EPIC (Erosion Productivity Impact Calculator) is a crop growth model developed by USDA to simulate crop growth for estimating crop yield under given natural conditions and agricultural land practices including crop calendar. By combining EPIC with GIS, spatial distribution of crop yield can be estimated if we have data faithfully representing the spatial distribution of natural conditions (e.g. soil, climate) and agricultural practices. However, it is not always easy to acquire such geographic data, especially data on crop combination and calendar. Although several existing studies suggested that the estimation accuracy can be improved by using such kinds of geographical data, there have been almost no studies which quantitatively report how much improvement is actually achieved by using such geographic data. Through a case study of integrating EPIC with GIS in Yellow River Basin (Mid-stream region) of China, this study revealed that the average estimation errors are reduced from 21.7% to 16.3% for wheat and from 47.2% to 22.3% for maize by using spatially-detailed geographic data on crop combinations and crop calendars. Since crop growth models like EPIC can simulate not only crop growth processes but also some of environmental impact processes such as leaching of nitrogen due to the excess fertilizer applications and soil erosion processes, the results imply that the integration of crop productivity models with GIS can effectively support decisions in striking balance between environmental conservation and agricultural activities in river basin management.

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Nonparametric DVR (DeVelopmental Rate) method is an efficient way to predict development of plants. The conventional nonparametric DVR method uses histograms of daily environmental data during growth period; it corresponds to construction of regression equations using 0-order B-spline. The use of cubic B-Spline enables this methodology to use environmental data in a more direct way.

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Using remote sensing data from 1992 to 1996, the expansions of lahar deposition and vegetation recovery situation were monitored. The lahar deposition area in Bamban river basin had spread from lower stream to upper and side ways from 1992 to 1996. Vegetation recovery had started from lower stream portions from 1993, where there was no new lahar deposition. Of the total 12,000 ha affected by lahar deposition from 1991 to 1996, vegetation recovery area was 6,200 ha in 1996. The spectral reflectance of 1,550-1,750nm wavelength (corresponding to Landsat TM band 5) determined by Spectral Radiometer had significant correlation with lahar surface moistures in the field. Area with band 5 DN range of 87 to 103 in 1992 and 92 to 110 in 1995, respectively, showed suitable moisture condition for high vegetation recovery for the following year. Vegetation recovery had started from lower stream portions of Bamban river basin from 1992 to 1996. Smaller particle size lahar materials were accumulated in the lower stream portion and water retentivity in this area was high, which could lead to fast vegetation recovery. The Landsat TM band 5 DN was estimated to be useful in identifying the suitable moisture condition for vegetation recovery in lahar affected area.

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We investigated the soil carbon budget in a grape orchard (trellis training type) in the Kofu basin, central Japan, from September 1998 to December 2000, and compared it with that in a peach orchard (standing-tree training type). Soil respiration rate (Rs) was measured monthly using the dynamic closed chamber method and annual carbon emission from the soil was estimated using the exponential relationship between the soil surface temperature and the measured Rs. To evaluate carbon supply into the soil, the amounts of litter from grapevines and floor vegetation, applied fertilizer and manure, and dead roots of grapevines were measured or estimated. The total carbon emission and the heterotrophic carbon emission in the grape orchard were estimated to be 422.7 g C m^-2 y^-1 and 222.5 g C m^-2 y^-1, respectively, and both values were one half of those in the peach orchard. The total carbon supply was 401.0 g C m^-2 y^-1 in the grape orchard (litter from floor vegetation 54.5%; litter from grapevine 34%, and fertilizer 11.5%), and was only one-third of the value in the peach orchard. It was determined that carbon from floor vegetation is the largest input to the soil in the grape orchard, which is similar to that in the peach orchard. These results indicate that the grape orchard sequestered carbon of 178.5 g m^-2 y^-1, which is one third of that in the peach orchard; hence, we suggest that soil in orchards acts as a carbon sink owing to a large amount of carbon input from the floor vegetation.

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We devised a nitrogen balance model to estimate the nitrogen load generated from food production and consumption in Thailand. The population of Thailand continues to grow, and income is growing too. As income grows, the demand for animal protein increases. Assuming self-sufficiency that food is supplied in Thailand and cereal planting area is constant, cereal yield must be increased. To achieve this, fertilizer application must increase. The nitrogen load to the environment generated from food supply and consumption was 0.21 and 1.46 million t y^-1 in 1980 and 2000 respectively. It is projected to increase to 2.99 million t y^-1 in 2030. The load will continue to increase, especially in the central and northeastern regions of Thailand.

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An open-top chamber technique for measuring soil respiration is tested for evaluating how the open-top chamber alters soil microclimate inside the chamber, and how its alteration influences soil respiration measurements. The temporal variation in soil respiration followed the variation in both air and soil temperatures. The high correlation between soil respiration and soil surface temperature inside the chamber indicates that the open-top chamber technique gives a reasonable estimation for the temporal variation in soil respiration. However, there was a parasol effect of the open-top chamber on soil temperature inside the chamber, suggesting that the open-top chamber technique underestimates the soil respiration when used in an irradiated area on a sunny day. The measurement at an open site showed the effect of wind on a temporal variation in soil respiration. Therefore the open-top chamber may be weak in a strong wind condition, and a reasonable estimation may be restricted to the measurements conducted under a closed vegetation. Our study indicates that the open-top chamber technique needs some further improvements.

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Accumulation of farmlands to leader farmer of regional agriculture is asked eagerly by replotting in land improvement process for efficiency in agricultural works. But it is very rare to accumulate farm lands together successfully because of difficulties in making mutual agreement between users and renders of farm lands. This paper reports analyzing the promoting/preventing factors to farmland consolidation from the view point of land users, land renders and the stages of land improvement planning. i.e. launching of land improvement, land consolidation planning, planning of large paddy fields and operation planning of dimensional land consolidation. As many of preventing factors are found in the side of renders, incentive policies for renders are considered. After their estimating application by the planning operators of replotting, new recommendation to promote dimensional land consolidation are proposed.

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