Greenhouse gas emissions in canola cropping systems: A western

Canadian perspective

R.E. Farrell1, R.L. Lemke2, J.D. Knight1 & D. Tomasiewicz2

1Dep. of Soil Science, University of Saskatchewan 2Agriculture & Agri-Food Canada, Saskatoon Research Centre

PresenterPresentation NotesGood afternoon. Today I’m going to talk to you about some of the greenhouse gas research that is underway in Saskatchewan – with an emphasis on the work relating to canola production systems,

This study is part of a larger research program aimed at quantifying and examining mitigation options to reduce GHG emissions (N2O in particular) from agricultural soils

(The overall goal of which is to provide a better assessment of N-cycling and devise strategies to increase N use efficiencies and reduce N losses to the environment)

Greenhouse Gas (GHG) Basics

• Greenhouse gases of concern – carbon dioxide (CO2); GWP* = 1 – methane (CH4); GWP = 25 – nitrous oxide (N2O); GWP = 298

*Global Warming Potential: a measure of the ability of each greenhouse gas to trap heat in the atmosphere relative to an equivalent mass of CO2 (over a specified time period).

C sequestration

N2O

Is there a role for producers in GHG mitigation?

Ag soils

Goals of Agricultural GHG Mitigation Enhance C sequestration

• Increasing soil carbon inputs by increasing crop productivity is largely in line with farm management goals of maximizing productivity – reduce or eliminate summerfallow – adopt low- or no-till practices – use crop rotations with high residue yields – efficient use of nutrient (fertilizers & manures) inputs – enhance irrigation efficiency (manage the rate, timing & placement of water)

N2O emission reductions • The best option for reducing emissions is to use fertilizer N more efficiently

– adopt 4R N management strategies (i.e., choosing the right source, rate, timing, and placement of fertilizer N)

– enhanced efficiency & ‘smart’ fertilizers

Nitrous Oxide (N2O)

• N2O emission factor (EF)

– percentage of applied N lost as N2O

– varies as a function of local climate

– EFeco = emission factor calculated specifically for each ecodistrict

(Source: Rochette et al., 2008)

Brown & Dark Brown soils (n = 48)

Grey & Black soils (n = 155)

Quebec & Ontario (n = 72)

Efeco < 0.0016 were set = 0.0016

Efeco > 0.017 were set = 0.017

(Adapted from Davidson et al., 2000)

• N2O emissions are a natural result of N-cycling processes

– nitrification (aerobic)

– denitrification (anaerobic)

GHG research: Case studies

• 4R N management for irrigated canola

• Crop and crop sequence effects on N2O emissions (pea-canola frequency study)

• Crop residue effects on N2O emissions (partitioning direct and indirect emissions of N2O from crop residues)

4R N Management for Irrigated Canola • Field plots established in 2014 at the Canada-Saskatchewan Irrigation

Diversification Centre (CSIDC) in Outlook, SK – RCBD with 4 replicates

• 4R treatments – Source: granular urea – Rate:

• 0, 55, 110, 165, and 220 kg N ha-1

• split application with half the fertilizer applied prior to seeding (broadcast & incorporated) and the remainder applied as a topdress prior to bolting

– Timing: • split application vs. single application at seeding (110 and 220 kg N ha-1)

– Placement: • broadcast & incorporate vs. side-band (110 and 220 kg N ha-1)

Seasonal patterns of N2O emissions

2014

2014 2014

2014

2014

Cumulative N2O emissions

2015

N2O emission and intensity factors

Treatment N rate (kg ha-1) Yield

(kg ha-1)

Cumulative N2O

(g N ha-1)

EF (%)

GHGi (g N2O-N kg-1

seed)

Check 0 2507 b 320 d - - - 0.128 d

Split 55 3358 a 424 cd 0.189 c 0.126 d

110 3554 a 477 c 0.143 cd 0.134 d

165 3596 a 538 bc 0.132 d 0.150 c

220 3534 a 615 b 0.134 d 0.174 c

Broadcast 110 3509 a 589 b 0.245 b 0.168 c

220 3649 a 1458 a 0.517 a 0.400 a

Side-band 110 3441 a 727 c 0.370 b 0.211 b

220 3629 a 1284 a 0.438 a 0.354 a

4R N Management for Irrigated Canola • Rate:

