FERTILIZERS FOR COFFEE IN PORTO RICO d 
Quarterly measurements of height were taken over the period of 
most rapid stem elongation, from October, 1914, when the trees were 
for the most part less than 2 feet high, to October, 1917, when they 
averaged 6 to 7 feet high, and most of them had borne two crops of 
fruit. These measurements failed to show any consistent and signifi- 
cant differences attributable to the kind of fertilizer applied. 
It has been thought that trunk diameters furnish the most accurate 
measurements of growth, and, consequently, the most reliable index 
of tree performance. 2 In November, 1924, measurements were taken 
of the trunk diameter at 3 inches above the base. The average trunk 
diameter for each plat is given in Table 1, which shows that, when 
the five divisions are considered as a unit, nitrogen and potash in 
combination, either with or without phosphoric acid, produced a very 
considerable increase in growth, but that nitrogen alone or in combi- 
nation with phosphoric acid, but without potash, produced a growth 
considerably below that of the check group. Ten of the 40 plats 
exceeded the highest check plat, and all except 1 of these received 
potash and 7 received both nitrogen and potash. 
Table 1. — Average diameter of differently fertilized coffee tree trunks at 3 
inches above base, November, 1924 
Division 
Rate of 
fertilizer 
applica- 
tion per 
tree i 
Plats receiving — 
K 
P 
N 
NK 
PK 
NP 
NPK 

l.__ 
Pounds 
¥i 
l 
I 
Inches 
2.3 
2.4 
2.6 
2.7 
3.0 
Inches 
2.0 
2.3 
2.4 
2.9 
2.7 
Inches 
2.1 
2.8 
2.6 
2.3 
1.8 
Inches 
3.1 
2.6 
2.9 
3.1 
3.4 
Inches 
2.3 
2.5 
2.4 
2.8 
3.0 
Inches 
2.2 
2.3 
2.4 
2.5 
1.8 
Inches 
2.3 
2.8 
3.2 
2.9 
3.3 
Inches 
2.2 
2 
2.4 
3-. 
4.. 
5_- 
Total.. 
2.7 
2.8 
2.8 
.... j 13.0 
12.3 
11.6 
15.1 
13.0 
11.2 
14.5 
12.9 
1 The figures in this column represent the rates of application of complete fertilizer. The single elements 
and combinations of two elements were applied at the same rates as in the complete fertilizer. 
Figure 1 graphically averages the trunk diameter for each plat. 
Considering the plats of each division in relation to their respective 
check plats only, it is seen that 17 of the 40 plats surpassed the 
checks. Of these 17, all except 2 received potash, and 10 received 
both nitrogen and potash. All the NPK and NK plats surpassed 
their checks in trunk diameter, whereas this held true for no other 
fertilizer combination or element when applied singly. The growth 
failed to show benefit from adding phosphoric acid to the NK 
combination. Fifteen plats fell below T their respective checks in 
trunk diameter. Of these, 4 received nitrogen alone, 4 phosphoric 
acid alone, and 4 nitrogen and phosphoric acid in combination. 
The injury done by nitrogen, either singly or in combination 
with phosphoric acid only, in very heavy applications was evident 
from the very poor growth made by the plats so fertilized in the 
fifth division. Plant growth on plats receiving identical quantities 
of nitrogen to which potash was added appeared in strong contrast. 
2 Hedrick, TJ. P., and Tukey, H. B., twexty-five years of fertilizers in a 
york apple orchard. N. Y. State Agr. Expt. Sta. Bui. 516, p. 16. 
NEW 
