Effects of Microbial Agents on Soil Improvement—A Review and Bibliometric Analysis

Microbial agents play a crucial role in improving soil quality, increasing soil fertility, enhancing crop yields, and reducing the incidence of diseases. The ecological benefits of these products contribute to environmental protection and to the promotion of sustainable agricultural development. Since the beginning of the 21st century, research in the academic community on the use of microbial agents for soil improvement has increased, yet a systematic summary of the progress in this field is lacking. In this paper, we review trends in microbial agent applications, focusing on their classification, mechanisms of action, and practical implementations. To achieve this, we conduct a bibliometric analysis based on the SCI-EXPANDED database of the Web of Science, using tools such as VOSviewer for visualization. We focus on microbial agents for soil improvement and analyze publication trends, research hotspots, and annual variations in relevant studies published between 2003 and 2024. The results show that (1) the number of publications on microbial soil improvement has steadily increased over the years, indicating that the academic community has maintained a high level of interest in this field. Keywords such as “soil”, “diversity”, “carbon”, and “nitrogen” have been central research hotspots in the past 20 years. The research has been highly concentrated in a few countries, including China and the United States, as well as in key institutions such as the Chinese Academy of Sciences and the United States Department of Agriculture. (2) We further analyze the principles governing microbial agent efficacy, address limitations in their application, and propose strategies to advance research in this field. Finally, several suggestions are proposed to promote the further development of research on microbial agents for soil improvement.