Edible Products. 



320 



[April, 1912. 



of ammonia was maintained. Consider- 

 able increases in the ammonia content 

 succeeded the use of ammonium sulphate 

 or soy bean cake ; but these were very 

 small, with the application of nitrates. 

 As regards the growth of the rice plants 

 in the pots, the best results were obtain- 

 ed where ammonium sulphate was used ; 

 those from soy bean cake were inter- 

 mediate between the returns from the 

 no-manure series and the ammonium 

 sulphate series ; there was only a slight 

 increase of growth with calcium and 

 magnesium nitrates. Lastly, with res- 

 pect to this series of experiments, the 

 kind of manure used had no great effect 

 on the percentage of nitrogen in the 

 straw and grain. 



Further experiments were made in 

 flasks, in order to determine whether 

 the loss of nitrates was due to denitri- 

 fication or absorption by the rice plants ; 

 they showed that the former was the 

 operating cause, and from a practical 

 point of view, that nitrates do not form 

 a suitable manure for rice. The investig- 

 ation was supplemented by trials with 

 sand cultures, both wet and dry, to 

 determine if nitrogen as ammonia is 

 capable of supplying all the require- 

 ments by rice in regard to that element, 

 and what behaviour is shown by this 

 plant when nitrogen is only available as 

 nitrates. In the result, it was shown 

 that ammonium nitrogen is sufficient 

 for the vigorous growth of the plant, 

 except in the case of ammonium nitrate, 

 while where the soil was kept wet, 

 nitrate of soda completely failed to 

 bring about any growth of the rice. 

 Where the soil was not saturated with 

 water, similar results were obtained, and 

 in both cases interesting observations 

 weie made with nitrates other than 

 sodium nitrate. It should be mentioned 

 that preliminary work with rice in sand 

 cultures demonstrated that the presence 

 of five or more parts of nitrates per 

 million of irrigation water was usually 

 fatal to the plant. 



In the discussion of the results of the 

 experiments, it is pointed out that the 

 conversion pf nitrates into proteids is 



essentially a reduction process ; that 

 nitrates as such do not occur to any con- 

 siderable extent in plants ; and that 

 proteids, whatever their source, do not 

 contain nitrogen derived immediately 

 from nitrates but from ammonium com- 

 pounds. It is thus to be concluded that 

 the nitrogen contents of plants is likely 

 to be greater when they are supplied 

 with ammonium salts than when they 

 are given nitrates, and this conclusion is 

 supported by the work of Russell, 

 Hutchinson and Miller, as well as by the 

 results of the investigations under 

 review. In this connexion the interest- 

 ing suggestion is made that the circum- 

 stance that rice has been raised for 

 centuries under conditions that preclude 

 to a large extent the formation of 

 nitrates, has to a great degree caused it 

 to lose the power of reducing nitrates 

 eventually to form proteids. This sug- 

 gestion is to be made the subject of 

 further investigation. 



It may be stated shortly that the 

 result of the work to which attention is 

 given has been to show that ammonium 

 sulphate is of the greatest use as a 

 manure for rice in wet cultivation, while 

 nitrate of soda produces little or no 

 effect ; that soy bean cake is useful, but 

 inferior to ammonium sulphate in this 

 connexion ; that denitrification takes 

 place in paddy soils, causing the form- 

 ation of nitrates, and possibly the loss of 

 free nitrogen ; that in submerged rice 

 soils the formation of ammonium salts 

 occurs to a considerable extent ; that the 

 provision of nitrate as the only source 

 of combined nitrogen, for rice plants, 

 gives unhealthy and stunted growth ; 

 that the greater the presence of nitrates 

 the greater is the extent to which 

 nitrites are formed, and that this may 

 reach such a degree as to injure the rice ; 

 and that the failure of rice properly 

 to assimilate nitrates is probably due 

 to a lack of nitrate-reducing enzymes, 

 caused through the non-use of these 

 over a long period of time. 



For the agriculturist, the matter of 

 practical importance is that ammonium 

 sulphate and orgaqic nitrogenous bodies, 



