At present, acoustic method for evaluation of the continuity between the atmosphere and soil air hasnot been fully investigated. We evaluated impedance at a sample surface using sound resonance, and estimated the amount of sample air affected by the resonance and the conductivity of the sample. Sand and glass beads were used for a comparison of the air conductivity estimated using the acoustic method and the conventional method based on Darcy’s law for air flow. Our results show that the impedance measurement provided good estimations of the continuous air content. We can more precisely determine the proportion of continuous air in the sample by combin-ing the acoustic method with typical bulk and particle den-sity measurements. Our calculation procedure was valid until the amount of air in the sample was less than 20 cm3. Comparison with results of the conductivity tests show that the impedance measurement provided the air conductivity for sample air connected to the atmosphere through one side of the sample.
Problems have been widely encountered when trying to scale erosion results from plot to catchment level. Due to the complex hydrological response in catchment, the soil erosion from plot level does not always correlate with erosion measured at the catchment scale. An exper-iment was conducted to measure the soil erosion at both plot and catchment levels under coffee tree based crop in Lampung, Indonesia. Runoff and sediment were measured at the catchment of 10.2 ha, while seven erosion plots of 75 m2 were constructed inside the catchment. The erosion plots were designed as follows; (a) bare soil (control), (b) natural weeds (NW), (c) clean weeded coffee, (d) coffee with Paspalumcon jugatum (PC) in spot weeding, (e) cof-fee with PC in strip along the contour line, (f) coffee with NW in spot weeding, and (g) coffee with NW in strips. After one and a half years measurement, the rate of soil loss ranged from 0.12 t ha−1 (natural weed plot) to 0.87 t ha−1 (bare soil plot). On the other hand, the sediment yield from the catchment was 6.7 t ha−1 for 8-months measure-ment during the rainy season. These experiments indicate that, the sediment yield from the catchment level is more than ten times that of soil loss from plot scale. This is sup-posed, to be responsible for the gully erosion, collapse and
soil erosion from paddy field which occurred in the catch-ment. This result showed that the soil conservation strategy which is now mainly focused on only cropped areas must be revised, and the other sources of sediment yield must be taken care of to curtail downstream soil erosion.
Sensor Service Grid (SSG) makes it possible to collect soil moisture sensor data from farms distributed in various parts of the world. It is useful for agricultural field manager and crop-soil researchers. SSG is the core system in Sensor Asia Initiative for easy setup and management of sensors. It realizes “sensor plug & play” which cov-ers sensor node installation, registration, calibration equa-tion and other sensor metadata, as well as visualization of processed sensor data. In order to evaluate the efficiency of SSG, a spinach field monitoring system has been setup near Chiang Mai, Thailand which collects soil data includ-ing moisture, temperature and electrical conductivity, to-gether with meteorological observation data. We have con-firmed that the data was accumulated in a SSG server over the Internet, and it was accessible by everyone easily. This system is currently utilized as a practical tool to secure the food safety between agricultural producers in Thailand and consumers in Japan. The real time information can be browsed easily by Japanese consumers using a mobile phone. Moreover, the system is extremely useful to stimu-late researches on application of soil sensors.