Comparative Greenhouse Gas Emission Intensities from Irrigated and ...

Comparative Greenhouse Gas Emission Intensities from Irrigated and Dryland Agricultural Activities in Canada Suren Kulshreshtha and Desmond Sobool

Abstract: Irrigation development may present trade-offs between economic and environmental quality.To assess this, a comparative analysis is undertaken of contributions of irrigation versus dryland production to greenhouse gas (GHG) emissions in two Canadian regions for the year 2000. This regional analysis was undertaken using three criteria—area, physical production, and economic value of production. Results indicate that irrigated agricultural crop production is responsible for 1.65 Mt of carbon dioxide equivalent (CO2E) GHG emissions in Canada. This is about six percent of the Canadian total GHG emissions from crop production. On a per hectare basis, irrigated crop production emits almost 6.5 times the GHGs of dryland crop production in western Canada, and four times the GHGs in eastern Canada. When factoring in physical productivity, western Canadian irrigated crop production, relative to dryland production, emitted an almost equal amount of GHGs. However, when the value of all crops and livestock enterprises are considered, irrigated production generates smaller GHG emissions than dryland farms in both western (2.15 kg per dollar of production for irrigation and 3.23 kg for dryland) and eastern (1.59 kg per dollar of production for irrigation versus 2.65 kg for dryland) Canada. Under the current crop mix and technology, Canadian irrigation can be considered both economically and environmentally efficient, if value of production is taken into account. Résumé : Le développement de l’irrigation peut être synonyme de compromis entre la qualité économique et environnementale. Pour évaluer le tout, une analyse comparative a été entreprise à l’égard de la contribution de l’irrigation, par opposition à la production en terrains arides, aux émissions de gaz à effet de serre (GES) dans deux régions canadiennes pour l’an 2000. Cette analyse régionale a été entreprise en fonction de trois critères : région, production physique et valeur économique de la production. Selon les résultats obtenus, les cultures agricoles en terrain irrigué sont responsables de 1,65 millions de tonnes d’équivalent CO2 de gaz à effet de serre au Canada. Cela représente environ six pour cent des émissions de gaz à effet de serre totales du Canada attribuables aux cultures agricoles. Par hectare, les cultures agricoles irriguées émettent presque 6,5 fois plus de gaz à effet de serre que les cultures agricoles en terrains arides dans l’Ouest canadien, et quatre fois plus de GES dans l’est du Canada. Lorsque l’on prend en compte la productivité physique, les cultures agricoles irriguées de l’Ouest canadien, par Suren Kulshreshtha1 and Desmond Sobool2 1 2

Department of Agricultural Economics, University of Saskatchewan, Saskatoon, SK S7N 5A8 Farm Credit Canada, Regina, SK S4P 4L3

Submitted March 2006; accepted August 2006. Written comments on this paper will be accepted until March 2007. Canadian Water Resources Journal Revue canadienne des ressources hydriques

Vol. 31(3): 157–172 (2006)

© 2006 Canadian Water Resources Association

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Canadian Water Resources Journal/Revue canadienne des ressources hydriques

rapport à l’agriculture sur des terres arides, ont émis une quantité presque égale de gaz à effet de serre. Cependant, lorsque l’on considère la valeur de toutes les cultures et de toutes les entreprises d’élevage, les cultures irriguées génèrent moins d’émissions de gaz à effet de serre que l’agriculture sèche tant dans l’Ouest canadien (2,15 kg par dollar de production pour l’irrigation par opposition à 3,23 kg pour la culture sèche) que dans l’est du Canada (1,59 kg par dollar de production pour l’irrigation par opposition à 2,65 kg pour la culture sèche). Donc, dans le contexte des mélanges pour cultures et des technologies agricoles modernes, si la valeur de la production est prise en compte, l’irrigation au Canada peut être considérée comme efficace tant du point de vue économique qu’environnemental.

Introduction Irrigation is the intentional application of water, associated with selected cultural practices, for the purpose of sustained crop production in arid and semi-arid regions of the world. Demand for irrigation has increased, in part due to the need for reducing the vagaries of nature, and in part from the desire to feed a growing population. In addition, irrigation is linked to farm level prosperity and to regional economic development and stability. However, irrigation could have implications for environmental damage, such as contribution to climate change through emissions of greenhouse gases (GHG). Past Canadian irrigation-related studies have focused on farm level profitability and on the catalytic role irrigation plays in regional economic development and economic stability through drought proofing (Brown et al., 1989; Kulshreshtha and Russell, 1988; and Kulshreshtha, 2002). Irrigation efficiency and water management have also been a subject of study (Skaggs and Samani, 2005; Reidhead, 2001; Schultz and de Wrachien, 2002). As well, some studies have addressed the issue of cost and pricing of water (Merrett, 2002; Perry, 2001; Tsur, 2005). However, none of these studies have undertaken a comprehensive assessment of GHG emissions from irrigation, although Kulshreshtha and Junkins (2001) did report results on GHG emissions from irrigation in Canada. Several studies, either in

