Straw ash-derived black carbon particles: Insights into potassium release and transport mechanisms

For centuries, plant ash has been repurposed as a fertilizer owing to its nutrient richness. Black carbon particles within plant ash serve as one of the vectors for potassium; however, their inherent high stability facilitates accumulation and migration in the soil, consequently impacting the release of potassium and other nutrients. In this study, based on the DLVO theory, the transport of black-carbon and endogenous potassium was studied by leaching released experiment. And the influence of black carbon from tobacco straw (TC) and corn straw (CC) on potassium ion (K⁺) release across varying conditions were compared. The results indicated that the endogenous potassium content in TC was 144 mg·g^-1, with approximately 78% being readily available, which was 1.5 times the potassium supply capacity of CC. In contrast, CC exhibited higher hydrophobicity, resulting in a much higher migration rate compared to TC. Notably, as the pH increased, so did the repulsive forces, ion concentration, and ionic valence, intensifying the compression of the electric double layer and impacting the transport of black carbon and potassium. This research offers valuable insights for the development of ecological fertilizers, highlighting the impact of black-carbon properties on potassium dynamics in agricultural systems.