Contrasting drivers of phosphorus dynamics across soil aggregates: The role of nutrient enrichment and mowing

Phosphorus (P) is an essential but often limiting nutrient for sustaining grassland ecosystem functions. Its soil dynamics are highly sensitive to land management practices and may vary across soil aggregate sizes due to differences in biotic and abiotic factors. However, the mechanisms affecting P fractions within aggregates remain largely unexplored.

Here, we conducted an eight‐year field study in a meadow steppe to investigate how the addition of nitrogen (N) and P, alone and in combination, along with mowing, influences soil P dynamics in macroaggregates and microaggregates.

In macroaggregates, nutrient addition and mowing stimulated the transformation of moderately labile P to resin P, likely reflecting enhanced recycling of microbial biomass P (MBP) and desorption via acidification. In contrast, lower P availability in microaggregates resulted from mobilization‐refixing processes between moderately labile P and occluded P fractions, mainly driven by increased activity of alkaline phosphatase (ALP) enzymes.

Our results suggest that under nutrient addition and mowing, P is transferred from moderately labile forms to more available forms in macroaggregates, but to more stable forms in microaggregates.

This study emphasizes the crucial role of macroaggregates in maintaining P availability and provides a mechanistic foundation for understanding how changes in soil aggregate affect nutrient cycling under land management interventions.