Phosphorus Adsorption and Availability from Two Phosphate Sources in Vertisol in Northern Mexico

Abstract

Phosphorus (P) is an essential nutrient for plant development; its study in soil is fundamental to optimize phosphate fertilizer management based on the specific soil characteristics and production systems. The present study aims to determine the maximum P adsorption capacity in Vertisol and evaluate the behavior of two phosphate fertilizers. Using Langmuir isotherm, the maximum P adsorption capacity in soil was 1080 mg kg–¹ with calcium triple superphosphate (SFT) and 1030 mg kg–¹ with phosphoric acid (H3PO4). Of the P applied as SFT, 30% was present as P-Ca and 28% as soluble P, while with H3PO4 these percentages were 40 and 31%, respectively. The two P sources showed dif ferentiated behavior when applied to soil. The P derived from H3PO4 was released quickly, reaching concentrations more than double of those obtained from SFT; however, at 24 hours post-application, regardless of the source or dose, 94% of the applied P was adsorbed, indicating the high adsorption capacity of the Vertisol soil. H3PO4 showed a greater initial availability of P, which could be advantageous in intensive production systems. In contrast, SFT shows a more gradual release, making it a viable option for base fertilization. Phosphorus adsorption capacity and availability in soil determine the selection of the most suitable phosphate fertilizer according to the production system.