Changes in material dynamics due to changes in nitrogen inputs in grasslands in the Nemuro region of Hokkaido

Abstract

Nitrogen fertilization is used to increase agricultural productivity. However, it has been suggested that increasing the amount of nitrogen applied may increase apparent surplus nitrogen. Therefore, we investigated the effects of nitrogen application to grasslands from commercially available compound fertilizers on apparent surplus nitrogen and grassland ecosystems in a grassland dairy farming area in the Nemuro region of eastern Hokkaido. At a nitrogen application rate of 15 kg/10a, the apparent surplus nitrogen was 5.4 kg/10a for timothy (Phleum pratense) and 7.0 kg/10a for quackgrass (Elymus repens), suggesting possible differences between grass species. Furthermore, an increase in nitrogen application rate tended to decrease the C/N ratio of grass matter. These results suggest that the nitrogen load on the natural environment may vary depending on the amount of nitrogen applied and the dominant grass species in the grassland.