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One of the underlying themes of this report is the tension between the rapid specialization of much of U.S. agriculture in the last few decades and its resulting high production of individual commodities (Chapter 2) with the requirements of robustness, resilience, and appropriate levels of environmental integration in sustainable production systems (as discussed in Chapter 1). That tension revolves around the balance between the “industrial philosophy” and “agrarian philosophies” (Box 1-7) and varies among different commodities and environments. This chapter illustrates a few system types that lie within the complex matrix of that balance. They represent modifications within industrial approaches, and, in some cases, a more aggressive departure toward an agrarian approach. Chapters 3 and 4 highlight advances in the scientific understanding of different management practices and approaches that can contribute to improving productivity and environmental, economic, and social sustainability. The practices are central to the examples below because they are components of a larger farming system.
“System” is interpreted in a broad sense, from the individual farm agroecosystem to the wider ecological system or biome. The systems approach recognizes the importance of interconnections and functional relationships between different components of the farming system (for example, plants, soils, insects, fungi, animals, and water). It also stresses the significance of the linkages between farming components and other aspects of the environment and economy. Understanding how the components function individually and the outcomes each produces becomes the foundation of systems agriculture research. The aggregate outcome of applying those practices in concert cannot be predicted from simply combining the anticipated outcome of each practice because they interact with one another. In some instances, the combination of practices has complementary or synergistic relationships; in other instances, combining two practices might have unintended negative consequences.
A systems approach to agriculture is generally guided by an understanding of agroecology, as a scientific basis, and agroecosystem interactions. Agroecology applies ecological concepts and principles to the design and management of agricultural systems to improve sustainability (Gliessman, 1998; Altieri, 2004; Wezel and Soldat, 2009). Agroecology provides a framework to integrate the biophysical sciences and ecology for management of agricultural systems. It emphasizes the interactions among all agroecosystem components (for example, biophysical, technical, and socioeconomic components of the farming system) and recognizes the complex dynamics of ecological processes (Vandermeer, 1995). The approach aims to maintain “a productive agriculture that sustains yields and optimizes the use of local resources while minimizing the negative environmental and socio-economic impacts of technologies” (Altieri, 2000).
When used in agriculture, agroecosystems have been defined as “communities of plants and animals interacting with their physical and chemical environments that have been modified by people to produce food, fiber, fuel, and other products for human consumption and processing” (Altieri, 1995). Agroecosystem design has been recognized as an important part of an agroecological approach, which is a more holistic concept of integrated resource management and understanding complex interactions than a reductionist approach (Swift et al., 1996).
This chapter uses a few farming system types to illustrate how they combine practices and to discuss the potential environmental, social, and economic outcomes. (See Box 2-1 for articulation of the distinction between “farming system”—the integrated system of a single farm management entity—and a “farming system type”—aggregations of farming systems defined by commonalities of commodity, management practices, or farming system approach.)