the acidity of certain glacial soils to the “hy¬ 
drolytic-ratio” between the salts of the alkaline earth metals on the one 
hand and those of iron and aluminum on the other. 
Hartwell and Pember (10) in 1918 have shown that the toxic effect of 
certain acid soils is due not to the true acids but to aluminum salts present 
in extracts from these acids soils. They checked the effects of aluminum 
salts added to nutrient solution with acid soil extracts and found the free 
acids were relatively harmless and that the toxicity was due to the active 
aluminum. This work was valuable because it made the plant test the 
final one for the effects of soil acidity. 
Mirasol (18) has studied aluminum as a factor in soil acidity. He 
has given a very extensive bibliography of this subject and conducted 
experiments which showed the beneficial effects of applications of lime 
and acid phosphate in reducing toxicity due to aluminum compounds. 
These aluminum salts are claimed to be derived from the acid-soluble 
aluminum hydroxid, or gibbsite. In soils sufficiently provided with 
calcium, toxic aluminum salts may never be formed, but in soils defi¬ 
cient in calcium and other bases, such as acid soils, toxic aluminum salts 
are largely the end products of sulfofication and nitrification. Of 
