Mar. io, 1923 
Aluminum and Iron Compounds in Corn Plants 
819 
The greater the intensity of the acidity the greater are the quantities of 
aluminum and iron salts which become available. 
When lime is added to acid soils it is believed that the conditions 
which operate to make the aluminum and iron compounds available are 
destroyed, and even though aluminum salts may still be available after 
calcium carbonate is added, the addition of soluble phosphates will 
rapidly precipitate the aluminum salts and render the aluminum inert 
so far as absorption by corn plants is concerned. 
Lime has a beneficial effect according to Hartwell and Pember (10 ), 
Mirasol (18), and Conner (7), although its action is markedly slower 
than that of acid phosphate. 
Aluminum phosphate is relatively insoluble, yet when used as a 
fertilizer it produces an increased growth of com plants, according to 
unpublished results obtained by Conner. This is perhaps due to the 
hydrolysis of the aluminum phosphate, as shown by Cameron and Bell 
(4 ), the result of which would yield inert aluminum hydroxid and available 
phosphorus to the plant. 
These statements are based upon studies of plants in fertilizer experi¬ 
ments in the field and greenhouse. 
DISCUSSION 
The rdle of phosphorus in plant growth and reproduction is a problem 
which has been worked upon by many investigators, and its relation to 
certain of the metabolic processes is fairly well understood. The ash 
content of kernels of com averages 45 per cent phosphoric acid. Its 
importance, therefore, in the production of seed corn needs no further 
emphasis. 
The fact that phosphorus is deficient in most acid soils is also well 
known and needs no discussion. The importance of available aluminum 
compounds in the soil, however, is just beginning to be studied intensively, 
and the fact that when the aluminum salts are available or become 
available the supply of available phosphates is not adequate for the 
needs of plants in normal growth is one which presents a complex problem 
for investigation. 
The r 61 e of lime in the soil in relation to the conditions under which 
aluminum and iron salts become available for absorption is probably 
that of a stabilizer of the soil reaction. The hydrogen-ion index of a 
black loam soil deficient in phosphates and lime varied markedly during 
the growing season of 1920. Therefore, if the soil reaction can be main¬ 
tained constantly near neutrality the quantities of available aluminum 
and iron salts will be less for absorption by the com plants. 
The growth phenomena of the corn plants can not be normal under 
such conditions of deficient phosphates and lime and available aluminum 
and iron salts. It is necessary, therefore, to isolate the phenomena due 
to specific ions, if possible, and study them separately. This was 
attempted in part by injecting solutions of supposedly harmful salts 
and others into normal plants. By this means it was found that alumi¬ 
num and iron ions were harmful and would produce effects similar to 
those which become manifest in many stalks which are affected by 
rootrots. A specific toxic action was stimulated by the aluminum and 
iron ions, respectively. Organic and mineral acids injected into the 
stalks in higher concentrations than are ever found in acid soils produced 
no specific results. Furthermore, when calcium ions were introduced in 
