Several studies have indicated that biodiversity in organic farming was higher than conventional farming, however, it still remains unclear how the management ways influence on ecosystem processes. We hypothesized that nutrient availability in the soil might regulate this processes and affect in biodiversity. Field researches were conducted to understand the abundance of arthropods in organic and conventional farming. In general, the herbivore abundance in conventional farming was higher than organic farming. In addition, to understand mechanism of ecosystem processes, experiments regarding feeding behaviour of the grasshopper were conducted in laboratory. Feeding preference and performance of the grasshopper also increased, while rice plants due to conventional farming were fed as food, because of soil nutrient such as Nitrogen. These results suggested that the method of management would influence on soil nutrient availability and give different impacts on herbivore abundance.