The planetary boundary is a concept that clearly indicates the extent to which the Earth's environment is approaching critical thresholds. In 2023, it was reported that, under the category of "biosphere integrity," excessive use of chemical fertilizers and air pollution have led to nitrogen runoff into the oceans and soils, resulting in nitrogen loads that have significantly exceeded the red zone. In response, this study evaluated the nitrogen load from the atmosphere to pastureland. Furthermore, field experiments were conducted to grow pasture using both compost and chemical fertilizers, and the associated environmental nitrogen load was assessed. The results showed that atmospheric nitrogen input to pastureland was 17.5 kg N/ha/year, equivalent to 4.5% of the chemical fertilizer application rate. In Okinawa, where atmospheric nitrogen input is relatively low, a decentralized model of compost utilization was evaluated. It was concluded that nitrogen runoff from land areas could be fully fixed by compost application, with 40% circulated within the island and 60% transported outside the region, thereby systematically reducing the environmental load on the surrounding coastal waters.

12:10 – 12:15　Introduction
Fumihiko Yokota, Associate Professor (Q-AOS Coodinator)

12:15 – 12:40 "Development of smart agriculture to optimize nitrogen fertilizer use in Okinawa through the integration of atmospheric environmental science and agricultural management”

Assistant Professor Kojiro Shimada
(Faculty of Science Chemistry, Biology and Marine Science, University of the Ryukyus)

12:40 – 12:50 Q&A

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