14 
BULLETIN 31, PORTO RICO EXPERIMENT STATION 
observed effect of fertilizer on size of cherry was indirect. A notable 
increase in yield was accompanied by a slight reduction in size of 
cherry. 
COMPARISON OF AMMONIUM SULPHATE AND SODIUM NITRATE 
Several comparative tests were made to learn the value of ammo- 
nium sulphate and sodium nitrate as fertilizer for coffee. 
BOURBON PLATS 
Sixty trees of Bourbon coffee were selected for one of the tests. 
The seed was planted in April, 1915, and the resulting seedlings were 
set in heavy clay soil in the fall of 1916. Later some replacements 
/9/2 /9/3 /9/4 /9/S /9/6 /9/7 /9/9 /9/9 /920 /ft?/ /922 /9£3 /924 
Fig. 9. — Average annual production per tree of Erecta plats to wbich different combina- 
tions wei;e applied 
of weak and missing trees were made from the original nursery. 
The planting contained 12 rows of 5 trees each, spaced 8 by 8 feet. 
The slope was steeply but very uniformly inclined and the short 
rows ran with the slope. Although the lower trees in each row were 
in more fertile soil than the upper trees, 1 row as a unit was very 
uniform with another as to elevation and soil. The 2 treatments 
were given to alternating rows throughout the planting. The plats, 
each containing 30 trees set in 6 alternating rows, furnished strictly 
comparable conditions for making the test. 
Fertilizers were applied semiannually. The first four applications, 
December, 1917, to June, 1919, inclusive, were of nitrogen only ; after 
that time phosphoric acid and potash were provided, the rate and 
formula being, as was the case with the Padang and Erecta tests, 
1 pound per tree per application of a 7 : 10^2 : 14 combination. 
