Effect of Polymer-Coated Urea/Urea Blends on Corn Yields under Short Growing Season Conditions in Eastern Canada

Abstract

Polymer-coated urea (PCU) was developed to better synchronize nitrogen (N) supply with crop needs and reduce N losses. The objective of this work was to evaluate the effects of different N rates prepared using combinations of urea and ESN (PCU) on corn (Zea mays L.), grain yield, yield components, in-season nutritional status, and residual soil N. Field experiments were conducted on two sites in eastern Ontario (Canada); Kemptville (sandy loam) and Winchester (clay-loam), and repeated over three years (2011–2013). A total of ten treatments were applied using combinations of three N rates (50, 100, and 150 kg N ha−1) and three fertilizer proportions (100% urea, 75:25 urea:ESN, and 60:40 urea:ESN) for each rate. The tenth treatment consisted of a non-fertilized control (0 N). Grain yield was significantly affected by N source, N rate, site, and year. There was no significant effect of the N source in most sites/years. In the wetter season 2013, treatment 100N60:40 in the sandy site produced a similar yield to treatments receiving 150 kg N ha−1. In the clay-loam site, the 150N75:25 treatment had a yield advantage of 11–12% compared with straight urea. Chlorophyll index generally increased with the higher N application rate. The other grain parameters were little affected by the N rate or source. Soil residual mineral N tended to increase with ESN blends at 100 and 150 kg N ha−1 compared with straight urea. Our findings indicate that replacing a portion of urea with PCU might save N in lighter soils prone to leaching especially in wet years without affecting yields.