GHG Emissions, Energy Use and Economics

of Alternative Cropping Systems

 

Review of Nitrous Oxide and Carbon Dioxide Release

 

The process level model for the PERD project should incorporate the different GHG mitigation measures that are technically and economically feasible at the Representative Farm/Cropping System level. Mitigation measures for nitrous oxide (N2O) and carbon dioxide (CO2) are outlined in the following sections. Also included are Appendix A: New Farm Technologies and Trends on Prairie Agriculture; Appendix B: Cropping System Selection; and Appendix C: Representative Farm Selection.

 

Section One: Mitigation Measures for N2O

Three major factors affecting N2O emissions are soil temperature, soil N availability and soil water content, Hutchinson (1995). Soil temperature affects the microbial processes of nitrification and denitrification with optimum temperature in the range of 15E C to 35E C. Also, the transport and release of N2O is affected by soil temperature. Corre et al. (1996) observed differences in spatial and temporal N2O flux related to topography and precipitation. Rain (especially after a long dry spell) and spring thaw are periods when larger than average amounts of N2O are emitted, Goodroad et al. (1984); Hutchinson (1995). Soil texture influenced N2O emissions as sandy soils had lower emissions than fine-textured soils. Fertilized crop land had higher N2O emissions than unfertilized. Mosier et al. (1996) list a number of practices that could be implemented to improve fertilizer and manure N use efficiencies to help reduce N2O emissions from agriculture.

1. Match N supply with crop demand.

a) Use soil/plant testing to determine fertilizer N needs.

b) Minimize fallow periods to limit mineral N accumulation.

c) Optimize split application schemes.

d) Match N application to reduced production goals in regions of crop over production.

 

2. Close N flow Cycles

a) Integrate animal and crop production systems in terms of manure reuse and crop production.

b) Maintain plant residue N on the production site.

3. Use advanced fertilizer techniques.

a) Controlled release fertilizers.

b) Place fertilizers below the soil surface.

c) Foliar application of fertilizers.

d) Use nitrogen inhibitors.

e) Match fertilizer amount and type to seasonal precipitation

4. Optimize tillage, irrigation and drainage.

 

The tillage system will influence soil temperature, N availability and soil water content. Snow trapping and surface residue affects the soil temperature by insulating the soil in winter resulting in warmer fall to spring soil temperatures, Winter Wheat Production Manual (1996). Lafond and Derksen (1995) monitored rooting zone soil temperature from spring to fall for conventional tillage (CT) and zero-tillage (ZT). ZT had a slightly higher temperature at the 40 cm depth while CT had a slightly higher temperature at the 80 cm and 120 cm depths. Mineralization of N is influenced by the mixing action of the tillage system, for tillage based systems mineralization peaks after tillage with low rates of mineralization between tillage operations. Mineralization occurs more evenly over the growing season for ZT systems, Man-ND (1997). Loam and clay soils generally have greater soil moisture due to conservation tillage but, not for sandy soils, Lafond and Derksen (1997). Generally, soil under ZT is moister with organic matter and soil microbial populations concentrated in the top layer of soil, Lemke et al. (1995).

Aulakh et al. (1982, 1984 a, b) found higher N2O emissions for ZT over CT during the growing season for a Dark Brown Chernozemic soil. Lemke et al. (1995) measured N2O emissions from CT and ZT on an annual basis for a Black Chernozem and a Gray Luvisol. Their findings showed that spring N2O emission was higher for CT while growing season emission was dependent on factors other than tillage. Annual differences between the two treatments were small. One problem with many of these studies is that the source and placement of N no longer represents current practice in western Canada, especially for ZT.

The banding of fertilizers in western Canada for annual crop production either before or during seeding is widely practiced in western Canada. Urea and anhydrous ammonia are the major sources of N, 43% and 34%, respectively for Saskatchewan, SAF (1996). Eichner (1990) in a review of N2O emission studies suggest that the source of N is important although, Mosier et al. (1993) in their review propose that soil management and cropping system has a greater impact than the source of N. McTaggart et al. (1993) show that timing and type of fertilizer can affect N2O emissions depending on the cause of the emissions. If denitrification is the cause of N2O emissions then ammonium is the best source of N. Nitrate based fertilizers are better when nitrification is the source of N2O emissions.