the context of irrigation or just dryland production systems, have focused on tillage methods and soil carbon sequestration (Lal, 2004; Follet, 2001; Eve et al., 2002; Entry et al., 2002; Schlesinger, 2000; Miller et al., 2004; and del Grosso, 2006). Studies dealing with a comparative analysis of the dryland and irrigated production systems are lacking although some studies have included crop production activities in studying GHG emissions. For example, del Grosso (2003), based on a study of crops and tillage effect on various crops, reported that irrigated corn and alfalfa could be a net sink. De Gryze and Six (2006) included winter wheat as a strategy under minimum tillage to reduce GHG emissions. Rotation-based analysis has been reported by Parton and Rasmussen (1994) in an attempt to develop GHG mitigation measures. One of the major limitations of these studies is that they are partial in nature and provide no comparison between dryland and irrigation production systems. In addition, as Mosier et al. (2006) have indicated, the impact of management on crop production and GHG intensity in irrigated agriculture is not well documented. For Canada, the issue of mitigation of GHG emissions is particularly important since the signing of the Framework Convention for Climate Change and the subsequent ratifying of the Kyoto Protocol (KP). To achieve the target agreed upon in the KP requires development of appropriate strategies. For agriculture, this may include adoption of irrigation and/or changing crop mix in irrigated and/or dryland production systems. In order to make informed decisions, information on the relative contribution of each production system to GHG emissions is required. This may include, among other measures, estimation of Greenhouse Gas Emissions Intensity (GHGEI), which has been used for comparative purposes in other contexts (see Government of Alberta, 2003, which compared the greenhouse gas intensity for the entire Alberta economy by estimating GHG emissions per Million $ of gross domestic product). This study was guided by these considerations.

Objective and Scope of the Study A comparative assessment of GHGEI for the irrigation and dryland production systems is undertaken. This is accomplished by comparing the respective GHGEIs in © 2006 Canadian Water Resources Association

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two regions of Canada—western and eastern Canada. Western Canada included the provinces of British Columbia, Alberta, Saskatchewan and Manitoba, whereas eastern Canada included all provinces east of Manitoba. The study focused on crop production enterprises first, but to make the analysis representative of a Canadian irrigation region, GHG emissions from both crop and livestock production activities were estimated. Finally, the study examines potential tradeoffs that may exist in terms of environmental quality (in the context of climate change) and economic development under an irrigation production system.

Salient Features of Irrigation and Dryland Production Systems in Canada In arid and semi-arid regions of Canada, irrigation has grown to be an industry providing transformation of agricultural production, land use, and regional economic development. In Canada, much of this activity is located in the southern portion of the Canadian Prairie Provinces, notably in southern Alberta and southwestern Saskatchewan. Canadian irrigated area rose from 421,000 hectares in 1970 (Shady, 1989) to almost 785,000 hectares in 2000 (Kulshreshtha et al., 2004) – almost doubling over the 30-year period. The scale of irrigation crop production in Canada is small in relation to total Canadian crop production. Canadian irrigated area comprised just 1.9 percent of the total cultivated land base in 2000 (Kulshreshtha et al., 2004). Even in areas with large tracts of irrigation,

such as in western Canada, irrigation only comprised two percent (707,358 hectares) of the total cultivated area (34.3 million hectares). In eastern Canada the irrigation area (77,445 hectares) comprised approximately 1.3 percent of the total cultivated area (estimated at 5.9 million hectares) in 2000, as shown in Table 1. Irrigated area in eastern Canada has remained relatively constant over the past decade with a national contribution level of ten percent of total irrigated area in Canada in 2000. Adoption of irrigation is not uniform in Canada; there are significant regional differences in terms of the scale of irrigated operations, cultural practices, and crops and enterprise mix. In 2000, a relatively larger number of farms adopted irrigation practices in western Canada than in eastern Canada. The irrigated area was primarily concentrated in Alberta (64 percent), followed by British Columbia (14 percent), and Saskatchewan (nine percent), with these three provinces contributing 87 percent of the national total. In 2001, there were 12,350 farms with irrigation, constituting 8.5 percent of the total number of farms in the west, as compared to 4,854 farms (constituting five percent of the total number of farms) in eastern Canada. Important determinants of such adoption decisions are related to differences in climate (particularly moisture availability during the crop production period) and economics of various crop enterprises. Area under irrigation per farm is also higher in western Canada (57 hectares) than in eastern Canada (16 hectares) (Table 1). In comparison, the dryland area per farm in western and eastern Canada in 2000 was 400 and 100 hectares,

Table 1. Regional Comparison of Dryland and Irrigated Activities, Canada by Regions, 2000. Activity

Unit

West Irrigated

Total Area Fuel Use per hectare Fertilizer use per hectare Cattle and Calves per farm Hogs per farm Sheep and lambs per farm Poultry per farm Other livestock per farm

Hectares Litres Kilograms Head Head Head Head Head

707,358 309 42 390 1,006 111 2,408 12

East Dryland

34,388,856 38 29 144 803 82 3,047 22

Irrigated

77,445 1,168 78 65 472 67 3,639 83

Dryland

5,901,888 87 38 78 949 108 7,351 45

Source: Statistics Canada (Special Tabulation).


