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Alfalfa Study May Help Growers Determine Returns as Water Resources Dwindle

27 November 2013

US - In a perfect world, alfalfa might be considered the perfect crop. It’s packed with nutrients, is highly digestible, can use precipitation efficiently because it roots deeply into western Kansas soils, and produces high economic returns.

But the semi-arid climate of southwest Kansas coupled with a depleting Ogallala Aquifer, is not a perfect world for alfalfa because it needs more water than other annual crops.

To help farmers evaluate the potential economic returns of growing alfalfa in that region even as the water supply is diminishing, Kansas State University researchers conducted a five-year study to better understand how alfalfa would fare with a limited water supply.

“Alfalfa creates the most economic return by far, compared with other crops for irrigators when water supplies are adequate for full irrigation,” said recently retired K-State Research and Extension water resources engineer, Norman Klocke, who cited consistent demand from the dairy and beef cattle industries, in particular.

“As water resources in this region decline, the question is whether or not alfalfa production is possible with limited irrigation – especially when the crop is stressed because of a lack of water during part or all of the growing season.”

Klocke along with researchers Randall Currie and John Holman designed a field study conducted at the Southwest Research and Extension Center in Garden City. The experiment was intended to reflect the declining ability of the aquifer to supply water for irrigation and also to reflect the constraints of water rights and irrigation management.

What they found was that yield response to the same amount of irrigation was highest during 2007 when the maximum yield was 9 tons per acre and lowest in 2011 when the maximum yield was 4.5 tons per acre. These maximum yields came from 24 inches of irrigation applied in all years.

Dryland yields were 4.5 tons per acre in 2007 and zero yield in 2011. The drought in 2011 certainly impacted yield, but precipitation filled the soil profile in 2006 and alfalfa benefited from this extra water in 2007 because its roots extended to a depth of at least 8 feet. After that, precipitation could not fully replenish the soil.

Klocke also compared alfalfa yield results from 2007-2011 with results from a study conducted at Garden City from 1921 through 1930. Like Klocke and the team, F.A. Wagner, a professor and early scientist with Kansas State, was also looking for the response of irrigation to different amounts of water. Back then irrigation was applied to the surface before irrigation pumps were available.

“The results from both experiments were similar, which tells us that conversion of atmospheric energy to plant dry matter through photosynthesis has not changed in alfalfa over all those years,” Klocke said.

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