Generally, manure will emit larger amounts of N2O than comparable amounts of commercial fertilizers, Bouwman (1990, 1994 a, b). The increased specialization of farming operations resulting in more large livestock enterprises and fewer mixed farming operations creates a break in the link between livestock and crop production. The cost of disposal for the livestock operation and the value of manure in crop production become significant in the economic assessment of this problem.

Differences in nitrogen use efficiency (NUE) between cropping systems will result in different N2O emissions, energy use and economics. Generally, NUE increases as soil moisture increases and decreases as N applied increases, Gauer et al. (1992), Campbell et al. (1993). Campbell et al. (1993) also found that as available soil N increased NUE decreased. Gauer et al. (1992) found NUE to range from 15.49% to 36.58% for six spring wheat cultivars using five N rates over two moisture regimes on Black Chernozemic soils. Significant differences in NUE among cultivars occurred at the high moisture level with the semidwarf cultivars having higher NUE than standard height cultivars. Badaruddin and Meyer (1994) found NUE for wheat following legumes to be 21% higher than for continuous wheat.

Soil testing on a yearly basis is not widely practiced in western Canada, Agriculture and Agri-Food Canada (1998). Soil mapping and variable rate fertilizer application are technologies that could help mitigate N2O emissions by matching fertilizer application with crop nutrient use. Urease inhibitors may be effective in increasing fertilizer use efficiency especially where broadcast application is required, Grant (1998). This will have a relatively greater impact on emissions of GHG, use of energy and economics for cropping systems that include forage grasses and winter cereals. The use of nitrogen inhibitors when fall banding may be an option to reduce N2O emissions during spring thaw. Shifting to spring application may also help in reducing N2O emissions by avoiding the spring thaw and allow for a more accurate assessment of expected crop nutrient requirements. The problem is that N is generally cheaper in the fall so the economics of on-farm storage and net environmental costs will have to be assessed. Storage constraints and the logistics of supplying all the fertilizer during the spring seeding period would increase fertilizer costs unless split application of N proves to be environmentally and economically feasible.

Protein premiums will be based on a .1 % grid for Canadian Western Red Spring Wheat for the 1999-2000 crop year. The emission of GHG and use of energy for foliar application of N to increase protein content is an area in need of further investigation. Also, differences in protein content have been observed between CT and ZT systems, McConkey et al. (1998); and between wheat seeded on legume and non-legume stubble, Wright (1990); Beckie and Brandt (1997); Beckie et al. (1997); Miller et al. (1998). Application of manure can also increase the protein content of wheat, Schoenau et al. (1998).

Nitrous Oxide Emissions from Legumes

Factors affecting N fixation are growth of bacteria and/or host plants, photosynthetic activity of host plants, available mineral N and type of bacteria, Stout (1990). The amount of nitrogen available for succeeding crops varies with the type of legume and growing conditions. N2O emission from legumes is from fixed N2 being nitrified or denitrified and from Rhizobia in the root nodules denitrifying N2, Galbally (1992); OíHara and Daniel, (1985).

 

Section Two: Factors Influencing Soil Organic Matter Content and CO2 Release

Direction of change depends on initial level of organic matter and subsequent cropping and tillage practices, Fenster and Peterson (1979); Campbell et al. (1991); Ismail et al. (1994). Carbon input is determined by crop choice, C/N ratio of crop residue, fertilization and climate. Carbon output is a function of grain and residue removal, biological oxidation, soil erosion and climate, Lindstrom and Reicosky (1995). Soil carbon at equilibrium is a balance between decomposition driven by nutrient demands of the biota and inputs of organic residues, Anderson (1995). Clay content of soils may enhance C storage by slowing decomposition of labile, energy- and nutrient-rich substrates. The type of soil and climate influences the rate of C sequestration and equilibrium level. Cooler soil, reduced aeration and higher moisture content inhibits decomposition of soil organic matter, Johnson et al. (1995). Soil organic matter loss, CO2 release factors and mitigation measures have been identified in the following studies.

