All plants can contain some nitrate, but buildup of nitrates to toxic levels in forage plants occur when they are under excessive stress. Certain plant species are more likely to accumulate nitrates. Certain weeds (such as pigweed), Johnsongrass, corn, sorghums, and Sudan grasses are the most common causes of nitrate poisoning, but any grass or weed with a high leaf-to-stem ratio can be a problem.
Nitrates are usually highest in young plants and nitrates decrease as plant mature, unless growth stress is encountered….
