Hydrogen agronomy: research progress and prospects.

Agriculture is the foundation of social development. Under the pressure of population growth, natural disasters, environmental pollution, climate change, and food safety, the interdisciplinary "new agriculture" is becoming an important trend of modern agriculture. In fact, new agriculture is not only the foundation of great health and new energy sources, but is also the cornerstone of national food security, energy security, and biosafety. Hydrogen agronomy focuses mainly on the mechanism of hydrogen gas (H) biology effects in agriculture, and provides a theoretical foundation for the practice of hydrogen agriculture, a component of the new agriculture. Previous research on the biological effects of H focused chiefly on medicine. The mechanism of selective antioxidant is the main theoretical basis of hydrogen medicine. Subsequent experiments have demonstrated that H can regulate the growth and development of plant crops, edible fungus, and livestock, and enhance the tolerance of these agriculturally important organisms against abiotic and biotic stresses. Even more importantly, H can regulate the growth and development of crops by changing the soil microbial community composition and structure. Use of H can also improve the nutritional value and postharvest quality of agricultural products. Researchers have also shown that the biological functions of molecular hydrogen are mediated by modulating reactive oxygen species (ROS), nitric oxide (NO), and carbon monoxide (CO) signaling cascades in plants and microbes. This review summarizes and clarifies the history of hydrogen agronomy and describes recent progress in the field. We also argue that emerging hydrogen agriculture will be an important direction in the new agriculture. Further, we discuss several scientific problems in hydrogen agronomy, and suggest that the future of hydrogen agronomy depends on contributions by multiple disciplines. Important future research directions of hydrogen agronomy include hydrogen agriculture in special environments, such as islands, reefs, aircraft, and outer space.