1. Frequency of summerfallow using mechanical tillage, Janzen (1987); Campbell et al. (1991a, b, 1995); McConkey et al. (1998); but not for Campbell et al. (1996).

 

2. Method of tillage and frequency of tillage affects carbon storage with ZT having higher organic C and total N in the 0-7.5 cm depth, Lamb et al. (1985); Arshad et al. (1990); McConkey et al. (1998).

 

3. Soil texture; clay content is directly related to carbon gains, Baur and Black (1981); Campbell et al. (1996); McConkey et al. (1998).

 

4. Fertility as more N is applied more residue is produced and more carbon is sequestered, Janzen (1987); Rasmusson and Rohde (1988); Campbell et al. (1991a); Ismail et al. (1994); Solberg et al.(1995); except where soil organic C is already high, Campbell et al. (1991 a, b); Nyborg et al. (1995).

 

5. Weather events; erosion (loss of organic matter), growing season precipitation, hail (crop residue), Campbell et al. (1995,1996).

 

6. Continuous cropping is about as effective as eliminating tillage in increasing soil C, McConkey et al. (1998).

 

7. Short-term CO2 release for fall tillage is related to depth of soil disturbance and soil surface roughness, Reicosky and Lindstrom (1995).

 

The net GHG warming effect is the basis for recommending adoption of mitigation techniques. Farm level mitigation measures should be incorporated into the representative farms if they are technically feasible. Fertilizer is a major factor in GHG emissions, energy use and economics of the farm enterprise accounting for up to 70% of the energy, 65% of the carbon in purchased inputs and 30% of the variable costs in cropping systems, Gulden and Entz (1995). The practice of fall or spring banding has been widely adopted in western Canada. Seed placed N is also a common practice in the moister regions of the prairie, Agriculture and Agri-Food Canada (1998). Recent improvements in sidebanding equipment make this a viable option for ZT. Split application of N is not a common practice for spring cereal and oilseed crop production in western Canada. The use of these technologies with soil and plant testing to better match fertilizer application with crop nutrient requirements can be modeled at the representative farm level. The inclusion of legumes in a crop rotation will reduce energy use and emission of carbon, Entz et al. (1995). The net N2O emission by including legumes in a rotation has not been studied for western Canada.

Tillage affects soil carbon by influencing the rate of increase or decrease in carbon to a new equilibrium level. The replacement of tillage with herbicides also reduces energy use, Entz et al. (1995); Henry (1992). Operating costs associated with ZT are lower as higher herbicide costs are offset by lower fuel, repair and labour costs, Farm Facts (1995); Nagy (1997).

 

 

 

 

 

Process Level Model Selection

 

Crop selection and sequence are important in optimizing available water and nutrient use over the length of rotation for a specific tillage system, SAF (1997). Cropping system (tillage + rotation) is then the basis for comparison of mitigation techniques. Fertilizer use, crop selection and tillage are key differences in the cropping systems that in turn influence GHG emissions. Soil texture is also important in analyzing GHG emissions. Clay content and initial organic matter content are the main factors in the determination of new equilibrium levels of carbon and nitrogen in the soil. Also, the impact of biological nitrogen fixation on N2O emissions is important in assessing the impact of cropping system changes.

Weather simulation will affect the analysis of GHG emissions. Spring thaw, and the amount and frequency of growing season precipitation will influence N2O emissions. Growing season weather will influence carbon sequestration through crop residue production.

Process Level Models

 

APEX - Agricultural Policy/Environmental eXtender, extension of EPIC to model whole farm or watershed, up to 99 subareas or fields can be linked.

 

Century - models soil carbon, nitrogen, phosphorus and sulphur cycles, multi-crop capability, generates weather from sample means and variances.

 

EPIC - Erosion Productivity Impact Calculator, models crop growth on soil erosion and productivity, multi-crop and multi-management capability, requires soil, crop and tillage parameters, can generate daily weather data from monthly data.