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respectively. The significant difference between irrigated and dryland farm area is crop mix. In western Canada, the irrigated crop mix includes some crops that are also grown under dryland conditions (such as grains and oilseeds), but includes a larger proportion of the “other crops” category. These crops include fruit crops, dry beans (Phaseolus vulgaris), and silage crops, and constitute 27 percent of the total irrigated area, compared to only eight percent under dryland production systems. In eastern Canada the irrigated area was devoted entirely to potatoes (Solanum tuberosum) and the other crops category (consisting mainly of grapes (Vitis vinifera), small fruits and vegetables). In eastern Canada, these crops are not grown under a dryland production system. The substantial difference in the area devoted to the other crops category in the two regions is a result of two major factors. First, in eastern Canada, many of these crops do not grow well without irrigation, and irrigation is therefore a necessity. Second, given the high capital cost requirements for irrigation development in the region, the subsequent irrigated crop mix must generate sufficient revenues for a positive profit margin to exist. This is only possible through production of speciality crops, although forage production is an exception since its economics are judged in the context of an integrated forage-livestock production system. One of the major crops on irrigated farms is forage production. This primarily supports livestock herds on irrigated farms, although some sales to neighbouring dryland farms may also take place. As shown in Table 1, an irrigated farm in western Canada had 390 head of cattle and calves per farm as compared with only 144 head on the corresponding dryland farms. Since forages are not a part of the crop mix on irrigated farms in eastern Canada, such a feature was not exhibited there. A comparison of other livestock types did not exhibit any significant differences between the two types of production systems. The other main feature of irrigation farms, in contrast to dryland farms, is their respective resource use. Some resource uses, such as fertilizer and fuel, are particularly relevant in the context of GHG emissions. In the year 2000, an irrigated farm in western Canada consumed 309 litres of fuel per hectare, while the same type of farm in eastern Canada used 1,168 litres per hectare. This is considerably higher than the respective uses on dryland farms, which were 38 litres and 87 litres per hectare in western and eastern Canada,

respectively. Similarly, fertilizer use is also higher on irrigated farms, perhaps on account of perceived synergy between moisture and nutrient availability. An irrigated farm on a per hectare basis used 1.5 times more fertilizer in the west and two times more in the east (Table 1). The above review indicates the possibility that on account of different enterprise mix, crop choices, and cultural practices, dryland agriculture and irrigated agriculture may possess characteristics resulting in a different level of GHG emissions.

Study Methodology A GHGEI coefficient was defined as the quantity of various GHGs emitted by a given production process per unit of a selected criterion. In this study three criteria were selected: Scale of activity, Level of production, and Value of production. Estimation of GHG emissions was done using the Greenhouse Gas Emissions Model for Agriculture, which was calibrated for the year 2000 (referred to as the GHGEMA2000). The model estimates GHG emissions from selected agricultural activities for 55 agricultural regions. Three main GHGs included in the model are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). To estimate GHGEI, the contribution of each gas was converted into carbon dioxide equivalents (CO2E) using the global warming potential of each gas, which was 21 for methane and 310 for nitrous oxide. The structure of the GHGEMA2000 was designed as a linear and additive modular system, where each module estimated emissions from a selected set of agricultural activities. The modules pertaining to this study included: (1) Crop Production Module; (2) Livestock Production Module; (3) On-Farm Transportation and Storage of Agricultural Products Module; (4) Indirect Emissions Module; and (5) Agroecosystem Module. Various activities included in each of these modules are shown in Table 2. The GHG emission coefficients were based on the IPCC suggested levels (Houghton et al., 1997). More details on these are shown in the Appendix. Since the time of development of the GHGEMA2000, IPCC has tentatively developed a revised set of GHG emission



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Table 2. Description of Activities included under Various Modules of GHGEMA2000, and their Interrelationship with GHG. Module

Activity

Emissions of CO2

Crop Production* Livestock Production

Indirect Emissions

Agroecosystems Other Farm Level Activities*

Crop Residues Application of N-Fertilizer N-Fixing Crops Enteric Fermentation Manure Storage Manure Handling and Application Atmospheric Deposition – Fertilizer Nitrogen Leaching – Fertilizer Atmospheric Deposition – Manure Nitrogen Leaching – Manure Cultivated soils Farm Machinery Fuel Use Fuel Use for Livestock Production On-Farm Transportation

CH4

N 2O

X X X

X X X

X X X X

X X X X X X X X X X X X

Note: Soil organic matter (SOM) emissions are not crop specific and are dependent on tillage practices, forage area, and area of permanent cover crops; thus in the analysis, SOM will not be included.

coefficients as reported in IPCC (2006). These revised coefficients are not incorporated in this study for two reasons: 1) These were not available at the time of developing the model, and are still subject to change; and 2) The next generation Canadian agriculture GHG emissions model is being developed under the auspices of the National Carbon and Greenhouse Gas Emission Accounting and Verification System (see Government of Canada Undated). This model will be based on Tier 2 coefficients and would reflect Canadian emissions more realistically.

