In this study, a sheet-type heat exchanger was installed in an irrigation canal in Nasushiobara City, Tochigi Prefecture, and a demonstration test was conducted to supply thermal energy using a heat pump to a greenhouse for growing strawberries adjacent to the canal, in order to establish an operational technology for a flow-through heat pump system for an irrigation canal. The heating and cooling tests using the heat pumps with agricultural water as the heat source showed that the thermal energy can be supplied stably even in an irrigation canal. When the heat pump system was heated using running water with a water temperature of 1.7°C as the heat source, it was confirmed that the heat pump system could stably supply thermal energy at an overall heat pump system coefficient of performance (SCOP) of 2.4 to 2.5 without shutting down. The results also showed that the heat pump system could supply heat efficiently with a SCOP of 5.4 to 6.0 if the irrigation canal water could be used as a heat sink.

The authors are conducting research with the aim of promoting resource recycling of sedimentation solids (fish feces, leftover food, etc.) collected from aquaculture tanks where saltwater fish are raised to agricultural land as fertilizer. As a part of this study, the desalination of sedimentation solids was examined in laboratory experiments, the laboratory experiments showed that (1) the hydraulic conductivity of the sedimentation solids was about 10^-5 cm/s, and (2) the EC and Na⁺ concentration of the sedimentation solids were less than 2.2 mS/cm and 240 mg/L, respectively, when desalinating water (pure water) five times the dry weight of the sedimentation solids was added to permeate the sedimentation solids in consideration of the water content of the sedimentation solids. These EC and Na⁺ concentrations were lower than EC of 4.8 mS/cm and Na⁺ concentration of 1,140 mg/L, which were proposed as a rough guideline for the desalination of sedimentation solids in a previous report by the authors. Based on the experimental results of Na⁺ concentrations, desalination of sedimentation solids was attempted to model using tanks-in-series model. The model calculations for each experimental case were estimated the amount of water required for desalination. The amount was 14.0 mm per unit area and 1.75 L/kg per dry weight of precipitated solids.

This study involved a comprehensive survey of all community-based agricultural corporations in Shiga Prefecture, assessing the adoption of ten smart farming technologies pertinent to rice production. We employed non-parametric tests to analyze differences among corporations that have adopted these technologies, those considering adoption, and those finding them unnecessary, correlating these differences with measures of organizational innovativeness. Our findings reveal an adoption rate of 44%, markedly lower than the 82.3% reported in the 2022 Agricultural Corporation Survey. Notably, large-scale machinery and data management systems were predominantly adopted by corporations managing rice cultivation areas of 20 hectares or more. In contrast, small-scale machinery was adopted across a diverse range of cultivation sizes, indicating potential growth in adoption among smaller corporations. Across all equipment types, corporations contemplating adoption demonstrated a greater need for consensus-building compared to those viewing the technologies as unnecessary. To facilitate this, it is recommended that corporations engage in regular internal discussions to foster dialogue and alignment on technological integration. This approach can help streamline decision-making processes and encourage broader acceptance and utilization of smart farming technologies.

This study examines methods for deriving a "field drainage depletion curve" from volumetric water content (θ) data to evaluate field drainage properties in converted paddy fields quantitatively. Time-series θ data collected 2-3 cm above the plow pan were analyzed to construct the depletion curve, effectively capturing key drainage characteristics. The curve, approximated by two fitted lines, revealed that the initial slope reflects evapotranspiration and gravitational drainage, while the latter represents water loss due solely to evapotranspiration. The inflection point of the curve corresponded to field capacity. Additionally, the influence of drainage measures on the curve was investigated: topsoil-focused techniques increased the difference between θ at the curve's initial intercept and the inflection point, whereas subsoil-focused methods enhanced the initial slope, thereby accelerating soil water depletion. These findings highlight the importance of soil moisture sensor installation depth and drainage measures in evaluating field drainage dynamics.

The breeding ecology of the Grey-headed lapwings is dependent on rice cultivation because they nest in paddy field. However, recent changes in the agricultural calendar (earlier maturity) have increased the risk of nest destruction due to ploughing and other agricultural activities and have led to a decline in breeding success. Therefore, avoiding ploughing during the nesting season is considered an effective conservation method. However, it cannot be denied that the surface condition created by ploughing, which are highly visible for them, may be beneficial to the breeding of them. Therefore, the aim of this study is to elucidate the effects of rice field conditions on nesting site preference and breeding performance of the Grey-headed lapwings by comparing the number of nests and breeding performance between ploughed and unploughed rice fields. The results suggest that Grey-headed lapwings choose nest sites regardless of ploughing, but the causes of breeding failure differ according to field condition, and the risk of predation by enemies was higher in untilled fields suggesting that ploughing before rice planting has a positive effect on their reproduction.