• N2O emissions increased with increasing N rate—especially when the amount of fertilizer N was increased from 110 to 220 kg ha-1

• Timing: – the timing of the fertilizer application had a significant impact on N2O

emissions and, again, this was most apparent at the highest N rate – split application < single application at seeding

• Placement: – fertilizer placement had a significant effect on N2O emissions—with

cumulative emissions (averaged across years) from plots receiving the side-banded application being greater than those from the plots receiving the broadcast/incorporated application

– side-banding the fertilizer N also resulted in a shift in the daily emission pattern—delaying the onset of the initial emission event and magnifying the emissions associated with early-season (DOY 135–175) precipitation/irrigation events

Pea–Canola frequency study • Field plots established in 1998 at the AAFC Research Farm in Scott, SK

– RCBD with 4 replicates

• Treatments with various crop sequences of field pea (Pisum sativum L.), wheat (Triticum aestivum L.) and canola (Brassica napus L.)

– W [±N] hard red spring wheat grown each year, with and without fertilizer-N

– P pea grown every year*

– P-W pea-wheat rotation*

– C-W canola-wheat rotation*

– P-C-W pea-canola-wheat rotation*

• All phases of the rotation present each year

*Nitrogen (urea) side banded at 75, 65 and 7.5 kg N ha-1 for canola, wheat, and pea, respectively

Cumulative & yield-scaled N2O: Crop specific Direct N2O Yield-Scaled N2O

Residue Type

Crop Grown

3-year cumulative

(g N2O-N / ha)

Residue Type

Crop Grown

3-year cumulative

(g N2O-N / kg C) C W 2120 a C W 0.62 a

W C 1440 b W C 0.50 ab W W 1360 b W(-N) W (-N) 0.48 ab

W P 1270 bc W W 0.45 ab P W 1120 bc W P 0.37 bc

W(-N) W (-N) 1110 bc P P 0.36 bc P C 1100 bc P C 0.36 bc

P P 990 c P W 0.30 c

Cumulative & yield-scaled N2O: Rotation basis Direct N2O Yield-Scaled N2O

Rotation 3-year cumulative (g N2O-N / ha) Rotation 3-year cumulative (g N2O-N / kg C)

C - W 1780 a C - W 0.59 a

cont. W (+N) 1360 b cont. W (-N) 0.48 ab

P - W 1190 b cont. W(+N) 0.45 bc

cont. W (-N) 1110 bc cont. P 0.36 c cont. P 990 c P - W 0.32 c

Pea – Canola frequency study: Summary

• Crop sequence/crop type influences N2O emissions, on both a per area and yield-scaled basis

• Including canola in the crop sequence “costs” the overall rotation on both a per area and a yield-scaled emissions basis

• Including a pulse in the crop sequence benefits the overall rotation on both a per area and a yield-scaled emissions basis

Why ??

Possible impacts of crop residue amendments on soil N2O emissions

PresenterPresentation NotesVariable (±) effect of crop residue – depends on aeration status

Positive (+) effect of crop residue – enhanced nitrification

Negative (-) effect of crop residue – microbial assimilation of N limits nitrification

Positive (+) effect of crop residue – residue supplies energy for enhanced denitrification

Variable (±) effect of crop residue – depends on relative abundance of electron donor and acceptor

Partitioning direct and indirect emissions of N2O from crop residues

• Soils: collected from long-term, continuous wheat plots at AAFC research farms located in the Brown, Dark Brown, Black, and Gray soil zones of Saskatchewan

• Soil Water Content: 50% and 70% water-filled pore space (WFPS)

• N Source − an unamended control (to determine background emissions)

− a fertilizer control (urea; reference treatment)

− four 15N-labelled crop residues (pea, wheat, canola and flax)

