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Unit 1: Basic Ecological Concepts and Principles Related to Agricultural Systems

(Water Education Foundation)
As agriculture has developed in different parts of the United States, we have often worked in opposition to regional abiotic factors, and modified ecosystems to create viable farms and ranches. The most prominent example of this is irrigation, which has allowed us to produce many different crops in what would naturally be classified as low-rainfall desert or savannah, environments ill-suited to agriculture.
Let’s explore this concept a bit more. Click on the different management practices listed below to discover how modifying a key environmental/ecological factor has resulted in the development of  various farming systems in the U.S.
Management Practice
Environmental Constraint Addressed
Irrigation
Climate (lack of water)
Levees / tile drains
Climate, Soil, Topography (excess water, flooding)
High tunnels
Climate, Weather (seasonal temperature extremes)
Terraces
Topography (slope)


(Jeff Vanuga, USDA NRCS)

Irrigation. Federal and state-supported irrigation projects are the basis for much of agriculture in the Western United States. Yuma County, Arizona, for example, has a desert climate with extremely hot summers and warm winters. Yuma is one of the hottest cities in Arizona, with average July high temperatures of 107 °F. Average January highs are around 70 °F (21 °C). The area receives, on average, about 3 inches of rain annually. Irrigation has allowed farmers to produce a rich variety of fruits, vegetables, hay and grains even in this extreme environment.


(Lynn Betts, USDA NRCS)

Terraces. The natural topography of an area is another ecological factor that might place limits on what can be grown, and where. Farmers have been dealing with those kinds of challenges for centuries. Take steeply sloped land, for example. The construction of terraces has allowed farmers to produce crops on hillsides or mountainsides that might otherwise be inaccessible or extremely prone to erosion and landslides.


(Mark Davis)

High tunnels. In many locations in the U.S., particularly at more northern latitudes, farmers are limited by the length of the growing season. In Minnesota, for example, the last spring frost date ranges from May 1 to 15 in the southern part of the state, and may extend into June in the northern zones. First frosts in the fall can occur in late September or early October. That makes for a very short growing season. One way that farmers have overcome this limitation is through the use of high tunnels, which can extend the growing season by several weeks on either end. Learn more: High Tunnels and Other Season Extension Techniques, University of Kentucky High Tunnel Video, Utah State University High Tunnel Information Resources, Kansas State High Tunnel Video Series


(Photo by worldislandinfo, CC BY 2.0)

Levees / tile drains. There are a variety of management strategies that have been used in areas that were once natural wetlands or that are subject to seasonal flooding (e.g., river deltas) or poor drainage. On a large scale, flood protection works such as dams and levees have allowed the development of agriculture in areas that would seasonally be under water. At the farm scale, to address problems with poorly drained soils, farmers in many parts of the country install a system of tile drains to divert excess water. Learn more: Understanding and Locating Tile Drainage Systems (University of Wisconsin)
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