Blackshaw: Nitrogen Dynamics

Date: March 2013
Term: n/a
Status: Completed
Researcher(s): Dr. Robert Blackshaw and Xiying Hao, AAFC Lethbridge, AB, John O’Donovan and Neil Harker, AAFC Lacombe AB, Eric Johnson, AAFC Scott SK and Cecil Vera, AAFC Melfort SK
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a

Project Summary

Nitrogen fertilizer costs have more than doubled in recent years, and therefore any increase in N use efficiency will reduce costs and increase farm profits. Researchers at AAFC in Lethbridge, Alberta led a multi-year study to determine the merits of polymer-coated urea (ESN) compared with urea on weed management and yield of hybrid and open-pollinated (OP) canola. Results confirmed that hybrid canola cultivars are more competitive with weeds than open-pollinated (OP) canola and yielded more than OP canola in 75% of the cases. Both hybrid and OP canola responded positively to higher than currently recommended N fertilizer rates in about 50% of the cases. ESN (polymer-coated urea) compared with urea fertilizer increased canola yield in 25% of the cases. The study also confirmed that nitrous oxide emissions are not a major concern on the Canadian prairies.

Fertilizer and herbicides are two major input costs for most canola growers. Nitrogen fertilizer costs have more than doubled in recent years, and therefore any increase in N use efficiency will reduce costs and increase farm profits. As well, the environmental impact of crop production systems, in particular greenhouse gas emissions such as nitrous oxide (N2O) and methane, are becoming an increasing important consideration for industry.

Researchers at Agriculture and Agri-Food Canada (AAFC) in Lethbridge, Alberta led a multi-year study to determine the merits of polymer-coated urea (ESN - Environmentally Smart Nitrogen-Agrium) compared with urea on weed management and yield of hybrid and open-pollinated (OP) canola. In the study, N fertilizer requirements of hybrid and OP canola were compared, and the benefits of ESN fertilizer in terms of yield, quality and herbicide requirements were determined. Researchers also wanted to determine whether using ESN or growing more productive cultivars with a greater N demand could reduce N2O emissions.

The study was initiated at three Alberta sites in 2005 (Lethbridge, Lacombe and Beaverlodge) and at two Saskatchewan sites in 2006 (Scott and Melfort). The field study portion was completed in 2009, followed by laboratory analysis, data analysis and final reporting over the next three years. For the study, two varieties of glufosinate-resistant canola (hybrid InVigor 5020 and OP LBD2393) were grown in rotation with two varieties of barley (hulled AC Lacombe and semi-dwarf hulled Vivar) in a no-till system and both crops of the rotation were grown each year. Fertilizer treatments consisted of urea or polymer-coated urea (ESN) at rates of 100% or 150% of recommended levels to reach target yields and in-crop herbicides were applied at 50% or 100% of recommended rates. The treatments were applied on the same plots in four consecutive years to determine cumulative effects over time.

Table 1. Wild oat, wild buckwheat, and cleavers N concentration response to cultivar, N fertilizer formulation, and N fertilizer rate determined 4 and 8 weeks after emergence when competing with canola.

a Means within a weed species, site, year, sampling time and treatment followed by the same letter are not significantly different (P > 0.05) according to Fisher’s protected LSD.

b Flooded conditions due to excessive rainfall prevented data collection at Lacombe in 2007.

c Data was not collected at Beaverlodge in 2006 and 2008 due to insufficient wild oat plants in many plots.

d Insufficient wild buckwheat plants in many plots in 2005 and semi-flooded conditions due to excessive rainfall in 2007 precluded data collection.

e Data was not collected in 2006, 2007 and 2008 in Beaverlodge due to insufficient wild buckwheat plants in many plots.

f Sufficient cleavers plants were only present in all plots in the latter two study years at Beaverlodge.

Results from the multi-year study confirmed that hybrid canola cultivars are more competitive with weeds than open-pollinated (OP) canola, with both weed tissue N concentration and weed biomass usually lower with hybrid compared to OP canola. As well, weed tissue N concentration was often lower with ESN than with urea, indicating that crop-weed competition for soil N might be reduced if ESN were utilized. (See Table 1)

Hybrid canola yielded more than OP canola in 75% of the cases. Both hybrid and OP canola responded positively to higher than currently recommended N fertilizer rates in about 50% of the cases. When compared with urea fertilizer, ESN (polymer-coated urea) fertilizer increased canola yield in 25% of the cases. (See Table 2). Canola yield was higher with 100% compared with 50% in-crop herbicide rates in 60% of the cases. Canola seed oil concentration was similar with ESN and urea in 19 of 20 site-years.

Table 2. Mean yield increase of hybrid compared with OP canola when significant (P<0.05) differences occurred (15 of 20 site-years).

Overall, nitrous oxide emissions across the three experimental sites (Lethbridge, Lacombe, Beaverlodge) and three growing seasons averaged 20% less with ESN than with urea, indicating the merits of ESN use especially in wet environments. Nitrous oxide fluxes varied over the growing season and peak fluxes were always associated with high rainfall events. This study confirms that nitrous oxide emissions are not a major concern on the Canadian prairies. This attribute can be used as a marketing advantage when selling prairie crops domestically and on the export market.

Scientific Publications

Blackshaw, R. E., X. Hao, R. N. Brandt, G.W. Clayton, K. N. Harker, J. T. O’Donovan, E. N. Johnson. and C. L. Vera. 2011. Canola Response to ESN and Urea in a Four-Year No-Till Cropping System. Agronomy Journal. 103:92-99.

Li, C., X. Hao, R. E. Blackshaw, J. T. O’Donovan, K. N. Harker, and G. W. Clayton. 2012. Nitrous oxide emissions in response to ESN and urea, herbicide management, and canola cultivar in a no-till cropping system. Soil and Tillage Research 118:97-106.

Full Report PDF: Long report not available

Other References to this Research Project

• Canola Research Hub Blog: Nitrogen dynamics

• Canola Digest: Canola Digest Science Edition 2013