Crop yield variation caused primarily by extreme weather events is a major risk in farm management. Farmers try to reduce yield damage through sufficient cultivation management. The damage can be correlated to the socioeconomic characteristics of rural areas, and such characteristics are represented by indices of labor, land, and capital. Understanding the nature of these relationships is important for the effective planning of agricultural policies. In addition, the understanding would allow a more realistic assessment of the impact of global warming on agricultural production when they are included in assessment models. Thus, an objective of this study was to reveal the qualitative relationship between damage in paddy rice and rural socioeconomic characteristics. The results showed that both the magnitude and interannual variability of damage is comparatively larger in areas with a higher ratio of non-commercial farm households, smaller cultivated paddy land under management, larger abandoned arable fields, lower percentage of young residents, and higher percentage of elderly ones. Such relationships are consistent throughout various topographic conditions. Two hypotheses are suggested to explain the comparative largeness in the magnitude and variability of damage: first, the deterioration of quantity and/or quality in labor resources; second, the lack of willingness to manage cultivations efficiently due to the lower percentage of on-farm income. The hypotheses propose the possibility that commercial farm households succeed in mitigating the damage by applying sufficient labor resources and self-reliant efforts, while elderly farmers fail at effective management due to shortage in resources and/or willingness.

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Evaluation of biophysical variables is usually a prerequisite in land suitability analysis for sustainable agricultural production. In Bangladesh, agriculture is the mainstay of national economy and rice is the major food but the production is very low. In particular the rice production of Bangladesh does not meet the demands due to its rapidly growing population. The aim of this study is to determine physical land suitability for rice crop using remote sensing and geographical information system (GIS) techniques and to compare present land use vs. potential land use. Integration of remote sensing and GIS is a new approach in Bangladesh because it has not been utilized to solve problems related to agricultural topics, such as in the case of identifying suitable areas for specific crops. The study was carried out in Haripur Upazila (sub district) of Thakurgaon district in Bangladesh. Relevant biophysical variables of soil and topography were considered for suitability analysis. All data were stored in GIS and the criterion/factor maps were generated. For Multi-Criteria Evaluation (MCE), Pairwise Comparison Matrix known as Analytical Hierarchy Process (AHP) was applied and the suitable areas for rice crop were identified. To generate present land use/cover map, Terra/ASTER 2003/03/22 satellite image was classified by maximum likelihood classification method. Finally, we overlaid the land use/cover map with the suitability map for rice production to identify differences and similarities between the present and potential land use. The results of this research identified in the study area, 37% of current paddy fields were under highly suitable areas and 25% of that was under moderately suitable areas. 35% of current paddy fields were under marginally suitable areas. This research provided information at local level that could be used by farmers to select cropping pattern and suitability.

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In order to assess the grain protein concentration of winter wheat before maturing stage, we proposed a new vegetation index of rbNDVI (red and blue Normalized Difference Vegetation Index) for the estimation of leaf chlorophyll concentration at heading to anthesis stage. rbNDVI derived from the hyperspectral measurements of red (630nm) and blue (445nm) showed the highest correlation with leaf chlorophyll concentration (r2=0.701 for 2006, 0.802 for 2007) comparing with the widely used NDVI (Normalized Difference Vegetation Index) and TCARI/OSAVI (Transformed Chlorophyll Absorption in Reflectance Index/Optimized Soil-Adjusted Vegetation Index). Moreover, difference of equations between 2006 and 2007 was also smallest in rbNDVI (RMSE: Root Mean Square Error=4.77µg cm-2）. In addition, simulation trial with ALOS/AVNIR-2 (Advanced Land Observing Satellite/Advanced Visible and Near Infrared Radiometer type 2) broadband (blue: 420-500nm, and red: 610-690nm), compared with narrowband (445nm and 630nm), obtained by spectral measurement resulted almost same accuracy level. It highlights the feasibility of satellite monitoring of leaf chlorophyll concentration using the newly developed rbNDVI in the earlier growth stage of wheat. Information by rbNDVI may suggest effective manuring practice for the current year to enhance grain protein concentration through nitrogen application of wheat at heading to anthesis stage.

