Spring Wheat Yields As Affected By Controlled-Release Urea on Two Contrasting Soil Textures.

Four nitrogen levels (0, 45, 90, and 135 kg/ha) and three nitrogen sources (urea, controlled-release urea (CRU), or a 50/50 blend of the two) were tested on hard red spring wheat in eastern Ontario, Canada. The trials were conducted between 2011 and 2013, and were repeated in two locations; Winchester (clay loam) and Kemptville (sandy loam), resulting in 6 location-years. For rainfall, 2011 was an average year, 2012 was a dry year, and 2013 was a wet year.

There was a significant (P<0.0001) effect of the location, year, and level on grain yield. The source of nitrogen was not significant due to interaction between sites and years. Across locations and years, urea/CRU blend increased the yield by a mere 3.7%. However, on the sandy loam soil, urea/CRU blend at 45 kg N/ha produced 16% and 12% more yield than straight urea in 2012 and 2013, respectively. Protein content increased with nitrogen level but was not affected by the source of N.