Alexander Lindsey, Ohio State University Extension
Around the state, there are many corn fields with young plants with standing water due to the intense storms that have passed through. But what are the long-term effects of standing water on emerged corn? Preliminary data from two locations in Ohio in 2017 suggests that as long as a sidedress N application can be made following the waterlogging, yield loss may be minimal if the waterlogged conditions lasted 4 days or less.
Waterlogging can affect yield in two main ways: 1) damage to the plant physiologically, and 2) N loss through denitrification or leaching. The presence of standing water in the field can affect corn yield by inhibiting growth and restricting ear development (which occurs during vegetative stages). Standing water also reduces the amount of oxygen in the soil, which can cause nitrate in the soil to be converted to forms that are unavailable for plant uptake and may be lost to the environment. Trials in Ohio conducted in 2017 suggest that corn can survive waterlogged conditions for 4 days or less in the early vegetative stages (V4-5) with minimal impact on yield if a sidedress application can be made after the soil has dried. However, if a sidedress application cannot be made on corn waterlogged for 4 days or more, a yield penalty of 13 to 45% was observed. When waterlogging extended to 6 days even with a sidedress N application, a reduction in yield of 9-33% was observed compared to corn flooded for 4 days or less. These results are consistent with past research (10-50% yield loss if flooded longer than 2 days), but will be repeated in 2018 for validation.
There are a few ways to evaluate for damage caused by flooding. For corn that’s emerged, check the color of the growing point to assess plant survival after ponding. It should be white to cream colored, while a darkening and/or softening usually precedes plant death. Disease problems that can develop include corn smut, and crazy top, but predicting damage from these is difficult until later in the growing season. However, the economic impact of these latter two diseases is usually negligible. Bacteria deposited in leaf whorls by flooding can also result in disease and kill plants. If plants are covered with mud due to the excess water, photosynthesis may be limited but it’s unlikely that the photosynthetic capacity of leaves has been completely destroyed. A light rain is usually sufficient to rinse the mud off of existing leaves, and new growth should be minimally affected.