The Asia-Monsoon region accounts for approximately 90% of the world's paddy rice cultivation, and is critical for food security. Improving rice productivity has become an urgent challenge owing to population growth and rising food demand. Despite high-yield strategies that rely on the heavy application of chemical nitrogen fertilizers being pursued for several years, their environmental consequences are becoming increasingly apparent. The consequences include groundwater pollution, greenhouse gas emissions, pests, and diseases.

Crops absorb approximately half of the applied nitrogen. The remainder leaches into the soil or is released into the atmosphere. Particularly, nitrous oxide has a greenhouse effect approximately 300 times greater than that of carbon dioxide; therefore, its impact on climate change as an agricultural emission source is of concern. Furthermore, methane emissions from paddy fields tend to increase during the vegetative growth period. Thus, revising fertilization systems and growth periods is crucial to reduce greenhouse gas emissions.

This report introduces the concept of nitrogen-use-efficient rice varieties and presents preliminary findings. These methods are based on the current status and challenges of fertilizer application in the Asia-Monsoon region. The proposed technology improves the nitrogen use efficiency by utilizing photosynthesis during the reproductive stage. This facilitates decreased environmental impact and increased productivity.

The goal of decreasing fertilizer application while maintaining and enhancing yields is rooted in a commitment to the future of regional agriculture and the environment.

Additionally, this report addresses the challenges and prospects of adopting this technology, and we hope that it will contribute to the transition to environmentally harmonious agriculture.