The two conditions have, in fact, sometimes been confused. Split the nitrogen application to decrease problems. Apply phosphorus and potassium as advised by your soil test report. Stage of growth Leaf blades normally contain higher levels of prussic acid than leaf sheaths or stems. Tillers and branches have higher levels than older plants because they are mostly leaves with little stalk material present.
Upper leaves contain more prussic acid than older leaves.
Thus prussic acid content of sudangrass and sorghum is highest in the earlier stages of growth. As plants mature, the stalk content increases, causing the prussic acid content in the total forage to decrease. However, the hazards associated with poisoning decrease only slightly with age if animals selectively graze the more tender new growth-those plant parts high in prussic acid. Sudangrass should not he grazed until it has reached a height of at least 18 inches. Species and variety Sorghums are generally much higher in prussic acid than sudangrass.