FERTILIZERS FOR COFFEE IN PORTO RICO 
13 
In both plantings complete fertilizer resulted in increased pro- 
duction, moderately so with Padang, and to a pronounced degree 
with Erecta. Were only the first four crops of the Erecta planting 
to be considered, it might easily be inferred that nitrogen was the 
limiting element since the three plats receiving it produced approxi- 
mately three to five times as great a yield as the check or the PK 
plat, with the XP plat leading. If the last six crops are considered 
as a unit, it is seen that the NPK plat produced more than any other 
two plats combined, and the plat from which nitrogen was omitted 
ranked ahead of the other two plats receiving incomplete fertilizer. 
The NPK plat for the 13-year period as a whole produced approxi- 
mately three times as much as the check plat, and sufficiently in 
excess of the plats receiving incomplete fertilizer to indicate the 
need of supplying all three elements to the soil. Figures 8 and 9 
graphically show the yields, the effect of fertilizer on yield, and the 
wide variation in production from year to year. 
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Fig. 8. — Average annual production per tree of Padang plats with and without fertilizer 
To determine the effect of fertilizer on size of fruit, counts per 
liter were made of samples of Padang cherries at intervals during 
six years, and of samples of Erecta cherries at intervals during four 
years, involving some 31,486 fruits. The average number of Padang 
cherries per liter from check plats differed from that of fertilized 
plats by less than 1 per cent, whereas those from the Erecta plats 
differed by 13 per cent. The size of cherry, as indicated by the 
number in a liter, bore an interesting relation to the yield per tree 
for the period involved. The total yield of the Padang plats showed 
a difference of 5 per cent for the period, and the size of cherry less 
than 1 per cent. The Erecta NPK plat produced 235 per cent more 
than its check, and a liter of the former contained 13 per cent more 
cherries than were required of the latter to fill the measure. Simi- 
larly for the five plats, the size of cherry was in direct relation to the 
yield, the sequence of the plat yields being the same as that of the 
average number of cherries per liter. In other words, the onlv 
