PORTO RICO AGRICULTURAL EXPERIMENT STATION 
MAYAGUEZ, P. R. 
UNITED 
Under the supervision of the 
STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 31 
Washington, 
D. C. 
November, 
1926 
EXPERIMENTS WITH FERTILIZERS FOR COFFEE 
IN PORTO RICO 
By T. B. McClelland, Horticulturist 
CONTENTS 
Page 
Field experiments 1 
South Field plats 1 
Fadang and Erecta plats 9 
Comparison of ammonium sul- 
phate and sodium nitrate 14 
Experiments in liming 21 
Page 
Pot tests 21 
Complete and incomplete ferti- 
lizers 21 
Comparison of ammonium sul- 
phate, sodium nitrate, lime, 
and sulphur 25 
Summary and suggestions 32 
Coffee occupies a prominent place in the agriculture of Porto Kico 
by reason of the large area planted with the crop, the many people 
engaged in its cultivation, and the income derived from its exporta- 
tion. Production per acre is generally low, however, and planters 
are interested in learning how to increase yields. Requests are fre- 
quently received at the station for information as to the use of chem- 
ical fertilizers for eoffee. This bulletin gives the results of experi- 
ments made during a series of years at the station and elsewhere in 
Porto Rico to determine the effect of fertilizer on growth and yield of 
coffee, and covers many of the points in question. 
FIELD EXPERIMENTS 
SOUTH FIELD PLATS 
In Porto Rico coffee is usually planted on steep slopes. Such loca- 
tions are not, as a rule, suited to coffee planting for comparative 
purposes, since variations in topography cause a high degree of 
variability in growth and yield of crop. To eliminate this disturbing 
factor a strip of apparently level land was selected as the site for 
field work. The land near by slopes toward the river and furnishes 
what would be good drainage were it not for the nature of the soil, 
which is a heavy, almost impervious brown Adjuntas clay. 1 The 
1 This type of soil is described in detail in Porto Rico Sta. Bui. 14, The Red Clay Soil 
of Porto Rico. 
11834—26—1 1 
