As a staple food for nearly half of the global population, the stable increase in rice production is crucial for ensuring food security. China, as the largest rice producer and consumer in the world, has raised its yield from 2.1 tons per hectare in 1950 to 6.8 tons per hectare in 2020 through variety improvement and increased inputs of fertilizers and water resources. However, the traditional “high input, high output” model has led to water resource utilization rates that are 40%–50% lower than the global average and a nitrogen fertilizer utilization rate of only 34%. This has also resulted in soil degradation and greenhouse gas emissions. So, how can we continue to improve yields while reducing resource consumption?
Recently, a review paper conducted by Professor Jianchang Yang from Yangzhou University, et al. pointed out that optimizing the “harvest index” (the ratio of yield to total aboveground biomass) can achieve a synergistic enhancement of rice yield and resource utilization efficiency. The study found that the harvest index of modern rice varieties generally hovers around 0.5, but there is still room for improvement through the regulation of physiological traits. Key strategies include three main aspects: first, increasing the “grain-to-leaf ratio”, which refers to the number of grains per unit leaf area, balancing the relationship between photosynthetic products and grain demand; second, enhancing the “sugar-to-spikelet ratio”, which is the ratio of non-structural carbohydrates stored in the stem before flowering to the number of grains, providing more energy for grain filling; third, optimizing the “proportion of productive tillers” to reduce the consumption of water and nutrients by ineffective tillers, thereby improving population structure and light utilization. The related paper has been published in Frontiers of Agricultural Science and Engineering (DOI: 10.15302/J–FASE–2025610).
Based on these physiological mechanisms, scientists have developed three core green technologies. The first is “moderate alternating wet and dry irrigation” (AWMD), which monitors groundwater levels using PVC pipes and sets irrigation thresholds based on different growth stages and soil types. For example, in sandy soil during the tillering stage, irrigation is triggered when the water level drops to 8–10 cm, while clay soil can tolerate a water level drop of 25–30 cm during the booting stage. This technology not only saves 35% more water compared to traditional flooding irrigation but also reduces methane emissions by 48.3%–57.9%. The principle is to inhibit methane-producing bacteria through intermittent drought, while promoting root development and the transport of photosynthetic products to grains.
The second is the “three-standard nitrogen fertilizer application technology”, which dynamically adjusts fertilizer amounts based on soil fertility, leaf color, and variety characteristics. For instance, by comparing the SPAD chlorophyll values of the third leaf and the first leaf of rice, precise top-dressing can be applied during the tillering and booting stages; for large panicle varieties, emphasis is placed on “flower-preserving fertilizer”, while for small panicle varieties, the proportion of “flower-promoting fertilizer” is increased. This method has improved nitrogen fertilizer utilization from 34% to 51%, approaching the global average.
The third is “water–nitrogen coupling regulation technology”, which quantifies the synergistic effects of soil moisture and nitrogen through mathematical models. For example, during the tillering stage, when the soil water potential is –10 kPa, the optimal nitrogen content for plants should be 2.94%, maximizing water and nutrient utilization efficiency. This precise management model has led to a 9.3% increase in rice yield and a 27% improvement in water utilization efficiency in trials conducted in Jiangsu and Heilongjiang.
These technologies have been promoted across seven major rice-growing regions in China, including Anhui, Hubei, and Sichuan, covering an area of 10.3 million hectares and generating direct economic benefits of approximately $2.2 billion between 2021 and 2022. The research emphasizes the need to further integrate smart agricultural technologies to simplify management practices and explore new ways to reduce greenhouse gas emissions to promote the sustainable development of rice production.
DOI: 10.15302/J-FASE-2025610