September 15, 1904] 



NA TURE 



491 



rate of \ kg. per looo kg. live weight was tried by Hansen 

 and Giinther and ImmendortT, the substance employed con- 

 taining fully 8 per cent. P.Oj. It was spread twice daily 

 on the litter in the stall. The result obtained by Hansen 

 and Giinther was that after lying for seventeen weeks in 

 Che pits the manure that had been untreated had lost 10-35 

 per cent, of nitrogen, whereas that treated with the phos- 

 phatic gypsum showed a loss of 1447 per cent. The loss of 

 nitrogen found by Immendorff when this substance was used 

 amounted to 19 S per cent. This substance, like the others, 

 would therefore appear to be valueless as a fixer of nitrogen. 



Effects of Gypsiityi. — This substance has long been re- 

 commended as an agent for conserving nitrogen in the dung- 

 heap. The results of its use, spread twice daily on the litter 

 in the stall at the rate of i kg. per 1000 kg., live weight, in 

 the experiments conducted by Hansen and Giinther, were 

 that in the presence of gypsum the loss of nitrogen amounted 

 to 1 1 89 per cent., which compares with a loss of 856 per 

 cent, when nothing was mixed with the dung. 



Schneidewind, using a much larger quantity of gypsum, 

 namely, 5 lbs. per 100 lbs. of dung, found that the loss of 

 nitrogen was reduced from 35-69 per cent, to 15-22 per cent. 

 In this connection he says : " The use of gypsum has 

 markedly reduced the loss of nitrogen. Assuming the con- 

 served nitrogen to have a good action on the crop, this 

 -agent may be said to have paid. But as the bulk of the 

 nitrogen so conserved was found to consist of slow-acting 

 albuminoid compounds, and seeing that the sulphate of 

 lime was largely reduced to sulphides, which are directly 

 injurious to plants, we cannot conclude that the use of 

 gypsum has been profitable. Investigations with this sub- 

 stance will, however, be continued." 



Hansen and Giinther carried their experiments the length 

 of using the various lots of manure on crops, but this part 

 of their researches w-as hardly more favourable to the use 

 of conservation agents than the other. They thus express 

 themselves : " When the various manures w'ere used on 

 crops, five times in six the treated manure acted no better 

 than the untreated. Only on one occasion was an improve- 

 ment observable. Field and pit experiments alike have 

 proved that the conservation agents emploved are of no 

 value." Schneidewind expresses himself equally forcibly 

 when he says : " As the result of many experiments con- 

 ducted by ourselves and others, we have arrived at the con- 

 clusion that chemical substances are valueless as conserving 

 agents." 



Pfeiffer also tried sulphuric acid sprinkled over the manure 

 as it was placed daily in the pit, when it was' found that 

 the loss of nitrogen was reduced from 27-8 per cent, to 

 7-1 per cent. In this connection Pfeiffer says: "The cost, 

 however, was nearly a mark for each kilo, of nitrogen con- 

 served, and the use of sulphuric acid is associated with so 

 many drawbacks that its employment cannot be recom- 

 mended. " 



Schneidewind came to a similar conclusion, and thus 

 expresses himself : "As a result of numerous conservation 

 experiments carried out with various quantities of sulphuric 

 acid, and with various acid sulphates, we cannot advise the 

 use of these substances." 



But although no benefits have been obtained from the use 

 of the substances indicated, some useful information is avail- 

 able as to the advantages of giving attention in other 

 directions to the management of farmyard manure. Hansen 

 and Giinther took four lots of manure of similar character, 

 .storing two of the lots in pits and placing the other two 

 in heaps in the open field. From the end of September 

 until the middle of December the pitted material had on 

 the average parted with 13-25 per cent, of total nitrogen, 

 whereas the loss in the manure in heaps averaged 25-3 per 

 cent. When the behaviour of the ammoniacal nitrogen was 

 investigated it was found that the loss was 35-73 per cent, 

 in the pits and 82-5 per cent, in the heaps. The loss, there- 

 fore, is greatest in that part of the nitrogen which is the 

 most active and the most valuable. 



In another series of experiments by the same investigators 

 the manure was all placed in pits, but in one case it was 

 spread equally and trodden down, while the escape of liquids 

 was prevented. In the other case the manure was simply 

 thrown loosely and irregularly into the pit without spread- 

 ing or treading, the surface being left uneven and therefore 

 much exposed to the air, while the liquids were allowed to 



NO. 1820, VOL. 70] 



dram away. After lying for twenty-two weeks the loss of 

 nitrogen was 15-76 per cent, in the pit containing the care- 

 fully treated manure, whereas in the other pit the loss 

 amounted to 34-58 per cent. 



