Abstract
A field experiment was carried out in orchardgrass (Dactylis glomerata L.), timothy (Phleum pratense L.) and meadow fescue (Festuca elatior L.) to clarify the effect of applied nitrogen regarding the relationships among the leaf area index (LAI), the net assimilation rate (NAR) and the crop growth rate (CGR), and to assess the interactions between nitrogen absorption and those three parameters. Two treatment levels of nitrogen (0g m<-2> and 8g m<-2>) were used in this study. Applied nitrogen increased the LAI, but had no great influence on the NAR. The CGR rose according to increased LAI, resulting in a higher yield of dry matter at the time of first cutting. The dry matter yield had the greatest timothy, followed by orchardgrass and meadow fescue during both treatment levels of nitrogen used. This ranking was derived from the CGR responses to nitrogen applied in the three grasses tested. The wide differences occurring in the CGR of the three grasses were attributable to the differences in the nitrogen absorption rates:A low absorption rate of meadow fescue is reflected by a low LAI, and the difference between the nitrogen absorption rate of timothy and orchardgrass is reflected in the NAR.
