Yield, Protein, Nitrate, and Prussic Acid Content of Sudangrass, Sudangrass Hybrids, and Pearl Millets Harvested at Two Cutting Frequencies and Two Stubble Heights1

Abstract

AbstractThree sorghum × sudangrass hybrids, one sudangrass hybrid, three pearl millet hybrids, and ‘Piper’ sudangrass were harvested at two stubble heights and two cutting frequencies during the 1964 and 1965 growing seasons. Growth and chemical composition responses were as follows: Yields of all varieties harvested three times per year were superior to those of varieties harvested four times per year. Yields of all varieties cut at the 7.6‐cm (3 inch) stubble height were higher than those of varieties cut at 15.2‐cm (6 inch) when they were cut three times per year, excepting PM × 1 and PM × 3 in 1964. The crude protein of all varieties was 2.6% higher when harvested four compared with three times per year. Crude protein levels were higher when varieties were cut at 7.6‐cm compared with 15.2‐cm stubble height in the 4‐cut system. In the 3‐cut system, only small differences in crude protein resulted from varying the stubble height. The nitrate nitrogen accumulation in the herbage of all varieties was higher when they were cut at the 7.6‐cm compared with the 15.2‐cm stubble height in the 4‐cut frequency. The nitrate nitrogen content of the herbage of the pearl millet varieties was higher than for Piper sudangrass and/or sudangrass hybrids. In the 3‐cut frequency, higher HCN levels were found for herbage cut at the 15.2‐cm stubble height, whereas, in the 4‐cut frequency, higher HCN levels resulted from herbage cut at the 7.6‐cm stubble height. The average HCN level and, with but one exception, the nitrate nitrogen content of the herbage of sorghum × sudangrass hybrids were higher than those for the herbage of Piper sudangrass.