Climate change

How does flooding affect farms?

In the spring of 2019, a perfect storm of conditions led to severe flooding across the Midwest. Farmers in many states had to delay spring planting because fields were too wet. What conditions led to the 2019 floods?

Abnormally cold weather through mid-March meant the winter’s snowfall hadn’t melted. Then, a sudden warming period and high rainfalls occurred. The rapid snowmelt and precipitation caused runoff on frozen soils in eastern Nebraska and southern Iowa.

above-ground view of water with very little ground demonstrating flooding in Iowa in 2011

Burt County, Nebraska, experienced severe flooding in 2011. For over three months, Burt County had more acres than any other county in Nebraska inundated with floodwater. In 2019, some stations along the Missouri River reported the river crested at 4 feet higher than 2011 levels. Credit: John Wilson

Compounding the problem, North and South Dakota and Minnesota received significant snowfall. This later melted in the spring, extending the flooding period. Flooding occurred on tributaries to the Missouri River, and levees along the Missouri River breached. The results were catastrophic; some farms still had standing water 6 months later.

Floods have long-term impacts. Here are issues a farmer must address after waters recede:

  1. Sediment and debris
  2. Erosion repair
  3. Soil repair and nutrient management
  4. Crop repair

How farmers deal with sediment and debris

Moving water carries soil particles. When the water slows, sediment is deposited on the soil surface, ranging from a few inches to 15 feet of sediment covering topsoil – or more.

Shallow deposits of 2 inches or less can be tilled into the topsoil with normal tillage equipment. Farmers need to till deep enough to thoroughly mix this sediment with the topsoil. This reduces differences in soil texture between the sediment and the original soil, which affects root development and water infiltration.

dry soil on left with a standing pool of water and severely eroded land on the right

One consequence of severe flooding is erosion. Farmers must fix their fields before sowing seed. Credit: John Wilson

For sediment deposits over 2 inches deep, more aggressive tillage equipment should be used to insure adequate mixing of sediment and the native soil. If more than 8 inches of sediment covers cropland, the farmer must remove sediment to get it to a manageable depth for their tillage equipment.

Debris that can be left behind after a flood range from uprooted trees and corn stalk residue, to building debris and household items. The latter need to be removed following state regulations. Corn stalks add organic matter to the soil – but the soil is saturated after flooding, making incorporating stalks a challenge.

How farmers deal with erosion repair

Fast moving floodwater destroys buildings, grain bins, roads, or anything else in its path. It also leaves eroded areas in cropland. This erosion ranges from a few inches to many feet deep.

Smaller eroded areas can be leveled during tillage. But others need a focused repair. Deposited sediment can help fill ditches created by floods. But, topsoil from other areas in the field need to be used on top of any sediment. In extreme cases, erosion can be so severe that farmers abandon farming parts of their fields. Programs like the wetland reserve may provide an alternative to farming this ground.

How farmers repair soil

After farmers have removed debris, incorporated sediment, and repaired eroded areas, they need to look at their soil. Healthy soil has a structure that allows root penetration and water infiltration. Structure can be destroyed in soils that have been under water for a long time.

How farmers repair crops

In 2019, most crops were not planted when flooding began in March, but pastures and alfalfa were affected. Depending on the duration plants are under water, farmers need to evaluate stands when floodwaters recede. Farmers may choose to interseed into existing forages to extend the life of the stand or they may establish alfalfa in new fields or completely reseed pastures.

Depending on the time of year when a flood occurs, many farmers want to establish cover crops as soon as possible after a flood. Cover crops help re-establish the beneficial soil microorganisms, improve structure and protect bare soil from further wind and water erosion.

When farmers have advance notice of flooding

With advance notice of a flood, farmers can take some precautions. This was the case preceding flooding in 2011. Farmers emptied grain bins, moved livestock and equipment to higher ground, moved or chained down propane tanks and removed power units from irrigation systems. These measures helped farmers reduce their losses. In 2019, there was very little advanced notice. Grain in many bins swelled when exposed to floodwater and split open, resulting in the loss of grain and the bin.

silver grain bins surrounded by water - yellow piles of grain show the bins were split during flooding

When farmers have advance notice that river levels are high, and there may be flooding, they can take precautions. In 2019, there was no advance notice. Shown, overflowing grain bins from grain that absorbed floodwater bursting through the bin. Credit: John Wilson

Repairing farm fields after floods is possible, but it can be time-consuming and labor-intensive. Farmers are eager to get in their fields and do something, but this can result in compaction, ruts, and further damage to fields. Patience is a virtue when bringing flood-damaged cropland back into production. Inventorying what needs to be done and planning your course of action is critical for flood recovery.

Answered by John Wilson, CCA, Extension Educator with Nebraska Extension in Burt County

Farmers and crop advisers interested in hearing all of John’s webinar “Farming after the Flood,” should visit https://www.agronomy.org/education/classroom/classes/712 .  or go to https://flood.unl.edu/ for more information.

About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.

Categories: Climate change, Food security

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