The seasonal variations of the urban heat island (UHI) phenomenon in Kumagaya, Japan were examined using multiple fixed-point observations of surface air temperature during a 1-year period. Horizontal distributions of surface air temperature observations in Kumagaya showed that UHI occurs continuously. The hourly average temperature difference between urban and rural areas was constant at ∼1°C. The UHI intensity (UHII) was calculated by dividing all observation points into urban and rural areas. Seasonal variation of daytime UHII was observed in Kumagaya, with maximum and minimum values in summer and winter, respectively. The observation of specific humidity during sunny days in summer suggested that the difference in the surface heat balance between urban and rural areas greatly contributed to the temperature difference between the two areas. Nighttime UHII in Kumagaya was the highest during April–May. These observations of maximum UHII may be explained by strong northwesterly flow over the mountains during winter and frequent calm and sunny days due to migratory anticyclone during April–May.

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Maize is the most important cash crop in Vietnam’s northern mountainous region. It is credited with eradicating hunger and alleviating poverty. However, the continuous decreasing trend in the global maize price since 2013 has resulted in various socioeconomic problems. Yen Chau district follows a cultivation regime of annually changing maize varieties. This goes against the objectives of national test procedures for new seed. This study aimed to establish whether the annually changing seed cultivation regime is the consequence of the fierce competition between seed enterprises. We found that the maize trading structure is centered on a three-level trader network that plays a crucial role in connecting stakeholders. Strong social relationships along with weak credit/production commitments between farmers and traders have facilitated maize production throughout the region. Seed and supply enterprises target traders to promote their products and are the most important information channel for farmers. This study’s findings suggest that seed selection in Yen Chau has no scientific basis but is the result of market factors.

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