This paper presents an erosion monitoring system on a laser distance meter for cementitious surface coating method used for agricultural concrete canals. In order to solve the problem of the measurement error due to the installation of the equipment, we develop a baseline correction method to remove the measurement error, which use a two anchor of stainless steel for a reference point embedded in the coating surface. From laboratory tests, we find four major factors that affect the measurement error; 1) moisture conditions on the coating surface, 2) an installation of the distance meter, 3) temperature, 4) unevenness of the surface. Influence of factors 2)∼4) gives the measurement result is less. It is confirmed that by removing moisture from the surface with rag, measurement with high reproducibility is possible. From field measurement, the accuracy of the monitoring system is measured value ±0.01 mm is estimated. In conclusion, it is found that the erosion monitoring system is applicable to field measurement of a cementitious surface coating in agricultural concrete canals.
Armoring of drainage canal beds in sloping paddy fields is one of factors which cause deterioration in habitats of organisms. In this study, laboratory experiments were conducted to see whether armoring of sandbar surface could be suppressed by installing notched spur dikes, which have sandbar creation function, in the drainage channel bed. The result showed that armoring of sandbar surface is not suppressed mainly due to sinking of fine sand into the sandbar subsurface. However, in the actual drainage bed around the study area, suppressing of the armoring in surface layer of sandbar was observed. It was inferred that graminaceous plants became possible to settle on the sandbar due to combining the drainage bed disturbance which is common in the sloping paddy field and creation of stagnation in sandbar resulted from installing notched spur dikes, and held fine sand in the sandbar. Thus, it was concluded that notched spur dikes, although indirectly, suppress armoring of sandbar surface in the drainage bed.
The official development assistance (ODA) by the Japanese Government has been providing various supports in the implementation of agricultural development projects of the Philippine Government based on the development assistance strategies. However, the assistance strategies are not always formulated based on the actual requirements in the Philippines, therefore there are cases that the supports required in the Philippines are not always provided. In deed, experience from past ODA, such as development surveys, grant aid and yen loans to agriculture development projects in the Philippines, has shown that there are gaps between the sector's needs and implementation strategy, and the changes of strategy prevent effective irrigation development from accelerating. For the effective implementation of important agricultural development projects in the country, more definite strategies shall be formulated in line with the Philippines' requirements, and the development survey shall be conducted to focus on the present major issues furthermore.
The USLE-based rainfall erosivity factor was calculated from the observational data of the Japan Meteorological Agency for the whole area of Hokkaido, and its distribution was clarified. The rainfall erosivity factors were calculated by adding the thaw and snowmelt factor to the rainfall and runoff factor. The USLE method of calculating the rainfall and runoff factor uses data recorded at 10-minute intervals. Because the 10-minute-interval measurement data was shorter than that of one hour value, bias were caused in calculated rainfall and runoff factor. In this study, rainfall and runoff factor was calculated from 1-hour-interval measurement data. To convert it into the value of rainfall and runoff factor that had been calculated from the 10-minute-interval measurement data, the conversion coefficient in which the regionality was considered was multiplied by rainfall and runoff factor of 1-hour-interval measurement data.
Phosphorus from fertilizers accumulates in the surface soil layer and runs off because of rainfall. In this study, we investigated the size-dependent particulate phosphorus concentration in surface runoff to elucidate the mitigating effect of sod culture using rattail fescue [Vulpia myuros (L.) C.C. Gmel.] on phosphorus loss from soil in a citrus orchard. Particles of 1-10 µm in diameter comprised 86% of suspended solids in sod culture, whereas particles >10 µm in diameter comprised 1%. In clean cultures (bare soil surface), particles of 1-10 µm in diameter comprised 62% and particles >10 µm in diameter comprised 32% of suspended solids. The phosphorus concentration in the surface runoff from sod culture was lower than that from clean cultures in all experiments. The phosphorus concentrations in the sod cultures were 33%, 36%, 6.3%, and 5.8% compared to those in clean cultures, when the particles were <0.45 µm, 0.45-1 µm, 1-10 µm, and >10 µm in diameter, respectively. This study has shown that sod culture reduces the size-dependent particulate phosphorus concentration in surface runoff in all experiments and that sod culture has mitigating effects on the loss of particulate phosphorus of various sizes.
In this paper, volumes of storage tanks for digested slurry are calculated by a model for planning transportation and spread of digested slurry to farmlands that was developed by the authors. The model calculated 2 cases for transportation and spread of annual volumes of 10,000 m3 digested slurry to 100 ha of paddy fields and 150 ha of upland fields. Case 1 modeled 1 storage tank in a methane fermentation plant without intermediate tanks. Case 2 modeled 1 storage tank in a plant with 1 intermediate tank. The Case 1 storage tank required a 4,725.9 m3 volume tank as calculated by the model, whereas Case 2 needed 4,555.6 m3. For Case 2, the intermediate tank required 1,837.9 m3. The intermediate tank volume was reduced to 815.9 m3 by adjustment of capacities for slurry transportation from the storage tank to the intermediate tanks in Case 2 though the storage tank volume was increased to 4,798.3 m3. The storage tank volume was reduced to 3,910.0 m3 by additional manual adjustment of periods for slurry transportation from the storage tank to the intermediate tank in Case 2, but the volume of intermediate tank was 815.9 m3. The total volume of the two tanks in the additional manual adjustment was the same volume as the storage tank in Case 1. This indicates that construction costs for the intermediate tanks are not absolutely additive. In addition, when plural tanks are planned as storage tanks in a plant, some of the tanks can be moved near the farmlands where the slurry will be applied. These tanks work as intermediate tanks and improve efficiency in transportation and spread of digested slurry to farmlands without large additional construction costs.
In order to contribute to labor saving in the field surveys during investigations on the status of generation and elimination of devastated farmlands, we propose a method to extract paddy fields that may be devastated, that is, a screening method of paddy fields targeted for field surveys based on the parcel mean values of NDVI using multitemporal satellite data and paddy parcel boundary data. We conducted extractions in Inashiki-city and Chikusei-city, Ibaraki Prefecture using RapidEye satellite data (some ALOS satellite data used) acquired in May, July, and August, and paddy parcel boundary data by the proposed method. Then, we examined the screening efficiency, which is the percentage of the actual devastated paddy fields in the extracted paddy fields that were thought be devastated, using field survey data. As a result, the screening efficiencies were 89% for the Inashiki A area, 74% for the Inashiki B area, and 47% for the Chikusei area. The screening efficiency was low in the Chikusei area because there were many paddy fields where crops were not planted after harvest of wheat (winter crops), and weeds overgrew some of the paddy fields in summer.