Long-term comparison of targeted soil test values and crop removal as a phosphorus fertilization strategy in corn

Finding effective phosphorus (P) recommendation strategies to optimize corn (Zea mays L.) yield under varying yield levels and environmental conditions is continuously sought after. A 16-year study was conducted in Concord, NE, on Nora silt loam soil initially measuring 16 ± 3 mg kg⁻¹ Bray-1 P. The study evaluated the impact of different P fertilization strategies on corn yield across various growing conditions (dry, normal, and wet years). Treatments included no P or N (NPNN), no P (NP), P applied at crop removal phosphorus (CRP), and maintaining soil P at 15 (B15), 30 (B30), and 45 (B45) mg kg⁻¹ Bray-1 P, with similar nitrogen (N) rates except for NPNN. Results showed a 25% and 33% reduction in soil test phosphorus (STP) for NPNN and NP treatments, respectively. The total P required by B30 and B45 treatments was 1.8 times more than that for CRP and B15. Although B30 and B45 treatments increased corn grain P concentration by 6%–12% compared to B15 and CRP, they did not increase yields in normal and dry years. The NP led to yield reductions of 9% and 12% in normal and wet years, respectively. In contrast, CRP achieved an 8% higher yield than B15 during wet years. Economic analysis revealed that B45 yielded a 56% higher net return in normal years, while CRP offered the highest return on investment (ROI) at 4.9. This study highlights the complexity of managing soil P under varying environmental conditions, emphasizing that while maintaining higher STP levels (B30 and B45) can enhance grain P concentration, it does not significantly boost yield and ROI compared to CRP and B15.