The dirt on soil loss from the Midwest floods

As devastating images of the 2019 Midwest floods fade from view, an insidious and longer-term problem is emerging across its vast plains: The loss of topsoil that much of the nation’s food supply relies on.

Today, Midwest farmers are facing millions of bushels of damaged crops such as soybean and corn. This spring’s heavy rains have already caused record flooding, which could continue into May and June, and some government officials have said it could take farmers years to recover.

Long after the rains stop, floodwaters continue to impact soil’s physical, chemical and biological properties that all plants rely on for proper growth. Just as very wet soils would prevent a homeowner from tending his or her garden, large amounts of rainfall prevent farmers from entering a wet field with machinery. Flooding can also drain nutrients out of the soil that are necessary for plant growth as well as reduce oxygen needed for plant roots to breathe, and gather water and nutrients.

As scientists who have a combined 80 years of experience studying soil processes, we see clearly that many long-term problems farmers face from floodwaters are steeped in the soil. This leads us to conclude that farmers may need to take far more active measures to manage soil health in the future as weather changes occur more drastically due to climate change and other factors.

Here are some of the perils with flooded farmland that can affect the nation’s food supply.

Suffocating soil

When soil is saturated by excessive flooding, soil pores are completely filled with water and have little to no oxygen present. Much like humans, plants need oxygen to survive, with the gas taken into plants via leaves and roots. Also identical to humans, plants – such as farm crops – can’t breathe underwater.

A fence encrusted with ice and cornstalks stands in Nebraska floodwaters. AP Photo/Nati Harnik
Essentially, excess and prolonged flooding kills plant roots because they can’t breathe. Dead plant roots in turn lead to death of aboveground plant, or crop, growth.

Another impact of flooding is compacted soil. This often occurs when heavy machinery is run over wet or saturated farmland. When soils become compacted, future root growth and oxygen supply are limited. Thus, severe flooding can delay or even prevent planting for the entire growing season, causing significant financial loss to farmers.

Loss of soil nutrients

When flooding events occur, such as overwatering your garden or as with the 2019 Midwest flooding, excess water can flush nutrients out of the soil. This happens by water running offsite, leaching into and draining through the ground, or even through the conversion of nutrients from a form that plants can utilize to a gaseous form that is lost from the soil to the atmosphere.