Demonstrating 4R nitrogen principles in canola

Project Summary

A field trial with canola was conducted near Indian Head, Saskatchewan in 2017 to demonstrate the response to varying rates, forms, and application method/timing options of nitrogen fertilizer.

The shatter tolerant variety InVigor® L233P was seeded in early May and, as side-banded urea, the total nitrogen rates were 35, 90, 145 and 200 kg/ha (included 35 kg/ha residual). At the 145 kg total nitrogen/ha rate, various nitrogen alternative management strategies incorporating untreated urea, urea ammonium-nitrate, Agrotain® and SuperUrea® and pre-seed surface broadcast or post-emergent (split) applications. Overall it was a dry season with less than half the long-term average precipitation but initial soil moisture and yield potential were high. In-season assessments using a handheld GreenSeeker (NDVI) or SPAD (chlorophyll) meter both distinguished between rates to some extent; however, the SPAD meter was better able to detect subtle differences amongst rates and management strategies.

Results

The yield response to nitrogen was high with strong increases through the 1x rate then levelling off between 145-200 kg/ha total nitrogen. Focusing on nitrogen management strategies, side-banded urea was the most effective overall and differences amongst the strategies where surface applications were incorporated were mostly not significant. This is consistent with previous research which has shown that early in-soil applications are most advantageous under dry conditions.

Under optimal moisture conditions, timing and placement methods tend to be less important while, under extremely wet conditions, enhanced efficiency products and split-applications generally have the greatest potential to be advantageous. Both application dates of (surface-applied) nitrogen were subject to stranding at the soil surface and volatilization as the most significant rainfall events of the season occurred over five weeks after the pre-seed applications and prior to the split applications.

Overall, these results support the recommendation of banding nitrogen during seeding and suggest that this is the least risky and most efficient application method for nitrogen regardless of form; however, results can vary widely from season to season with weather conditions.

Funding acknowledgement

This project was supported by the Agricultural Demonstration of Practices and Technologies (ADOPT) initiative under the Canada-Saskatchewan Growing Forward 2 bilateral agreement and Fertilizer Canada as part of their 4R nutrient stewardship program.