Migration and transformation of soil phosphorus by organic acids: a global meta-analysis.

Purpose: Phosphorus, an essential limiting nutrient for plant growth, has been a significant challenge due to its low utilization efficiency in recent years. The application of organic acids has become one of the most effective means to activate insoluble soil phosphorus. This study aims to elucidate the global mechanism of soil phosphorus activation by organic acids and provide guidance for maximizing its effectiveness. Methods: A meta-analysis of 7870 samples from 37 studies worldwide was done. The structural equation model was used to test two hypotheses based on meta-analysis results. Results: Our study demonstrates that organic acids enhance soil phosphorus availability, primarily by promoting the transformation of phosphorus into plant-available forms. This transformation process is collectively influenced by organic acid types, soil properties, and treatment conditions (ranging from −14.58 to 185.77%). Acetic acid exhibits the strongest effect, increasing available phosphorus by 185.77%. Furthermore, soil and treatment conditions are found to have significant impacts on the transformation of available phosphorus by organic acids through the structural equation model, and excess organic acids are detrimental to this process. Conclusion: This study unequivocally demonstrates that organic acids significantly enhance soil phosphorus availability. The application of organic acids, particularly acetic acid, promotes the conversion of phosphorus into plant-available forms. Low concentrations of organic acids in neutral loam maximize this effect. This research contributes to the advancement in identifying more effective ways of utilizing organic acids as phosphorus activators and improving nutrient management strategies, ultimately paving the way for sustainable agricultural practices. Graphical bstract: [ABSTRACT FROM AUTHOR]