Nitrogen Fertilizer and Urease Inhibitor Effects on Canola Emergence and Yield in a One-Pass Seeding and Fertilizing System

Field studies were conducted over 3 yr at two locations on the eastern Canadian prairies to evaluate the impact of urea and urea ammonium nitrate (UAN) placed near the seed-row in a one-pass seeding and fertilizing operation on seedling damage, biomass yield at flowering, and final seed yield of canola (Brassica napus L.). Seedling damage occurred in canola with increasing rates of urea or UAN fertilizer applied as a side-band targeted to place the fertilizer placed 2.5 cm to the side and 2.5 cm below the seed row at the time of seeding. Decrease in stand density with UAN was similar to that resulting from urea application. The urease inhibitor (UI) N-(n-butyl) thiophosphoric triamide (NBPT) decreased seedling damage in canola from both urea and UAN fertilizer. Dry matter yield at flowering was only rarely affected by seedling damage, but NBPT increased canola seed yield at high rates of N application in three of six site-years and decreased seed yield at one site-year. Chlorophyll concentration in the seed increased as stand density decreased, indicating a negative effect of seedling damage on both maturity and seed quality. Caution should be used to ensure that seed and fertilizer separation is adequate and safe rates of N application are not exceeded when fertilizer is banded near the seed-row. Use of NBPT can reduce the risk of seedling damage and increase the amount of urea or UAN that can safely be side-banded in a one-pass seeding and fertilizing operation.