22 
BULLETIN 3 4, PORTO RICO EXPERIMENT STATION 
merits with the commonly used fertilizers on the older palms, salt 
was applied, but without any observed effect on production. Salted 
and check plats alike showed a decline in production which was 
notable principally for uniformity. 
These results do not justify the recommendation of any particu- 
lar element or combination as a fertilizer for coconuts. The most 
striking thing about the results is their inconsistency. In seeking 
for a more satisfactory answer to the question of fertilization of 
coconut palms, fertilizer experiments should be made with a much 
larger number of trees than were used in this case, and in replicate, 
in view of the pronounced variation in productivity between indi- 
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Figure 15. — Average nut diameters by periods of five harvests each, Boquillas 
plantation 
vidual palms and the impossibility of securing uniformity through 
asexual propagation. 
The study of production in relation to elevation of palms grown 
at 4.2 to 9.2 feet above sea level showed that the better drainage 
afforded by higher elevation was an important factor in the pro- 
motion of heavier production. Adequate drainage ditches would 
presumably greatly increase production in many plantations, as the 
low-lying littoral usually planted to coconuts is often very poorly 
drained. General soil-improvement practices, such as providing 
drainage and supplying humus through the growing of leguminous 
cover crops, may accomplish far more than applications of fertilizers 
and at a smaller cost. 
