122 Decomposition of Cyanamide and Dicyanodiamide 



Barley-Field Trials. 



The following nitrogenous dressings were tested on a heavy loam on 

 the Rothamsted Farm at the rate of 30 lbs. nitrogen per acre : 



(1) Ammonium sulphate. 



(2) Cyanamide. 



(3) Cyanamide 9 parts, 

 Dicyanodiamide 1 part. 



(4) Cyanamide 1 part, 

 Dicyanodiamide 9 parts. " 



The soil contained 1-7 per cent, carbonate of lime. The plots, 

 measuring J^j acre, were arranged in duplicate, including controls 

 without nitrogen, and all received 3 cwts. superphosphate per acre. 

 Both dressings were applied to the plots on 26th March, that is, 10 days 

 before sowing, in order to avoid any possible retardation of germination 

 by the cyanamide. The seed was sown on 5th April and the crop 

 harvested on 6th September. 



The yields are set out under Table VIII. 



The above experiments showed that in pots dicyanodiamide caused 

 no appreciable injury to the plants when supplied in quantities not 

 exceeding 18 mgs. N per kilo soil. In larger amounts, however, it 

 proved increasingly harmful and depressed the yields more or less 

 proportionately. 



In the actual field no significant injurious effect was produced by a 

 dressing of dicyanodiamide, equivalent to 27 lbs. nitrogen per acre. 



The influence of dicyanodiamide on plant growth has previously 

 been investigated by several experimenters, and a brief resume of the 

 results may be given here. M. Gerlach and P. Wagner (12) and 

 InimendorfP(i3) were the first to observe its harmful effect on plants, 

 but have given no details as to the amounts used and the quantitative 

 effect on the yield. 



In Seelhorst and Miither's(i4) experiments the effect of dicyanodi- 

 amide varied with the soil: on a sandy soil barley showed white tips 

 and died several days after germination. In a loam the plants developed 

 nearly normally although retaining the white tips. 



R. Perotti(i5) found that dressings of dicyanodiamide not exceeding 

 1 gram in 1400 grams soil produced considerable increases in the yield 

 of wheat, buckwheat and flax, and concluded that the value of nitrolim 

 depended upon the formation of dicyanodiamide in the soil. C. Ulpiani (iG) 

 took a similar view. 



