Moreover, the definitions that once clearly demarcated conventional from ecologically based farming systems have become muddled. One example is the “conventionalization” of the organic farming industry in the United States (Guthman, 2004), characterized by the entry of large-scale farms in the market for USDA-certified organic products. Most farms present examples of hybrid or intermediate stages on a continuum between the extremes of agricultural practices, and their adoption of various new practices has produced apparent gains in environmental performance (Keystone Center, 2009). Some of the “mixed farming systems” also have been given names (Box 1-5).

The committee concludes that no simple typology or set of categories can capture the complexity of the farming practices and systems used on diverse U.S. farms. The lack of a single accepted typology complicated the writing of this report. Because so much of the research literature is based on comparisons of particular farming practices, or of one or more of those stylized “farming systems,” research findings are cited throughout the report using the categories described by the scientists who conducted the research. For this reason, this report cites organic farming systems more frequently than other ecologically based systems. The illustrative use of organic systems is not intended to imply that organic

BOX 1-5

Examples of Mixed Farming Systems

Conservation agriculture is a term used by the United Nation’s Food and Agricultural Organization (FAO) to refer to the use of resource-conserving but high-output agricultural systems. According to the FAO, conservation farming typically involves the integrated use of minimal tillage systems, cover crops, and crop rotations (http://www.fao.org/ag/ca/).

Reduced- or low-input farming is based on a reduction of materials imported from outside the farm, such as commercially purchased chemicals and fuels. Low-input farming employs technologies and is structured in such a way that tightens flow loops and provides ecosystem services internal to the farm and field, and therefore reduces input use. Such internal resources include biological pest controls, solar or wind energy, biologically fixed nitrogen, and other nutrients released from green manures, organic matter, or soil reserves. Whenever possible, external resources are replaced by resources found on or near the farm. Many reduced-input or low-input farming systems are examples of integrated farming systems (see below).

Integrated farming system is a term commonly used in Europe to describe widely adopted production systems that combine methods of conventional and organic production systems in an attempt to balance environmental quality and economic profit. For example, integrated farmers build their soils with composts and green manure crops but also use some synthetic fertilizers; they use some synthetic or natural pesticides in addition to biological, cultural, and mechanical pest control practices.

Alternative livestock production systems refer to farms that use lower-confinement housing and rely more on pastures than conventional and industrial livestock farms. A common example in dairy farming is the use of intensive rotational grazing practices that involve the use of short duration, intensive grazing episodes followed by long rest periods that allow pastures or fields to recover.

Mixed crop-livestock farming is characterized by livestock enterprises where a significant fraction of the animal feed inputs are generated on cropland and pastures that are under the direct control of the livestock farmer. Those systems capitalize on the ability of the enterprise to use synergies between the crop and livestock enterprises to efficiently recycle nutrients, promote crop rotations, and insulate livestock farmers from price fluctuations in feed and input markets. They reflect the resurgence of traditional mixed crop-livestock farming systems that characterized most production units in the first half of the 20th century. On the other hand, the scale and sophistication of many 21st century mixed crop-livestock farms reflect the effects of new technologies, breed improvements, and greater awareness of environmental issues than their predecessors.



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