Results and Discussion Greenhouse gas emissions from irrigated and dryland crop production are presented here in terms of: (1) Total emissions from the two production systems by region; (2) Relative GHGEI coefficient on an area basis; (3) Relative GHGEI coefficient on volume of production basis; and (4) Relative GHGEI coefficient on value of production (crops and livestock) basis.

Total Emissions from Irrigated Agriculture

The relative level of GHG emissions from irrigated agriculture in Canada may be considered insignificant in comparison to the total agricultural emissions, since it contributes only 6.1 percent of the Canadian total. However, in absolute terms, irrigation activities contributed almost 1.65 megatonnes (Mt) of CO2E (see Table 3). In contrast, dryland agricultural activities in Canada were responsible for 25.37 Mt of CO2E. The regional distribution of irrigation production related GHG emissions revealed that the western region contributed 84.8 percent of the total (1.40 Mt of CO2E). The remaining 15.2 percent of the total Canadian GHG emissions from irrigation activities were generated in eastern Canada (0.25 Mt of CO2E). In comparison, dryland agricultural activities in western Canada contributed a total of 18.78 Mt of CO2E, while eastern Canada’s dryland agriculture emitted 6.59 Mt of CO2E. The structure of emissions from irrigated crop production activities is shown in Figure 1.


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Figure 1. Structure of GHG Emissions (CO2E) from Irrigated Production Systems in Canada, 2000.

Irrigation fuel use was by far the largest source of GHG emissions at 73 percent. Irrigation fuel-based emissions were from machinery operations, onfarm transportation of farm products and other onfarm fuel use, including fuel required for irrigation pumping purposes. Nitrogen fixing crops contributed 11 percent of the total GHG emissions, while nitrogen fertilizers added another six percent to the total, followed by crop residues and indirect sources emissions (five percent each). Area Based Crop Production GHG Intensity Coefficients

The regional level GHGEI coefficients expressed on a per hectare basis for irrigated and dryland crop production activities are shown in Table 4. These are measured in kilograms (kg) of CO2E per hectare. The crop list included all major crops in the region under irrigated conditions, except summer fallowing activities. In western Canada, irrigated crops, on average, have higher per hectare GHGEI coefficient than do dryland crops. For every hectare of irrigated land, on average, 2.6 tonnes (t) of CO2E GHGs are emitted in western Canada compared to 3.8 t in eastern Canada. In contrast, dryland production systems in western and eastern Canada had emissions of 0.3 t and 0.9 t of CO2E, respectively. Thus, in western Canada, if a hectare of land is converted from dryland to irrigation, an additional 2.2 t of CO2E GHG would be added

to the atmosphere. In eastern Canada, for a similar conversion, the marginal change in additional emissions would be 2.9 t per hectare. This suggests that irrigated agriculture, on an area basis, emits almost 6.6 times the GHGs as dryland agriculture in western Canada, and 4.2 times in eastern Canada. Thus, on this basis it may be perceived as being in conflict with environmental quality (with respect to GHG emissions). Further analysis of the data suggests that a higher level of GHG emissions from irrigated production systems is a result of higher fuel and fertilizer application rates, and a higher proportion of area devoted to nitrogen fixing crops. As noted above, fertilizer application, in addition to direct emissions, is also related to indirect emissions—atmospheric deposition and leaching. In addition, crop residue emissions are higher for irrigated crops than dryland crops because irrigated yield outweighs those from dryland production. As well, a higher proportion of total irrigated area is devoted to crops (as opposed to some area being devoted to pastures) under dryland production systems. In eastern Canada, differences between dryland and irrigated emissions are explained solely by differences in crop mix. In this region, irrigated crops include speciality crops and potatoes. These crops demand more intensive operations, leading to higher fuel cost per unit of land. In fact, this source of emissions is the largest contributor to the increase in GHG emissions on irrigated land. Although fertilizer application rates on irrigated crops in eastern Canada are higher © 2006 Canadian Water Resources Association


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Table 3. Total Crop Production-Related GHG Emissions from Irrigated and Dryland Farms, Canada by Regions, and Source, Kilotonnes of CO2E, 2000. Source

Western Canada Irrig.

Crop Residues Nitrogen Fertilizer N-Fixing Crops

Dryland

Eastern Canada Irrig.

