Loss of rice paddy levelness causes herbicides and fertilizers to act unevenly, and also has significant impacts on rice plant growth and yield, such as the submergence of transplanted seedlings and the seedling emergence rate in directly seeded fields.
To ensure stable production in large rice fields, we therefore conducted a demonstration test in fields using a tractor-drawn laser land leveler developed within the last few years for use when tilling. Our test found, among other things: 1) The laser land leveler offers precision leveling of field surfaces, but it is not as precise at plowsole leveling; 2) high precision is often not maintained when leveling paddy surfaces; and 3) efficiency varies with the operator. Additionally, we observed how a skilled operator performs leveling, and 4) proposed a procedure that takes advantage of the laser land leveler's features.

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Since the amount of water requirement for puddling irrigation is large, investigating the factors that determine the water requirement is important. In this study we observed the process of water ponding during irrigation for puddling in a paddy field with peat subsoil of relatively high permeability, and analyzing the components of the water requirements. Before the irrigation, soil water contents and air volume ratios in soil profile were measured and infiltration tests using cylindrical infiltrometers were conducted. As a result, the surface water ponding spreaded with a constant velocity, indicating that the vertical drainage loss should not be significant and the water requirement mainly depend on the soil water deficit for saturation. This character of the field is not caused by the permeability of hardpan or shallow subsoil, but is brought about by a clay layer exists below 1m deep. The result implies that the puddling water requirement in this type of lowland paddy field is independent on the size of the field lot.

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One of the most prospective measures to solve the global warming problem is afforestation of desert, leading to the fixation of carbon dioxide from the atmosphere into the plant organic materials. The poor vegetation in desert is formed due to the higher potential evaporation than precipitation and shortage of water. It has been proposed that the permeability and water retention should be improved with various kinds of water retainers mixed with original soil. In the present study, the mixing effects of water retainers, peat, SAP (super absorbent polymer) and bauxite, to the Toyoura sand on permeability and water retention were evaluated. Permeability was reduced and water retention for water potential less than-10^1.8cmH₂O (pF>1.8) was improved in all of experiment, especially by mixing peat under the present experimental condition. The water retention of the calcinated bauxite for water potential less than-10^5.0cmH₂O (pF>5.0), which corresponds to high dryness resistance region was found.

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We conducted a study aimed at calculating the energy balance and CO₂ emissions of various scenarios for rice straw recycling, employing the concept of Life Cycle Assessment. The actual energy gain per mass of rice straw harvested in one ha of paddy field was the greatest in the Fuel Gas Production Scenario (45.5GJ), followed by Methanol Production Scenario (15.4GJ) and then the Electricity Generation Scenario (4.5GJ). The energy balance per ha, including nutrient input, was as follows: production of 40.2GJ for Fuel Gas Production and 10.1GJ for Methanol Production, and consumption of 0.8GJ for Electricity G eneration, 6.1GJ for C omposting-Nutrient R estoration and 5.3GJ for D isposal/Incineration. T he E lectricity Generation Scenario produced the largest CO₂ emission and the Fuel Gas Production Scenario produced the least emission. The CO₂ emission, which was the sum of emissions in each Scenario and the consumption of energy equivalent to the calorific value produced in the energy production Scenario, was estimated with the following results: the emission in the Methanol Production Scenario was the lowest (11, 614 kg of CO₂/ha) and that in all energy production Scenarios would be smaller than that in the Composting Nutrient Restoration and Disposal/Incineration. It is considered that these outcomes indicate the necessity of multi-dimensional approaches for the evaluation of energy production from biomass and biomass recycling in rural development planning.

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Today in Japan, agricultural productivity of rice cropping farmers is low. In order to get sufficient agricultural productivity, its necessary to carry out land consolidation project, through that core fanners' farm size should be extended to more than several ten hectares by increase of leased land, and large-sized paddy plots more than several hectares should be constructed by land consolidation of core farmers' many small and scattered lease plots (=land owners' plots). In order to make clear how to consolidate those leased plots into large-sized paddy plots, we investigated three land consolidation project areas in which large-sized paddy plots more than several hectares were constructed by consolidation of land owners' substitute lots. As the result, we showed 1) large-sized paddy fields were settled in inferior areas of project areas, for instance, far from land owners' residence area. 2) Basically land owners don't accept their substitute lots to be settled into large-sized paddy plots in such inferior areas, 3) but some land owners whose land holding size are remarkably small accept their substitute lots to be settled into such inferior areas, 4) Subsidy and increase of land rent gotten by construction of large-sized paddy plots are effective for land owners to accept their substitute lots to be gathered into large-sized paddy plots in inferior areas

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This research evaluated the hydraulic/pozzolanic properties of fly ash and cinder ash when used in combination with ordinary Portland cement (OPC) and fine aggregate as constituent mineral additive materials replacement. In order to determine the differences that could be responsible for the changes in mechanical properties of massive concrete and cement paste, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to study microstructural features and pozzolanic reaction of fly ash and cinder ash. XRD analysis showed that the paste was essentially composed of calcium silicate hydrate gel (C-S-H). This was confirmed by SEM observation, which revealed that the matrix was compacted and tends to be more amorphous than crystalline. It was also observed that the cinder ash had the same pozzolanic reaction as fly ash, and the hydration product of calcium hydroxide (CH) did not only surround the particles of cinder ash as in fly ash but also penetrated the small holes within cinder ash. This implies that the cinder ash could contribute to the strength development of concrete like fly ash because of analogous chemical composition, which leads to form additional C-S-H gel. SEM observation showed that the fly ash concrete was more homogenous and the strength contribution was better than the concrete without additional materials. Suggesting that the fly ash and some fine particles of cinder ash improved the interface structure betweenthe paste and the aggregates and acted as micro aggregates in fly ash concrete.

