Various beneficial microorganisms colonizing on the surface of biochar primarily originated from the storage environment rather than soil environment

Recently, the effects of biochar on soil microbial communities have gained a lot of interest. However, researchers have paid little attention to microbial colonization of biochar surfaces and the effect of soil potassium (K) availability on specific colonization In this study, the microbial colonization on the surface of biochar was systematically investigated using carbon-13 nuclear magnetic resonance (13C NMR), scanning electron microscopy (SEM), and metagenomics based on a four-year pot culture experiment. The results showed that the main microorganisms colonizing the surface of biochar were all potentially beneficial bacteria (g_Streptomyces, g_Pseudonocardia, g_Amycolatopsis). The main carbon source for microbial colonization was the alkoxy carbon component of biochar. Under normal storage conditions, biochar colonized a large number of beneficial microorganisms from the storage environment, but the amount of colonization increased when applied to the soil. Among them, the amount of colonization in the high-K environment was slightly higher than in the low-K environment, but the primary composition and functions of microorganisms were the same (carbon metabolism, biosynthesis of amino acids, ABC transporters). In general, a large number of beneficial microorganisms can colonize the surface of biochar in any environment, which provides more cutting-edge theoretical support for the application of biochar in agriculture.