Effect on Soil Reaction of Nitrogenous Fertilizers under the Anaerobic Conditions of Rice Production 1

Fertilizer reconnnendations for soils in the different areas of the world devoted to the production of rice are very different. This is particularly true with regard to the form of nitrogen which should be used to secure the best yields. While the results from numerous experiments have been reported, the conclusions drawn have not harmonized and indicate that a11 factors controlling the availability of the nitrogen were probably not controlled. Unfortunately, in many of the experiments, conditions such as reaction, texture, structure, and previous cropping history were not recorded so that variations in results can not be explained as due to these factors. The production of rice, because of the anaerobic condition developed after irrigation, requires a special type of agriculture in which the growth conditions are different from those of any other crop. Am0n~ the different factors whi.ch might affect the growth of rice that of reaction changes due to the forms of nitrogen used may be of considerable importance. The work reported in this paper was started in order to secure more information upon this subject. With the exception of changes due to continued applications of soditun nitrate and ammonium sulfate, very little inform~ttion regarding the reaction changes produced by nitrogenous fertilizers under either aerobic or anaerobic conditions is available. Pierre (~)3 recently reported reaction changes due to a number of nitrogenous fertilizers in soil studies under aerobic conditions. He grouped the compounds into two classes, such as sodium nitrate, calcium nitrate, and calcium cyanamid which reduced the H-ion concentration, and ammonium sulfate,, ammonium phosphate, Leunasalpeter, ammonium nitrate, and urea which increased the H-ion concentration in the order named.