Abstract

Due to the increase in CO₂ emissions over the past 60-70 years, there has been a growing concern over documented increases in atmospheric carbon. The speculated effects of this increase include an imbalance of surface/atmospheric C concentrations and global warming due to the "greenhouse effect" elevated levels of atmospheric CO₂ have on irradiated solar heat. One means of alleviating or mitigating these effects is through carbon sequestration (CS). This process takes C out of the atmosphere and stores, or sequesters it, in certain bodies, including oceans, geologic formations, and terrestrially in soils. This proposal will focus on the potential of terrestrial sequestration in soils.

Soil C is the largest terrestrial carbon reservoir, containing twice as much C as atmospheric CO₂ (Percival et al., 2000). The ability of soils to sequester C as soil organic matter (SOM) is enhanced by certain management practices such as non-till planting, reduced fallow, and irrigation. In much of the Northern Great Plains CS is limited by lack of water for biomass production. By supplementing rainfall on previously non-irrigated soils modeled after those found in the semi-arid regions of eastern MT and WY, plant growth and vigor may be enhanced, thus facilitating CS in those soils.

Water supply for this project will be water representing the discharge from coal bed methane (CBM) mining. CBM product water is considered a waste product because it is typically saline and sodic and the large amount of water produced by individual wells has resulted in a controversial management issue in the Powder River Basin (PRB) of WY and MT. By utilizing CBM product water to supplement and facilitate plant growth, a beneficial use has been developed for a waste byproduct of CBM extraction, thus reducing costs of energy development while potentially mitigating presently perceived environmental concerns associated with disposal of saline-sodic water.

The amount of organic matter in the soil and the rate of accumulation or decomposition is a result of a balance between organic matter production, climatic and environmental factors causing decomposition, and land use practices (Bauder, 2002). In the PRB, several of these relationships between climate and organic matter are conducive to biomass production and CS. The table below illustrates the specific geographic, climatic, and environmental conditions within the PRB of MT and WY which lend this area suitable for significant potential for SOM accumulations and CS.

Geographic, Climatic, and Environmental Conditions within the PRB
Growing degree days (May - Oct)	(40oC base)= 3900
	(50oC base)= 2400-2600
Mean # days >90 degrees F	14
Elevation	2400 - 4300'
Penman ET (annual)	48"
Thornwaite ET (annual)	23.5"
Precipitation (annual)	10-14"
April - July precipitation (% of annual)	57.5%
July - February precipitation	<10% annual/month
Mean annual air temperature	45 oF
Mean soil temperature	46 oF
Mean monthly air temperature	June= 63 oF
	July= 70 oF
	August= 69 oF
	September = 58 oF
(Source: MAPS, Montana Ag Potential System, 1994)

Goals and Objectives: Project goal is to: 1) examine the potential beneficial use of coal bed methane (CBM) product water to 2) enhance plant growth and biomass production, thus 3) facilitating carbon (C) sequestration in soils. Research objective is to explore a mechanism that helps reduce carbon dioxide (CO₂) levels in the atmosphere, and provide a beneficial use of coal bed methane waste water.

The focus of the research is to monitor biomass production and C accumulation in soils and convert findings into predictions of CS potential in the PRB. The effects of saline water on CS and biomass production have not been determined. Thus, the research will be investigating a new and potentially innovative means of supplemental water supply for the region. The proposed research will have three primary stages of action:

1. A three-part greenhouse project focusing on soil C levels in soil replicating those most common in eastern MT and northeastern WY. Each of these locations constitutes an present area of aggressive CBM development. Supplemental water source will replicate CBM product water. Soil C levels will be monitored throughout the growth stages of the plant and at maturity. Incubation studies will be completed to assess residual CS tenure.
2. A field project replicating conditions specific to the natural occurrence of plant and soil systems found in the Montana and Wyoming portions of the most intensive CBM development play in the intermountain US. Soil C will be monitored, as well as biomass production and soil features.
3. Based on outcomes of greenhouse and field studies, bench-top modeling efforts will be undertaken to derive estimates of gross CS potential in the Powder River Basin, site specificity, and regional suitability. Projected locations for regional suitability include the Wind River, Green River, Raton, San Juan, and Uinta-Piceance Basins.

Experimental Design

Basic agronomical research in a greenhouse will focus on specific components. Greenhouse facilities at Montana State University's Plant Growth Center will support all research needs. Two halophytic plant species, one wetland, and one upland grass species will be planted in soils replicable to those in the PRB.

