Abstract
In order to determine the optimum water supply for dry matter production of orchardgrass (Dactylis glomerata L.) during the first growing period, the effect of water supply in orchardgrass on growth was examined by analyzing the relation between the nitrogen uptake by orchardgrass and the yield components. The results were as follows. 1) The lack of water supply from the sprouting stage to the internode elongation stage (a period of about 20 d) resulted in a remarkable decrease in the yield of plants in pot experiments. 2) These findings were ascribed to the fact that the number of tillers per pot, which strongly affected the yield in the pot experiment, could not increase sufficiently throughout the experimental period, because the lack of water supply restricted nitrogen absorption by orchardgrass and then delayed the production of tillers. 3) Compared with the results of the pot experiment, the effect of. water supply on the growth of orchardgrass under field conditions was not appreciable, probably because of the presence of a large amount of water stored in soil, which was derived from melted snow. 4) The results obtained in the present study showed that the optimum water supply for dry matter production of orchardgrass during the first growing period extended from the sprouting stage to the internode elongation stage, namely during a period of about 20 d.
