Low zinc availability limits the response to phosphorus fertilization in cotton.

Background: Cotton productivity is commonly limited by the imbalanced nutritional status of phosphorus (P) and zinc (Zn) in Brazil. Evaluating the effect of the P–Zn interaction on nutrient availability in soil is crucial, as this interaction promotes plant adaptations that modify the availability of these nutrients in the rhizosphere. However, the influence of root growth on the P–Zn interaction and its adsorption in rhizosphere soil remains poorly understood. Aim: We tested the interaction of P and Zn rates in two classes of soil cultivated with cotton. The aim of this investigation was to evaluate the P and Zn availability and adsorption capacity by rhizosphere soils cultivated with cotton plants subjected to P and Zn rates. Methods: Cotton plants were grown under greenhouse conditions in two different soils (Entisol and Oxisol), with different P and Zn rates. Phosphorus fractionation and Zn sequential extraction were assessed in rhizosphere soil, while total P and Zn concentrations were measured in the shoot and roots. Results: Soil type significantly affected the P–Zn availabilities on rhizosphere soils. Although increased P‐rates raised P‐soil availability on bulk and rhizosphere soils, cotton growth was not increased under low soil‐Zn availability. The labile inorganic P content was influenced by P and Zn rates just in Oxisol. In both soils, the Zn‐ Zn‐exchangeable content was decreased by P rates, while Zn bound to oxides increased. Conclusions: Soil‐type effects on P–Zn interaction could have important implications for increasing cotton productivity. Increased cotton productivity by P application was only achieved with an adequate supply of Zn. [ABSTRACT FROM AUTHOR]