By Sean Ellis
Despite adding 250,000 cows between 2002 and 2022, Idaho’s dairy industry is not using more water in Idaho.
In fact, it’s using less.
That’s according to a recent study by Pat Hatzenbuehler, an assistant professor of crop economics with University of Idaho.
The study shows that Idaho’s dairy industry should not be used as a scapegoat by people trying to assess blame for water challenges in the state.
Hatzenbuehler discussed the findings of the report in the December 2023 edition of the Ag Proud – Idaho magazine.
He used data from the U.S. Geological Survey and other sources to estimate the change in total water usage by Idaho’s dairy industry over time.
What he found is the state’s dairy operations are actually using slightly less water now than they were 20 years ago.
This is due largely to a switch in feed rations by Idaho dairymen, who are feeding their cows more corn and less alfalfa hay than they were two decades ago.
Idaho’s milk cow inventory increased from just under 400,000 in 2002 to more than 650,000 in 2022.
Hatzenbuehler’s study showed that during that same period, Idaho hay acres declined slightly, from about 1.15 million to about 1.03 million, while the state’s total corn acreage rose, from less than 200,000 to more than 350,000.
University of Idaho Extension specialists estimate that the amount of alfalfa hay used in Idaho dairy cow rations has gone down, while the amount of corn silage used in rations has almost doubled.
The shift in feed rations has resulted in a slight decrease in water usage by Idaho dairies, due to the fact that alfalfa hay requires more water to produce than corn silage.
Hatzenbuehler’s report estimates it takes 36 inches of water over a full season to grow alfalfa, while corn silage takes 30 inches of water per season to grow.
The report estimated a decline of 384,000 acre-feet of water in Idaho used for alfalfa hay and an increase of 362,500 acre-feet of water used for corn.
Factoring in the increased amount of water consumed per animal, the result was a net decline in water usage by the state’s dairies of 14,300 acre-feet.
Hatzenbuehler said there are a couple of things to keep in mind about the study.
One, it doesn’t explore the seasonal differences in when water is applied to corn or hay and the seasonal impact on water flow levels.
More water is required for alfalfa hay earlier in the season, while more water is used for corn production later in the season, he said.
The report also didn’t look at whether the shift in feed rations has resulted in more or less water being used in certain watersheds
“I crunched from a very broad level that corn requires a little bit less water than hay overall,” Hatzenbuehler said. “But the distribution during the growing season is different as well. I don’t get into those issues” in this report.
Hatzenbuehler said he didn’t know what to expect when he started looking at the issue, and there are several things that should require more targeted, in-depth study.
For example, when during the season the water is applied and the impacts on different water sheds should be looked at.
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