Sustainable Intensification Enhances Forage Yield, Livestock Productivity, and Soil Carbon in an Espinal Agroforestry System of Central Chile

The espinal agroforestry system is a valuable grazing resource for sheep and cattle in the Mediterranean region of central Chile. It is characterized by a woody stratum dominated by Vachellia caven and an herbaceous grassland stratum that together provide important ecological services. Despite its relevance for extensive livestock production, ongoing land-use change threatens the integrity of the espinal agroforestry system, underscoring the need for sustainable management strategies to enhance productivity. This study assessed the long-term impacts of improved management practices in a representative espinal agroforestry system, including annual fertilization, supplementary cereal crop integration, and progressive increases in stocking rate, on plant diversity and soil carbon storage in Cauquenes, Maule Region, Chile (35°58′ S, 72°17′ W), during 2014–2019. A production system was established on 10 ha of espinal grassland, complemented by 1 ha of supplementary crop rotation (oat–purple vetch intercropping and triticale). Due to the scale of the system, a single experimental unit was used; however, multiple sampling areas were evaluated over time to assess the botanical composition, forage yield, and soil carbon. Grasslands were annually fertilized with phosphorus, potassium, and boron. The forage yield in spring ranged from 2 to 4 t dry matter ha−1 year−1 over six years, with strong interannual variability driven by rainfall. The stocking rate increased progressively from 2 to 8 sheep ha−1 and lamb live weight from 80 to 370 kg ha−1 over six-years. The grassland botanical composition shifted markedly, with increased abundance of annual legumes (Trifolium subterraneum, Medicago polymorpha) and Leontodon leysseri. Supplementary crops yielded between 6.0 and 10.5 t DM ha−1, while soil organic carbon increased from 1.6% to 2.2%. These results demonstrate that sustainable intensification of the espinal system can enhance productivity while maintaining environmental sustainability.