The natural ¹⁵N abundance (δ¹⁵N value) of organic rice tends to be higher than that of conventional rice. However, as δ¹⁵N values vary in both organic and conventional rice, it might be difficult to use a particular δ¹⁵N value as an indicator of organic growth conditions. This review describes an approach that was developed at the Tohoku Agricultural Research Center, National Agriculture and Food Research Organization. The relationship between the δ¹⁵N values of rice and those of soil under organic or conventional farming conditions has been investigated. Regardless of the farming method, the δ¹⁵N values of rice reflect those of the soil. The δ¹⁵N values of organically grown rice tend to be higher than the regression line obtained from the δ¹⁵N values of rice and soil without the application of an N fertilizer. The δ¹⁵N values of conventionally grown rice tend to be lower than the regression line. Thus, the relationship between the δ¹⁵N values of rice and soil without an applied N source could be used to differentiate between organic and conventional rice. However, the existence of regional variation in the relationship between the δ¹⁵N values of rice and those of unamended soil can confound the use of this discriminant method. Such variation may occur due to the differences in δ¹⁵N of natural N inputs, and also through ammonia nitrification and subsequent denitrification. Temporal variation can also occur, though the reason for such variation is unknown. When the relationship between the δ¹⁵N values of rice and those of unamended soil is employed to distinguish between organic and conventional rice, regional and temporal variations in that relationship should be taken into account.

This study examines the role of agricultural investment growth in food loss, and international rice price using a partial equilibrium model. The developed Rice Economy Climate Change (RECC) model covers rice markets in 24 countries and regions. The purpose of this study is to conduct simulations on how agricultural investment for agricultural machinery and equipment can impact the food loss rate of rice and the world rice market. The result of this study concluded that an increase in agricultural machinery and equipment investment in the eight ASEAN countries, Bangladesh, Sri Lanka and Nepal would contribute to increasing not only the rice yield but also to reducing the food loss rate of rice, as rice consuming continues to grow and its production becomes increasingly affected by climate change. This study suggests that reducing the food loss rate of rice can contribute to coping with growing global rice consumption without increasing rice production. Consequently, policy makers should promote constant agricultural machinery and equipment investment not only to increase agricultural productivity, but also to reduce the food loss of rice.

Rice is a staple food across Southeast Asia. However, not all Southeast Asian countries are self-sufficient in rice production, and there is significant import-export trade. Foodstuffs and agricultural products have significant environmental impacts, which in the case of rice include demand for water, as rice farming is water-intensive. It is therefore important to understand the dynamics of rice paddy fields. Satellite remote sensing is one of the most effective methods of grasping the area and distribution of farmland. However, East and Southeast Asia have distinct rainy seasons, making clear skies rare and data collection difficult during the growing period in visible and near infrared image data. Synthetic Aperture Radar (SAR) is unaffected by cloud cover, and can thus offer a method of monitoring agricultural areas. This paper introduces a method of identifying paddy rice planted areas using SAR and some case studies in Japan.

Acquiring a high grain yield while maintaining the required grain protein content (GPC) level is vital for profitable wheat farming, but doing so is typically difficult as GPC is affected by climatic and soil-related factors and management. This study was conducted to investigate the applicability of N application at flowering time, with an emphasis on late sowing conditions, for adjusting GPC to expected levels without compromising the yield of hard and soft wheat in volcanic ash soils with high nitrogen supplying capacity. Two groups of field experiments were conducted between November 2010 and June 2013, with two hard wheat and two soft wheat cultivars under early, standard, and late sowing conditions with two split N regimes, wherein N was applied: as basal, at the stem elongation stage, and at flowering. Our results suggested that the N management strategy at flowering time for increasing GPC is suitable under optimum sowing conditions, and that the GPC of both hard and soft wheat sown at an optimum timing can be adjusted for fitting into the quality bonus window, by altering the fertilizer application rate at flowering time. This study contributes toward improving our understanding of the effects of split N fertilizer application at the stem elongation and flowering stages, and the effect of sowing time on the grain yield and GPC of both hard and soft wheat grown in volcanic ash soils.

In this study, we aimed to identify the factors underlying the spatial variation of total carbon (TC) and its relationships with soil color parameters in the surface soil (0 to 15 cm in depth) of the White Volta River floodplain in northern Ghana. The 75 soil samples collected in 2014 from an area of about 3 km × 4 km in this floodplain showed a large variation in TC content (4.1-40.1 g kg⁻¹), and to cover this variation, 63 soil samples were additionally collected from two line transects (1419 and 1177 m long), across the same floodplain in 2015. TC content in these two transects ranged from 3.7 to 54.9 g kg⁻¹, and most of the carbon (> 75.9%) was in the heavy fraction (> 1.6 g cm⁻³) of the soil in 2014. Soil TC content was significantly correlated with clay content and soil moisture content (r = 0.87 and 0.84, respectively; P < 0.001 for each) in 2015. Soil TC content decreased exponentially with the increase in downward gradient (R² = 0.41; P < 0.001) in 2015. Sloped areas, where the downward gradient was larger than 0.3%, had low soil TC content (ranging from 3.7 to 20.2 g kg⁻¹ with a mean of 10.0 g kg⁻¹), while the other locations had high soil TC content (ranging from 5.5 to 54.9 g kg⁻¹ with a mean of 26.1 g kg⁻¹) in 2015. Soil moisture content and clay content decreased exponentially with the increase in downward gradient (R² = 0.39 and 0.43, respectively; P < 0.001 for each) in 2015. Chromaticity values of soil color such as a*, b*, and C* decreased exponentially with the increase in soil TC content (R² = 0.68, 0.63, and 0.65, respectively; P < 0.001 for each), and would be better indices for the estimation of TC than the lightness of soil color (L*, R² = 0.32; P < 0.001) in the studied floodplain.