Due to the shrink-swell characteristics of the soil used in the experiment, all 24 columns were saturated and allowed to dry so that an adequate amount of soil could be added. Once the columns were filled with soil, barley was planted in each column to establish equilibrium in soil structure for all columns.

Baseline Soil Carbon Data
	Dec 2003 Pre-Planting Average: N=2	April 2004 Barley harvest Average: N=4
Total Carbon	1.35%	1.45%
Total CaCO3	4.56%	2.53%

Stage 1-b: April 2004 - October 2004

After the columns were equilibrated and the barley crop harvested, the study species were planted. During the first growth period, plants were treated with non-saline/sodic water to get baseline data for all factors. At harvest, the plants will be monitored and quantitative measurements taken for above ground biomass, root mass, residual soil C, and soluble C in simulated groundwater from wetland columns. After harvest and sampling, columns will be placed in cold storage for an 8 week hibernation period. Soil will be analyzed after hibernation to establish soil C tenure.

During Stage I-c, the plants will be monitored and quantitative measurements will be taken for the same parameters listed in Stage I-b. Plants will be removed from cold storage to begin the second growth stage. Supplemental watering regimes with water characteristic of CBM well discharge will be utililized, as well as one watering with water replicating a rainfall event. Affects of saline-sodic water on the soil and SOM will also be observed. In addition to the greenhouse experiment, an incubation model will also be utilized to examine if there is a way to retain soil C once it is sequestered. If C retention is possible, predictions of CS potential in the PRB of MT and WY could be determined.

Field research will bring into play the climatic and ecological conditions seen in the PRB. For the proposed research biomass vitality, soil structure, and soil C will be observed for the affects of temperature and precipitation factors, slope of landscape, and animal impacts. Field research will be located in one of two locations:

1. MSU Horticulture Farm
2. Established field plots within the PRB owned by producers with a long standing relationship with researchers at MSU. Incorporation of field work will also aid in cooperative contact between researchers, land managers, and industry to facilitate demonstration and collaboration efforts to promote CBM product water utilization for CS and biomass production.

If research concludes that biomass production and CS can be obtained by utilizing a saline-sodic supplemental water source, efforts toward modeling these potentials in the PRB will be initiated. CS models such as CENTURY and EPIC have been utilized with economic models such as RAPS to estimate the impact of field level management decisions on soil C (Paustian et al., 2003). For example, the EPIC (Erosion Productivity Impact Calculator) is a widely used system of modeling agro-ecosystem processes such as wind and water erosion, runoff, soil density, leaching processes, and tillage effects (Izaurralde et al., 2001). The ruggedness and validity of the CENTURY model was tested through research by Bricklemyer and Miller (2002) at Montana State University. The proposed research will reference such programs to help build a localized model of CS potential in the PRB. A successful model would benefit producers and industry by offering a tool that would help offset the environmental and financial concerns associated with CBM development. CBM product water could be utilized in a beneficial and economical capacity to enhance range and crop production for landowners in semi-arid regions not only in the PRB, but potentially elsewhere in the Northern Plains and Rocky Mountain region. Enhancing biomass production in these areas will help mitigate excess CO₂ in the atmosphere by providing an untapped reservoir to capture and store excess carbon.

References

Bauder, J.W. 2002. Personal communication. Montana State University.

Bricklemyer, R.S., R.L. Lawrence, and P.R. Miller. 2002. Documenting no-till and conventional till practices using Landsat ETM+ imagery and logistic regression. J. of Soil and Water Cons. 57(5):267-271.

Izaurralde, R.C., J.R. Williams, W.B. McGill, N.J. Rosenberg. 2001. Simulating Soil Carbon Dynamics, Erosion, and Tillage with EPIC. Proc. First Nat. Conf. on Carbon Sequestration. U.S.D.O.E. - Nat. Energy Tech. Lab, Washington, DC, May 14-17.

Percival, Harry D., Roger L. Parfitt, and Neal A. Scott. 2000. Factors Controlling Soil Carbon Levels in New Zealand Grasslands: Is Clay Content Important? Soil Sci. Soc. Am. J. 64:1623-1630.

Paustian, K., C. Kling, D. Griffith, J. Antle, and S. Capalbo. 2003. Integrated assessments of greenhouse gas mitigation at field and farm scale: Consortium for Agricultural Soils Mitigationand Greenhouse Gases Task 3, subtask 7. (Available only on the web at http://casmgs.colostate.edu/insider/vigview.asp?action=2&titleid=229).

If you are interested or have any questions contact Suzanna Roffe at sroffe@montana.edu..