 

GHG model

 

 

Appendix A: New Farm Technologies and Trends in Prairie Agriculture

 

(1) Chemical Application Systems

GPS/GIS - remote sensing for disease, weeds and pests

Application with High-clearance sprayers (i.e. pre-harvest glyphosate)

Reduced application rates and/or selective chemical usage (i.e. Detect Spray)

Herbicide rotation to counteract the buildup of resistant weeds

 

(2) Seeding Systems

Reduced Tillage - spacing, crop density, rotation, crop diversity

Nutrient Management - GPS/GIS, soil mapping, legumes, manure, green manure, nitrification inhibitors, improved legume inoculant,

Variable Rate Fertilizer - matching fertilizer use with expected crop requirements for soil/topography

Tillage intensity - surface residue, moisture conservation

 

(3) Harvest Systems

Stripper Headers- moisture conservation high stubble

Straight Cut - moisture conservation high stubble

Pre-harvest spraying - crop quality, cost, weed control

Grain Drying Equipment, grain cleaning, Central Thrasher

GPS/GIS - yield mapping

 

(4) Low Input Systems (Organic or reduced input usage)

Companion Crops - Nitrogen, ground cover, weed competition, Pest control

Inputs: Labour, management, fertilizer, herbicides, fuels, capital

Forages/legumes supply organic matter and nitrogen

 

(5) Integrated Weed/Pest/Disease Management (Knowledge Based-Derksen)

Crop Sequencing - rotation, tillage, seed management, chemical use, crop growth habits, seeding dates, seeding rates and efficient use of resources to reduce weed pest and disease to non-economic thresholds.

 

 

(6) Genetic Technology

Herbicide Tolerant Crops -management in rotations i.e. fall seeded Canola

"Canola Quality" Mustard,

nitrogen fixing bacteria

(7) Livestock Production

Marginal lands for grazing, intensive grazing (Paddocks), GPS pasture mgt.

Cattle Feedlots and large hog barns

Genetic technology, feed conversion efficiency

Manure production and disposal issues

 

(8) Centralized on farm grain handling/ Centralized Delivery Points

substitution of gas engines with electric motors for grain transfer

grain drying, cleaning etc.

grain transport costs from field to farmyard

grain transport costs from farmyard to market

 

(9) Trends:

Rented Land 40.8% Alberta, 38.9% Sask., 37.1% Man., average age of farmers

49(Prairie Provinces), herbicide resistant weeds, six species have shown resistance to

one or more of the herbicide groups in western Canada, Beckie (1996). Off-farm

income is a major factor for 2/3 of farms Stats Can (1996). Specialty crop were 9%

of seeded acres in 1997 for Saskatchewan up from 1.6% in 1984.

 

 

Saskatchewan Agriculture Trends

 

1991

1996

% Change

Total Farms

60,840

56,979

-6.3%

Total Operators

78,025

72,925

-6.5%

Avg. farm Size(ha)

436.4

460.8

5.6%

Total Beef Cows

898,339

1,135,027

26.3%

Total Pigs

808,968

757,027

-6.4%

Total Chickens

3,618,109

3,516,027

-2.8%

Avg. Operating Expense

$62,137

$76,460

23.1%

Gross Farm Receipts

$76,436

$98,700

29.1%

Source: Stats Canada 1996

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix B: Cropping Systems

 

A cropping system is a combination of tillage system, rotation, cropping strategy and technology. Evaluation of cropping systems for water efficiency, energy efficiency, GHG emissions and economics (profit and risk) to assess potential GHG mitigation measures at the farm level.

 

Cropping System = Tillage System + Rotation + Strategy + Technology

Tillage System1

Rotation2

Strategy3

Technology4

High disturbance

Monoculture

Integrated Management

Pest Control

Medium disturbance

Oilseed/ Cereal

Substance Based

Seeding Systems

Low disturbance

Broadleaf/Cereal

 

Harvest Systems

 

Winter/Broadleaf

   
 

Forage

   
       

 

1. The amount of soil surface disturbance and resulting surface residue has implications for energy use, GHG emissions and economics of the cropping system. The set of feasible crop rotations may be restricted by the choice of tillage system.

 

2. Five basic rotations are combinations of spring cereals, oilseed, pulses, winter cereals, grass and forage legumes that are suitable for a soil/climate region.

 

3. Cropping strategy refers to how inputs and technology are coordinated with the choice of tillage system and rotation. Integrated management is the use of natural biological forces to help in weed, pest and disease management. Substance based is the use of herbicides, pesticides, fungicides and fertilizers at recommended rates to address any weed, pest, disease or nutrient problem.

