The effect of nitrogen fertilization on yield, HCN potential, and nitrate nitrogen content of three varieties of sorghum

The effect of nitrogen fertilization on yield, hydro cyanic acid potential (HCN-p), and nitrate nitrogen accumulation was studied in three varieties of sorghum in 1965.

The five nitrogen treatments used in this field study at Knoxville were: N₀ which received no applied nitrogen, N₁ which received 54 kg. of nitrogen per ha. at planting, N₂ which received 27 kg. per ha. at planting and 27 kg. after the second harvest, N₃ which received 108 kg. per ha. at planting, and N₄ which received 27 kg. per ha. of nitrogen at planting and 27 kg. after each of the first three harvests.

The plants were cut to a 20 cm. stubble height each time they reached a height of 75 cm. and analyzed for yield, HCN-p, and nitrate nitrogen content.

The sodium picrate method was used for determining HCN-p, and the official A.O.A.C. phenoldisulfonic acid method was used for nitrate nitrogen determinations.

Yield was affected more by the distribution of nitro gen application than by the total amount applied. However, plants receiving some nitrogen at any time during the growing season produced higher yields than plants receiving no applied nitrogen. Suhi-1 produced significantly higher yields than Greenleaf or Piper in this study.

HCN-p was affected by nitrogen fertilization. In general, higher nitrogen rates produced higher levels of HCN in the plants. Split nitrogen applications produced higher season averages of HCN than the same total amounts applied only at planting; however, the highest harvest readings occurred in plants receiving all their nitrogen at planting. Suhi-1 was the only variety which consistently produced HCN levels that would be considered dangerous (above 800 ppm).

The data were inconclusive as to nitrate accumulations. The range of the readings was from 1475 to 3750 ppm. No trends or patterns were detected.