Phosphorus availability and legacy in highly weathered soils: Unveiling the interplay with soil aggregation across diverse agricultural land uses as integrated systems

Le résumé fourni par la source

Phosphorus (P) availability is a critical concern in tropical agriculture, particularly in highly weathered soils. Because soil functions are structured hierarchically and organized through aggregate-scale process, land use is closely associated with P availability and legacy through alterations in soil structure. However, the impact of integrated agricultural systems (IAS), such as integrated crop-livestock-forestry (ICLF), on soil P cycling remains unclear. This study evaluates the relationship between P lability and soil structural parameters—including water-stable aggregates (WSA), aggregate stability (AS), and maximum phosphorus adsorption capacity (Q max )—in three Oxisols of varying textures under different long-term conservative and non-conservative land uses. Results indicate that IAS maintained soil structure indicators comparable to native vegetation (NV), particularly regarding large-WSA proportions and AS, unlike non-conservative practices such as conventional tillage (CT). Across all sites and land uses, micro-WSA acted as the primary sink for total P. In IAS, the Q max values decreased within micro-WSA, especially under intensive land management; however, there was no clear trend of increased non-labile P compared to extensive grazing (EG) or NV, even after prolonged phosphate fertilization. The delta non-labile phosphorus (DNLP) ratio indicated that conservative systems such as NV and permanent pasture (PP) retained greater proportion of non-labile P in surface aggregates, whereas CT showed negative DNLP values consistent with vertical redistribution patterns. Principal component analysis further showed that IAS was positively associated with total and non-labile P, WSA, and AS, while CT showed negative associations with WSA and AS but remained positively correlated with total and non-labile P. Although non-labile P contents were similar across land uses, IAS combined greater structural stability with lower apparent P sorption capacity in micro-WSA, suggesting a potential to modulation of P retention dynamics, particularly in sandy Oxisols. These findings highlight how land use and aggregate architecture jointly regulate P storage and redistribution in highly weathered tropical soils.

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