FERTILIZERS FOR COFFEE IN PORTO RICO 
19 
fertilizer, surpassed the check each year in production per tree and 
per plat for the 1921-1924 period. The difference in production in 
the peak year of 1923 was pronounced. Evidently the complete 
fertilizer produced a decided increase in yield. The effectiveness of 
ammonium sulphate alone was less pronounced and no benefit what- 
ever was observed as a result of using sodium nitrate alone. 
J9/6 /9/7 /9/S /9/9 /92Q /92/ /922 /923 /924 
Fig. 13. — Average yield per tree of plats at Lopez plantation 
WEST FIELD PLATS 
In 1911 for fertilizer tests a planting of 33 plats of 18 trees each 
was made on an almost level plain promising uniform conditions. 
The tests were discontinued in 1915, however, because of the unsatis- 
factory growth made by the trees owing to poor drainage. The 
salient features of the test are given herewith : 
The basal formula used was 7 : IOV2 : 14 and the rate one-half 
pound per application. Five applications were made from 1912 to 
1914. In addition to complete fertilizer, combinations of two ele- 
ments, single elements, lime, guano, coffee pulp, and manure were 
