22 
to doubt that better conditions would thus be established and greater 
profits obtained. 
In the carrying out of the experiments reported in this bulletin 
assistance has been rendered by various members of the station staff, 
to whom thanks are hereby extended. 
SUMMARY. 
(1) Hawaiian rice soils have originated from basaltic lava, but 
also contain small amounts of coral limestone. 
(2) In texture most of the rice lands are clay loams, and contain 
approximately equal quantities of fine sand, silt, fine silt, and clay. 
(3) In chemical composition these soils are quite similar, with 
the exception of those from the Waikiki and Kaulaunui districts, 
the former of which contain abnormal amounts of magnesia, while 
the latter are highly organic. In general, the nitrogen and phos- 
phoric acid are high, while the potash is 1ow t , due largely to the 
solubility of potash, which is leached from the soil. 
(4) From fertilizer experiments carried on through seven crops it 
was found that the application of 150 pounds per acre of ammonium 
sulphate produced notable increases in the yield, but 300 pounds per 
acre proved the more profitable. Potash and phosphoric acid were 
without effect. The application of ammonium sulphate to both the 
spring and fall crops yielded considerably more profit than when 
made to the spring crop only. The residual effects on the fall crop 
from the spring application are small. The immediate effects ob- 
tained from making the application to the fall crop were about the 
same as those obtained w T ith the spring crop. 
(5) A complete fertilizer proved no more effective than ammonium 
sulphate alone, whereas the application of both ammonium sul- 
phate and potassium sulphate caused a decrease as compared with 
that obtained from ammonium sulphate alone. 
(6) Nitrogenous fertilizers only are recommended for Hawaiian 
rice soils, and for immediate effects a given amount of nitrogen in 
the form of ammonium sulphate will produce greater returns than 
from organic sources. Under no circumstances should nitrates be 
used as fertilizer for rice. 
(7) With nitrate as the only source of combined nitrogen for rice 
poor growth results. In addition nitrates in submerged soils become 
reduced to nitrites, wmich are poisonous to rice. Ammoniacal nitro- 
gen, on the other hand, is well suited to the needs of rice. 
(8) Very little nitrification takes place in submerged soil; am- 
monification, however, goes on, not so vigorously as in aerated soils, 
but sufficiently to supply the nitrogen needs of rice, provided suffi- 
cient organic matter is present in the soil. 
