Combined application of sheep manure and organic fertilizer improves soil quality and microbial community structure and function in alpine mining areas

ABSTRACT The harsh soil conditions in alpine mining areas severely restrict plant growth, necessitating the urgent development of an optimal fertilization strategy to facilitate soil restoration and ecosystem recovery. Six treatments were incorporated: control with no fertilization (CK), 100% sheep manure (S), 100% commercial organic fertilizer (F), 60% sheep manure + 40% commercial organic fertilizer (M1), 50% sheep manure + 50% commercial organic fertilizer (M2), and 40% sheep manure + 60% commercial organic fertilizer (M3). The treatments’ impacts on soil properties, microbial composition, functionality, and their interactions were systematically analyzed. The combined application of sheep manure and commercial organic fertilizer significantly enhanced soil organic matter (SOM) and available nutrients. The findings revealed that the M1 treatment showed the greatest improvement, with total nitrogen (TN), total phosphorus (TP), SOM, available nitrogen (AN), and available phosphorus (AP) increasing by 211.07%, 136.27%, 388.18%, 564.97%, and 282.53%, respectively, in comparison to the CK treatment. Nutrient addition significantly altered the structure of soil microbial communities and the abundance of functional microorganisms. But it had no significant effect on the Shannon and Simpson indices of the soil fungal community. Key factors such as TP, SOM, TN, AP, and AN significantly influenced bacterial distribution, while TP, AN, and AP played a crucial role in fungal distribution. Bacterial diversity and fungal functionality were mainly regulated by TP, while bacterial functionality was primarily controlled by pH and SOM. In conclusion, the M1 treatment appears to be a viable strategy for promoting soil restoration in alpine mining areas. IMPORTANCE Ecological restoration in mining areas is a global challenge. We systematically investigated the effects of sheep manure, commercial organic fertilizer, and their combined application on soil physicochemical properties, microbial community structure, and functions in the Muli mining area of the Qinghai-Tibetan Plateau. Results showed that the combined application significantly improved soil quality, with the optimal ratio being 60% sheep manure and 40% commercial organic fertilizer. Furthermore, the study revealed the mechanisms by which nutrient addition enhances soil quality by analyzing the relationships between soil properties and microbial communities under different treatments. These findings provide valuable insights for restoring ecosystem functions in alpine mining areas of the Qinghai-Tibetan Plateau and promoting sustainable grassland agriculture.