Battling Soil Saturation

Poorly drained soils cause headaches for landowners

Poorly drained soils cause numerous headaches for landowners, including reduced crop production and environmental nitrogen loss.

It’s a problem that Peter Motavalli and Kelly Nelson, both with the University of Missouri College of Agriculture, Food and Natural Resources, have worked for years to combat. One of their field trials was published in the first Agronomy Journal of 2017. The trial was conducted at the Greenley Research Center, in Novelty, from 2013-15, and was titled, “Soil Waterlogging and Nitrogen Fertilizer Management Effects on Corn and Soybean Yields.”

Claypan soils, which are common in the mid-Missouri region, have problems draining, especially when strong storms leave behind high precipitation amounts. These flooding events can stunt crop growth and lead to important nutrient loss.

Peter Motavalli said that when flooding is mentioned, the public generally thinks of catastrophic, large-scale events which cause extensive crop damage. However, intensive rainfall events can also cause short-term soil saturation which can also negatively affect crop production and increase environmental nutrient losses, especially for crops planted on poorly drained soils. Peter Motavalli said that when flooding is mentioned, the public generally thinks of catastrophic, large-scale events which cause extensive crop damage. However, intensive rainfall events can also cause short-term soil saturation which can also negatively affect crop production and increase environmental nutrient losses, especially for crops planted on poorly drained soils.

“The incidence of soil saturation is increasing,” said Motavalli, a soil fertility and plant nutrition professor in the School of Natural Resources. “We’re getting more wetness in the spring and dryer times in the summer. Spring is a time where we’re observing higher rainfall intensity. That coincides with when many growers apply nitrogen fertilizer to their fields.

“We have a fairly long research history with this. Our goal is to develop some options for growers in their nitrogen fertilizer management to deal with the nitrogen loss and loss of productivity, as well as quantify how much loss there is. Farmers are already adapting to these changing rainfall patterns, and our goal is to assist them with that process.”

Missouri has a large area of floodplains as well which are extremely productive, however, those areas have also experienced increased flooding. Motavalli and Nelson have worked to research how producers can prepare for those saturation events, as well as deal with the effects after a precipitation event.

The duo also focuses on how producers can improve their nitrogen-use efficiency. Motavalli and Nelson are working to make sure producers get the most out of each pound of nitrogen they use.

“Every pound of nitrogen represents money from a grower’s pocketbook,” Motavalli said. “There has been a lot of effort to look at rescue nitrogen applications. We don’t know what’s going to happen during the growing season. Some years, we may get a lot of rain, and some years we may not get anything. It’s possible to come in a little later in the growing season and add nitrogen in response to those conditions. The idea here is that we may be able to do the same thing after a saturation event and add extra nitrogen.”

Motavalli and Nelson have researched the effects of flooding at various growth stages of corn. This study was specific to a later stage, the V6 stage specifically.

“It’s really tough for plants to recover when they face these saturation events,” said Nelson, agronomist at the Greenley Research Center. “We saw significant damage to corn in the V6 stage depending on the duration of saturated conditions. The V3 stage damage wasn’t as dramatic since it had more time to recover and the temperature is not as warm as at the time V6 occurs.”

Motavalli said that when flooding is mentioned, the public generally thinks of catastrophic, large-scale events which cause extensive crop damage. However, intensive rainfall events can also cause short-term soil saturation which can also negatively affect crop production and increase environmental nutrient losses, especially for crops planted on poorly drained soils.

“We’ve worked hard to quantify the daily loss,” Nelson said. “We found, in this study, that for every day of additional flooding, at the V6 stage, you lose about six to 12 bushels per acre of corn. There is definitely a linear relationship – with more time of saturation you have more loss.

“We have a fairly long research history with this. Our goal is to develop some options for growers in their nitrogen fertilizer management to deal with the nitrogen loss and loss of productivity, as well as quantify how much loss there is. Farmers are already adapting to these changing rainfall patterns, and our goal is to assist them with that process.”
―Peter Motavalli, a soil fertility and plant nutrition professor in the School of Natural Resources

“What really struck me was this linear relationship in loss. We’re realizing that the temperature at the time of flooding makes a big difference, too. If you get water logging when it’s hotter out, it really sets the plant back.”

There are several ways for producers to battle these saturation events, including drainage water management. Nelson has developed a large program at Greenley which focuses on subsurface drainage water management, which producers can use to help with their poorly drained soils. This management style is designed to keep nutrients in the field and send cleaner water downstream. This research has been ongoing at Greenley since 2001.

“There have been several studies throughout the Midwest looking at drainage water management when it came to reducing nitrate loss,” Nelson said. “We knew that drainage water management could reduce nitrate loss. We also knew it would be better than just free-flowing drainage.”

The findings at Greenley have backed up those studies. Based on his results, there was a more than 70 percent reduction in nitrate loss and an 80 percent reduction in phosphorus loss compared to the free-flowing drainage.

Other ways to battle saturation events include placing fertilizer in specific areas where saturation is most likely to occur. Motavalli and Nelson have a patent for applying fertilizers on areas of the field which are more prone to saturation. Rescue nitrogen can also be used.

“We found that the rescue nitrogen only helped during one of the years,” Motavalli said. “One of the reasons for that is because when you apply it, there’s no guarantee you’re going to get rain after application.”

Motavalli said their approach is part of precision agriculture. The goals are to make the best use of the resources available and to reduce risk.

“This is why it’s important to focus on improved management practices that are cost-effective and increase crop nutrient use efficiency,” Motavalli said. “This matters a lot, especially when prices are low.”