Enhanced Efficiency Urea Sources and Placement Effects on Nitrous Oxide Emissions

Abstract

The effects of band placement of enhanced efficiency fertilizers (EEF) on nitrous oxide (N2O) emissions are uncertain. Placement and EEF on N2O emissions from spring wheat (Triticum aestivum L.) at two locations in Manitoba, in 2011 and 2012 were examined. Treatments were a no N control and 80 kg N ha−1 at planting of five combinations of placement and granular N source: broadcast‐incorporated urea (UreaI) and, subsurface side‐banded urea (UreaS; each row side‐banded), midrow‐banded urea (UreaM; placement between every other set of rows), midrow‐banded environmentally smart nitrogen (ESN, Agrium, Inc.) (ESNM), and midrow‐banded SuperU (Koch Industries Inc.) (SuperUM). Planting in 2011 was delayed 40 d compared to 2012. Planting coincided with higher soil temperature and moisture resulting in three‐ to sevenfold more growing season N2O emissions (∑N2O) in 2011 than 2012. In 2011, SuperUM and ESNM reduced ∑N2O, emission factor (EF) scaled by N‐applied EF, and yield‐scaled N2O emission intensity (EI) by 47, 67, and 55%, respectively, compared with UreaI. In 2011, increasing placement concentration of N in order broadcast‐incorporation, side‐banding, and midrow‐banding tended to decrease ∑N2O, EF, and EI of granular urea, but not statistically significant. The ∑N2O and nitrate exposure (NE), were significantly correlated over the site‐years, indicating N availability from treatments in part determined emissions. Grain yield and crop N uptake were unaffected by sources and placement. These results suggest for early season wet and warm conditions, EEF N sources can reduce emissions compared with granular urea. Further studies are required to clarify placement effects on N2O emissions.