Dissolved Organic Matters, an Intermediary of the Microbial Community and Potassium Fertilizers in A. carmichaeli rhizosphere Soil

Purpose  Aconitum carmichaeli Debx. (Ranunculaceae) is a traditional Chinese medicine with large-scale artificial cultivation in China. Potassium fertilizer is commonly supplemented to increase the yield of lateral roots of A. carmichaeli. This study aims to reveal the effect of inorganic potassium fertilizer on rhizosphere microbial communities and the dissolved organic matters (DOMs). Furthermore, the relationship between DOMs and microbial community variation is studied.
Methods: A pot cultivation experiment of A. carmichaeli in a greenhouse was conducted. The low, medium, and high amounts of potassium sulfate, potassium chloride, and potassium humate were supplemented for each treatment. The yield of A. carmichaeli lateral roots was weighed, and the alkaloids’ contents were measured. Soil properties, DOMs, and soil microorganisms communities were analyzed.
Results: The yield of A. carmichaeli lateral roots was enhanced in PHM (medium amount of potassium humate) and PCM (medium amount of potassium chloride). The dissolved organic carbon contents in the PSM (medium amount of potassium sulfate), PSH (high amount of potassium sulfate), PCL (low amount of potassium chloride), and PCH (high amount of potassium chloride) were 7.24 ± 0.32 g·Kg^{− 1}, 7.68 ± 0.50 g·Kg^{− 1}, 8.54 ± 0.22 g·Kg^{− 1} and 8.58 ± 0.38 g·Kg^{− 1} respectively, which were significantly decreased compared to the control. The Shannon index of the fungal community increased in PHL (low amount of potassium humate), reaching 7.42 ± 0.17, 7.07 ± 0.44, and 7.52 ± 0.12, respectively. Besides, it was decreased in PCL (5.69 ± 1.58), PCM (6.41 ± 0.82), and PSL (low amount of potassium sulfate) (6.78 ± 0.90). The proportions of Acidobacteria were reduced in the PSL (10.29% ± 2.32%), PCM (15.73% ± 0.81%), and PHL (16.44% ± 0.55%), and the proportions of Ascomycota were increased in PSM (61.21% ± 3.46%), PCM (59.87% ± 5.53%), and PCL (58.02% ± 21.02%). The supplementing of potassium fertilizers varied the diversity of fungal communities and shifted the structural composition of both bacterial and fungal communities. The soil ammonium, nitrate, soil organic carbon, dissolved organic carbon, and pH were related to the microbial community in specific potassium fertilizer treatments of A. carmichaeli rhizosphere soil. The bacterial community variations were related to soil dissolved organic carbon and the DOMs indices, including the A: T, C: A, C: T, β: α, and biological index (BIX). Correspondingly, the fungal community variations were related to some DOMs indices, including C: A, C: M, and BIX.
Conclusion: Potassium fertilizers promoted the yield of A. carmichaeli lateral roots. The soil organic carbon (SOC), dissolved organic carbon (DOC), ammonium, nitrate, and DOMs indices were associated with supplementing potassium fertilizers. The potassium fertilizers varied the diversity of fungal communities and shifted the structural composition of both bacterial and fungal communities. Ulteriorly, the bacterial and fungal community variations were related to the DOMs indices in A. carmichaeli rhizosphere soil. The dissolved organic matter may act as an intermediary between the microbial community and the potassium fertilizers in A. carmichaeli rhizosphere soil. This study will contribute to understanding the mechanisms of potassium fertilizers affecting soil microbial communities.
© The Author(s) under exclusive licence to Sociedad Chilena de la Ciencia del Suelo 2024.