370 



THE AGRICULTURAL NEWS 



XoVEMBER 25, 1911, 



because little or no nitrification can take place in them, 

 in their water-logged condition, on account of the diffi- 

 culty of the access of aii; in fact denitrificalion is likely 

 to occur, especially as such soils often contain large 

 quantities of organic matter which probably tend to 

 assist in denitrification. After shortly dealing with 

 past experiments that have been made in relation to 

 nitrogen assimilation by rice, the Bulletin jiroceeds to 

 describe nianurial experiments with that crojj that have 

 been conducted at, the Hawaii Kxperimorit 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 applica- 

 tion. It is pointed out that the greater lo.'s 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 circ\imstance, ' for the yields from the 

 single application of nitrate of soda were greater two 

 times out of three than the yields from the repeated 

 applications.' 



The impoitance 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 denitrifica- 

 tion, led to the making of pot operiments, 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 superphos- 

 phate; the differences of treatment were comprised in 

 the em])loyment of ammonium sulphate, sodium nitrate, 

 calcium nitrate, magnesium nitrate and soy bean cake, 

 in quantities providing 0-6 grammes of nitrogen per 

 pot. Tests made at intervals showed that nitrites 

 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 containing nitrates. In no 

 case was the accumulation of nitrites greater than two 

 parts per million of the -irrigating water. As time 

 elapsed the nitrate content was reduced to a low mini- 

 mum, except where it was applied repeatedly; whereas 

 that of ammonia was maintained. Considerable increas- 

 es in the ammonia content succeeded the use of ammon- 

 ium sulphate or so}' bean cake: but these were very 

 small, with the .ipplication of nitrates. As regards the 

 ■growth of the rice plants in the p(jts, the best results 

 were obtaini'd where ammonium sulphate was used; 

 .those from soy bean cake were intermediate between 



the returns from the no-manure series and the ammon- 

 ium sulphate seri^; there was only a slight increase of 

 growth with c:dcium and magnesium nitrates. Lastly 

 \\ith respect to t|?is series of experiments, the kind of 

 ni.uuire used had no great effect on the percentage of 

 nitrogen in the straw and g-raiu. 



Further experiments were made in Masks, in order 

 to determine whether the loss of nitrates was due to 

 dentritication 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 investigation was 

 supplemented by trials with sand cultures, both wet 

 and dry, to determine if nitrogen as ammonia is capable 

 of supplying all the requirements by lice in reward to 

 that element, and what behaviour is shoivn by this 

 plant when nitrogen is only available a:i nitrates. In 

 the result, it was, shown that ammonium nitroo-en is 

 sufficient for the vigorous growth of the plant, except 

 in the case of ammonium nitrate, ivhile where the soil 

 was kept wet, nitrate of soda completely failed to bring 

 about any growth of the rice. Where thj soil was not 

 saturated with water, similar results were obtained, and 

 in both cases interesting observations were tnade with 

 nitrates other than sodium nitrate. It should be men- 

 tioned that preliminary work with rice in sand cultures 

 demonstrated that the presence of five or more parts of 

 nitrites per million of irrigation water was usually fatal 

 to the plant. 



In the discussion of the results of the experiments, 

 It is jtointed out that the conversion of nitrates into 

 proteids is essentially a reduction process; that nitrates 

 as such do not occur to any considerable extent in 

 ])lants; and that proteids, whatever their source, do not 

 contain nitiv,gen derived immediately from nitrates but 

 from ammonium compounds. It is thus to be concluded 

 that the nitrogen content of plants is likely to be 

 greater when they are supplied with ammonium 

 salts than when they are given nitrates, and this 

 conclusion is Sl\ppor^ed by the work' of Russell, 

 Hutchinson' and .Aliller, as well as bv the results 

 of the investigations under review. In this connexion 

 the interesting 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 tc'a great degree caused it to lose the 

 power of reducing nitrates eventually to form proteids. 

 'I'his suggestion 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 