• Each treatment combination was replicated four times, with the microcosms arranged using a completely randomized design

Direct and indirect residue-induced N2O emissions

- - - N2O-15N - - - - - - - - - - - - - N2O-N (mg) - - - - - - - - - - - - - - - - - - Emission Factors (%) - - - - - - - -

Soil N-Trt (mg) (% 15N) TotE netRIE RDE RISE EFN EFRIE EFRDE fRDE

Black Ctrl 0.0583 --- 0.0608 - - - - - - - - - 0.41 - - - - - - - - - Black Urea 1.1057 0.164 0.0958 0.0349 0.0175 0.0174 0.38 0.33 0.16 0.50 Black Wheat 0.5518 0.108 0.1319 0.0710 0.0264 0.0446 0.34 0.29 0.11 0.37 Black Pea 2.3755 0.188 0.2019 0.1410 0.0908 0.0502 0.32 0.29 0.19 0.64 Black Flax 1.3525 0.201 0.2164 0.1556 0.0618 0.0937 0.48 0.51 0.20 0.40 Black Canola 3.2972 0.237 0.3584 0.2975 0.1503 0.1473 0.46 0.47 0.24 0.51 Gray Ctrl 0.0071 --- 0.0171 - - - - - - - - - 0.11 - - - - - - - - - Gray Urea 0.4779 0.074 0.0372 0.0202 0.0078 0.0123 0.14 0.19 0.07 0.39 Gray Wheat 0.3238 0.069 0.0683 0.0513 0.0170 0.0343 0.17 0.21 0.07 0.33 Gray Pea 1.4475 0.117 0.1789 0.1619 0.0565 0.1054 0.28 0.34 0.12 0.35 Gray Flax 0.5117 0.079 0.0841 0.0670 0.0241 0.0429 0.18 0.22 0.08 0.36 Gray Canola 2.2165 0.162 0.2280 0.2109 0.1025 0.1084 0.29 0.33 0.16 0.49 Dark Brown Ctrl 0.0000 --- 0.0108 - - - - - - - - - 0.86 - - - - - - - - - Dark Brown Urea 0.2201 0.034 0.0168 0.0060 0.0037 0.0023 0.14 0.06 0.03 0.61 Dark Brown Wheat 0.2745 0.060 0.0449 0.0341 0.0147 0.0194 0.17 0.14 0.06 0.43 Dark Brown Pea 2.0277 0.165 0.1502 0.1394 0.0795 0.0599 0.30 0.29 0.16 0.57 Dark Brown Flax 2.4874 0.387 0.2556 0.2448 0.1188 0.1259 0.80 0.80 0.39 0.49 Dark Brown Canola 5.3021 0.388 0.3870 0.3762 0.2460 0.1302 0.60 0.59 0.39 0.65 Brown Ctrl 0.0176 --- 0.0374 - - - - - - - - - 0.74 - - - - - - - - - Brown Urea 0.4413 0.066 0.0575 0.0201 0.0071 0.0131 0.37 0.19 0.07 0.35 Brown Wheat 0.4540 0.096 0.1039 0.0666 0.0234 0.0432 0.35 0.27 0.10 0.35 Brown Pea 1.2107 0.097 0.1452 0.1078 0.0468 0.0611 0.27 0.22 0.10 0.43 Brown Flax 0.7859 0.120 0.1446 0.1072 0.0367 0.0705 0.40 0.35 0.12 0.34 Brown Canola 1.3838 0.100 0.1997 0.1623 0.0634 0.0990 0.29 0.26 0.10 0.39

Emission summary: 50%WFPS

b b b b b b a ab ab a

b c b c a b b c a a

d c d c c b a a b a

c b b a bc a a a b a

Emission summary: 70%WFPS

- - - N2O-15N - - - - - - - - - - - - - N2O-N (mg) - - - - - - - - - - - - - - - - - - Emission Factors (%) - - - - - - - -

Soil N-Trt (mg) (% 15N) TotE netRIE RDE RISE EFN EFRIE EFRDE fRDE

Black Ctrl 0.0291 --- 0.0364 - - - - - - - - - 0.25 - - - - - - - - - Black Urea 0.3394 0.049 0.0518 0.0154 0.0052 0.0103 0.20 0.14 0.05 0.34 Black Wheat 0.1963 0.037 0.0877 0.0514 0.0089 0.0424 0.22 0.21 0.04 0.17 Black Pea 1.0314 0.081 0.1668 0.1304 0.0393 0.0911 0.26 0.27 0.08 0.30 Black Flax 2.0113 0.309 0.3029 0.2665 0.0947 0.1718 0.67 0.87 0.31 0.36 Black Canola 1.8812 0.136 0.3273 0.2909 0.0859 0.2050 0.42 0.46 0.14 0.30 Gray Ctrl 1.3109 --- 0.0721 - - - - - - - - - 0.45 - - - - - - - - - Gray Urea 6.5321 0.817 0.8367 0.7646 0.0871 0.6775 3.14 7.18 0.82 0.11 Gray Wheat 6.2113 1.074 2.6646 2.5925 0.2623 2.3302 6.60 10.62 1.07 0.10 Gray Pea 25.5910 1.972 4.2570 4.1849 0.9519 3.2330 6.63 8.67 1.97 0.23 Gray Flax 20.7180 3.021 6.7909 6.7188 0.9272 5.7916 14.56 21.89 3.02 0.14 Gray Canola 68.4010 4.913 10.8935 10.8214 3.1127 7.7087 13.73 17.08 4.91 0.29 Dark Brown Ctrl 0.1021 --- 0.0652 - - - - - - - - - 5.18 - - - - - - - - - Dark Brown Urea 10.6563 1.652 0.5708 0.5057 0.1760 0.3297 4.79 4.75 1.65 0.35 Dark Brown Wheat 3.8860 0.829 0.5212 0.4561 0.2025 0.2535 2.03 1.87 0.83 0.44 Dark Brown Pea 25.1539 2.034 1.7289 1.6637 0.9822 0.6815 3.49 3.45 2.03 0.59 Dark Brown Flax 21.1935 3.283 1.6974 1.6322 1.0077 0.6245 5.31 5.32 3.28 0.62 Dark Brown Canola 109.5606 8.015 7.6668 7.6016 5.0783 2.5233 11.86 12.00 8.02 0.67 Brown Ctrl 0.5682 --- 0.3674 - - - - - - - - - 7.23 - - - - - - - - - Brown Urea 7.8646 1.231 0.8906 0.5233 0.1311 0.3922 5.66 4.91 1.23 0.25 Brown Wheat 2.1661 0.475 0.6068 0.2394 0.1160 0.1234 2.06 0.98 0.48 0.48 Brown Pea 45.4847 3.694 3.4310 3.0637 1.7835 1.2802 6.43 6.35 3.69 0.58 Brown Flax 21.4238 3.335 2.2290 1.8617 1.0235 0.8381 6.23 6.07 3.34 0.55 Brown Canola 89.2773 6.537 6.5177 6.1503 4.1418 2.0085 9.52 9.71 6.54 0.67

d c cd c c c a a b b

b c b c b bc a b a a

b cd c d bc c b b a a

b c c c b b b b a a

Direct and indirect residue-induced N2O emissions

Total and 15N2O emission summary • Under conditions that promote nitrification (50% WFPS):

- N source (residue type) had a significant (P = 0.0001) effect on N2O emissions ÿ canola = flax = pea > urea = wheat

- significant soil ¥ N-source interaction (P = 0.0001)

- in general, RDEs < RISEs (accounting for an average of 45% of the total emission)

- regardless, EFs are generally low (< 0.40%)

• Under conditions that promote denitrification (70% WFPS):

- considerable “potential” for N2O emissions from crop residues

- significant (P = 0.0001) effect of N source (residue type) ÿ canola > flax > pea > urea = wheat

- significant soil ¥ N-source interaction (P = 0.0001)