Dryland

Crop Production Related Emissions Module 74.66 4,074.62 5.29 1,680.43 86.33 4,437.95 8.33 428.66 173.18 2,682.47 0.00 1,904.20

Dryland

5,755.06 4,866.61 4,586.67

137.01 513.78

16.38 61.44

802.83 3,010.63

-61.78

-2.73

-445.47

Other Farm (Crop) Activities Related Emissions Module 941.35 4,221.49 214.02 1,800.50

1,155.37

6,021.99

65.59 2.22 1,646.07 100.0% 6.1%

563.38 210.65 25,372.35 100.0% 93.9%

Indirect Emissions Module 665.83 2.50 2,496.85 9.39

13.88 52.05

Cultivated Soils*

Agroecosystems Related Emissions Module -2.51 -383.69 -0.22

Total CO2E GHG Emissions in kg per ha Ratio Irrigation to Dryland Total CO2E GHG Emissions in kg per Tonne of Physical Product Ratio Irrigation to Dryland

Irrigated

79.95 94.66 173.18

Atmospheric Deposition Nitrogen Leaching

Machinery Fuel Use including for water lifting and crop application On-Farm Transportation Other On-Farm Fuel Use Total Emissions % of Regional Total % of Canadian Total

Canada

56.13 1.59 1,396.65 84.8% 5.2%

9.47 0.64 249.41 15.2% 0.9%

111.14 79.11 6,593.05 26.0% 24.4%

Average GHG Emission Intensity 2,582.90 391.77 3,796.25

897.25

255.86

452.24 131.54 18,779.30 74.0% 69.5%

6.59

266.29

0.96

537.17

4.23

178.99

3.01

* A negative number refers to a sink.

than those on other crops, they still capture only a small portion of the increased GHG emissions from converting land under dryland production to irrigated production systems. The irrigated GHGEI coefficients in Table 3 were disaggregated into various crop categories, such as grains, oilseeds, other crops and forages, to determine which crop category has higher emission intensity. The results are shown in Table 4. In western Canada, other crops were a source of 3.06 t of CO2E GHGs per ha, followed by forages at 2.6 t, grains at 2.1 t and oilseeds

at 1.7 t of CO2E. In eastern Canada, other crops emitted 3.8 t of CO2E GHGs per ha. Based on an analysis by source of GHG emissions for various crop groups, grain crops have the largest level of GHGEI from crop residues, at a level nearly twice that of oilseeds, and two and a half times as much as from the other crops category. The reason for the difference is that crop residues GHGEI coefficients are dependent on crop type and production levels. Forages do not have a GHGEI coefficient from crop residues © 2006 Canadian Water Resources Association

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Table 4. Irrigated GHG Emission Crop Intensity Coefficients based on Crop Production, by Type of Crop, Kilograms CO2E Hectare-1, 2000. East

West GHG Emission Intensity Category Grains



Cultivated Soils

Oilseeds

Other Crops1

Crop Production Related Emissions Module 403.86 220.82 155.95 225.90 232.11 280.87 0.00 0.00 29.93

Forages

Other Crops

0.00 55.29 655.65

80.47 126.74 0.00

42.58 159.66

10.93 41.00

38.10 142.89

Agroecosystem Related Emissions Module -3.28 -3.28 -3.28

-6.16

-3.28

1,826.78

3,257.58

0.00 2.61 2,586.09

144.07 9.67 3,796.25

Indirect Emissions Module 35.22 36.24 132.06 135.90

Other Farm (Crop) Activities Related Emissions Module 1,297.19 1,044.98 2,044.56 Machinery Fuel Use including Water Lifting and Crop Application 45.22 29.03 345.47 On-Farm Transportation 3.34 3.25 3.15 Other On-Farm Fuel Use 2,139.51 1,699.05 3,058.89 Total Emissions 1

The other crops category includes specialty crops and potatoes.

as the data on crop residues from this source were poor and thus excluded from the GHGEMA2000. To further investigate the GHGEI for individual crops, data in Table 4 were further disaggregated by specific crops. These GHGEI coefficients, based on area, are shown in Table 5. In western Canada, crops with the highest GHGEI coefficient per hectare are potatoes (Solanum tuberosum) at 4,408 kg CO2E, field peas (Pisum sativum) at 3,170 kg CO2E, alfalfa (Medicago sativa) at 3,026 kg CO2E, and other crops at 2,707 kg CO2E. The crop with the lowest intensity coefficient is flax (Linum usitatissimum) at 1,572 kg CO2E. In general, the specialty crops (i.e., other crops, field peas (Pisum sativum), potatoes (Solanum tuberosum)), forage crops (i.e., hay (Phleum pratense) and alfalfa (Medicago sativa)) have higher total crop production related emissions. In eastern Canada, potatoes (Solanum tuberosum) emit 3,534 kg of GHGs while other crops emit 3,821 kg per ha.

Production Based Crop Production GHG Emission Intensities

Comparison of dryland and irrigated production systems on an area basis can provide a somewhat distorted picture of GHG emissions from irrigation. This is because of the implicit assumption that both parcels of lands produce the same quantity of product. Since irrigated yield for almost all crops is higher than under the dryland production system, to provide a fair comparison, results were converted to per unit of production basis. Average GHGEI coefficients are shown at the bottom of Table 3. For every tonne of irrigated crop production in western Canada, 226 kg of CO2E GHGs are emitted whereas the same for eastern Canada was estimated to be at 537 kg of CO2E GHGs. Compared to the dryland production systems, these emissions are slightly lower for western Canada (at 0.96) but significantly higher for eastern Canada (at 3.01). A partial explanation for the difference © 2006 Canadian Water Resources Association


