In temperate rice fields, leaving the soil untouched during the cold season can lead to a decrease in soil organic carbon. By comparing different farming methods, researchers found that planting cover crops like barley or vetch during the fallow season can help increase soil organic carbon levels. Barley, with its high carbon-to-nitrogen ratio, was particularly effective at boosting soil carbon. However, vetch, with a lower ratio, also showed some improvement. Overall, incorporating cover crop biomass into the soil before planting rice can help maintain or increase soil organic carbon levels, which is important for soil health and productivity.