Tenuta: Canola Response and Minimizing Nitrogen Losses in Two-Pass Seeding-Fertilization Systems with Varying Placement Methods in Manitoba
Date: August 2017
Term: 3 years
Status: Completed
Researcher(s): Mario Tenuta, Kevin Baron, Brad Sparling, Mervin Bilous, Don Flaten, University of Manitoba
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: MCGA, Koch Agronomic Services
Project Summary
With increasing pressure to complete field operations in a timely manner and the trend to using fertilizer custom applicators, a segment of growers in Western Canada are transitioning towards surface applications of granular urea; which represents a departure from the recommended practice of deep banding. Researchers at the University of Manitoba conducted a three-year project to evaluate combinations of right placement and N source practices in canola, with specific emphasis on changes in source and placement that increase nitrogen use efficiency and reduce N2O emissions. The results verify past research that subsurface banding of granular urea improves yields (3 to 5 bu/ac) compared to surface application. As well, surface application in fall is much less efficient than spring application. Although there was no benefit to yield in using granular urea with urease alone or urease plus nitrification inhibitors, urease plus nitrification inhibitor did reduce N2O and NH3 loses for surface applied granular urea.
With increasing pressure to complete field operations in a timely manner and the trend to using fertilizer custom applicators, a segment of growers in Western Canada are transitioning towards surface applications of granular urea; this represents a departure from the recommended practice of deep banding. However, surface applications of fertilizer increase the risk of nitrogen loss through NH3 volatilization. While deep banding is a superior technique with respect to protecting nitrogen fertilizer from gaseous losses via NH3 volatilization or N2O emissions, the placement technique does require additional horsepower, can slow field operations at seeding time, and may also have undesirable effects on seedbed quality and moisture content. As a compromise, many canola growers are shallow banding (<1”) urea or using commercially available enhanced efficiency fertilizers (e.g. SuperU or Agrotain) to reduce NH3 losses from surface application.
Researchers at the University of Manitoba conducted a three-year project from 2014 to 2016 in the Red River Valley to provide critical information to growers to apply towards managing fertilizer nitrogen inputs and selecting appropriate strategies to increase the management intensity of canola production, while simultaneously reducing the overall environmental footprint per unit of canola produced. The project included six research trial sites to evaluate combinations of right placement and N source practices in canola, with specific emphasis on changes in source and placement that increase nitrogen use efficiency and reduce N2O emissions.
The objectives of the project were to evaluate the agronomic and environmental performance of treatment combinations of source (urea, Agrotain, SuperU), placement (surface, shallow and deep mid-row banded) and rate (100 and 70% of soil test recommendation) for spring applications. Inclusion of the 70% rates was purposely to short nitrogen for the canola crop to determine treatments providing better nitrogen use efficiency evident as yield improvements. In addition, fall surface placement treatments were done for the 2016 growing season. Nitrous oxide (N2O) emissions from urea and SuperU as well as ammonia volatilization using dosimeters were also detailed.
The results of the study indicate that the N source products examined did not affect canola yield. However, for the spring application timing, surface placement had lower yields (3 to 5 bu/ac) than shallow or deep banding (see Figure 1) in five of six sites. One site was not included in the results due to poor emergence. Fall surface application of granular urea and enhanced efficiency fertilizer products with urease and nitrification inhibitor at 100% of Provincial recommendation rates had lower yield (13 bu/ac) than spring surface applications of the products.
Figure 1. Yield of canola across five of the six trial sites in response to spring N addition placement at the 70% recommended N rate.
Across the whole study, there was no clear pattern of a placement effect on N2O emissions. At some sites, subsurface placement decreased emissions while for some others, increased emissions. Granular urea with urease and nitrification inhibitor (SuperU) did consistently reduce N2O emissions from ¼ to ¾ of that for regular granular urea. Surface application of granular urea consistently had greater NH3 emissions than subsurface placement. For surface application, granular urea with urease and nitrification inhibitor (SuperU) consistently reduced or delayed NH3 loses compared to regular urea.
The results verify past research that subsurface banding of granular urea improves yields compared to surface application. As well, surface application in fall is much less efficient than spring application. There was no benefit to yield in using granular urea with urease alone or urease plus nitrification inhibitors. However, urease plus nitrification inhibitor did reduce N2O and NH3 loses for surface applied granular urea.
Future studies are recommended to examine N2O and NH3 loses and canola yield on lighter texture soils. In addition, future studies should also examine in-season application of N to canola. For soils prone to N loses, such as with good drainage or prone to fall and spring water-logging, in-season N application may reduce loses and improve yields.