JOURNAL OF AGRKULTDRAL RESEARCH 
Vol. XXVII Washington, D. C., March 8, 1924. No. 10 
EFFECT OF NITRATE APPLICATIONS UPON THE 
HYDROCYANIC-ACID CONTENT OF SORGHUM 1 
By R. M. Pinckney 
Research Assistant , Division of Soils, Minnesota Agricultural Experiment Station 
INTRODUCTION 
It is now generally recognized that growing plants of the sorghum 
family contain hydrocyanic acid, which is present largely as a glucoside 
(dhurrin), from which hydrocyanic acid is set free by the action of an 
enzym normally present in the sorghum plant. Under conditions favor¬ 
able to the action of this enzym all the hydrocyanic acid is liberated, 
the time required varying from less than 2 hours at 45 0 C., to less than 
20 hours at room temperature (20° C.). 
The proportion of hydrocyanic acid varies much, young plants gener¬ 
ally containing a higher percentage than more mature ones grown under 
like conditions. In green plants the leaves contain a higher percentage 
than the stems, a fact which may explain part of the difference found 
between young and old plants, as the leaves of the former constitute a 
much greater proportion of the total weight of the plant. 
In 1903 Briinnich, 2 in Australia, found that sorghum plants fertilized 
with sodium nitrate contained more hydrocyanic acid than those grown 
on unfertilized soil. 
Four years later Alway and Trumbull, 3 in Nebraska, from the analy¬ 
sis of large, dark green, and of small, yellowish green sorghum plants 
• growing as volunteers, concluded that the higher percentage of prussic 
acid found in the larger and greener plants was due to more available 
nitrogen in the soil where they grew. 
In 1915 Willaman and West 4 concluded from field experiments in 
Minnesota that “on soils deficient in nitrogen, added nitrogen may 
slightly increase the prussic acid in sorghum,” while “with a fertile soil 
and abundant nitrogen this effect may not be produced” , 5 and from 
later studies 6 that, “unhealthy plants usually contain more hydrocyanic 
acid than healthy ones. The unhealthy condition may be due to mal¬ 
nutrition, to improper transpiration, to insect pests, or to other causes,” 
while “adequate water supply is usually accompanied by low, and in¬ 
adequate by high, hydrocyanic-acid content.” Vinall 7 from a critical 
1 Received for publication Jan. u, 1924. Published with the approval of the Director as Paper No. 435 
of the Journal Series of the Minnesota Agricultural Experiment Station. 
2 Brunnich, J. C. hydrocyanic acid in fodder plants. In Jour. Chem. Soc. [London], v. 83, pt. 2, 
p. 788-796. 1903. 
* Alway, F. J., and Trumbull, R. S. on the occurrence of prussic acid in sorghum and maize. 
In Nebr. Agr. Exp. Sta. 23d Ann. Rpt., 1909, p. 35-36. 1910* 
4 Willaman, J. J., and West, R. M. notes on the hydrocyanic-acid content of sorghum. In 
Jour. Agr. Research, v. 4, p. 179-185. 1915. 
5 -op. err., p. 184. 
5 -the effect of climatic factors on the hydrocyanic-acid content of sorghum. 
In Jour. Agr. Research, v. 6, p. 271-272. 1916. 
7 Vinall, H. N. a study of the literature concerning poisoning of cattle by the prussic acid 
in sorghum, Sudan grass, and Johnson grass. In Jour. Amer. Soc. Agron., V. 13. p. 267-280. 1921. 
Journal of Agricultural Research, 
Washington, D. C. 
83798—24 - 1 
Vol. XXVII, No. 10 
Mar. 8, 1924 
Key No. Minn.-49 
(717) 