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Quantification Theory Type III is used for idealizing the future land use in Kurogi town where the residents have some intentions to land improvement. GIS, which is becoming popular tool for the geographic information analysis, was progressively used in this study.
First, paddy fields, upland crop fields, orchard and tea fields were classified into 8 categories depending on the present natural and sociological conditions. Second, “Quantification Theory Type III” was applied forgrouping the characteristics of each field. Each field was classified into 3 groups, i.e., natural, urbanization, land improvement area, respectively. It was proved that for clarifying the group, simple categories should be used. Finally, paddy fields, upland crop fields, orchard and tea fields were evaluated synthetically for visualizing a development plan in the future. The method presented here would be effectively applied for planning the future agricultural land use without any complex considerations.

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On conducting agricultural land reclamation projects, prevention of turbid water is one of important issues. In order to evaluate physico-chemical factors which play predominant role in dispersion of soils, relations between the factors, cation exchange capacity (CEC), surface area, organic water content and dispersion-flocculation properties of the soils from agricultural lands in Chugoku and Shikoku region were studied. From the experimental results, clay dispersion showed higher correlation with specific surface area and cation exchange capacity of the soils. Change in surface charge characteristics of clay particles due to gypsum application was discussed based on DDL theory, and the reasons of changes in dynamic stability of clay suspensions against sedimentation were discussed. In course of surface potential calculation, permanent charges measured by potentiometric titration method were used. Smaller particles with larger surface area showed higher stability of suspension against sedimentation. Application of gypsum enhanced flocculation of soil suspensions and decreased clay dispersion. Surface potentials and edge potentials decreased remarkably on the soils which showed greater flocculation effect by gypsum application.

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In recent years, the concentration of nitrate nitrogen (NO₃-N) in groundwater has increased gradually in the Nasunogahara basin that is known for its abundant and high quality groundwater. As a first step for considerin conservation method of groundwater quality, the present study aims i) to understand the reality of groundwater quality condition and the trend of NO₃-N concentration change in shallow aquifer, ii) to clarify the mechanism of nitrogen pollution of groundwater, and iii) to determine nitrogen balance in the study area by delineating flow diagram of each pollutant source. The results of long-term observation of groundwater quality showed the trend that NO₃-N concentration is not diluted but polluted by rainfall. Besides, the mechanism that pollutant load accumulated in soil flows into groundwater with rainfall infiltration was found to be the reason for this trend. From the results of nitrogen balance analysis, excrements of livestock were considered as the most influential source of nitrogen pollution of groundwater. In this area, the river's underflow water was thought to have a big role in keeping NO₃-N concentration relatively low.

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Today in Japan, both average farm size of rice cropping farmers and their farm land size are so small that productivity of rice cultivation remains low. In order to get sufficient productivity, it's necessary to extend farm size of core farmers more than several ten hectares by accumulating user rights of farmland, gather core farmers'(tenant farmers') scattered tenanted plots into certain areas, and construct large-sized paddy plots more than several hectares in these areas. Adjustment of tenanted fannland is the method of land consolidation by exchanging user rights of farm plots between tenant farmers and owner farmers. And this method is considered efficient for such farmland consolidation. In order to clarify this efficiency of tenanted-farmland-adjustment method, we investigated three study areas in which large-sized paddy plots were constructed. As a result, we showed 1) Even in case that tenant farmers couldn't gather substituted plots of their tenant land into large-sized paddy plots, they could consolidate their tenanted farmland into large-sized paddy plots by the tenanted-farmland-adjustment method. 2) Owner farmers accepted this adjustment on their farmland in such cases that they could get superior plots, they could gather their scattered cultivating plots into one place, they decided to retire in several years and so on.

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Hydraulic fracturing tests were performed using tri-axial apparatus considering seepage failure of small earth dams, which often failures induced, by heavy rain. Using soft X-ray, propagation of crack by hydraulic fracturing was observed. It is cleared that hydraulic fracturing is tensile failure, which progresses intermittently with repetition of crack propagation and water seepage onto crack surface. Hydraulic fracturing always progressed with parallel to the minimum principal plane in these tests, because water pressure decreases in the crack immediately after fracture occurred. Under uniform injection pressure condition, the injection volume was not suddenly increased, but the displacement in the direction of the minimum principal stress was rapidly increased the moment the crack created.

