Carbon sequestration in agricultural soils : an integrated modeling approach
Date
1997-01-01
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Doctoral
Abstract
The purpose of this study was to measure the impacts of increasing the ratio of conservation tillage in a selected region on farm level profitability and soil organic matter (SOM) level. The objective was sought through developing an integrated model in which an economic mathematical optimization model was linked to a soil simulation model, which predicted dynamics of the SOM as a function of climate, initial level of SOM, and management factors. Tillage operation and corresponding cost data were introduced into the soil simulation and the economic model, respectively. The direct linkage approach allowed interaction between the two models in terms of simulated crop yields and economic response to fertilizer use by agricultural producers over time. The empirical model was run on a site-specific region in Saskatchewan (Soil Polygon 1814, about 100 km west of Saskatoon), Canada. Relevant data for the 10 crop activities included in the analysis were obtained from the Scott Agricultural Experimental Station. Thestudy utilized average cost and crop yield data on two rotations--canola-wheat-fallow, and canola-wheat-wheat--which had been running at the Scott Experimental Station since 1978. The results indicated a trade-off between the economic and SOM indicators: an increase in one indicator was accompanied by a simultaneous decrease in the other. In other words, increasing the ratio of conservation tillage system for the purpose of conserving more organic matter within agricultural soils led to lower producers' net returns relative to the results obtained under the base (business as usual) scenario. The SOM decreased in all rotations except that of the canola-wheat-wheat of no-till system. However, the rate of decrease in SOM in scenarios with a higher ratio of SOM was considerably less than that of the base-scenario. The trends were all consistent with the results of other studies conducted on the same soil zone. It was also found that, contrary to the impacts of crop yield interaction, fertilizer interaction had minor effects on the empirical results and trade-off analysis. By comparing the economic loss to producers in moving to a scenario in which the area under conservation tillage is increased by 30 percent to an estimate of society's willingness to pay for storage of SOM, equal to $4.88 to \$50.37 per hectare, it was concluded that, on an economic basis, neither private producers nor society may have enough incentive for conservation of more organic matter in agricultural soils in the selected area. Sensitivity analysis indicated that even under climate change (an average increase of 2.5°C in average monthly temperature) in the study region, producers lost 1.06 percent of their net return for each tonne increase in the level of SOM by moving from their current production pattern to a 30 percent increase in the area under conservation tillage. The results also indicated that, in moving from a base scenario to a higher ratio of conservation tillage, producers' economic loss was higher when the integrated model was run without incorporating the interrelationships between sub-models. (Abstract shortened by UMI.)
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Degree
Doctor of Philosophy (Ph.D.)
Department
Agricultural Economics
Program
Agricultural Economics