Nitrate‐N Levels of Perennial Grasses as Affected by Time and Level of Nitrogen Application1

Abstract Increased interest in perennial forage grasses has been further augmented by their versatility in use and by moderating prices of commercial N. Relatively little information is available, however, on nitrate levels in the grasses managed and fertilized to maximizef forage production in the fall. In this study, timing and levels of N applications to orchardgrass(Dactylis glomerata L.), smooth brome (Bromus inermis Leyss.), tall fescue (Festuca arundinacea L.), and reed canarygrass (Phalaris arundinacea L.) were varied. Split or bulk applications of N, ranging from 0 to 540 kg/ha, were made in April, June, and late July. Nitrate ‐N (NO3‐N) percentages greater than 0.15% were considered as potentially “unsafe.” Such percentages were observed in some instances after applications of 135 kg/ha of N in April or June and 540 kg/ha in late July. Results of analyses showed that orchardgrass and tall rescue were significantly higher in percent NO3‐N than either smooth brome or reed canarygrass. Tall fescue tended to be high in percent NO3‐N the fall. Thus, as with sudangrass (Sorghum vulgare sudanense) and orchardgrass, tall rescue may be a forage potentially unsafe under certain conditions of N fertilization.