Oil tlie Beliavior of Nitrate in Paddy Soil. ^5 



This result shows again that the well rotten compost when sterilized 

 has no depressing effect upon the efficiency of nitrate-N, while when not 

 sterilized it depresses the yield very much, owing certainly to the 

 importation of denitrifying organisms into the soil. The efficiency of nitrate-N 

 is also much depressed by the simultaneous application of rape cake. 



CONCLUSIONS. 



(i). When nitrate is applied to the paddy soil it is reduced to some 

 extent first to nitrite and then to ammonia and to elementary N, the loss of 

 which varies according to the species of denitrifying organisms and the 

 amount of soluble organic compounds present originally in the soil. 



(2). When nitrate is applied to the paddy soil together with much 

 organic matter in easily available form for microbes such as glycerine, 

 Na-acetate, starch, fresh oil cakes and straw, it is destroyed extensively by 

 denitrification, the most part of its nitrogen being lost as free N, while only 

 a certain portion of it remains in the soil, being partly assimilated by microbes 

 and partly absorbed as ammonia by the soil or plants. 



(3). The question why nitrate is not a favorable manure for plants 

 grown in paddy land can be answered as follows : 



a). The loss of N by denitrification is larger in paddy soil than in dry 



land, 

 b). More of the poisonous nitrites are formed there than in dry land.^^ 

 c). Loss of nitrate takes place easily by the system of irrigation^ 

 practiced with paddy plants, being inevitable in the farmers practice. 

 (4). Dry land surface soil when no organic manures are applied along 

 with nitrate,-^ does not favor tlenitrification nor nitrite -formation while in 

 the subsoil reduction occurs to some extent. In very moist conditions, 

 however, as in the rainy season and especially when much organic manure 

 is applied along with nitrate, some denitrification takes place even in top- 



i). Young rice plants placed in a potassium nitrite solution of 0,1 % died after 5 days. 



2). According to Ainpola calcium nitrate is less attacked by denitrifying microbes than sodium 

 or potassium nitrate, but in most soils calcium nitrate added will surely ht changed by alkali-salts 

 and nitrates of sodium or potassium be formed. 



