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Preface to Special Section “Recent Progress of Agro-Environmental studies in the East Asian region”

The East Asian region is blessed with a mild climate and relatively high precipitation caused by monsoons. This mild, wet climate characterizes the agriculture of this region, whose main staple crop is wetland rice. East Asia is one of the most dramatically changing regions of the world in terms of economic development. This development, in addition to agriculture, has caused various environmental problems. While agriculture itself affects the environment, agriculture is affected by changes in the environment as well. Soil Science and Plant Nutrition (SSPN) has published many studies relating to various agro-environmental issues. On behalf of the Editorial Board, I have compiled this special section ‘‘Recent progress of agro-environmental studies in the East Asian region’’. Three reviews and 4 original research papers were carefully selected from among the manuscripts submitted for this special section. These papers were peer reviewed by entirely the same processes as used for other papers published in SSPN. Historically, to meet the food requirements of a growing population, the farming style in East Asia was more intensive than that in other regions. With the growing economic development in the region, its agriculture has further intensified. As a result, environmental pollution due to agricultural activities, such as nitrogen and phosphorus pollution in aquatic environments, has become a problem. Although environmental problems first appeared in Japan, they now occur throughout the region and are becoming especially serious in China. To solve these nutrient-related environmental problems, not only nutrient management in crop production but also nutrient dynamics at the watershed level should be optimized to minimize the environmental loads of nutrients derived from agricultural activities. Ammonium emission and deposition, two key processes of the nitrogen cycle in agro-ecosystems, have been investigated rigorously in Europe and North America, but not much research has been conducted on this topic in the East Asian region. In this section, Hayashi and Yan (this issue, pp. 2–18) review the current knowledge regarding airborne nitrogen load including ammonium emission and deposition in East Asia and discuss future directions of this research. With the development of modern industries in East Asia, various hazardous chemicals have polluted the region’s environments. The contamination of arable soils with hazardous chemicals such as heavy metals seriously influences the sustainable production of crops that are safe to consume. Furthermore, as public concern regarding food safety increases, the international food standards for hazardous chemicals, including cadmium, have been tightened. In Japan, cadmium contamination caused the tragedy of Itai-Itai disease. As a countermeasure, large areas of rice fields polluted with cadmium have been ameliorated by soil dressing. However, such soil dressing is expensive, and it is not always and not everywhere applicable. More appropriate technologies for soil remediation and for reducing cadmium contents in crops grown in contaminated soils must be developed. Hesu et al. (this issue, pp. 31–52) review the situation regarding soils contaminated with heavy metals in Taiwan, as well as current advances in remediation technologies. Global warming is another challenge for scientists who study soil and plant nutrition, because various aspects of global warming are closely related to our research field. In order to deal with issues related to global CO2 dynamics, however, we must first understand the terrestrial carbon cycle. The mild climates in the East Asian region favor plant biomass production and carbon accumulation in soil. Takahashi et al. (this issue, pp. 19–30) review the current knowledge regarding the carbon stock in Japanese forest ecosystems in comparison with agricultural soils, which will deepen our understanding of this important issue. Various international collaborative projects on agro-environmental problems have been conducted in the East Asian region. Both basic and applied research activities in the soil and plant nutrition sciences contribute to finding solutions for these agro-environmental problems not only in this region but globally as well. One of the original articles in this section describes the findings of such international collaborative projects (Li et al. this issue, pp. 66–71). Finally, I thank all the individuals who contributed to this special section.