April, 1912.] 



319 



Edible Products, 



taken in by green plants in the form of 

 nitrates, hut that they can make use of 

 it directly by absorbing ammonium 

 sulphate through the roots. In this way, 

 the old opinion that nitrates alone were 

 available for absorption from the soil by 

 plants has received considerable modi- 

 fication, and it is the purpose of the 

 present article to review investigations 

 that have been undertaken lately in 

 connexion with the matter. 



Some of this work has been done at the 

 Hawaii Agricultural Experiment Sta- 

 tion, and is described in Bulletin No. 24 

 of that Institution. In this, it is pointed 

 out that the usual practice is to refer to 

 the nitrogen in nitrates as being present 

 in a mere available form than that con- 

 tained in ammonium sulphate, dried 

 blood or hoofs and horns. As regards 

 this, as is stated, while the application 

 of nitrates is more economical and more 

 stimulating to plant growth than that 

 of ammonium salts, it is not a necessary 

 consequence that nitrates are more 

 easily changed into proteids, or that they 

 are more readily assimilated than the 

 naturally occurring ammonium com- 

 pounds. The difference between the 

 behaviour of nitrates and that of ammo- 

 nium salts of the latter are likely to 

 cause an unfavourable soil acidity, and 

 the fact that the former are less firmly 

 fixed in the soil, and therefore more 

 easily taken up by plants. In connexion 

 with the subjects, reference is made to 

 the researches of Russell, Hutchinson 

 and Miller, and to that of other observ- 

 ers. The investigations of the experi- 

 menters just mentioned, it may be said, 

 receive special attention in the Agricul- 

 tural Neivs, Vol. IX., pp. 33 and 98. 



Returning to the matter in the Bulle- 

 tin mentioned, it is pointed out that the 

 soils on which rice is cultivated form a 

 useful means of investigating the ques- 

 tion of the direct assimilation of ammo- 

 nium sulphate, because little or no nitri- 

 fication can take place in them, in their 

 water-logged conditions, on account of 

 the difficulty of the access of air ; in fact 

 denitrification is likely to occur, especi- 

 ally as such soils often contain large 



quantities of organic matter which prob- 

 ably tend to assist in dentrification. 

 After shortly dealing with past experi- 

 ments that have been made in relation 

 to nitrogen assimilation by rice, the 

 Bulletin proceeds to describe manurial 

 experiments with that crop that have 

 been conducted at the Hawaii Experi- 

 ment Station for the past two years. 



On a field scale, the trials have shown 

 that only slight effects were produced by 

 the employment of nitrate of soda, 

 either in one application before trans- 

 planting, or applied at intervals during 

 the growth of the crop. The results 

 were different with ammonium sulphate, 

 for its use gave considerable increases in 

 the return, more especially from the 

 single application. It is pointed out that 

 the greater loss of nitrate of soda by 

 leaching may contribute to this effect, 

 but that it is unlikely that the condition 

 was brought about solely through this 

 circumstance, ' for the yields from the 

 single application of nitrate of soda were 

 greater two times of the three than the 

 yields from the repeated applications,' 



The importance of deciding whether 

 nitrates are carried out of the reach of 

 the roots of the plants, and if they are 

 lost to any great extent through denitri- 

 fication, led to the making of pot experi- 

 ments, with soil taken from a rice field 

 after it had been aerated for a period of 

 two months. In the trials each pot 

 received the same amount of sulphate of 

 potash and of superphosphate; the diffei- 

 ences of treatment were comprised in 

 the employment of ammonium sulphate, 

 sodium nitrate, calcium nitrate, magne- 

 sium nitrate and soy bean cake, in quan- 

 tities providing 0"6 grammes of nitrogen 

 per pot. Tests made at intervals showed 

 that nitrates were formed in all the 

 pots, within five to ten days after water 

 had been added and were present in the 

 largest amount, by far, in pots contain- 

 ing nitrates. In no case was the accu- 

 mulation of nitrites greater than two 

 parts per million of the irrigating water. 

 As time elapsed the nitrate content was 

 reduced to a low minimum, except where 

 it was applied repeatedly ; whereas that 



