Abstract
Dominance in vegetation by Japanese lawngrass was observed in such areas of pasture as those with application of low level of fertilizer. As a result, the pasture come to be composed of two areas with different types of vegetation : one dominated by temperate grasses (TG area), and the other dominated by Japanese lawngrass (JL area). To analyse the cause of the differentiation into two types of vegetation, the following five parameters were measured in the TG and the JL areas : (1) Amount of nitrogen and potassium in soil. (2) Number of dung lumps, (3) Total treading time by cattle (total standing, walking and grazing time), (4) Amount of grazed herbage of standing crop, and (5) Soil water content. The results of these examination showed that Japanese lawngrass invaded the area where nitrogen amount in the soil and number of dung lumps were small. Cattle ate temperate grasses more than Japanese lawngrass in the area. Then the proportion of Japanese lawngrass increased, and the area dominated by Japanese lawngrass became to appear in the pasture. In the area where the nitrogen amount in the soil and the number of dung lumps were large, dominance in vagetation by temperate grasses continued. These result suggested that it was necessary to apply more amount of nitrogen fertilizer than those application so far in order to maintain a vegetation dominated by temperate grasses in the pasture.