 

4. Technology

 

Pest control HighTech - GPS/GIS remote sensing for disease, weeds and pests

MedTech - Reduced application rates and/or selective chemical usage

LowTech - intercropping, changing seeding dates, timing of tillage

 

Seeding Systems 1-Pass, one pass seeding and fertilization, pre-seed burn-off

2-Pass, spring/fall fertilizer/herbicide pass, plus seeding operation

Multi-Pass tillage operations for weed control, herbicide incorporation, residue control

* can be combined with GPS soil mapping and variable rate application

Harvest Systems PHSC pre-harvest spraying, straight cut, grain drying

SHS swath harvest system

* can be combined with GPS yield mapping

 

Possible Cropping Systems

 

Cropping System

Tillage System

Rotation

Strategy

Technology

Organic

high disturbance

broadleaf/cereal

Integrated Mgt

LowTech, Multi-Pass, SHS

   

forage

Integrated Mgt

LowTech, Multi-Pass, SHS

Extensive

high disturbance

Monoculture

substance based

HighTech, Multi-Pass, SHS

   

Oilseed/cereal

substance based

HighTech, Multi-Pass, SHS

Min-Till

medium disturbance

Oilseed/cereal

substance based

HighTech, 2-Pass, SHS

   

Broadleaf/cereal

substance based

HighTech, 2-Pass, SHS

   

Broadleaf/cereal

Integrated Mgt

MedTech, 2-Pass, SHS

Zero-Till

low disturbance

Broadleaf/cereal

substance based

HighTech, 1-Pass, PHSC

   

Broadleaf/cereal

Integrated Mgt

MedTech, 1-Pass, PHSC

   

winter

substance based

HighTech, 1-Pass, PHSC

 

 

Existing Databases

 

Brown Soil Zone

Swift Current - monoculture wheat (conventional tillage- minimum tillage-zero tillage)

Swift Current - mixed rotation (minimum tillage- zero tillage)

 

Dark Brown Soil Zone

Scott - cereal/oilseed (conventional tillage-zero tillage)

Scott - organic

 

Black Soil Zone

Indian Head - winter rotation (conventional tillage- minimum tillage -zero tillage)

Indian Head - Derksen Integrated management

 

Melfort - mixed rotation (conventional tillage- minimum tillage -zero tillage)

 

Gray Soil Zone

Loon Lake - mixed rotations

 

 

 

 

 

Appendix C: Representative Farms:

to model a regionís (1) Economic (2) GHG (3) Energy characteristics

 

Economic Factors

1) Size

2) Capital

3) Debt

4) Correlation between output and prices for the products produced influence the

profitability and risk

5) Soil/ Climate influences the relative profitability of crops

 

Factors that affect GHG emissions

 

Enterprise type (a) grain (b) mixed (c) livestock

 

Grain

Tillage System (a) high disturbance (b) medium disturbance (c) low disturbance

Crops grown i.e. cereals, legumes, forage, oilseeds

Rotation (a) intensity (b) diversity

Soil/Climate influences the rate of GHG emissions

 

Livestock

confined or free roaming,

efficiency of livestock in converting feed to end product

Climate influences the consumption of feed

 

Factors that affect Energy use

 

Enterprise type (a) grain (b) mixed (c) livestock

 

Grain

Tillage System (a) high disturbance (b) medium disturbance (c) low disturbance

Crops grown i.e. cereals, legumes, forage, oilseeds

Rotation (a) intensity (b) diversity

Soils - a soilís inherent productivity affects fertilizer use

Climate - cropís nutrient requirements, crop and weed growth

 

Livestock

confined or free roaming, efficiency of feed production, use and waste

efficiency of livestock in converting feed to end product

Climate affects heating/cooling costs and winter feed requirements

 

 

 

 

 

 

 

 

 

 

 

 

GHG Emissions, Energy Use and Economics

 

of Alternative Cropping Systems

 

 

 

A Review of Nitrous Oxide and Carbon Dioxide Release

 

 

Cecil N. Nagy

 

April 23/98