EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE, 57 
since its yield nearly equaled that of the raw-rock plot. In 1892 and 
1894 (particularly in the latter year), however, the plot receiving 
raw rock phosphate two and four years previously forged ahead very 
noticeably. 
In 1896 Merrill? published the results of the box experiments be- 
%oun by Ballentine? a number of years before and continued after 
the latter’s death. The work was carried on still further, however, 
and all the results published by Merrill * in 1899. 
This experiment was undertaken in order to determine the rela- 
tive availability of various phosphates and also to test the ability — 
of some of the common crops to obtain phosphoric acid from these 
- different sources. The work was conducted in one of the green- 
houses, and the plants grown in wooden boxes 14 inches square and 
12 inches deep. The boxes were filled to within 1$ inches of the 
top with 120 pounds of sand. The sand was taken from a knoll 
near the river, at a depth of 3 or 4 feet, and was nearly free from 
organic matter. Traces of phosphoric acid were present. Before 
filling the boxes, the sand was carefully screened and mixed 
thoroughly with the various fertilizers. 
Eighteen species of plants were grown, representing seven orders: 
(1) peas, horse beans, clover, and alfalfa (Leguminose) ; (2) tur- 
nips, rutabagas, cauliflower, and kohlrabi (Cruciferz) ; () barley, 
oats, and timothy (Graminez); (4) tomatoes and potatoes (Solan- 
acee); (5) carrots and parsnips (Umbelliferz); (6) buckwheat 
(Polygonacez) ; and (7) sunflower (Composite). 
It was planned to carry each plant through three periods of 
growth, but the clover would not mature in the time it took for the 
other plants to do so, hence only two crops were grown. The sun- » 
flower and buckwheat did not thrive under the conditions of the 
experiment; and, after a single trial, were replaced by carrots and 
parsnips, which were grown for the two following periods. — 
In each period 12 boxes were employed for each kind of plant. 
The boxes were divided into three sets of four each, the various 
phosphate treatments as well as the checks being run in triplicate. 
No attempt was made at pollination, and since but few insects 
were present during the growth of the plants, the fruiting was very 
irregular. As soon as the plants seemed to have attained their 
maximum development they were harvested, dried, weighed, and the 
total amount of dried matter determined for each crop grown. 
The phosphates used in this experiment were acid phosphate, 
Redonda phosphate (phosphate of iron and alumina) made largely 
citrate soluble by ignition, and Florida finely ground phosphate rock 
1Me. Agr. Exp. Sta. Ann. Rept. for 1895, p. 10-14 (1896). 
2Me. Agr. Exp. Sta. Ann. Rept. for 1893 (1894). 
$Me. Agr. Exp. Sta. Ann. Rept. for 1898 (1899). 
