Fertilizer application increases nitrate nitrogen concentration in Urochloa brizantha cv. MG5 as annual summer grass in temperate zone

In southwestern Japan, palisadegrass (Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster) is used as annual summer grass with fertilizer application. In this system, the risk of a poisonous nitrate nitrogen concentration in grass is high. Nevertheless, no report describes a study of nitrate nitrogen in palisadegrass as annual summer grass. Therefore, we clarified the effects of chemical fertilizer to nitrate nitrogen concentration in palisadegrass cultivated as annual summer grass for two years. Treatments were factorial combinations of three basal fertilizer applications (0, 100 or 200 kg N, P₂O₅, K₂O/ha) and two additional fertilizer applications (0 or 100 kg N, P₂O₅, K₂O/ha) in a randomized complete block design with five replicates. Results well demonstrated that nitrate nitrogen concentrations in palisadegrass increase with fertilizer application, especially with fertilizer added after decreased growth of palisadegrass caused by lower temperatures. Harvest of palisadegrass after additional fertilizer application requires awareness of its nitrate nitrogen content.