766 Journal op the Department of Agriculture. 



into use as a fertilizer. As a supplier of nitrogen it has the adxantage 

 over sulphate of ammonia that it Joes not render acid any soils 

 deficient in carl)onate of lime. 



It may l)e said at once that caJcium cyauaiiiide, as such, is (_»f 



Xo Use wiiatevek to Plants, 



but in the soil it slowly breaks up, and eventually compounds are 

 formed from it which are of distinct value to the plant. The ap})lica- 

 tion of calcium cyanamide to the soil is not without risk to the crop, 

 and in more than one way. As in many other cases, when a new idea 

 is introduced people do not take to it at once, but when once its value 

 heg-ins to dawn on them they fly to the opposite extreme and misuse 

 it or apply it in excess. After the first introduction of chemical 

 manures they speedily fell into disfavour simply because they had 

 been applied injudiciously or ig-norantly and brought disaster. This 

 is no arg-ument against the use of calcium cyanamide, but means 

 merely that it must be used with circumspection, and with brains. 



Calcium cyanamide, as above remarked, breaks up in the soil. 

 This is due to the action on it of the soil water, and dicyanamide, a 

 substance poisonous to plants, is produced. The dicyanamide in turn 

 also decomposes, and ammonia is formed, with subsequent nitrifica- 

 tion. When first applied, therefore, calcium cyanamide is poisonous 

 in its action, but this effect slowly passes away. It follows, naturally, 

 from this that cyanamide must be applied some time before sowing-, 

 otherwise it v/ould prevent g-ermination of the seed. Hence, too, it 

 cannot as a rule be used as a top-dressing" when the young- crop has 

 appeared above ground. It has, nevertheless, been recommended foi' 

 cereals in this form. It must, in consequence, be looked upon as a 

 slow-acting" fertilizer. 



The poisonous effect of cyanamide shortly after its a})i)licati()u io 

 the soil is not without its advantages. It is well known that heating- 

 the soil may increase the ultimate crop. A similar result has followed 

 the addition of such substances as carbon disulphide, naphthalene and 

 other g"ermicides, which destroy pests in the soil, not only such as 

 wireworms and others of that class, but also microscopic organisms, 

 whicl) may either injure the plant itself directly or indirectly by 

 destroying" the bacteria which aid it in its growth. Calcium carbide 

 has been used for such a purpose, and it is also easy lo see how similar 

 must be the action of the poisonous emissions from the cyanamide 

 when once it begins decomposing in the soil. 



As far as the 



Practical ArpnicATiON , 



Ihe effects, and the efficacy of cyanamide as a fertilizer is concerned, 

 there have been no investigations in South Africa, so that all our 

 information must be based on experiments carried on in other coun- 

 tries. Of some of these experiments I propose to give an outline, and 

 it will be seen m what respect their results are explained by the fore- 

 going remarks. 



In Austria it has been found {Exp. Stn. Rec, vol. 33, p. 818) that 

 cyanamide retards the germination of both wheat and barley, particu- 

 larly the wheat, if supplied in proportions varying from one-tenth of 

 a ton to half a ton per acre. That, however, should not be regarded 



