Root traits and rhizosphere phosphorus dynamics regulate phosphorus uptake in peanut across contrasting soils

Abstract Aims Peanut ( Arachis hypogaea L.) efficiently explores soil phosphorus (P) through root plasticity and rhizosphere modifications. However, how root system adjustments vary across soils with contrasting P availability remains unclear. This study evaluated peanut root traits, P uptake, and bulk soil and rhizosphere P dynamics under contrasting soil types and P levels. Methods Two peanut cultivars contrasting in growth cycle and root development were grown under greenhouse conditions in three soil-specific experiments (sandy loam, silt loam, and silty clay loam) adjusted to low, medium, and high P levels. Plant biomass, root morphological traits, and P uptake were quantified, together with changes in bulk soil and rhizosphere P fractions. Results Plants with more extensive root systems exhibited greater P uptake under low P conditions. In silt loam, root growth sustained biomass production even at low P, with minimal response to additional fertilization. Rhizosphere soils had, on average, 0.4 units lower pH than bulk soil and showed marked depletion of labile phosphorus fractions near roots. The degree of P depletion correlated with P uptake, particularly for water-extractable P. Despite higher total P in the silt loam, its lower solubility limited plant availability compared with sandy loam and silty clay loam. Conclusion Enhanced P uptake in low-P soils was primarily driven by greater carbon allocation to roots, increased root length, and a mild, localized rhizosphere acidification, enabling the solubilization of less labile P forms. These findings highlight the potential of breeding and selecting peanut cultivars with superior root systems to improve P use efficiency and reduce reliance on phosphate fertilizers.