K-State Research and Extension News
November 26, 2013
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Alfalfa Study May Help Growers Determine Returns as Water Resources Dwindle


GARDEN CITY, Kan. – 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. 

Results of the study have been published in Transactions of the American Society of Agricultural and Biological Engineers. More information is available at Alfalfa Response to Irrigation from Limited Water Supplies.

“The bottom line is that alfalfa produces good economic returns when it has plenty of water, but yields fall off over years when stored soil water is depleted due to less than optimum water from irrigation,” Klocke said. “Using yield results from this experiment, producers can make comparisons of the profitability of alfalfa and other irrigated crops.”

K-State’s Crop Water Allocator, which can be accessed at the Mobile Irrigation Lab, also helps producers evaluate economic returns, not only from alfalfa but also corn, wheat, sorghum, soybeans, and sunflowers getting zero to 24 inches of irrigation.

“Results show alternatives through crop selection and irrigation management to compensate for less irrigation, but water is still essential for crop production and unfortunately less water means smaller yields,” Klocke said.

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by: Mary Lou Peter
mlpeter@ksu.edu
K-State Research & Extension News

Dr. John Holman – 620-276-8286 or jholman@ksu.edu; Dr. Norman Klocke – nklocke@ksu.edu