30 BULLETIN 52, HAWAII EXPEEIMENT STATTOX. 
The value of each of these numerous treatments was judged by 
the average restoration of the green color and the general health and 
vigor of the plants treated in comparison with the plants in the check 
rows and with those receiving different treatments. Table 15 gives 
the results of these treatments. 
Table 15 shows that ferric chlorid is not to be recommended for 
field use. In most cases it was only slightly more effective than iron 
sulphate, but even a 4 per cent solution burned the plants somewhat. 
The high cost of ferric chlorid is also a drawback to its use. 
The application of iron solutions to the under surface of the leaves 
gave slightly better results in most instances than did spraying the 
upper surface, but there was a greater tendency toward burning. 
The results obtained were not such as would justify, for present large- 
scale practice, the spraying of plants from below. The addition of 
acids slightly increased the effectiveness of the iron sulphate but did 
not prevent burning in some cases. 
The most practical, convenient, and economical treatment ap- 
peared to be the application to the plants of three or four sprayings 
of an 8 per cent solution of iron sulphate. A 16 per cent solution 
was more effective than the latter but burned the plants considerably. 
RESULTS OF SOIL TREATMENT. 
An experiment was made in cooperation with F. K. Benedict, of 
Libby, McNeill & Libby, Honolulu, in which flowers of sulphur was 
applied to a manganese soil in field plats at the rate of 500 to 3,000 
pounds per acre. Additions of a red, very acid, upland soil con- 
taining apparently considerable quantities of available iron were also 
made to the manganese soil at the rates of 1 to 6 tons per acre. A 
third treatment tried was the application to the soil of bagasse soaked 
in very strong solutions of iron sulphate. None of the treatments 
was effective, the treated plats yellowing as did the check plats. 
Even when the solution carried by the bagasse contained 3,000 
pounds per acre of iron sulphate no effect was apparent. The yellow 
plants in this experiment oecame green rapidly and made vigorous 
growth when they were sprayed with only a few pounds per acre of 
iron sulphate in solution. The plants on the sulphur plat showed 
some stimulation caused by the sulphur. 
PRACTICAL TESTS OF THE METHOD OF SPRAYING. 
THE SPRAYER USED. 
The benefits resulting from spraying yellow pineapple plants on 
manganese soils with iron solutions were so evident that the cooper- 
ating plantation applied this treatment as soon as possible to all of its 
fields where " manganese yellows" appeared. Check rows only were 
left unsprayed. As a spraying machine could not easily be secured, 
a hand sprinkler was used at first with fairly good results. An 
ingenious modification of the old carbon dioxicl orchard spray was 
devised for the first large-scale treatments of extensive areas. This 
sprayer was designed by S. T. Hoyt, of the Hawaiian Pineapple Co., 
and was built at a low cost by the plantation blacksmith. The 
sprayer is mounted on a single iron wagon wheel, so that turning is 
easy at the end of the rows. It holds 30 gallons of iron sulphate solu- 
tion. An ordinary carbonic-acid tank in the rear furnishes pressure 