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To assess sustainability of rural management in Changjiang (Yangtze) River basin, human behavioral (food consumption and human waste disposal) impact on nitrogen flow was quantitatively evaluated. A survey of day-to-day activities was conducted in 2 representative counties: Taoyuan (a modernized agricultural area in Hunan province that uses farm machines mainly in the plains) and Taihe (a traditional agricultural area on hilly lands in Jiangxi province). Daily nitrogen intake from food per capita and potential nitrogen load on the environment from human waste were calculated. The survey showed that daily per capita nitrogen intake from food in Taoyuan and Taihe is 17.0 g-N and 16.0 g-N respectively. It was also noted that in Taoyuan, 47% of total calorie intake is from grains and 33% from animal products such as meat, egg, fish and dairy products; while in Taihe grains accounts for 50% and animal products 29% of total calorie intake. As for human waste disposal/management, 26 % in Taoyuan and 67% in Taihe are utilized or returned to agricultural lands while 74% in Taoyuan and 33% in Taihe are washed-off by drainage runoff into river systems. Therefore, with regards per capita potential nitrogen load from human waste onto the environment in Taoyuan, approximately 1.61 kg-N returns to farmlands and 4.58 kg-N discharges directly into river systems annually. Similarly, approximately 3.91 kg-N returns to farmlands and 1.93 kg-N discharges directly into river systems annually in Taihe. Furthermore, the impact of changing patterns of human life-style on nitrogen flow was examined by comparing the two areas using a nitrogen flow model that incorporates not only food production processes, but also human food consumption process. It was shown that economic growth and urbanization push up: (1) consumption of animal products in rural areas, which in turn makes secondary products such as meat, egg and dairy lot more important than primary/crop products; (2) less use of organic recyclables such as disposed human waste, which in turn makes rural communities more dependent on chemical fertilizers and imported animal feeds. China is facing serious water pollution problems, and in such a development, recycling organic matter within communities needs reconsideration.

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Production of whole crop rice silage as feed (forage rice) and application of cattle manure to the forage rice fields are considered to be a better strategy to maintain rice fields and solve environmental problems resulted from animal production. In this study, the characterization of dairy farms in Takashi area of Tokushima Prefecture was achieved based on interviews with farmers of 15 dairy farms producing and utilizing forage rice as feed. The typology of the farms was established on the basis of 4 variables ((1) application rate represented as the ratio of actual manure application into crop fields to predicted total feces excretion in a farm, (2) proportion of forage rice to total rice, (3) application rate represented as the ratio of actual manure into forage rice fields to predicted total feces excretion in a farm and (4) the ratio of leased land for forage rice fields) using cluster analysis. Two groups of dairy farms were categorized from the analysis: the first group consisted of farms which aim at increasing income from dairy production and the second group consisted of smaller farms which aim at enhancing resource recycling within a farm. The comparisons between the two groups indicated that the farmers in the first group tended to evaluate forage rice as cheaper feed than hey, expect to be subsidized for cultivation of forage rice by governments and to reduce labor loads through help of contractors.

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Stable isotopes are a powerful research tool in ecosystem carbon balance studies and their use in ecosystem research is increasing. Stable isotope measurements together with CO₂ concentration and CO₂ flux measurements provide empirical means for understanding the processes that control CO₂ exchange between atmosphere –ecosystem and the mechanisms that govern patterns of carbon storage and release in terrestrial ecosystems. Combining stable isotopes and concentration measurements allows the identification of the isotopic composition and the contribution of ecosystem, or ecosystem components, to the exchange fluxes with the atmosphere. Recent modifications of stable isotope signatures of CO₂ along with CO₂ concentration measurements permit examination of CO₂ recycling within canopies (i.e., refixation of respiratory CO₂ before it leaves the system). Recycling of respired CO₂ can be possible factor that contributes to errors in partitioning net ecosystem exchange of CO₂ into photosynthetic assimilation and respiration using eddy covariance techniques and isotopic mass balance equations. Thus, the studies for CO₂ recycling are increasing during the several years. In this review, we introduce and discuss the relevant details underlying the use of carbon isotopic compositions in research for CO₂ recycling. To progress quantitative evaluations of CO₂ recycle in various ecosystems makes it possible to distinguish among the components contributed to the net CO₂ flux and to obtain insights into the processes underlying ecosystem responses to climate forcing.

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We observed shallow groundwater levels with temperatures and discussed their seasonal fluctuations under a series of agricultural land uses along a gentle sloping topography in northeast Thailand. When the study sites were characterized into such three categories on the basis of their land uses and topographies as A: lower (paddy fields), B: middle (paddy fields) and C: upper (upland), we recognized that the shallow groundwater temperatures tend to be in the order of A<B<C. As one of the main possibilities to explain this groundwater temperature regime, we suggested that the latent heat loss by evapotranspiration would remain larger in the lower sites than in the upper sites due to the hydrologic location of the lower sites which is subjected to higher soil water content.

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