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

In dryland no-till wheat in the U.S. Southern Great Plains, urea fertilizer is commonly surface broadcast and producers rely on unpredictable precipitation for incorporation into the soil. Several enhanced-efficiency fertilizer technologies are designed to reduce nitrogen loss in this scenario, though there is not published literature on evaluations of these in regional wheat systems. Here we report on our evaluation of two types of enhanced-efficiency fertilizer, polymer-coated urea (PCU) and urease/nitrification inhibitor-stabilized urea (SU), which were compared to untreated urea with different application rates (0, 31.5, and 70 kg N ha^-1) and timings (at-planting and split). The fertilizer was broadcast, except for PCU, where subsurface placement is recommended. 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. Canopy cover data indicated that the SU product was successful at accelerating early-season crop growth and sustaining it throughout the season. Yield improvement with SU was associated with greater grain nitrogen concentration and uptake efficiency. 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 nitrogen application. Economic analysis showed that use of these enhanced-efficiency fertilizers was not favorable with low wheat prices, but increased in favorability as price increased.