Located at the downstream end of the Dong Nai-Saigon river basin, near the mouth of the Saigon River, which is known as the “green lungs” of Ho Chi Minh City (HCMC) due to the ecosystem functions of the Can Gio mangrove forest, is a very complex hydrodynamic and geomorphic region with crossing estuaries, forming the so-called Can Gio Bay. Given its flat, low-lying topography, this area is strongly influenced by two main factors: (1) upstream flooding and (2) tidal regimes. The historical flood event of 2000 indicated that the downstream region of HCMC suffers from serious flooding, and that the Can Gio area is the worst affected, with approximately 90% of its area being inundated. This research aims to investigate the impact of tides and inflows in Can Gio Bay in the context of sea level rise and a sea dike structure connecting Go Cong to Vung Tau. A two-dimensional hydrodynamic model combined with a wetting and drying scheme is used to determine the locations of inundated areas. This research also shows how sea level rise and upstream flows cause flooding in Can Gio Bay, and identifies the negative and positive impacts of sea dike construction on Can Gio Bay.

In this study, we continuously observed water temperatures in the main irrigation canal and the main branch and farm drains of a paddy area with independent irrigation and drainage canals. We focused on the flow-down pathway that changes with various water management practices. As a result, we found that the maximum temperature in the farm drain was higher in July than in August, a trend similar to reported temperature changes of water stored in paddy plots. It appears that water temperature in the farm drain strongly reflects paddy outflow. At drainage canals, water temperature was reduced in July and rose in August. Our findings clarified that water temperature changed in the drainage canal not only because of heat exchange due to weather conditions but also because of inflow from the irrigation canal and outflow from the paddy plots. This study provides evidence for the strong impact of water management on paddy area water temperatures with independent irrigation and drainage canal settings, as farmers control the amount of inflow from irrigation canals and outflow from drainage water, depending on the stage of growth and weather conditions.

Bacillus subtilis is widely used to produce a variety of fermented soybean foods in Asian countries. These foods are classified into two types: salted (e.g., tuong of Vietnam) and unsalted (e.g., natto of Japan). To explore the effect of salt on the fermentation process, cell growth and the extracellular production of poly-γ-glutamic acid (γPGA), which confers the sticky texture to natto, were examined under high salt conditions (0.5-1.5 M NaCl). The expression of the γPGA synthetic gene was monitored using the lacZ-fusion reporter method, and the production of γPGA was detected by immunoelectrophoresis. Although B. subtilis (natto) does not usually produce γPGA in carbon source-limiting media such as LB broth, it was found to synthesize γPGA when excess salt was added to the medium. The need for genes such as degU, degQ, comP and sigB for this salt-induced γPGA production suggests that both the general stress response induced by sigma B and activation of DegU protein through phosphorylation are involved in this process.

This study was conducted to clarify how climate change is expected to affect the demand and supply of rice in India, an important rice-producing and rice-consuming nation. The method, a supply-demand model, includes six functions: yield, area, export, stock change, demand, and price linkage. To reflect topographic and climate diversity, these analyses use state data instead of national data. Results for rice supply show the benefits and shortcomings of temperature, precipitation, and solar radiation as determined by location and season. Scenario analyses that combine the three dimensions of Representative Concentration Pathways (RCP) and Shared Socioeconomic Pathways (SSP) scenarios elucidate the future supply and demand of rice, revealing that rice production andper-capita consumption can be boosted most if India undergoes conventional development. Alternatively, a fragmented society that faces higher challenges regarding mitigation and adaptation is expected to engender lower rice yields. To maintain sufficient rice production, the government must undertake social development projects and adequately address climate change-related difficulties.

This study examines the impact of Japan’s participatory development projects, in which communities design proposals for farmland consolidation projects (FCPs), on community-level social capital. The analysis uses large-scale community data that include detailed information on social capital for 29,179 communities (of which 8,067 communities implemented the project and 21,112 did not). We provide propensity score matching estimates. The results reveal a positive impact on bonding social capital, although there is limited evidence of a negative effect on bridging social capital. Further, FCPs increase the number of community meetings held. Treated communities opt for governance that requires higher cooperative levels for irrigation management. Focusing on social ties outside the community, FCPs negatively affect holding direct sales of rice products among urban residents.