Pfeiffer in a series of experiments proved that much of 

 the nitrogen that disappears from manure is lost before 

 the manure is transferred from the stall to the dungstead. 

 He is strongly of opinion that stalls, boxes, and the like, 

 should either be cleaned out twice daily, or, if the con- 

 struction admits, the manure should be left to accumulate 

 until it is some feet in depth, as in the system of manage- 

 ment that prevails in cattle-courts and yards in this country. 



The general conclusion arrived at, and clearly expressed 

 by Pfeiffer, is that excessive loss in manure can be best 

 avoided by storing it in a deep mass in a water-tight dung- 

 stead placed in a well-shaded situation, in which the material 

 I is firmly compressed. The necessary compression can be 

 secured in various ways, perhaps most conveniently and 

 effectively by means of the treading of cattle. The use of 

 a considerable proportion of moss-litter is strongly recom- 

 mended. This substance not only absorbs and retains the 

 liquids, but, being acid, it fixes ammonia. In the absence 

 of moss-litter, loamy soil rich in humus will prove a useful 

 substitute. 



The Chemical Fixation of Atmospheric Nitrogen. 



It has for long been the dream of chemists to discover, 

 or welcome the discovery of, a chemical process, capable 

 of industrial application, by which the nitrogen of the air 

 could be made available to replace or to supplement our 

 rather limited supplies of nitrogenous manures. In his 

 Presidential .i^ddress. Sir William Crookes had something 

 to say on this fascinating subject, and looked hopefully to 

 electricitv to solve the problem. He pointed out that with 

 I current costing one-third of a penny per Board of Trade 

 I unit a ton of nitrate of soda could be produced for 26/. ; 

 while at a cost of one-seventeenth of a penny per unit — 

 a rate possible when large natural sources of power, like 

 Niagara, are available — the cost of such artificial nitrate 

 of soda need not be more than 5L per ton.' 



Dr. von Lepel, in giving an account of recent work on 

 this subject to the winter meeting of the German Agri- 

 cultural Society in February of this year," puts the cost of 

 electric nitrate, as compared with Chili nitrate, in the pro- 

 portion of 24 to 39, which is in close agreement with Sir 

 William Crookes's estimate. Lepel points out that the 

 material obtained, neutralised by some alkali, consists of 

 a mixture of nitrate and nitrite. When used in pot-culture 

 experiments it has given results closely agreeing with those 

 furnished by Chili nitrate. 



Good progress would also appear to have been made in 

 another direction in the commercial fixation of atmospheric 

 nitrogen, and a short account of the results was communi- 

 cated bv Prof. Gerlach, of Posen, to the meeting of the 

 German Agricultural Society already referred to, and i^ 

 published in the same issue of the Mittheilungen. 



When air which has been freed of o.xygen is conductei- 

 through finely disintegrated calcium carbide at a high 

 temperature, one atom of carbon is displaced by two atoms 

 of nitrogen, and calcium cyanamide (CaCN,) is formed. 

 This substance is also produced when a mixture of lime or 

 chalk and charcoal is heated to a temperature of 2000° C. 

 in a current of air.' When pure, this substance holds 35 

 per cent, of nitrogen, but in its crude commercial form it 

 contains only about 20 per cent. Treated with acids, calcium 

 cyanamide is changed into dicyandiamide, a substance hold- 

 ing nearly 67 per cent, of nitrogen, but directly poisonous 

 to plants. Or, if heated in superheated steam, calcium 

 cyanamide parts with all its nitrogen as ammonia, which, 

 of course, is easily brought into a portable form. 



But experiments conducted at Posen and Darmstadt 

 during the past three years, both in pots and in the open 

 field, have shown that calcium cyanamide itself is a useful 

 nitrogenous manure, field experiments giving results about 

 20 per cent, below those obtained by the use of an equal 

 amount of nitrogen in the form of sulphate of ammonia. 



1 Crookes, "The Wheat Problem," p. 47. 



- Dr. von Lepel, " Neuere , Versuche zur Nutzbarmachung des atnio- 

 spharischen Slickstoffs durch Elektrische Flammenbogen," MMeil. d. 

 Dent. La7id. GescU., 1904, Stuck 8. 



'■'• Bull, /;;.-/. Insi. June 30, '904. 



