18 
BULLETIN 31, PORTO RICO EXPERIMENT STATION 
ing high and plat 4 low. Plat 5, which received acid phosphate in 
addition to sodium nitrate, ranked high in 1919, but very low in 1918 
and 1920. The treatment was changed in January, 1920, because of 
the poor performance of the fertilized plats. 
Semiannual applications have been made from January, 1920, to 
date, plat 1 receiving ammonium sulphate (11% pounds per applica- 
tion), plat 2 nothing (check), plat 3 ammonium sulphate (HVi 
pounds), acid phosphate (15 pounds), and potassium sulphate (5 
/9/6 /9/7 /9/<9 /9/9 /920 /92/ /&22 /923 /924 
Fig. 12. — Yield from coffee plats of ^ acre each at Lopez plantation 
pounds), plat 4 sodium nitrate (15 pounds), and plat 5 sodium 
nitrate and acid phosphate (15 pounds each), and potassium sul- 
phate (5 pounds), the formula combining nitrogen, phosphoric acid, 
and potash in approximately equal quantities. The production of 
plat 4, which received sodium nitrate alone, on the whole fell below 
that of the check. Plat 1, which received ammonium sulphate alone, 
surpassed the check in yield during three years and approximated it 
in the very small crop of 1924. Plats 3 and 5, receiving complete 
