If there is any doubt then test the feed. During initial growth, much of the nitrate taken up by the plant is used for root and shoot development. At this stage, the roots are able to take up more nitrate than is required and it accumulates in the stems and leaves of the plant. Annual forage crops tend to accumulate greater amounts of nitrates than perennial forages. These crops are usually planted into well fertilized, manured or recently plowed grassland or pasture.
Nitrate concentrations vary in different parts of the plant.
The highest levels are found in the lower stems. Concentrations in the leaves and flowers are lower and the seeds or grain kernels are usually nitrate free. Specific species can become nitrate accumulators if appropriate conditions exist. The common problem crops and weed species are presented in the following table. Crops hurt by frost or hail have a reduced photosynthetic capacity.