Seed safety limits for cereals and canola using seed-placed ESN urea fertilizer

Abstract

Environmentally Smart Nitrogen (ESN) (Agrium, Calgary, AB) is a polymer-coated form of urea N that provides controlled-release, allowing higher seed-placed safe rates. Field studies were conducted from 2009 to 2012 near Lethbridge, AB, Canada, to determine how upper limits of seed safety using seed-placed ESN in cereals and canola change with increased N rates and alterations to the coating integrity of ESN. Alterations to the coating integrity of ESN were created in the laboratory (consistent within an incremental range of 20 to 80% N release after 7 d immersion in 23°C water) and then arranged in a factorial combination with five rates (30, 45, 60, 75, and 90 kg N ha-1) of the seed-placed ESN lots and urea (100% N release). Low N release rates (20-40%) were important for all three crops and increased the safe rate of seed-placed ESN to the optimum range of 60 to 90 kg N ha-1 for spring cereals and 60 kg N ha-1 for canola. This confirms three times the safe rate of urea (observed at 30 kg N ha-1 for cereals) can be seed-placed and achieve N sufficiency for spring wheat in one operation. Canola stand establishment was negatively affected by greater N release and rates. However, reductions to canola yield were modest (5%) unless ESN was replaced with urea, which reflects its greater compensatory response to stand thinning. Results from this study confirm the substitution of urea with ESN allows 3× rates of seed-placed N provided N release was ≤40%, which is readily achieved through proper handling. © 2014 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved.