CHAPTER V. 



Decomposition of Cyanamid in the Soil. 



FACTORS INVOLVED. 



When Cyanamid is applied to the soil as a fertilizer it must 

 undergo decomposition before the nitrogen can be assimilated 

 by plants. The course of this decomposition, however, has 

 been in dispute since the adoption of Cyanamid in agriculture, 

 and a great deal has been written on the subject. Owing to 

 the incompleteness of many of the reports, and the omission 

 of essential data, no attempt will be made here to review all 

 of them. Of the recent work on the subject the most con- 

 sistent seems to be that of C. Ulpiani and H. Kappen. 



Experiments of Ulpiani. — In 1908 Ulpiani reported the 

 results of some experiments^ that indicate the difficulties sur- 

 rounding the solution of this important question. The results 

 of these tests are summarized in the table on page 33. 



Aqueous solutions were used containing 0.5 per cent, pure 

 cyanamide, together with various added materials as noted. 

 Calcium was added in the form of calcium hydroxide, two 

 equivalents to one of cyanamide. By "secondary products" 

 is meant dicyandiamide, urea, and traces of amidodicyanic 

 acid and ammonia, amounting to 33 per cent, of the total 

 nitrogen present. Soil was added where shown in the table, 

 in the proportion of 10 grams to 100 cc. of solution. The 

 "nutritive substance for bacteria" consisted of 0.05 per cent, 

 potassium phosphate, o.oi per cent, asparagine and o.oi per 

 cent, glucose. Bacteria were introduced into flasks 3 to 8 by 

 extracting soil with the water to be used to make the cyana- 

 mide solution. No bacteria were present in flasks i and 2. 

 0.4 per cent, chloroform was present in flasks 7 and 8. Deter- 

 minations for cyanamide nitrogen in the solutions were made 

 at frequent intervals. The percentages of cyanamide decom- 

 posed in 4 and 8 weeks respectively are shown in the table : 

 1 Gaz. Chim. Ital., 1908, II, No. 4, 358-417. 



