On Ike Behavior uf Xitrate in Paddy SoV. ij 



energetically by peculiar bacteria of the paddy soil, and these nitrites may- 

 persist for a time before they are further reduced to ammonia. Certaini 

 bacteria reduce nitrates very quickly to ammonia so that the intermediary^ 

 step, the formation of nitrites, can not be recognized. Certain other bacteria,, 

 however, produce considerable quantities of nitrites from nitrates. Nitrites 

 however show a strong poisonous character, since ihey act very powerfully^ 

 on the amido-groups and hence will also attack the amido-groups of proteins, 

 and thus kill the living protoplasm. 



In order to decide whether denitrification takes place extensively in. 

 paddy soil the following experiments were made : 



LABORATORY EXPERBIENT. I.^> 



One hundred g of soil were placed in an Erlenmeyer's flask of 300 cc 

 capacity and added 1 50 cc. of a solution containing 2 g of sodium nitrate and 

 0,2 g of K2HPO4 which liquid kept the soil covered in a thin layer. A humy 

 soil from our experimental field, a sandy loam soil from Kinai Branch 

 Station and a heavy clayey soil from Kaga Province served for this experi- 

 ment. The experiment was started on March 23, 1905 ; the flasks were 

 shaken every day and tested from time to time for nitrite by the reaction 

 of Griess. The room temperature during this experiment was i6-26°C. 

 After 24 hours a very decisive reaction for nitrite was already observed witb 

 the humus soil, much less than in the sandy soil, and only a trace was 

 found in the clayey soil. After 5 resp. 6 days, the maximum point of 

 formation of nitrite (0,003 resp. 0,002% KNOJ-^ was attained in the humy 

 and the sandy soil, whereupon the nitrite decreased, disappearing after 

 3 resp. 4 weeks, much nitrate still remaining in the solution. In the 

 clayey soil, however, the reduction of nitrate was very slow and the 

 maximum point was reached (0,01% nitrite) after 4 weeks; a little nitrite 

 was still present even after 5 months. From the start of the experiment 

 ammonia was occasionally tested for and reactions obtained in all of the 



i). Laboratory experiment I, II, III, IV, V and VI (d) were carried out by G. Daikuhara, and. 

 Laboratory expt. VI (a), (b) and (c) by T. Imastki. 

 2). By colorimetric determination. 



