40 FERTILISERS CONTAINING NITROGEN [chap. 



per cent, of nitrogen, the theoretical substance being 

 CaCNg with 35 per cent, of nitrogen. As a fertiliser, 

 calcium cyanamide has been subjected to a series 

 of sufficiently conclusive trials which show that on most 

 soils it is almost but not quite as effective as sul- 

 phate of ammonia supplying an equal amount of 

 nitrogen. For example, Table IX. shows the results of 

 four trials at Rothamsted in 1905, mangolds and 

 barley being the crops under experiment. On soils 

 poor in lime, doubtless the cyanamide would give 



Table IX. — Rothamsted Experiments with Calcium Cyanamide, 



1905. 



comparatively better results, because then the carbonate 

 of lime, which is the bye-product of the decomposition 

 taking place in the soil, would itself be of considerable 

 value. The Rothamsted soil, however, contains sufifiicient 

 carbonate of lime to minimise the effect of this factor. 

 The chief drawback to the practical employment of 

 calcium cyanamide as a manure is its light, blow-away 

 character, and the injurious effect upon germinating seeds 

 of the ammonia and other gases given off when it is 

 first applied to the soil. It has, therefore, to be sown 

 on the land alone, and it should be incorporated with 

 the soil a week or so before any seed is sown. For 

 similar reasons it should not be used as a top dressing 

 unless mixed with earth beforehand, though recent 

 experiments suggest that this objection has been 



