Center pivots

NWU Radio Script

8-20-01

The number of Nebraska acres irrigated by center pivot has doubled in the past 25 years, according to research by a University of Nebraska agricultural economist.

Center pivot irrigation is the primary system being used to water nearly two-thirds, or 4.6 million of the state's 7 million acres of irrigated, cultivated cropland, notes Bruce Johnson, an Institute of Agriculture and Natural Resources agricultural economist.

If the conversion of gravity irrigated land to center pivots continues at the present rate and some dryland acres continue being developed with center pivot technology, as much as 70 percent of Nebraska's irrigated acres could be under center pivots by 2010, predicted Johnson.

"The implications of that are for much more than state bragging rights," Johnson said. "Our irrigated land base represents a vital resource that will increasingly become the envy of a water-deficient world. The fact that the bulk of that acreage is using a form of technology that is water efficient and complementary to precision agriculture, (means) we can be more assured of its sustainability in the future."

Center pivot technology, which was developed in Nebraska, opened land for crop production that otherwise would not be irrigable, he said. It also has greatly enhanced water use and other input efficiencies on land that previously was gravity irrigated.

The inventory of the state's irrigated cropland acreage was compiled as part of Johnson's ongoing analysis of the dynamics of Nebraska's farm real estate market. He was assisted by undergraduate students Peter Brummels of Coleridge and Lance Kuenning of Imperial.

The research team used a variety of state, federal and university data to draw conclusions about Nebraska's total cropland, total irrigated cropland and the number of irrigated acres watered by center pivot or other types of irrigation. Johnson assessed irrigation statewide and by region, using the eight Nebraska Agricultural Statistics Service reporting districts.

Center pivot irrigation use is most concentrated in Nebraska's north and northeast districts, where it accounts for nearly 97 percent and 89 percent, respectively, of irrigated acres. Pivot use is least concentrated in the central and south districts, with 44 percent and 45 percent, respectively.

Percentages of irrigated acres under pivot in other districts are about: northwest, 60 percent; east, 54 percent; southwest, 80 percent; and southeast, 57 percent.

Johnson's inventory indicates Nebraska has a total of 22.1 million acres of cropland, of which about 7.4 million acres, or 33 percent, are irrigated. About 4.6 million, or 62 percent, of those acres are irrigated by center pivots while 2.8 million acres use other irrigation methods.

According to the Department of Agriculture's 1997 National Resources Inventory, only California and Texas have more irrigated acres than Nebraska and Texas has been experiencing a steady decline in irrigated acres over the past 25 years, Johnson said.

However, he found now clear consensus on how many of the state's cropland acres actually are irrigated or what type of irrigation is used.

The 1997 Census of Agriculture indicates Nebraska has a total of 6.94 million acres of irrigated land, while the Nebraska Agricultural Statistics Service estimates a total of 8.1 million acres that have wells or ditch water available could be irrigated if conditions warranted.

"The 8.1 million-acre figure is the one most often seen published, but it's not necessarily the definitive answer," he said.

Identifying irrigated acres by the types of irrigation system proved more challenging.

"We relied on UNL Conservation and Survey Division's satellite imagery of the state, which reveals the center pivot circles in graphic details. Using the satellite map for 1997, the latest one available, we were able to develop center pivot acreage estimates that were reconciled against our previously developed irrigated acreage totals and the final center pivot irrigation estimates were made," Johnson said.

This research was conducted cooperation with IANR's Agricultural Research Division.

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