Deep banding and EEFs reduce N loss in light soils

Nitrous oxide is a major contributor to greenhouse gas emissions from agriculture in Canada (accounting for 54 per cent of agriculture emissions, according to Environment Canada 2017). Mario Tenuta, in an earlier study, showed that adoption of 4R Nutrient Stewardship practices can reduce nitrous oxide emissions from Manitoba soils by 50 per cent. These practices also reduce ammonia losses and other nitrogen losses which, though not greenhouse gases, represent a major reduction in nitrogen use efficiency.

This study showed how farmers with light-textured soils can reduce nitrous oxide (N2O) and ammonia (NH3) emissions through better management of fall-applied nitrogen fertilizer, use of newly available enhanced efficiency fertilizer products, management of depth of nitrogen fertilizer placement and utilization of in-season nitrogen application.

Treatments included application timing (fall, spring, and split with spring and in-season), source (urea, SuperU, UAN with Agrotain, urea with eNtrench, urea with DMPSA, and ESN and urea in a 70-30 blend), placement (surface, shallow and deep band), and combinations of all three. Rate for all treatments was 100 per cent of soil test recommendation. A zero nitrogen control was included.

Researchers established the trials on commercial fields in southern Manitoba, targeting light textured soils such as sandy loam. A total of six trial sites were conducted with two sites each for 2019, 2020 and 2021. Trials were not sited on the same location between years to avoid growing canola on canola stubble. InVigor L140P was grown at all sites. All three years of the study were drier than normal.

Results

Enhanced efficiency fertilizers. Urea, whether shallow or deep banded, had the highest cumulative emissions of nitrous oxide. Enhanced efficiency fertilizer products greatly reduced emissions. Treatments SuperU surface applied, SuperU shallow banded, ESN shallow banded and urea plus DMPSA deep banded all had low emissions. Emissions for DMPSA-treated urea and Super U-treated urea specifically were similar to the control treatment with zero added nitrogen.

Deep banding. Researchers applied band treatments with a Bourgault disc-style mid-row bander at 2-2.5cm (1”) or 7.5-10cm (3-4”) depth. For straight urea, the deep band treatment had lower emissions than the shallow banding treatment. Adding an inhibitor reduced losses even further.

Split applications. Split application of urea, with both time-of-seeding and in-crop treatments applied as deep bands, had lower emissions than the single deep application of urea at seeding. Split application where UAN was streamed in-season at rosette stage reduced emissions compared to shallow urea and deep urea at the time of seeding.

Results from this study confirm conclusions from the previous Red River Valley study that nitrification-inhibited urea (single or dual) should be used when shallow banding. Results also confirm that urea with the single nitrification inhibitor treatment can reduce emissions as effectively as dual-inhibited (urease and nitrification) urea.

EEFs and deep banding reduce emissions from urea