Spatial modeling of potential yields of cultivated forages in China and implications for livestock-grassland balance

The growing demand for ruminant livestock products in China has intensified the conflict with grassland grazing pressure. The intensification of cultivated forage production is increasingly recognized as a key strategy to support increasing livestock feed demand and to reduce grazing pressure. This study developed a novel approach to estimate potential yields of three major cultivated forages, including alfalfa, silage maize, and forage oats, under data-limited conditions, using data sourced from 713 papers published between 1985 and 2023, covering 11,822 entries on forage yields across China. By combining K-means clustering with high-yield sample selection and random forest modeling, we mapped potential yields of alfalfa, silage maize, and forage oats across China. Results show that improving yields without expanding sown area could provide an additional 35.6 million tonnes (Mt) of forage nationwide, equivalent to 48.3% of their current production of these forages. This yield increment corresponds to an additional 171.0 PJ of net energy supply, sufficient to meet 10.9% of the energy requirements of beef cattle, dairy cattle, sheep, and goats in 2022. Consequently, 36-41% (46.7-52.3 million hectares) of currently utilized grasslands could be spared for ecological protection if the potential forage yield predicted in this study can be achieved. These findings highlight the role of cultivated forage in securing feed supply, alleviating grassland degradation, and supporting national ecological restoration, while also supporting the "small land for large protection" principle, which advocates using modest areas of cultivated land to safeguard natural grasslands.