Sampling numbers that were necessary to get the mean air dose rate in the range ±10% with a 95% confidence interval were estimated with data of seven grasslands in Iwate Prefecture, Japan. Air dose rates of six grasslands were collected in 2011, and of a grassland were collected from 2011 to 2016. Mean air dose rates of five grasslands, located at central part of Iwate Prefecture, ranged from 0.070 to 0.103 μSv/h, and of two grasslands, located at southern part of Iwate Prefecture, ranged from 0.318 to 0.793 μSv/h. Sampling numbers necessary for estimating accurate mean air dose rate by bootstrapping ranged from 1.2 to 4.6 per hectare. This result shows that unbiased five samples per hectare are necessary to estimate accurate mean air dose rate of grasslands. Six years' data showed that sampling number could be reduced after the third year of the nuclear power plant accident.
Cool-season grasses, widely cultivated in Japan, have their optimum growth under cool climate condition. Therefore, summer depression of grasses often occurs in a wide area of Japan except for Hokkaido area. As global warming progresses, it is predicted that the places where summer depression occur will shift to north and grassland productivity of mid and western Japan will gradually decline. In this study, a model that represents the effects of fertilizer application, growing season temperature and grassland renovation to orchardgrass (Dactylis glomerata L.) productivity was constructed and adaptation strategies to global warming were evaluated. In Iwate Prefecture, the area with high productivity of orchardgrass was predicted to shift further towards north under global warming condition. Evaluation of the model shows that 9, 8 and 7 years’ renovation cycles of grasslands are expected to be necessary in order to keep the present grassland productivity of Iwate Prefecture under 1, 2 and 3℃ elevated condition, respectively. Additional application of nitrogen fertilizer (from 150 to 180 kgN/ha) is predicted to be required to retain the present grassland productivity under 1℃ elevated condition.
The beef fattening production system in Japan typically uses a large amount of imported feed under housing management. Since this system has several economic and environmental problems, the grazing fattening system using Japanese Brown cattle (a local breed which is thought to be suitable for grazing system) has recently been receiving attention. However, there have been few studies about the amounts of movement and energy expenditure (EE) of fattening Japanese Brown cattle in the grazing condition, and consequently, beef producers must be subjective to determine the amount of supplemental feeds. Therefore, in the present study, we evaluated the movement and energy expenditure of fattening Japanese Brown cattle under grazing conditions using Global Positioning System (GPS). The experiments were carried out during 2 seasons in 2015: summer and autumn. The experiments were conducted at three pastures of Kumamoto Agricultural Research Center with nine Japanese Brown fattening steers (Three steers for each pasture). Using GPS collars, positional data were collected at 1-min intervals during one week for each steer in a period. Home range, slope gradient, average walking speed, walking distance, vertical locomotion and the ratio of EE in walking to standing (EE ratio) were calculated from GPS points and Digital Elevation Map (DEM) model. The data were separated into two fattening stage (early and late stages of fattening) by the threshold value of 500 kg of body weight. We analyzed the effects of the fattening stage and season on the calculated values, and gained the least square means. The results indicated that EEr and movements varied significantly (P<0.05) between fattening stages and seasons; EEr and movements were higher in the late stage of fattening than the early stage and in summer than autumn.