Morphological Development, Yield, and Chemical Composition of Orchardgrass at Several Soil Nitrogen Levels1

Abstract

AbstractThe effect of high nitrogen fertilizer applications in prolonging vegetative development has not been reported. This phenomenon, if it exists, would affect the most optimum time of harvest and hence, stand longevity. The effects of N fertilizer at rates up to 1,800 kg·ha−1 (vernalized plants) and up to 2,100 kg·ha−1 (non‐vernalized plants) on yield, morphological development, total N, nitrate‐N (NO3‐N), and fructosan concentration of vernalized and non‐vernalized orchardgrass (Dactylis glomerata L.) plants grown under controlled environments were studied.Herbage yields increased with applied N up to 600 kg·ha−1 and remained essentially the same over the range of 600 to 1,500 kg N·ha−1. At maximum rates of 1,800 and 2,100 kg N·ha−1, yields were drastically reduced. The number and maturity of floral tillers of vernalized orchardgrass plants was greatest at 600 kg N·ha−1 and least at 1,200 and 1,800 kg N·ha−1 indicating that high N delayed floral tiller production. Foliage burn was noted at 1,800 kg N·ha−1 but not at 1,200 kg N·ha−1.With unvernalired orchardgrass, little change in vegetative tiller production was observed during the 3‐week period where no N was applied. Where 300 to 1,500 kg N·ha−1 was applied, an increase in tiller production was found from week 1 to 2 followed by a decrease in number of new tillers during the third week. At 1,800 or 2,100 kg N·ha−1, only a few new tillers were produced until the third week of the study.Percent total N and NOa‐N in herbage increased, in general, with increasing N fertilization up to 1,200 kg N·ha−1. At higher N levels (1,500‐2,100 kg N·ha−1), the percentage of these constituents was essentially the same or lower than that noted at 1,200 kg N·ha−1. Percent fructosan in the stubble was inversely related to N fertilization rate.Although N fertilization is required for economic forage yields of orchardgrass, excessive N caused severe plant stress and modified plant development that could result in reduced yields and severe stand reduction, particularly if harvested at the improper stage of plant development.