Updating soil‐test‐based phosphorus fertilizer recommendations for soybean

Abstract Phosphorus (P) management is pivotal for soybean [ Glycine max (L.) Merr.] productivity, yet overapplication can increase environmental risk. We conducted 61 site‐year field trials from 2020 to 2023 across Louisiana to evaluate soybean yield response to fertilizer‐P (triple superphosphate), correlate yield with Mehlich‐3 soil‐test P (STP) at commonly used depths of 0–10, 0–15, 0–20, and 0–30 cm, and calibrate fertilizer‐P rate. Trials were designed as randomized complete blocks with four to five replications and three to five fertilizer‐P rates (0–78 kg ha −1 ). Mehlich‐3 STP decreased with depth due to P stratification, and strong linear relationships ( r 2 = 0.96–0.98) among depths allowed conversion of STP measured at nonstandard depths to the recommended depth. Across depths,…