Claire LaCanne, Extension Educator, Vasudha Sharma, Extension Irrigation Water Management Specialist, and Lindsay Pease, Extension Nutrient and Water Management Specialist
After several years of drought, the excessive rain in many parts of the state this growing season has caused farmers to think about their strategies for irrigation and drainage management. To discuss management and considerations for the future, Vasudha Sharma, Extension Irrigation Water Management Specialist, and Lindsay Pease, Extension Nutrient and Water Management Specialist, joined moderator Anthony Hanson, Extension educator - IPM, in the August 14 session of Strategic Farming: Field Notes.
To demonstrate the difference this year, at one site at the research station in Becker, there were about 9 inches of rain from May to mid-August last year, and this year at the same site, there have been more than 20 inches in that same amount of time.
Getting rain doesn’t mean we do not need to irrigate. Regardless of the higher precipitation, areas are still irrigating fields because sandy soils still need that water during any dry periods, but there have been far fewer irrigation events than the last several years. For example, at a site in the central sands region, there have been one to two irrigation events this year versus eight or nine by this time last year.
Coarse, sandy soils that require irrigation generally still need it, even during wet years. There was an instance where a site in the central sands region received four inches of rain last week, but the high spots with coarse, sandy soil may still need additional water this week because those areas are starting to show signs of stress. These sandy soils dry out quickly because water moves rapidly through the soil, but again, we are seeing less frequent irrigation needed in general with the rain events that we have been having.
When is the cutoff for when you don’t have to worry about irrigation/water anymore? Usually, at this time of the year, where crops are in the reproductive stage, water is still critical but not as intensely critical as June and July. Farmers might need a few more irrigation events for corn this year if it’s dry and hot, maybe for other crops as well. If it happens to become really dry, we may need to irrigate in September, even though crops should be in the later stages of reproduction that do not need much water.
Variable rate irrigation is perhaps most applicable in years like this, where we have plenty of rain but may have variation in the field such as slope, different soil types. Variable rate irrigation can pay off when there’s lots of rain and lots of leaching; you can save your nitrogen and save on water by applying water only at the locations within a field where you really need it.
Water in the field has prevented many farmers from performing timely field operations - from planting, to weed management, to possibly harvest. Looking at how moisture affected your field operations this year may help you make decisions about adding subsurface drainage. Some folks may not have gotten a crop in some fields this year, so it could be an opportunity to add drainage tile if you decide it’s necessary.
To give you a holistic perspective about whether drainage might be helpful, think about how often your fields are wet versus how often they are dry and think through or pencil out what your return on investment might be. For reference, in northwestern Minnesota where Dr. Lindsay Pease does her work, there has been approximately one wet year every four years, with three dry years. So when thinking about that return on investment, a drainage system is very likely not going to pay off in year one; you will want to think of it as a long term investment for your farm and for your land. Consider future plans for that land, whether it'll be staying in the family, or if you're renting it, and whether the investment will ultimately benefit your operation.
An additional tool worth thinking about, beyond just the subsurface drainage infrastructure itself, is adding some controlled drainage management in your system as well. This is something that University of Minnesota researchers have studied, and have found that it’s really good at reducing excess drainage during times of the year when you don’t need it. If you have a controlled drainage system, you can make use of the rainfall you’re getting and you’re not going to over drain the soil.
Thanks to the Soybean Research and Promotion Council and the Corn Research and Promotion Council for their generous support of this program.
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| Photo: Vasudha Sharma |
Irrigation considerations
What is different about irrigation in a wet year?
Although farmers ran irrigators pretty intensely throughout the crop growing seasons the past 3 years (2021 - 2023) due to drought, they are generally not needing to use them as much this year.To demonstrate the difference this year, at one site at the research station in Becker, there were about 9 inches of rain from May to mid-August last year, and this year at the same site, there have been more than 20 inches in that same amount of time.
Getting rain doesn’t mean we do not need to irrigate. Regardless of the higher precipitation, areas are still irrigating fields because sandy soils still need that water during any dry periods, but there have been far fewer irrigation events than the last several years. For example, at a site in the central sands region, there have been one to two irrigation events this year versus eight or nine by this time last year.
Coarse, sandy soils that require irrigation generally still need it, even during wet years. There was an instance where a site in the central sands region received four inches of rain last week, but the high spots with coarse, sandy soil may still need additional water this week because those areas are starting to show signs of stress. These sandy soils dry out quickly because water moves rapidly through the soil, but again, we are seeing less frequent irrigation needed in general with the rain events that we have been having.
