FERTILIZERS FOR COFFEE IN PORTO RICO 33 
served following the continuance of sodium nitrate alone. In pot 
tests equal quantities of sodium nitrate were much more effective 
when applied in small monthly rather than in larger semiannual 
applications, and the addition of sulphur proved beneficial. Monthly 
applications of sodium nitrate with semiannual applications of sul- 
phur proved more effective than semiannual applications of ammo- 
nium sulphate. The latter, however, retained its established position 
of superiority over sodium nitrate alone in semiannual applications. 
Both pot and field tests failed to indicate any benefit from liming. 
It is evident that the coffee tree responds to fertilization. On cer- 
tain soils a large increase in production may be expected to follow 
the application of suitable chemical fertilizers in sufficient quantity. 
The need for potash is particularly evident. This is in harmony 
with analyses of the fruit. Ansteacl and Pittock 6 state that " when 
a chemical analysis of parchment coffee, or coffee berries, is critically 
examined one fact at once strikes one as being prominent. * * 
Potash is a dominant factor in the mineral constituents of the coffee 
bean. This is prominently brought out in the ash analysis where 
there is more potash than anything else. This being so it is only 
logical to suppose that a fertilizer containing a preponderance of 
potash should help the coffee tree to ripen up and hold its crop." 
Either ammonium sulphate or sodium nitrate may be used to 
supply nitrogen, but the employment of the former is preferable, 
since in a majority of the tests it has clearly demonstrated its superi- 
ority over sodium nitrate in semiannual applications. 
The heavy clay soils so extensively planted with coffee in Porto 
Rico are for months at a time washed by heavy and frequent rains. 
The surface is generally steeply inclined and subject to rapid drain- 
age. Under such conditions it is probable that much of the nitrogen 
from large semiannual applications of sodium nitrate would be 
washed away without benefit to the trees to which it was applied. 
The beneficial effect of potash and nitrogen in combination has been 
clearly demonstrated, but the most favorable ratio between the two 
remains a problem for future investigations. Until further evidence 
is obtained on this point, it is believed that a fertilizer for coffee 
should run proportionally high in potash, such, for example, as one 
obtained by mixing ammonium sulphate and potassium sulphate in 
equal parts by weight and containing approximately 10 per cent 
nitrogen and 24 per cent potash. This combination may prove ade- 
quate without the addition of phosphoric acid for certain soils. In 
other cases it may be advisable to include phosphoric acid, adding to 
the mixture an equal part by weight of superphosphate. It is sug- 
gested that each planter who uses chemical fertilizers for his coffee 
determine the need of his soil for phosphoric acid by applying to 
experimental plats each of these two mixtures. The plats should pref- 
erably be adjacent and as nearly as possible alike in slope, soil, and 
condition of trees. The fertilizer combination containing only the 
two elements *may be applied at the rate of 300 pounds to the acre. 
and the other at the rate of 450 pounds. 
c Anstead, R. D., and Pittock. C. K. the varying composition of the coffee berry 
at different stages of its growth and its relation to the manuring of coffee 
estates. Planters' Chronicle, vol. 8, No. 36, pp. 455. 456. Sept.. 1913. 
