Million-dollar rain

What is 1 inch of rainfall worth to irrigators at peak time of importance?

Corn field with rain puddles

The farmers around the coffee shop used to call it $1 million rain, a nice, even 1-inch or greater rainfall at a very crucial point in corn or soybean production. So what is 1 inch of water applied through rainfall or irrigation actually worth and how much does it cost?

In the middle of July 2020, a nice, 1-inch, gentle shower fell overnight in St. Joseph County, Michigan, which has 123,000 irrigated acres, according to the 2017 United States Department of Agriculture (USDA) Census of Agriculture. The Ag Census also tells us the average producer has a cost of about $3.50 per acre inch of water in energy cost. Recent work with a half dozen producers in the Michiana area looking at energy and irrigation costs came up with a figure of about $4 an acre inch over about 3,000 acres for energy and labor.

When you do the math, it costs almost a half million dollars to apply the 1-inch irrigation to St. Joseph County’s irrigated land. If you do the same math for the irrigated land in Michigan and Indiana using 2017 USDA Ag Census data, the savings from a 1-inch rainfall in reduced energy and labor cost is $2.7 million and $2.2 million for Michigan and Indiana, respectively.

The value to farmers is far greater than the $4 an acre inch to apply the water, otherwise irrigation would not be nearly as popular. The greatest value for irrigation is preventing drought stress during and just after pollination for most crops. Research at Iowa State University estimates 3-9% yield loss per day of drought stress from pollination through blister stage for corn and 3-6% yield loss per day of drought stress in corn at milk stage.

One inch of water during hot and dry conditions will feed most crop production for four days at an evapotranspiration of 0.25 inch per day. Using the conservative estimate of 4% yield loss per day for four days of drought, yield reduction at early reproductive stages for corn is at 16% for every inch of water received. With a 230-bushel expected yield and a $3.80 per bushel market value, that would result in a $140 loss per acre. When compared to the estimated $4 per acre cost to irrigate, there is a $35 per dollar return for each dollar spent on irrigation energy and labor. Most of the cost of irrigation is in equipment, not energy and labor.

This financial impact projection uses corn, Indiana and Michigan‘s most irrigated crop, as an example. It is important to note that gains from irrigation are likely much higher in vegetable and specialty crop production. To expand the discussion further, if all of Michigan’s irrigated acreage was planted to corn, a 1-inch rainfall or irrigation on irrigated land at a crucial stage of growth could easily result in protection of 24.7 million bushels of potential yield loss statewide. This would have a value of almost $94 million to the state’s economy. The same example for the state of Indiana results in protection from 20.4 million bushel of potential yield loss to irrigated lands statewide at a value of almost $78 million.

Some believe the fallacy that producers with irrigation do not want it to rain. However, a typical 1,000-acre irrigated farm will have nearly $7,000 in energy bills per week in times of drought. That cost would be more including the wear and tear on equipment and people. The best answer to this misconception comes from an irrigator who stopped me in the parking lot and commented how good last night’s rain was, saying, “No one prays for rain like a farmer who’s behind on irrigating.”

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