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

Authors: Goden Mabaya; Koichi Unami; Junichiro Takeuchi; Masayuki Fujihara; Hidekazu Yoshioka

Addresses: Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake-Cho, Sakyo-ku, Kyoto 606-8502, Japan ' Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake-Cho, Sakyo-ku, Kyoto 606-8502, Japan ' Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake-Cho, Sakyo-ku, Kyoto 606-8502, Japan ' Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake-Cho, Sakyo-ku, Kyoto 606-8502, Japan ' Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu-Cho, Matsue 690-8504, Japan

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; Japan; agricultural watersheds; water pollution; optimisation modelling; water diversion; joint crop production.

DOI: 10.1504/IJISD.2017.080618

International Journal of Innovation and Sustainable Development, 2017 Vol.11 No.1, pp.69 - 84

Received: 06 Apr 2015
Accepted: 02 Sep 2015
Published online: 01 Dec 2016 *

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