- proportion of N2O derived from the residue depended on the size of the available soil-N pool ÿ increasing as the available N pool decreased

• Under conditions that promote nitrification (50% WFPS):

- N source (residue type) had a significant (P = 0.0001) effect on N2O emissions ÿ canola = flax = pea > urea = wheat

- significant soil ¥ N-source interaction (P = 0.0001)

- in general, RDEs < RISEs (accounting for an average of 45% of the total emission)

- regardless, EFs are generally low (< 0.40%)

Possible impacts of crop residue amendments on soil N2O emissions

50% WFPS canola, flax, pea

50% WFPS wheat

70% WFPS canola, flax, pea

70% WFPS Black soil

PresenterPresentation NotesPositive (+) effect of crop residue – enhanced nitrification – this is what we saw at 50% WFPS when canola, flax and pea residue was added to the soil

Negative (-) effect of crop residue – microbial assimilation of N limits nitrification – this is what we saw at 50% WFPS when wheat residue was added to the soil

Positive (+) effect of crop residue – residue supplies energy for enhanced denitrification – this is what we saw at 70% WFPS when canola, flax and pea residue was added to the soil

Variable (±) effect of crop residue – depends on relative abundance of electron donor and acceptor – this is what we saw at 70% WFPS when crop residues were added to the Black (silty clay) soil

Knowledge gaps . . . . future research ?

• Identify plant factors that contribute to enhanced N2O emissions from oilseed residues.

• What is the influence of crop type (e.g., winter wheat), particularly long-term influence?

• Assess the mitigation potential of EEF N products.

• Can we manage cropping systems to stimulate N2O consumption?

• Spring thaw period – who’s doing what, when and why?

• What is the appropriate intensity metric to assess emissions?

• Continued development of models, particularly for scenario testing.

• Concerted, integrated effort to identify/develop mitigation and “environmentally optimal” crop production strategies.

Acknowledgements

Funding Personnel 凬 Darin Richman

凬 Ken Achtymichuk

凬 Darrell Hahn

凬 Dwayne Richman

Saskatchewan Ministry of Agriculture

麥 Agriculture Development Fund

麥 Strategic Research Program − Soils & Environment

PresenterPresentation NotesI’d like to take a moment to acknowledge the people, and funding agencies, who helped make this work possible.

? Questions ?

PresenterPresentation NotesThank you for listening.

At this point, I’d be happy to answer any questions.

Total and 15N2O production

Orthic Black Chernozem (pH 6.5; 5.73% OC; C:N = 11.5; 31 mg NO3-N g-1; 31 mg NH4-N g-1)

Melfort - Black; 50% WFPS Melfort - Black; 70% WFPS

Total and 15N2O emission summary

• EFs were generally greatest for the canola residue and lowest for the wheat residue and urea fertilizer

− EFs for pea and flax were generally intermediate, with the flax yielding values that were often higher than those for pea

• Canola residues (and to a lesser extent, those of flax) appear to stimulate N2O emissions

− both direct emissions from the residue-derived N and indirect emissions associated with enhanced nitrification and/or denitrification of the native soil N pool

− reasons for this stimulatory effect are, at present, not known

Greenhouse gas emissions in canola cropping systems: A western Canadian perspectiveGreenhouse Gas (GHG) BasicsGoals of Agricultural GHG MitigationNitrous Oxide (N2O)Slide Number 5Slide Number 6Seasonal patterns of N2O emissionsSlide Number 8Slide Number 9Slide Number 10Slide Number 11Cumulative & yield-scaled N2O: Crop specificCumulative & yield-scaled N2O: Rotation basisPea – Canola frequency study: SummaryPossible impacts of crop residue amendments on soil N2O emissionsPartitioning direct and indirect emissions of N2O from crop residuesDirect and indirect residue-induced N2O emissionsDirect and indirect residue-induced N2O emissionsTotal and 15N2O emission summarySlide Number 20Slide Number 21Slide Number 22Slide Number 23Slide Number 24Total and 15N2O emission summary