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.