Abstract
This study was conducted to establish the optimum level of nitrogen fertilizer application on Giant stargrass stand (Gs) and the overseeded with Italian ryegrass stand (Gs+Ir) during the winter season in south western islands of Japan. The averaged dry matter yield of Gs and Gs+Ir at three cutting times increased with the increasing levels of nitrogen fertilizer application. Dry matter yields of Gs+Ir tend to be high in comparison with that of Gs in the case of 0 kgN/a and 0.5 kgN/a application. In case of 1.0 kgN/a and 2.0 kgN/a application, the values were adverse. In the same manner as the averaged dry matter yield, the total dry matter yields of Gs and Gs+Ir were significantly (p<0.05) increased with the elevating levels of nitrogen application. The nitrogen content, the dry matter digestibility and the digestible dry matter yield were higher in Gs+Ir than those in Gs, irrespective of the levels of nitrogen fertilizer application. The efficiency of nitrogen fertilizer application in Gs and Gs+Ir was the highest for the 0.5 kgN/a and the lowest for the upper limit of nitrogen fertilizer of 2.0 kgN/a.
From these results, it might be concluded that the most effective level of nitrogen fertilizer application is 0.5 kgN/a for the cultivation of Gs and Gs+Ir during winter season in south western islands of Japan.
