6 
BULLETIN 31, PORTO RICO EXPERIMENT STATION 
In the harvests for each of the eight years 1917-1924, inclusive, 
the NPK group and the NK group outyielded the unfertilized group. 
The K group for seven of the eight years and the PK group for 
five years outyielded the check, whereas the P group and the NP 
group surpassed the check only once each and the N group did not 
surpass it at all. Figure 6 graphically averages the total yield per 
tree for the 1917-1924 period as the plats lie in the field. Each line 
represents the production of a kilogram of coffee cherries. In divi- 
PO/NTS DETEPM//VED BY TREES' //V 
DM /S? 2-3 3-4 4S 
GATE OF FEPT/L/ZEP PEP TPEE PEP s4PPL/C/7T/OaV 
'/t-'/aPOUND ye-ZPOC/ND /-2POUA/DS 2-4 POUNDS 
3.3 
3.2 
3/ 
3.0 
2.9 
2.3 
2.7 
2.6 
2.S 
2.4 
2.3 
2.2 
2/ 
2.0 
A.9 
A3 
A.7 
/£ 
AS 
A4 
A3 
A2 
AA 
AO 
.9 
.6 
.7 
.6 
5 
.4 
3 
a 
fe 
\ M . ' *!! * ***^*'*" - 
„+. -T- ■> + ' 
^*£ 
K£Y TO 6MPH SH0W/N6 rceriL/zces APPLIED 
SYMBOLS *e£ COAfB//V£D TO /NDJ&ITE 
F£BT/UZ£e COMB/N/IT/ONS 
PHOSPHOetC AC/D 
POTASH ++++++++++ 
SULPHUe ooo o o ooooo 
□oacaaaa 
_L 
Fig. 2. — The depressing effect on growth of heavy applications of nitrogen unaccompanied 
by potash and the stimulating effect of the two together, as shown by tree trunk 
diameter measured November, 1924 
sions 4 and 5 nitrogen in heavy applications and without potash 
very adversely affected fruiting, whereas the same quantity used in 
conjunction with potash proved beneficial rather than injurious. 
The appearance of the trees as well as their production was affected 
by the treatments, the plats receiving nitrogen alone in heavy appli- 
cations producing only sparse foliage and poor growth in contrast 
with the luxuriant foliation and growth on the plats receiving 
nitrogen and potash in combination. (PI. 1.) 