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Table 5. Irrigated GHG Emission Crop Intensity Coefficients, by Crop Type, Kilograms CO2E Hectare-1, 2000. Crop Type

Botanical Name

GHGI per ha in kg

GHGI per Tonne of Production in kg

Hay Alfalfa Wheat Barley Oats Flax Canola Lentils Field Peas Other Crops Potatoes

Phleum pratense Medicago saativa Triticum aestivum Hordeum vulgare Avena sativa Linum usitatissimum Brassica napus Lens culinaris Pisum sativum Solanum tuberosum

West

East

2,064.19 3,026.17 2,218.24 2,076.30 1,963.56 1,572.37 1,709.53 2,045.77 3,169.71 2,707.12 4,407.84

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3,821.16 3,533.88

West

271.34 393.39 507.32 409.72 506.44 511.76 680.31 1,014.96 907.37 145.68 161.63

East

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 869.97 132.81

Note: SOM was excluded from analysis due to emission coefficients not being crop specific.

Table 6. Irrigated GHG Emission Crop Intensity Coefficients, by Crop Type and Source of Emissions, Kilograms CO2E Tonne Crop Production-1, 2000. East

West GHG Emission Intensity Category Grains



Cultivated Soils

Oilseeds

Other Crops1

Crop Production Related Emissions Module 86.38 86.41 7.85 48.32 90.82 14.15 0.00 0.00 1.51

Forages

Other Crops

0.00 7.22 85.67

11.39 17.93 0.00

2.14 8.04

1.43 5.36

5.39 20.22

Agroecosystem Related Emissions Module -0.70 -1.28 -0.17

-0.80

-0.46

238.68

460.95

0.00 0.34 337.89

20.39 1.37 537.17

Indirect Emissions Module 7.53 14.18 28.24 53.18

Other Farm (Crop) Activities Related Emissions Module 277.44 408.90 102.98 Machinery Fuel Use including water lifting and crop application On-Farm Transportation 9.67 11.36 17.40 0.72 1.27 0.16 Other On-Farm Fuel Use 457.60 664.83 154.07 Total Emissions The other crops category includes specialty crops and potatoes.

1


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in eastern Canada is the relative differences in crop mix between the two production systems. The irrigated GHGEI coefficients per tonne of production were further disaggregated for various crop categories. These results are shown in Table 6. On a per tonne of production basis, oilseeds have the highest GHGEI coefficient at 665 kg CO2E, followed by grains at 458 kg CO2E, forages at 338 kg CO2E, and other crops at 154 kg CO2E. The crops that have the higher GHGEI coefficient on a per hectare basis are generally the highest yielding crops, and thus by utilizing a higher level of inputs can achieve greater production efficiencies. Further disaggregation by crop showed a lower GHGEI coefficient for other crops, including potatoes. Value of Production Based Crop and Livestock GHGEI Coefficients

So far this analysis has concentrated on direct water use enterprises (crops). However, both dryland and irrigated farms have other enterprises, particularly

livestock operations. In the GHGEMA2000, irrigated and dryland livestock activities were not differentiated, but using data obtained from Statistics Canada (Special Tabulation) irrigated livestock were separated from dryland livestock. Combining the two types of enterprises provides a more realistic picture of emission intensity for the irrigated and dryland production systems. On average, in western Canada, irrigated crops have a lower GHGEI per dollar of production than that for dryland crops. On a typical irrigated farm, crop production per dollar emitted only 1.13 kg CO2E compared with 1.59 kg CO2E under dryland production systems (Table 7). In the east, the converse is true with irrigated crops intensity coefficient of 1.61 kg CO2E per dollar exceeding the dryland value of 1.45 kg CO2E per dollar. However, when all enterprises are included, in both regions irrigation was estimated to be more environmentally efficient. The per dollar value GHGEI coefficient for western Canada was 2.15 kg CO2E for irrigation as compared to 3.23 kg CO2E for dryland production system. The same conclusion is drawn for eastern Canada where GHGEI for irrigated farms is

Table 7. Relative Dryland and Irrigated GHG Emission Intensity Coefficients, in Kilograms CO2E per Dollar Value of Production, 2000. Category

Hay Alfalfa Wheat Barley Oats Flax Canola Lentils Field Peas Other Crops Potatoes Average for All Crops Cattle and Calves Hogs Poultry Sheep and Lambs Average for All Livestock Average Crop and Livestock Production

Botanical Names

Phleum pratense Medicago saativa Triticum aestivum Hordeum vulgare Avena sativa Linum usitatissimum Brassica napus Lens culinaris Pisum sativum Solanum tuberosum

West

East

Irrigated

Dryland

Irrigated

Dryland

14.08 20.88 2.34 2.39 2.91 0.81 2.12 3.71 5.41 0.32 0.88 1.13 3.60 2.35 3.60 1.38 3.47 2.15

9.24 11.18 1.30 1.33 1.84 0.71 1.36 1.85 3.95 0.38 0.60 1.59 3.47 2.31 3.27 1.38 3.27 3.23

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.94 0.68 1.61 4.85 2.29 2.71 1.38 3.59 1.59

1.66 3.43 0.89 1.25 0.00 0.00 0.00 0.00 0.00 0.35 0.32 1.45 4.85 2.29 2.65 1.38 3.60 2.65



1.59 kg CO2E compared with 2.65 kg CO2E for dryland farms. It appears that Canadian irrigation production is more efficient in reducing GHG emissions on a value of production basis.

