When Mother Nature provides timely, right-sized rainfall, the benefits for the environment and farmers can quickly add up. Crops drink the moisture to promote plant growth and farmers irrigate less, preserving groundwater and saving power.
2024 was one of those years. After several seasons of inconsistent rainfall and drought conditions across Minnesota, last summer was much wetter. Precipitation varied in our growing region:
- At our Park Rapids farm, rainfall averaged about 20 inches between the northwestern part of the farm near Pine Point, the midpoint near Park Rapids, to the southeastern part of the farm near Hubbard, according to RDO Farm Manager Luke Warmbold.
- At our Becker, Minn. farm near the Twin Cities, RDO Farm Manager Daran Solbreken said his fields received between 20 - 23 inches of rain.
- And, around Brooten, Minn., RDO Farm Manager Chris Strom said his potato fields received between 21.5 to 24 inches of rain.
That rainfall allowed RDO to irrigate less - only using between 41 to 50 percent of our annual permit allocations. But, there is a lot more to understand about the relationship between water and potato plants.
How much water do potato plants need to grow?
Well, the answer to that question depends. According to Nick David, RDO Midwest Director of Agronomy, crop water use is determined by how much sun is intercepted by the potato crop.
“A potato crop can require between 18 – 20 inches of water if the summer months are sunny, relative humidity is low, and temperatures aren’t too warm,” David said. “However, we generally have periods that are not meteorologically ideal for potatoes during the growing season.”
To manage this variability and to determine how much water each individual field is using, David said RDO monitors canopy development and utilizes published crop water use (evapotranspiration or ET) models to only apply the amount of water the plant has removed from the soil.
According to David, understanding soils is the other part of the equation to determine when and how much to irrigate in absence of natural rainfall.
“The amount of water held by the soil varies depending upon its texture,” David said. “Coarse-textured soils drain more rapidly and don’t hold as much water as fine-textured soils.”
David said that in general, coarse-textured sands hold approximately 1” of water per foot of soil depth, while fine-textured sandy loam soils hold up to 2” of water per foot of soil.
“Understanding how much water is available for plant use in our soils and how much water the plants are using on a daily basis allow us to meet the needs of the crop, while minimizing drainage below the root zone,” David said.
Monitoring potato plant growth between 2024 rainfalls
Throughout the season, Strom, Warmbold and Solbreken and their teams closely monitored soil moisture levels against the potato growth cycle and consulted with RDO agronomists to understand each field’s soil characteristics.
“Like every year, we visited our fields daily in 2024, putting shovels in the soil, using moisture monitors and measuring crop water use,” Solbreken said. “But given Mother Nature’s generosity, providing the right amount of rain at the right time as our plants grew, we were able to irrigate less.”
Strom noticed the same thing around Brooten, only using about five inches of water from his Minnesota Department of Natural Resources permits, with many of those inches being applied in the fall to establish cover crops. He and his team used a tool to verify the amount of water to ensure accurate reporting.
“We use an ultrasonic flow meter to check the amounts of water flowing from the well through our pivots,” Strom said. “This allows us to identify any well maintenance needs and to be confident in our reporting numbers to the DNR.”
As the RDO Farm Managers prepared to turn in water usage reports to the DNR in mid-February, they found consistency in the numbers. In 2024, RDO farms only used 40 to 51 percent of the total amount of water allocated in DNR permits. That usage is on par with RDO’s long history of water conservation, as records indicate our farms are under permit allocations 97 percent of the time.
Closing out the books on the 2024 season, Warmbold noted another big benefit of the seasonal rainfall, with irrigation power and repair costs far below budget at the farm in Park Rapids.
“Rainfall makes a big difference on farm financials … when we don’t irrigate, we save on energy and equipment maintenance costs as well as staff time,” Warmbold said. “Now if we could only order timely, right-sized rains every year, it would make our jobs as farmers much easier.”
