16 
BULLETIN 31, PORTO EICO EXPERIMENT STATION 
pounds. Changes incident to the war prevented the continuation of 
the test. During the brief period in which it was under way no ap- 
parent benefit in vigor or yield was observed to result from sodium 
nitrate. 
The second group of plats, located on the Lopez plantation (Las 
Vegas) consisted originally of four -^-acre plats, to which a fifth 
was later added. The 4 original plats contained 3 rows each and 
had guard rows between plats. The trees ranged in number from 98 
to 115 per plat in 1916, and from 95 to 112 in 1924. The fifth plat 
contained 121 trees. 
& The plats are located on 
a uniform and gentle 
slope and the soil is 
a stiff, reddish-brown 
clay. The first 4 plats 
have approximately 
the same elevation and 
plat 5 is slightly lower 
on the slope. The 
coffee trees said to be 
6 years old were in 
moderately good con- 
dition and set in rows 
approximately 9 feet 
apart. The 1916 crop 
was measured in ac- 
cordance with the 
usual plantation prac- 
tice. After that the 
crop was weighed also 
as a check on the re- 
corded measure. The 
two periods into which 
the experiment was 
divided by a change 
in treatment in 1920 
require separate con- 
sideration. The 1920 
crop may be included 
in the first period. 
Since the plats varied in the number of trees they contained, produc- 
tion should be considered both per unit area (fig. 12) and per indi- 
vidual tree (fig. 13). 
Eight applications were given between February, 1916, and June, 
1919, plat 1 receiving sodium nitrate (5 pounds per application), 
plat 2 nothing (check), plat 3 sodium nitrate (15 pounds), and plat 4 
sodium nitrate (30 pounds). Four applications of sodium nitrate 
and acid phosphate (15 pounds each per application) were given plat 
5 between December, 1917, and June, 1919. No increase in yield at- 
tributable to sodium nitrate was apparent at the end of the first 
period. The check plat remained in the lead except for the peak 
year 1919. From 1916 to 1918, inclusive, the average production per 
tree for plats 1 to 4, inclusive, showed no great difference, plat 2 rank- 
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Fig. 10. 
-Average height per tree of Bourbon coffee, 
January, 1920 