Conclusions This study examined the greenhouse gas emission intensity (GHGEI) coefficients for irrigated and dryland crop and livestock production systems in Canada. These coefficients were estimated using the GHGEMA2000 computer model at three different levels, namely area, production, and value of production. Results indicate that, on average, area based crop intensity coefficients show that irrigation activities are larger emitters of GHGs than the dryland production activities. When factoring in the production efficiencies that exist under irrigation systems, western Canada’s irrigation GHGEI coefficient is lower than that for dryland. Even when all crop and livestock production activities are included, GHGEI coefficients for irrigated production are lower both for western and eastern Canada. These results are summarized in Figure 2. When the ratio of GHGEI coefficients from irrigated to dryland production

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system reaches one, both systems are equally efficient in terms of their respective GHG emissions. Irrigation in eastern Canada is more environmentally efficient in terms of production and value, whereas in western Canada irrigation is more efficient per unit of value of production. The implication of these results is that expansion of irrigated production systems in Canada for meeting the need of increased farm level prosperity, or to drought proof the regional economy, is both economically and environmentally efficient under the current crop and livestock enterprise mix. Any increase of low value crops would naturally increase the GHGEI coefficients and any shift away from such crops would lead to a production system that is even more environmentally efficient. Thus, irrigated production systems are desirable not only from an economic point of view (measured in terms of farm level profitability) but also in terms of emissions of GHG per $ of production. A number of limitations of this study must be noted. First, the model used here was based on the old IPCC Tier 1 coefficients. As new Tier 2 coefficients become available, the results should be re-evaluated. Secondly, published data on irrigation practices, particularly soil carbon sequestration and water use, are

Figure 2. Ratio of GHG Emissions from Irrigation to Dryland Production Systems using Alternative Critieria.


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very poor. This has prompted Burton (2004) to suggest “…for greater research examining GHG emissions and C sequestration from organic and irrigated land and the potential for land management to influence these processes.” Thirdly, development of optimal mitigation measures must be done in an interactive model, similar to that suggested by McCarl and Schneider (2001). In such a model, inclusion of both agriculture and forestry on dryland and irrigated production systems may lead to better results in terms of developing an optimal set of mitigation measures.

Acknowledgements This study was financially supported by BIOCAP Canada, and Social Sciences and Humanities Research Council of Canada.

References

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Appendix Details on the Estimation of Emission Coefficients Details on the estimation of emission coefficients in GHGEMA2000 for irrigation and dryland production systems were based on IPPC’s Tier 1 methodology, as reported in Sobool and Kulshreshtha (2005). A copy of the model is available on request from the author. A brief overview of the estimation is provided in this Appendix. A.1

Crop Production Module

Crop Production module included GHG emissions from three sources: (1) crop residues; (2) nitrogenous fertilizer use; and (3) growing of nitrogen fixing crops. Crop residues related emissions included those for the nitrous oxide (N2O), and were estimated by crop (c) and regions (r) using equation (A.1). N2O_EC(c.r)cr = N_CONT(c) × YIELD(c.r) × N2O_EF × 44/28 where N_CONT(c) YIELD(c.r) N2O_EF

= = =

(A.1)

Nitrogen content of crop type (c), in tonnes ha-1, Yield for crop type (c) in region (r), in tonnes ha-1, and Nitrous oxide emission factor (default value of 0.0125 kg N2O-N kg N-1).

The estimation of the emission coefficient for crop (c) in a region (r) (N2O_EC(c.r)FRTU) was based on the amount of fertilizer applied to the crop, the nitrogen content of each fertilizer, and the proportion evolved as nitrous oxide. The emission coefficient was estimated using equation (A.2). N2O_EC(c.r)FRTU = QNTY(c.r)FRT × N_CONT(p)FRT × 44/28 where QNTY(c.r)FRT = N_CONT(p)FRT =

(A.2)

Quantity of fertilizer applied to crop (c) in region (r), in tonnes ha-1, and Nitrogen content of fertilizer in province (p), in tonnes per tonne of fertilizer.

The nitrogen content of fertilizers (N_CONT(p)FRT) in province (p) was based on the total consumption of various types of fertilizers. The emission coefficient for the nitrous oxide released to the atmosphere from the growing of nitrogen fixing crops {N2O_EC(c.r)BNF} depends on the proportion of nitrogen contained in each N-fixing crop type (c) in region (r). This value was estimated using equation (A.3). N2O_EC(c.r)BNF = N_CONT(c.r) × N2O_EF × 44/28 where

A.2

N_CONT(c.r) = = N2O_EF

(A.3)

Nitrogen content of N-fixing crop type (c) in tonnes ha-1, and Nitrous oxide emission factor.

