MANGANESE CHLOROSIS OF PINEAPPLE. 27 
plants under comparative conditions and in nutrient solutions con- 
taining varying amounts of iron and having the availability of the 
iron diminished by the addition of manganese dioxid or calcium carbon- 
ate. The results of such tests should indicate whether plants differ 
greatly in their iron requirements or whether the resistance to chlorosis 
is due^ to some special relation of the plants' roots to the soil. 
A SUCCESSFUL TREATMENT FOR THE YELLOWING OF PINEAPPLES 
ON MANGANIFEROUS SOILS. 
i 
RESULTS OF SUPPLYING IRON TO THE PLANTS. 
Since the injurious effects of manganese seem to be due simply to a 
deficiency of iron in the plant, attempts were made to overcome 
" manganese poisoning" occurring on manganiferous Hawaiian soils 
by supplying the plants with iron. Experiments were made with the 
pineapple crop because of its susceptibility to injury and the fact 
that it is the principal crop of economic importance in the region 
where the manganese soils occur. 
Experiment I. — An effort was made to overcome the toxic effects 
of the manganese by supplying sulphate of iron and sulphuric acid 
to the soil in pot experiments. Young pineapple plants which were 
transferred from a normal soil to a manganese soil to which iron 
sulphate had been applied gave better results than did plants which 
were transferred to manganese soil alone. 
In a series of pot experiments 25 pounds of manganese soil was 
used for each pot in which a pineapple plant was grown. Six pots 
were used as checks. Ferrous sulphate (copperas) was applied to 
4 pots at the rate of 500 pounds per acre and to 4 others at the rate 
of 1,000 pounds per acre. Stable manure at the rate of 12 tons per 
acre was applied to 4 pots and sulphuric acid (strength 66°) was 
added at the rate of 1.000 pounds per acre to 2 other pots. Twenty 
pineapple plants of equal size and appearance were selected from a 
large number of plants and set in these pots for observation. 
The plants in pots to which ferrous sulphate had been added made 
a slightly better growth at first than did the others. With sulphuric 
acid a slight stunting was evident in the earlier stages, but in a short 
time no difference was observed between these and the check plants. 
Plants in pots to which stable manure was applied were apparently 
the same as the checks. 
At the expiration of five months all of the pineapple plants were 
fairly uniformly yellow and none of the treatments applied to the 
soil had any beneficial effect. A solution of iron sulphate was then 
applied to the leaves of these yellow plants with the result that the 
normal careen color and healthy appearance was restored. 
Experiment II. — Experiments on plants in the field were under- 
taken in cooperation with the Hawaiian Pineapple Co. The leaves 
of yellow pineapple plants in a field suffering from a severe case of 
"manganese yellows " were brushed four times at intervals of a week 
with a 2 per cent solution of iron sulphate. Two weeks after the 
brushings were completed a striking change was noticeable, and in a 
month's time the plants had resumed their green color and were 
making vigorous growth. The condition of the untreated plants 
adjoining was unchanged. Since then this field has been sprayed 
