Vol. X. No. 250. 



THE AGRICULTURAL NEWS. 



371 



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 

 denitnfication takes place in paddy soils, causing the 

 foi'mation of nitrites, and possibly the loss of free nitro- 

 gen; 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 com- 

 bined 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 mm- use of these over 

 a long period of time. 



For the agriculturist, the matter of practical im- 

 portance is that ammonium sulphate and organic 

 nitrogenous bodies are preferable to nitrates, in paddy 

 cultivation. For the investigator, the suggestion arises 

 regarding lines of research for the purpose of en(juiring 

 further into the forms in which nitrogen is assimilated 

 directly by plants. 



SEED STERILIZATION AND INOCULATION 



Before inoculating the seed of leguminous plants with 

 the nodule-forming organism (FseHclomonaf radiricola) it is 

 often the custom to disinfect the seed, in one of the approved 

 ways, in order to prevent interference from other organisms 

 with the growth of the nodule organism, or in order to ensure 

 that the latter is not already present. The question has 

 naturally arisen as to the possibility that the development of 

 this organism suffers interference through the presence on the 

 seed of the substances used in disinfection. . In order lo gain 

 information concerning the matter, work has been carried out 

 recently by the Bureau of Plant Indu.stry of the United 

 States Department of Agriculture. The results of this are 

 given in Circular No. 67 of that liureau, and the informatior 

 is employed in the presentation of the following facts. 



In the investigation, the object of the first trial was to 

 gain some knowledge as to the eflect of disinfectants with 

 respect to germination, and in rendering seeds free from bac- 

 terial infection. In regard to the first, hydrogen peroxide 

 was found to cause the least injury, being innocuous even 

 when used on germinating seed. Leguminous seeds possess- 

 ing hard coats withstood the poisoning action of formal- 

 dehyde and corrosive sublimate much better than the non- 

 leguminous seeds. As far as the .second consideration, above, 

 is concerned, all the disinfectants (corrosive sublimate, formal- 

 dehyde and hydrogen peroxide) were found to be effective. 



The succeeding part of the experimentation had relation 

 to the residual effect of the treatment ot seeds with di.sinfect- 

 ing substances. The seed after treatment with the latter 

 was rinsed several times in test tubes with sterile water, and 

 then attempts were made to grow a micro-organism in the 



rinsing water, that employed being Bacillus suOiilis. In 

 the case of corrosive sublimate the proportion contained in 

 the water used for washing the seed the fourth time was 

 still sufficient to be fatal to Ji. subtilis. Similar tests were 

 made with formaldehyde and hydrogen peroxide; with the 

 latter, two rinsings were not found sufhcient to remove 

 it from the seed, and even in the case of the third wash 

 water there was a slight interference with the growth of the 

 bacillus, though much less in degree than that from formal- 

 dehyde or corrosive sublimate. 



Repetition of the experiment, using Hasks instead of 

 test tubes, whereby about five times as much washing water 

 could be employed, showed complete removal of the disinfect- 

 ants, at least as far as their effect on B. subtilis was con- 

 cerned, by the employment of the larger amounts of water. 

 A result obtained during the course of the investiga- 

 tions was that the disinfectants which are least able to 

 pass through the seed coat are more nearly removed when 

 small quantities of water are used for washing, than are those 

 capable of penetrating to the interior of the seed. Further, 

 reference is made to the work of Hutchinson and Miller, 

 in .showing that incomplete sterilization of seed often arises 

 from the presence of air bubbles upon it or inside it (the 

 Journal "f Agricultural Science, Vol. Ill, p. 179). The 

 matter was improved by carrying on the disinfection beneath 

 a vacuum pump, whereby a greater amount of penetration of 

 the disinfectant was obtained. In relation to this subject, it 

 was observed, further, that in the latter method of seed 

 disinfection, the difficulty of removal of the sterilizing agent 

 by rinsing was increased. 



In the case of hydrogen ))eroxide used as a seed disin- 

 fectant, seeds were treated with this, the strength of the 

 solution being 3 per cent., washed three times with sterile 

 distilled water, and then inoculated with cultures of the 

 nodule organism. A duplicate series was washed several 

 times before inoculation, and it was shown that these seeds 

 were nearly sterile as regards the presence of organisms oq 

 the coat. In the result, the l)acteria on the sterilized seed 

 showed a rapid mortality — a fact which indicates that some 

 influence was present which lowered their normal vitality; the 

 decrease in vitality varied with the vigour of the culture. 



The conclusion of the whole matter indicates that when 

 seeds are disinfected before being treated with cultures of the 

 nodule organism, the work should be done with special care, 

 and where very accurate control is necessary, disinfection is 

 required to eliminate the chances of accidental contamination 

 with the nodule organism. Further, the use of corrosive 

 sublimate prior to inoculation is harmful, and that while 

 hydrogen peroxide has been found to be effective as a disin- 

 fectant, it does much less damage than that which the nodule 

 organism is likely to receive from corrosive sublimate or 

 formaldehyde. 



In Diplomatic and Consular Reports, No. 4716 Annual 

 Series, it is shown that the value of the exports from the 

 Zanzibar Protectorate rose from £1,011,364 in 1909 to 

 £1,033,467 in 1910. The principal increases during the 

 period took place under copra, grain, petroleum, and sugar, 

 and the decreases under cloves and clove stems, gum copal, 

 ivory and piece-goods. The value of the export of cloves — 

 the principal product — was £-330,410. as compared with 

 £264,960 in 1908 and £396,121 in 1907; the actual export 

 in 1909 was greater than in 1907, but the value was smaller 

 on account of the fall of prices. 



