Agronomic and Economic Effects of Two Enhanced‐Efficiency Urea Fertilizer Technologies on Southern Great Plains Winter Wheat

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Abstract
Core Ideas: Stabilized urea improved wheat grain yield and protein in the Southern Plains. Stabilized urea at a higher rate brought higher net profits than untreated urea at all price points. A safe seed‐placed rate for polymer‐coated urea in regional wheat is lower than 30 kg N ha–1. No benefit was observed in splitting nitrogen application in this study. In no‐till wheat (Triticum aestivum L.) cropping systems of the US Southern Great Plains, urea fertilizer is commonly surface broadcast and producers rely on unpredictable precipitation in dryland conditions for incorporation into the soil. Several enhanced‐efficiency fertilizer technologies are designed to reduce N loss in this scenario, though there are not published reports on evaluations of these in regional wheat systems. Here we report on an evaluation of two enhanced‐efficiency fertilizer technologies, polymer‐coated urea (PCU) and urease/nitrification inhibitor‐stabilized urea (SU), which were compared to untreated urea at different application rates (0, 31.5, and 70 kg N ha−1) and timings (at‐planting and split) in two locations differing in soil type (clay loam and loamy fine sand). The fertilizer was broadcast, except for PCU, which was drilled in‐row. The greatest yield was observed with a high at‐planting rate of SU, where yield was 26% greater than with untreated urea and 34% greater than with no fertilizer. Yield improvement with SU was associated with greater grain N uptake efficiency and protein content. The high SU rate brought higher net profits than untreated urea at all price points analyzed and surpassed the no‐fertilizer control as price increased. As might be expected with seed placement, there was substantial crop damage at the high rate of PCU, but even minor damage at the lower rate. The results suggest that a safe seed‐placed rate for PCU in wheat in this environment is somewhat lower than 30 kg N ha−1. No benefit was observed in splitting the N application.

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