Recent rainfall has resulted in localized flooding of low-lying areas. The length of time grain crops are underwater affects the extent of the damage. Oxygen is essential for plant growth. Generally, oxygen is
entirely depleted in soils that are flooded for more than 24 hours.
When fields are covered with water, whether it is from floodwater or standing water in low spots, waterlogged soils lead to oxygen-deprived plants. Oxygen is needed by the plant for respiration. Respiration releases energy from sugars which are used for growth. If adequate oxygen is not available, the plant cannot grow. After extended periods of time without adequate oxygen, plant tissue death occurs.
The damage from floodwater is dependent upon several factors. The temperature of the water, the movement of the water and the duration of the flooding, all combine to determine the extent of the damage. At higher temperatures, respiration is faster and the available oxygen is used up more quickly. Faster moving water is more turbulent, which results in slightly higher levels of oxygen in the water. Many of the effects of oxygen deprivation are reversible if the duration is not too long. Generally, 36 to 48 hours is the length of time grain crops can tolerate flooding.
When deciding if a stand is salvageable, see the University of Missouri Guide G4091, Corn and Soybean Replant Decisions. This guide provides information about assessing the existing stand and determining if it is adequate given the cost of replanting and the reduction of yield due to planting at a later date.
For more information contact Valerie Tate, field specialist in agronomy for University of Missouri Extension in Linn County by e-mail at firstname.lastname@example.org or call at 660-895-5123. University of Missouri Extension programs are open to all.