Vol. XI. No. 272. 



THE AGRICULTURAL NEWS. 



307 



CONSIDERATIONS REGARDING NITROGEN 



FIXATION. 



The fact that nitrogen from the atmosphere becomes 

 fixed (that is united to other substances) in the soil, in the 

 presence of air, by a group of organisms called Azotobacter 

 nas become a matter of common knowledge among agricul- 

 turists since its discovery by Beijerinck in 1901, and the 

 group of organisms itself has received much investigation. 

 The results of this work have, however, been conflicting, 

 especially as regards the food requirements of the organisms, 

 although it is generally agreed that these include some form of 

 fermentable carbohydrate (a sugar) and a certain amount of 

 phosphorus in a form in which it is available. A further 

 investigation of these matters has been made in recent years 

 at the University of Wisconsin Agricultural Experiment 

 Station, the results of this being presented in Research 

 Bulletin No. 12 of that station: and these form the subject 

 of the present article. 



Trials with different soils showed that the power of the 

 Azotobacter in these to fix nitrogen varies greatly; in actual 

 experiments the amount of nitrogen fixed, fur every pram of 

 mannite (a sugar) consumed, ranging from 01.5 to 14 47 mgr. 

 The best sugars to use lor obtaining the greatest 

 amount of fixation in impure cultures of the organism were 

 found to be mannite and lactose (milk sugar): while maltose 

 and sucrose (cane sugar) enabled the bacteria to fix only 

 a comparatively small (juantity of nitrogen. In pure cultures, 

 the highest results were obtained with mannite and dextrin. 

 The superiority of milk sugar in impure cultures was not 

 maintained in those which were pure. 



The activity, and therefore the etticiency, of Azotobacter 

 was found to be increased when small quantities of the 

 carbohydrates were used. This is important in regard to the 

 fact that, where it is intended to inoculate soil with pure 

 cultures, the organisms should be exhibiting the greatest 

 activity that is possible 



In impure cultures, at any rate, dicalcium and tricalcium 

 phosphate were found to produce better results, respecting 

 nitrogen fixation, than monocalcium phosphate. 



When the period of incubation of the organisms in 

 a soil is unduly extended, losses take place of the nitrogen 

 that has been fixed already, and it is evident that in such 

 conditions the amount of nitrogen found is not a true indica- 

 tion of the amount actually fixed. Itesults obtained in the 

 investigation under consideration indicated that the period 

 of incubation for impure cultures shoulil not exceed fourteen 

 to eighteen days. 



The presence of small quantities of calcium carbonate is 

 sufficient, for the fixation to take place. It was not found 

 that there was a greater amount of nitrogen fixation when 

 the quantity of that substance was increased 



Difficulty was met during the experimentation in 

 obtaining a large growth of the organisms in liquid culture 

 media. This was overcome by the employment of a sand 

 slope of white quartz sand in tlie following way. The 

 culture solution to the amount of 20 c.c. was placed in 

 a conical flask of 150 c c. capacity, and 10 grams of 

 the quartz sand, previously washed, dried, screened and 

 ignited, was added in such a way that its surface formed 

 a slope going down into the culture medium. The enhanced 

 supply of air caused the bacteria to form a profuse growth all 

 over that surface. This method did not serve, however, 

 when large quantities of the organisms were required for 

 the purpose of determining their nitrogen content, as for 

 this object pure Azotobacter cells free from all other solid 

 matter were required. The means adopted finally comprised 



the use of 11-inch Petri dishes, containing the sterilized 

 nutrient medium, on to which, when it had solidified, 5 to 

 10 c c. of sterile salt solution, containing Azotobacter in 

 uniform suspension, was poursd. 



It seems that the protein content of Azotobacter cells 

 is influenced by the age of the culture in which they occur; 

 in any ca.se the results obtained were considerably lower than 

 those found by other investigators, and it is suggested that 

 the method of growing the organisms may possibly be 

 a cause of the difference. Another condition influenced by 

 the age of the culture was the phosphorus content of the 

 cells. 



Preparation of Tobacco by Electricity.— 



A short article in the Journal d Aijnculuire Tropicale for 

 June 1912 states that the journal De Indi.iche J/er/niiir has 

 recently given notice of the discovery by an engineer of 

 Sourabaya of a new process for preparing tobacco: in place 

 of submitting the leaves, for several weeks to the action of 

 warm air, as is usual, they are exposed for twenty-four hours 

 to the action of electricity. Unfortunately, nothing is said 

 as to the way in which the operation is conducted nor 

 concerning the manner of action of the electricity: whether 

 there is an electrolytic action on the very damp leave.s, or if 

 the change comes about through discharges at high voltage 

 or in any other way. 



The matter of importance is, however, that this mode of 

 working should not only greatly shorten the time required 

 for the operation, but should bring under complete control 

 the extent to which the colouring of the product takes place. 

 It should be added that, according to the report, the results 

 are yet far from being conclusive, but if they are eventually 

 confirmed, the new manner of procedure will completely 

 overthrow the ordinary methods for tobacco preparation that 

 are employed up to the present in the many factories in 

 .lava, which, it is said, are eager to adopt its application. 

 The journal mentioned first, above, states that return will be 

 made to the subject when an opportunit)- has been given for 

 obtaining additional information. 



DEPARTMENT NEWS. 



The Imperial Commissioner of Agriculture return- 

 ed to Barbados, from an official visit to St. Vincent, by 

 the S.S. 'Ocamo', on September 14, 1912. 



Mr. P. T. Saunders, Veterinary Officer on the Staff 

 of the Imperial Department of Agriculture for the 

 West Indies, returned to Barbados, from visits to 

 St. Vincent and the Northern Islands, by the R.M.S. 

 'Thames', on September 18. 



The exports of raw cotton from Shanghai fell from 

 1,482,299 cwt. in 1910 to 928,444 cwt. in 1911, a decrease 

 of nearly 40 per cent., and liusiness in raw cotton duiuig the 

 year was most unsatisfactory from the point of view of 

 exporters to Japan. The chief reason was to be found in 

 the destruction of an unusually large proportion of the crops 

 by the abnormal summer rains; the difficulty of forwarding 

 money to the producing centres owing to the position of 

 the native banks, and the unprecedented fall in prices in the 

 United states caused by the abundant crops in that country, 

 were also important determining elements. (From Diplo- 

 matic and Consular Eeports, No. 4966 Annual Series.) 