Livestock Production Module

The Livestock Production module was comprised of emissions through enteric fermentation and manure related emissions (i.e., manure from grazing animals, manure storage systems, and manure used as fertilizer). Enteric fermentation was based on types of livestock on farms using IPCC Tier 1, whereas those for the manure were © 2006 Canadian Water Resources Association


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based on type of manure, which in turn is related to type of livestock and their management (pastures versus confined facilities). Emissions of both CH4 and N2O are associated with these activities. A.3

Indirect Emissions

The Indirect Emissions module included two major emission sources: atmospheric deposition and leaching from nitrogen sources (i.e., fertilizer and manure). The emission coefficient for atmospheric deposition from synthetic fertilizer application was estimated using the amount of nitrogen fertilizer sold in Canada, the fraction of synthetic fertilizer that volatizes, and the emission factor for nitrogen deposition. The atmospheric emission coefficient (N2O_EC(c.r)ADF) for crop (c) in region (r) was estimated using equation (A.4). N2O_EC(c.r)ADF = FERT_QTY(c.r) × FRACGASF × EF × 44/28 where FERT_QTY(c.r) = FRACGASF

=

EF

=

(A.4)

Quantity of fertilizer consumed for crop (c) in region (r) (CRAM output), in tonnes ha-1, Fraction of synthetic fertilizer nitrogen that volatizes (IPCC default factor of 0.1 kg (NH3-N+NOX-N) kg N-1), and Emission factor due to volatilization (IPCC default value of 0.01 kg N2O-N kg N-1).

For manure, emission coefficient for each livestock type (l) in region (r) (N2O_EC(l.r)ADM) was estimated using nitrogen content of livestock excretions, the number of animals grazing, the emission factor for nitrogen deposition, and the fraction of nitrogen from manure that volatizes and was estimated using equation (A.5). N2O_EC(l.r)ADM =N_CONT(l) × (1- FRAC(l)GRZ)× FRACGASM × EF × 44/28 where N_CONT(l) FRAC(l)GRZ FRACGASM

= = =

EF

=

(A.5)

Nitrogen content of manure for livestock type (l), in kg hd-1, Fraction of livestock type (l) that are grazing, Fraction of manure that volatizes (IPCC default factor of 0.2 kg (NH3-N+NOX-N) kg N-1), and Emission factor due to volatilization (IPCC default value of 0.01 kg N2O-N kg N-1).

The estimation of the emission coefficient for leaching and runoff for crop (c) in region (r), namely {N2O_EC(c. r)LR}, was estimated using equation (A.6). N2O_EC(c.r)LR = FERT_QUANT(c.r) × FRACLR × EF × 44/28

(A.6)

where FERT_QUANT(c.r) = Quantity of fertilizer consumed for crop (c) in region (r), in tonnes ha-1; = Fraction of nitrogen fertilizer lost to FRACLR leaching and runoff (EC default value of 0.15 kg N kg N Fertilizer-1), and EF = Emission factor for indirect emission (IPCC default value of 0.025 kg N2O-N kg N leaching and runoff-1).


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Similarly, for manure emissions from leaching (N2O_EC(l)LRM) were estimated for livestock type (l) using equation (A.7). N2O_EC(l.r)LRM = N_CONT(l) × FRACLR × EF × 44/28 where N_CONT(l) FRACLR EF

A.4

(A.7)

= Nitrogen content of manure for livestock type (l) in kg hd-1, = Fraction of nitrogen manure lost to leaching and runoff (EC default value of 0.15 kg N kg N manure-1), and = Emission factor for indirect emissions (IPCC default value of 0.025 kg N2O-N kg N leaching and runoff-1).

Agroecosystem Related Emissions

The Agroecosystem module contained methane emissions from cultivated soils. The CH4 emission coefficients were adapted from data obtained from Mosier et al. (1991) and from Kessavalou et al. (1998). The data obtained from Mosier et al. (1991) was for continuously cultivated systems and as such did not account for different tillage systems on cultivated land, which are provided by Kessavalou et al. (1998). A.5

On-Farm Transportation and Other Crop Related Emissions

The Other Farm Crop production-related activities included on-farm fuel used for transportation of crop products, the procurement of farm inputs and energy requirements for other agricultural activities, such as lighting of farm buildings and fuel use for irrigation pumping. Estimation was based on type of fuel and its use in various types of operations (farm machinery, trucks, etc.). Data were obtained from the Agriculture and Agri-Food Canada (1997). Standard emission rates, as published by Environment Canada (2005), were used for each fuel type. A.6

Soil Carbon Sequestration

Soil organic matter emissions are dependent on tillage practices, forage area, permanent cover crops and summerfallowing activities. Since these activities are not crop specific in nature (excluding forages), and due to a lack of evidence on the effect of irrigation on level of soil organic matter in Canada, total GHG emissions for specific crops were estimated excluding this emission source. However, the total crop related emissions included this source/sink.
