Lignite-derived organic fertiliser enhanced the carbon sequestration capacity of woody plant by improving soil quality and promoting plant growth

As essential natural carbon sinks, woody plants play a key role in urban ecological restoration. The lignite-derived organic fertiliser (LOF) may promote plant growth and carbon sequestration by improving soil properties. This study investigated LOF effects on three typical woody plants – Styphnolobium japonicum (L.) Schott. with taproots, Malus micromalus Makino with fibrous roots, and Malus domestica Borkh. with both taproots and fibrous roots – focused on soil properties improvement during a three-year planting experiment (2021–2023). The results indicated that LOF application significantly increased soil organic matter (SOM) content, with and without woody plants, by 82.3% and 54.9%, respectively. Concurrently, LOF influenced soil microbial characteristics, especially enhancing the 16S rRNA gene copy number by 0.99 times. For plant growth, LOF application increased root length, volume, and tip number in Malus domestica Borkh. by 37.4, 27.4, and 26.0%, respectively, and in Styphnolobium japonicum (L.) Schott by 43.8, 76.7, and 26.6%, respectively. However, in Malus micromalus Makino, while root volume increased by 3.8%, root length and tip number decreased by 10.0% and 26.9%, respectively. Additionally, the LOF application increased the soil plant analysis development (SPAD) values of woody plant leaves by 5.3%, indicating improved chlorophyll content and plant health. These findings demonstrate that LOF applications may significantly enhance soil quality and promote plant growth, contributing to improved terrestrial carbon sequestration.