The purpose of this study was to evaluate the sustainability of agroecosystems. The framework developed within this study is systems-based with the dynamic linkages between the system components explicit. The primary objective of the study was to develop a computer model, the Sustainable Agroecosystem Model (SAM), that dynamically integrates the economic and ecological components of an agroecosystem. The model was used to assess the sustainability of agroecosystems, defined by ecodistrict boundaries, in the Brown soil zone of southwestern Saskatchewan. The SAM was comprised of three components: (1) a soils model that simulated soil and crop growth parameters; (2) an economic model that simulated land use and cropping decisions; and (3) a habitat model that calculated habitat and biodiversity parameters. These components were largely self-standing models comprised of important processes of the soil, economic and ecological sectors of the agroecosystem respectively. To simulate the co-evolutionary changes of the agroecosystem the component models were dynamically linked, based on a one year time step, through selected input and output parameters. The output of the component models reflect elements of the natural and man-made capital stock of the target agroecosystems and were used as sustainability indicators. The concept of strong sustainability was adopted in the analysis such that changes in these indicators signal changes in the relative sustainability of the system. The study focused on two types of simulations: (1) the relative sustainability of four ecodistricts was assessed using baseline simulations. This analysis highlighted the importance of biophysical constraints to the sustainability of an agroecosystem. These simulations indicated that the development of production technologies and policy initiatives, targeting agroecosystem sustainability, should explicitly consider the regional biophysical constraints faced by farms; and (2) the relative sustainability of a single ecodistrict subjected to economic (carbon credit and carbon tax policies) and environmental (climate change) perturbations was evaluated. These simulations highlighted the difficulty in identifying a single policy that leads to a sustainable agroecosystem. In general, policies that resulted in improvement in some components of the capital stock caused degradation of other components. The Identification of preferred policy, in terms of agroecosystem sustainability, requires a weighting of system effects based on societal preferences, ethical responsibilities, degradation thresholds and system co-evolution.

The purpose of this research was to investigate how sustainable agriculture is being conceptualized and implemented in Saskatchewan. Zero tillage, organic farming, and the discourses surrounding them were examined as theoretical and practical responses to sustainable agriculture. Characteristics of 33 organic and 33 zero tillage farming systems located throughout the soil climatic zones of southern Saskatchewan were compared, as well as farmers' perceptions of sustainable agriculture and factors influencing their management decisions. The analysis was extended beyond the local level by examining the links between major socio-political forces shaping agriculture and farmers' perceptions and choices. Central to this analysis is an examination of the role of informal and formal knowledge systems in the development of sustainable agriculture, and how relations of power affect the knowledge that is being produced and ultimately the direction of change in agriculture. Interdisciplinary and exploratory approaches were used to identify and examine a range of emergent issues. The data gathered was analyzed both quantitatively and qualitatively. This study revealed commonalities between zero tillage and organic farmers' basic views on sustainable agriculture, and important differences in the ways these two groups of farmers translated these ideas into practice. Most farmers defined sustainability at the farm-level, focusing on land stewardship and the preservation of the family farm. Farmers adopted zero tillage because of specific environmental, economic and labour advantages, whereas organic farming was adopted for a combination of environmental, health, economic, philosophical/spiritual and labour factors. In general, zero tillage and organic farming systems differed in size, in production and management operations, in land tenure, and in the use of purchased inputs and labour. Zero tillage farms tended to be large, capital-intensive, specialized cropping operations, with a significant proportion of rented land and non-family hired labour. Organic farms were moderate-sized, diversified crop and livestock operations that substituted biological and cultural practices for purchased (agrochemical) inputs, had a high degree of ownership, and relied more upon labour exchange. These characteristics create distinct environmental, economic and social advantages and disadvantages. Zero tillage, compatible with the dominant agricultural paradigm and the industrial model, continues to be promoted by agricultural institutions and agribusiness as the best solution to farm-level sustainability. Interest in organic agriculture and the alternative agricultural paradigm is increasing, however, due to the current crisis in the farm economy and changes in consumers' perceptions and choices.