Field Verification of the Barber–Cushman Mechanistic Phosphorus Uptake Model for Maize

Abstract

A two‐year field study in southeastern South Dakota examined how phosphorus (P) fertilizer applied to a silt loam soil affected the predictability of P uptake in maize (Zea mays L.) using the Barber–Cushman mechanistic P uptake model. Liquid ammonium polyphosphate was applied to provide 0, 10, 20, and 40 kg P ha−1 comparing a concentrated single or double band application, or comparing a concentrated single band to a fertilizer band diluted with water. Soil, plant tissue, and roots were sampled intensely. The model simulation used observed measurements as well as reasonable estimates and assumptions derived from the literature. Predicted P uptake was affected more by soil solution P (C li ) than applied fertilizer P rate. The agreement of observed with predicted P uptake was improved when their regressions were grouped according to C li ranges rather than applied P rates. In 1991, the model predicted 86–90% of observed P uptake at the high C li range (21–77 µmol L−1) but only predicted 23–44% of observed P uptake at the low C li range (1–16 µmol L−1) at the V6 (6th leaf) and V12 (12th leaf) growth stages. Predicted P uptake was much lower than observed at all C li ranges for the simulation period at the R2 (silking) growth stage. Parameters used in simulating maize P uptake were suitable at the high C li values up to the V12 growth stage. At low C li values at the V12 and R2 growth stages, additional soil factors that may affect maize P uptake (i.e., root hair proliferation, mycorrhizal infection, rhizosphere acidification, root architecture) should be included in a simulation model to improve P uptake predictability.