Sorghum sickness

  • The crop residue of a crop having a wide CN ratio takes a long time to decompose. During the process of decomposition, part of soil nitrogen is temporarily immobilized. (When CN ratio is more than 30 immobilization occurs.)
  • Such an effect is pronounced in sorghum. It is a fast-growing crop that exhausts the nutrient status of the soil. Also, stubbles of sorghum have a wide CN ratio hence take a long time to decompose.
  • Temporary immobilization of Nitrogen affects the growth of succeeding crops.
  • Early nitrogen deficiency symptoms appear in succeeding crops due to the wide CN ratio of sorghum residue. This is called the sorghum effect or sorghum sickness.
  • To reduce the sorghum effect, 25% more nitrogen is applied at the time of the first fertilizer dose of a succeeding crop. It increases the rate of decomposition and overcomes the immobilized nitrogen.