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Laboratory tests are performed to investigate the geotechnical characteristics of two water plant sludges stabilized with lime and combined lime-granular activated carbon (GAC). The sludges are tested at high water contents to examine the water content dependency of undrained shear strength, pore pressures parameter and deformation stiffness parameter. It was observed that the lime-GAC treated sludge had greater compressibility and higher plasticity than the lime-treated sludge. Despite the high water contents used the sludges yielded cohesion strengths at failure. Linear relationships were found between the secant Young's modulus and the initial water contents of the lime-treated sludge. The secant Young's modulus of the lime-GAC treated sludge specimens increases up to 93% water content and then decreases for wetter specimens. Based on the laboratory tests it was concluded that the relatively inexpensive sludges have the prerequisite properties for geotechnical applications.

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For estimating the crop water consumption, it is necessary to determine meteorological data in greenhouse from open fi eld data and calculate potential evaporation. In this study, temperature, humidity, wind velocity and solar radiation were measured in greenhouse as well as in open field. Then, we compared the meteorological data of greenhouse with that of open field. Results of the comparison differed from the reference values of the Official Manual (1997). Humidity during heating period and wind velocity in the greenhouse cannot be evaluated from the steps of the Official Manual. We applied the original equation that was derived in this observation to calculate the potential evaporation in the greenhouse. It became apparent that the potential evaporation could be estimated using open field data.
A portion of irrigated water was consumed by vegetation and remainder was discharged from rock wool bed. Mean daily water consumption during the measurement period was 2.50 (mm/d), with a monthly maximum occurring in July with 3.54 (mm/d). Discharged water amounted to 9% of irrigated water. Tomato's crop coefficiency with rock wool cultivation was calculated by potential evaporation and water consumption. In this field, this value was smaller than those recorded in the Offcial Manual.
The amount of irrigation was same in all segments of the greenhouse. However, water consumption was affected by incident energy. A portion of discharged water (5% of irrigation water in this greenhouse) could not be saved because there existed a differencial volume need for some plants which consumed more water in relation to others.

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This study attempted to evaluate the influence of excavated domain in buried anchor foundation. The sand bed was prepared by pluviating air dried Toyoura sand. The anchor was flat circular with diameter (D) of 5cm. The diameters of excavated domain were 5cm, 6cm and 7cm, and the tests were performed in h/D (h: sand mass depth) of 2. The excavated domain was prepared in loose condition and outer domain was prepared in dense condition. The result showed that the uplift resistance was higher in the case which the diameter of the excavated domain was as same as the one of the anchor. In all cases, the shear band had not progressed over the boundary of excavated domain. It is concluded that the difference of uplift resistance was the difference of shear resistance due to propagation of shear band along the boundary of excavated domain.

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In the absence of a reservoir on the downstream side, river flow which increases temporarily by rainfall cannot be stored and discharged apart from requirement in the beneficial area. This unused water (excess water) occurs to some degree even in a draught year and effective use of this supply is considered as one of the countermeasures for water shortage. Setting up a regulating reservoir on the upstream side of head works is regarded as one of the methods to make effective use of excess water. The inflow to the river and water delivery loss which occurs from rainfall are stored in the regulating reservoir and supplied to the beneficial area on the downstream side as agricultural water. It is thought that the effect is achieved by increasing the cycles of the storage and discharge in a short term, though the capacity of regulating reservoir is smaller in comparison to the dam. In this study, the excess water was calculated for a canal system which has a water shortage tendency, and an operational method for the regulating reservoir to effectively utilize this excess water was examined by simulation.

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One of the major concerns in rural areas these days is destruction of habitats of aquatic animal life and consequent loss of biodiversity, partly attributed to implementation of farmland consolidation projects. To cope with this problem, increasing efforts have been made to create animal sanctuaries in and around project areas. What we have yet to know, however, is how best to space these sanctuaries across the tracts of consolidated farmland. Obviously an index for their minimal spacing required is the dispersal distance of the aquatic life in question.
In this study, we targeted at the aquatic dragonflies of the Ischnura asiatica, supposedly low in flight ability, and investigated how far they flew away from their breeding ground and what environmental factors affected where they reappeared, using the mark-and-recapture method. We conducted the field survey in Utsunomiya City during the August-September period, 2000. The survey revealed that they moved no farther than 1.1-1.2km and submerged fallow paddies greatly affected where they reappeared.

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The decrease in the number of farm households makes it increasing difficult for the farm households alone to maintain canals adjacent to paddy fields. Hence, the problem is who maintains canals. In Takatsuki Town in Shiga Prefecture adjacent to Lake Biwa, ownership, utilization and maintenance of irrigation and drainage canals or water were investigated through interviews on digging or cleaning up of the canals. The main findings were as follows:(1) In rural area irrigation water flows into communities. After residents in upstream communities used the water for domestic purposes, it is then used by downstream communities as irrigation water. With regards to utilization of communal water, there is hardly any distinction between domestic and irrigation water.(2) Ownership of canals and water including maintenance responsibilities were for communities whose residents had water rights and used the water for irrigation and not communities whose residents used the water for domestic purposes.(3) Doing Kawahori (digging of canals before land consolidation projects) meant publicity and acknowledgement of ownership of canals and water. Doing Kawasouji (cleaning up of canals after land consolidation projects) also means more or less the same.

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