Evaluation of the agronomic effectiveness of enhanced efficiency nitrogen fertilizers on yield and nitrogen uptake of sorghum

Abstract

Enhanced‑efficiency nitrogen (N) fertilizers (EENFs) are designed to improve N use efficiency and minimize losses. Their performance depends on soil properties and the behavior of coating and inhibitor chemistries. We evaluated surface application of 11 EENFs, two conventional fertilizers (Urea, urea ammonium nitrate [UAN]), deep placement of a urea supergranule (urea‐brick with deep placement [UDP]), and a control (zero N fertilizer) on sorghum ( Sorghum bicolor ) yield and N uptake in two soils from Iowa (higher soil organic carbon [SOC, pH 6.19]) and Minnesota (low SOC, pH 5.79) in greenhouse. EENFs tested included three nitrification inhibitors (3,4‐dimethylpyrazol succinic acid [DMPSA], Pronitridine, Nitrapyrin), one urease inhibitor (N‐(n‐butyl) thiophosphoric triamide [NBPT]); two dual‐inhibitors (Dicyandiamide [DCD] + NBPT + Urea, DCD + NBPT + UAN), and five polymer‐coated fertilizers (three with Polyurethane, one with polylactic acid [PLA]/poly[butylene succinate] [PBS], and one bio‐based), Across soils, grain yield increased with N rate. In the Iowa soil, most EENFs matched the performance of split‑applied Urea and UAN at 100 kg N ha −1 , while UDP, DMPSA, Pronitridine, and PC‑Poly‑3 performed best overall. At 250 kg N ha −1 , several EENFs exceeded their references, including Pronitridine, dual inhibitor (UAN + DI, and PC‑Poly‑1). In the Minnesota soil, with low inherent N, Pronitridine consistently performed the best at 100 kg N ha −1 , while DMPSA and Pronitridine performed the best at 250 kg N ha −1 .Most polymer‑coated products underperformed at both N rates, consistent with a release–demand mismatch under low inherent soil‐N. UDP was the best among Urea‑based treatments. Stover yield and total N uptake mirrored grain‑yield patterns, with strong correlations between N uptake and grain yield across soils. Overall, DMPSA, Pronitridine, and UDP delivered the most reliable agronomic gains. Dual‑inhibitor formulations performed well only in the Iowa soil. These findings underscore that EENF performance is highly soil‑specific.