In the Water Erosion Prediction Project (WEPP) simulation model, soil particle size distribution is employed in numerous calculation processes. To elucidate the impact of soil particle size distribution on the outputs of WEPP analysis, three methods of particle size test were utilized: the specific gravity method, the integral suspension pressure method, and the laser diffraction/scattering method. The results were characterized differently depending on the test method and the operator. Soil erodibility parameters and effective hydraulic conductivities of WEPP were calculated using the measured soil particle size distribution, organic matter, and CEC. The amount of erosion was then subsequently calculated using WEPP. The estimated soil erodibility parameters and effective hydraulic conductivities varied depending on the soil particle size distribution. The calculated amount of erosion exhibited differences by a factor of up to approximately three, depending on the test method, and by a factor of up to approximately two, depending on the operator. In order to properly estimate the amount of erosion using WEPP, it is essential to ensure proper dispersion treatment and washing process in the soil particle size test.

Hydraulic performance of concrete irrigation channels degrades as the surface roughness increases due to frictional wear. In this study, we investigated a method to estimate the surface roughness from digital images of the surface of concrete irrigation channels employing a convolutional neural network (CNN), a sort of deep learning, to improve the functional diagnosis. The CNN model trained and validated with approximately 30,000 images and arithmetic mean roughness data of the open channels could estimate the roughness with a root mean squared error (RMSE) of approximately 0.1 mm. Although the model showed overfitting due to a lack of training data, it had practical accuracy and workability.

Applying the paired-catchment method, we conducted comparative hydrological observations between deciduous broad-leaved forest and coniferous planted forest. Based on observations, we evaluated Si dynamics and Si load from each catchment. We confirmed a single LQ equation could be applied with good accuracy in each catchment, regardless of whether it was raining or not, so the load amount was estimated using the obtained LQ curve. The result showed that Si load from deciduous broad-leaved forest is 1.5 times larger than that of coniferous planted forest. The characteristics of the Si concentrations of the potential end members of Si in stream water, such as rainwater outside the forest, through fall, soil water, and bedrock, and consideration of flow duration curve, suggested that clear difference in concentration between the two catchments is thought to reflect the difference in groundwater residence time.

This study investigated and analyzed the trends in the rate of not setting substitute lots, the unit price of liquidation money, the characteristics of landowners who chose not setting substitute lots, and the recipients of not setting substitute lots in districts with high rates of not setting substitute lots in Niigata Prefectures, all of which have completed farm land consolidation projects in hilled rural areas. As a result, it was found that (1) the ratio of not setting substitute lots increased and the unit price of liquidation money decreased; (2) that the choice of not setting substitute lots is seen to be related to small farmers; (3) in districts with high rates of not setting substitute lots, there is an increase in the amount of not setting substitute lots held by large farmers; (4) the method of receiving not setting substitute lots can be divided into two: one is to consolidate the land with farmers who are the large scale farming farmers, and the other is to distribute the land to many small scale farming farmers; (5) it has become clear that the situation has become more and more financially viable for recipient farmers to acquire not setting substitute lots because of the decline in the unit price of liquidation money. In addition, it is discussed that the decrease in the number of landowners due to the occurrence of setting substitute lots facilitated the collection of consent for project and contributed to the promotion of the project.

Despite increasing frequency and severity of disasters, it has been difficult to put into practical use the prediction of damage costs due to heavy rain disasters. In response to this situation, this study aims to quickly predict the amount of direct damage to farmland and land improvement facilities caused by heavy rain disasters, as an easy method in administrative practice. We have developed a 3-layered ensemble model and a system that can estimate the total amount of damage on a national scale. In this examination, we have addressed issues such as the constraints on the number of data points and lack of precision, and the handling of outstanding values in the actual damage amounts. We conducted predictive calculations for 8 disasters from 2022 to 2023. As a result, we have confirmed the accuracy of the model and the reproducibility of the total damage amount, and we evaluate that it has reached a level that can serve as the basis for administrative operation.

The severe wear testing was carried out for pump stations that had been in service for a long time and were scheduled for renewal. Temperature, vibration, and acoustic emission that were considered as parameters for condition monitoring, were measured during the severe wear testing. The number of metal wear particles in lubricant oil was also measured to verify the detection sensitivity for signs of deterioration. As a result, the changes in operating conditions could be detected by changes in vibration. Furthermore, the changes in the number of metal wear particles in lubricating oil were effective for a trend monitoring of the deterioration. Also, abnormal wear in lubricated sliding parts such as bearings and gear reducers could be detected at an early stage by monitoring the ratio of increase to the number of metal wear particles in a healthy state.

In concrete construction, quantities of ready-mixed concrete are ordered in excess of the actual requirements. The surplus concrete returned to the plant without being unloaded is an unresolved issue. Accordingly, the effective use of the returned concrete is strongly desired. This study conducted physical and mechanical tests on the recycled sand made from sun-dried and classified the returned concrete sludge to clarify the properties of the recycled sand. Moreover, as a specific example of the effective use of recycled sand, the roadbed and frost heave suppression layer material are suggested, and several laboratory tests were conducted. As a result, sufficient applicability of the remaining concrete sludge recycled sand as roadbed material was determined. Furthermore, the results also showed that it is applicable as a frost-heaving suppression layer material.