Robust optimal model for sustainable joint production of green tea and paddy rice in Japanese agricultural watersheds

Abstract

Abstract:In Japanese hilly agricultural watersheds, green tea is a profitable crop, whereas paddy rice cannot endure without subsidies. Environmentally, green tea plantations are the highest nitrate pollutant emitters to water bodies, whereas paddy fields are the most significant nitrogen sinks. This study investigates the effectiveness of diverting nitrate-contaminated drainage water from upland tea fields to the lowland paddy fields, in terms of reduction of downstream pollution and rice production cost, using the robust optimal model. The model optimally maximises diversions to reduce nitrate pollution to the adjacent rivers, and is environment risk averse to possible malfunctioning denitrification processes in the respective paddy fields. The application shows increased diversions to paddy fields during the rice growing season, thereby facilitating rice plants to have optimal access to substantial amounts of nitrogen nutrients and water. Thus, the robust optimal model has the potential to support sustainable joint production of the two crops.Keywords: robust optimisation; sustainable production; green tea; paddy rice; agricultural drainage water; nitrogen pollutants.Reference to this paper should be made as follows: Mabaya, G., Unami, K., Takeuchi, J., Fujihara, M. and Yoshioka, H. (2017) 'Robust optimal model for sustainable joint production of green tea and paddy rice in Japanese agricultural watersheds ', Int. J. Innovation and Sustainable Development, Vol. 11, No. 1, 70 G. Mabaya et al.Biographical notes: Goden Mabaya, MSc (Water Science and Engineering) 2012 UNESCO-IHE, Netherlands, is a PhD student in Water Resources Engineering at the Graduate School of Agriculture, Kyoto University, Japan. He has an extensive technical experience in planning, designing, construction and water management of multiuser irrigation and drainage systems in Africa. His research interests are robust optimisation of integrated agricultural watershed management with an emphasis on environmental sustainability, environmental water quality management, and post-modernisation of irrigation and drainage systems.Koichi Unami, PhD (Agriculture) 1998, Kyoto University, is an Associate Professor at Graduate School of Agriculture, Kyoto University, Japan. His research topics include theories and practices of water resources and environment management in rural areas, with specific emphasis on robustness in decision-making under uncertainty. For example, he determines operation rules for irrigation dams with irregular occurrence of recharge events in the framework of stochastic control. He is also an expert in field studies with different agro-ecological climates in Asia and Africa, such as Lake Biwa Basin of Japan and Volta Basin of West Africa.Junichiro Takeuchi, PhD (Agriculture) 2010, Kyoto University, is an Assistant Professor of Water Resources Engineering at Graduate School of Agriculture, Kyoto University, Japan. His main research interests include fluid flow and solute/energy transport through porous media and environmentally so...