When is the cutoff for when you don’t have to worry about irrigation/water anymore? Usually, at this time of the year, where crops are in the reproductive stage, water is still critical but not as intensely critical as June and July. Farmers might need a few more irrigation events for corn this year if it’s dry and hot, maybe for other crops as well. If it happens to become really dry, we may need to irrigate in September, even though crops should be in the later stages of reproduction that do not need much water.
Look to in-field data for decision making
Although there have been plenty of rain events throughout the state, they are not uniform and vary greatly by location. Even fields on the same farm may get different amounts of rain in the same storm, so be sure to use rain gauges and soil moisture sensors to give you reliable, field-specific data. It is a good idea to not rely on the local weather station alone, but rather monitor individual fields to best manage soil moisture and irrigation needs.What are some things on the horizon for irrigation management?
Precision irrigation technology and variable rate irrigation
Variable rate irrigation is a precision agriculture tool that allows farmers to apply different amounts of water to different areas of a field based on the field's characteristics. Variable rate irrigation can help farmers improve irrigation scheduling, which is beneficial for many reasons. It can also help farmers avoid irrigating non-farmed areas like waterways, wetlands, and roadways. This Crop News article touches on how variable rate irrigation might combat groundwater issues in Minnesota.Variable rate irrigation is perhaps most applicable in years like this, where we have plenty of rain but may have variation in the field such as slope, different soil types. Variable rate irrigation can pay off when there’s lots of rain and lots of leaching; you can save your nitrogen and save on water by applying water only at the locations within a field where you really need it.
Considerations about drainage during a wet year
How can I decide if adding subsurface drainage would be beneficial for a particular field?
Having a subsurface drainage system can really show advantages during an excessively wet year like this year.Water in the field has prevented many farmers from performing timely field operations - from planting, to weed management, to possibly harvest. Looking at how moisture affected your field operations this year may help you make decisions about adding subsurface drainage. Some folks may not have gotten a crop in some fields this year, so it could be an opportunity to add drainage tile if you decide it’s necessary.
To give you a holistic perspective about whether drainage might be helpful, think about how often your fields are wet versus how often they are dry and think through or pencil out what your return on investment might be. For reference, in northwestern Minnesota where Dr. Lindsay Pease does her work, there has been approximately one wet year every four years, with three dry years. So when thinking about that return on investment, a drainage system is very likely not going to pay off in year one; you will want to think of it as a long term investment for your farm and for your land. Consider future plans for that land, whether it'll be staying in the family, or if you're renting it, and whether the investment will ultimately benefit your operation.
An additional tool worth thinking about, beyond just the subsurface drainage infrastructure itself, is adding some controlled drainage management in your system as well. This is something that University of Minnesota researchers have studied, and have found that it’s really good at reducing excess drainage during times of the year when you don’t need it. If you have a controlled drainage system, you can make use of the rainfall you’re getting and you’re not going to over drain the soil.
Are there potential N credits from cover crops in a wet year like this?
If you are planning to seed a cover crop that will overwinter, it will typically hold nutrients over the winter and its nitrogen will continue to be tied up into the next crop. This is good for water quality, but won’t be beneficial in providing nitrogen credits. To complement a cover crop, it may be beneficial to do a starter fertilizer instead of pre-plant application so that you can get targeted nutrients closer to the seed. Later on in the growing season, nutrients from the cover crop will become available, so it can be beneficial to take a soil test before you decide to do a sidedress application.What does excessive water and nutrient leaching mean for next year?
There was nitrogen leaching and underperforming corn this year. Where a crop has underperformed, take a soil test to see what nutrients you have left out there. After several drought years followed by a year with moisture, there may have been a lot of nutrient movement through the soil. There can also certainly be variability within the field where you’ve had a crop underperform. Soil testing is going to be your best friend this year to help make decisions for next year’s growing season.Structures that aid in water and nutrient management in a subsurface drainage system
Lift stations and when they are useful
Lift stations, also called pump stations, are used in flat or low-lying areas where there isn't enough slope or gravity to move water out of the field quickly. They are common in the extremely flat topography of the Red River Basin, but aren’t as prevalent in other parts of the state where there has historically been more drainage infrastructure in place. Lift stations could be used anywhere, however. You could put a lift station in places in the landscape where you don't have deep roadside ditches into which you can outlet your system.Bioreactor structures to help filter nutrients
A bioreactor is basically a buried trench filled with a carbon source – usually wood chips – installed at the edge of a field. Tile drains from the field divert a portion of the drainage water into the bioreactor and a bioreactor reduces nitrates in the water. University researchers are doing some work with bioreactors across the state. These edge-of-field structures can be helpful especially on sandy soils, to add an extra filter.Thanks to the Soybean Research and Promotion Council and the Corn Research and Promotion Council for their generous support of this program.
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