LETTER OF TRANSMITTAL 
Honolulu, Hawaii, October 1, 1913. 
Sir: I have the honor to submit herewith and recommend for publication, as 
Bulletin No. 31 of the Hawaii Agricultural Experiment Station, a paper on Rice 
Soils of Hawaii : Their Fertilization and Management, by W. P. Kelley, chemist. 
The experiments on rice as carried out by this station indicate quite conclusively 
that for the most successful production of rice all conditions which tend toward 
nitrification should be avoided. The application of nitrates has been found to 
be of little or no avail, and sometimes even positively injurious, while the use 
of ammonium sulphate brings about greatly increased yields. In harmony with 
this finding is the evidence that conditions which allow nitrification to take 
place in rice soils result in a diminished yield of rice. It appears, therefore, 
that ammonium sulphate should be the form of commercial nitrogen to apply 
to rice and that rice soils should not be aerated between crops. These results 
are probably applicable to other regions than the rice lands of Hawaii. 
Respectfully, 
E. V. Wilcox, 
Special Agent in Charge. 
Dr. A. C. True, 
Director Office of Experiment Stations, 
U. S. Department of Agriculture, Washington, D. C. 
Publication recommended. 
A. C. True, Director, 
Publication authorized. 
D. F. Houston, 
Secretary of Agriculture, 
CONTENTS 
Page. 
Introduction 5 
Origin or rice soils 
Mechanical composition ' . 6 
Chemical composition 8 
Fertilizer experiments 10 
The form of nitrogen for rice 17 
Ammonification and nitrification in rice soils 20 
The management of rice soils 22 
Summary 24 
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