Effects of saturated soils on recently planted corn and soybeans


Tony Nye - OSU Extension



The recent rain sure put a stop to planting progress. In parts of Clinton County, farmers are reporting 60 to 70 percent complete with planting progress while others are still to plant the first seed, with many more somewhere in between these scenarios. Certainly there is still time to get crops planted and have very productive yields.

We proved that in 2019, planting well into June last year. Let’s hope we don’t have to repeat that again this year.

Rain totals in the area ranged from almost two inches to well over three inches. With the status of our planting/growing season, to what extent should we be concerned with the recent excessive rainfall?

The extent to which ponding injures corn is determined by several factors including: plant stage of development when ponding occurs; duration of ponding; and air/soil temperatures.

Prior to the 6-leaf collar stage (as measured by visible leaf collars) or when the growing point is at or below the soil surface, corn can usually survive only 2 to 4 days of flooded conditions. Since most corn is well below the V3 or V4 stage, it’s vulnerable to damage from ponding and saturated soil conditions.

The oxygen supply in the soil is depleted after about 48 hours in a flooded soil. Without oxygen, the plant cannot perform critical life sustaining functions; e.g. nutrient and water uptake is impaired, root growth is inhibited, etc.

If temperatures are warm during ponding (greater than 77 degrees F) plants may not survive 24 hours. Cooler temperatures prolong survival so the moderate temperatures we have had this week should be beneficial.

Once the growing point is above the water level the likelihood for survival improves greatly.

Even if ponding doesn’t kill plants outright, it may have a long term negative impact on crop performance. Excess moisture during the early vegetative stages retards corn root development.

As a result, plants may be subject to greater injury during a dry summer because root systems are not sufficiently developed to access available subsoil water. Ponding can also result in losses of nitrogen through denitrification and leaching.

Even if water drains quickly, there is the possibility of surface crusts forming as the soil dries that can impact the emergence of recently planted crops. Growers should be prepared to rotary hoe to break up the crust to promote emergence.

For soybeans, there is less information about how flooding affects the germination of recently planted soybean seed. A 2001 journal article, “Flooding and temperature effects on soybean germination,” by Wuebker et al. is a commonly cited reference on this topic.

Research suggests that overall, flooding adversely affected germination more severely at 59F than at 77F. This was true regardless of the duration of the flooding. They also showed that damage was reduced by warmer soil temperatures when the flooding occurred one to two days after imbibition (seed swell or 12 hours after planting).

At 59F, flooded conditions lasting for only 1 hour reduced germination rates by 22%.

Research also suggests that when seed was flooded one day after imbibition, the duration of the flooding had less effect on germination than when the flooding occurred two to three days after imbibition.

Germination was reduced by 33% when flooding occurred after two days and lasted for 48 hours and by 43% when flooding occurred after three days and lasted for 48 hours.

Disease problems that become greater risks due to ponding and cool temperatures include pythium, corn smut, and crazy top in corn. In soybean, pythium and phytophthora are favored by wet conditions.

Fungicide seed treatments will help reduce stand loss, but the duration of protection is limited to about two weeks. The fungus that causes crazy top depends on saturated soil conditions to infect corn seedlings.

There is limited hybrid resistance to these diseases and predicting damage from corn smut and crazy top is difficult until later in the growing season. However the economic impact of these latter two diseases is usually negligible.

Even if ponding doesn’t kill plants outright, it may have a long term negative impact on crop performance. Excess moisture during the early vegetative stages retards corn and soybean root development.

As a result, plants may be subject to greater injury during a dry summer because root systems are not sufficiently developed to access available subsoil water.

For corn and soybean 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.

For corn and soybean not yet emerged, evaluate the appearance and integrity of seeds or seedlings that have yet to emerge (likely rotting if discolored and softening). Look for new leaf growth 3 to 5 days after water drains from the field.

Final Rule

Finally this week, the Ohio State University Farm Office team has digested the Final Rule issued on May 19 for the Coronavirus Food Assistance Program (CFAP) Direct Support to Farmers and Ranchers program. You can read a very helpful news bulletin that is posted at https://farmoffice.osu.edu/ .

This Bulletin will be provide helpful details on producer eligibility, eligible commodities, payment limitations, application and timeline, and payment calculations.

OSU Extension and Ohio FSA will conduct a webinar in the upcoming days to outline program materials and answer questions.

For information about the webinar and additional information on CFAP, please visit farmoffice.osu.edu. Information provided on the program by USDA along with a webinar for new FSA program participants is available at https://www.farmers.gov/cfap .

Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for over 30 years, currently serving Clinton County and the Miami Valley EERA.

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Tony Nye

OSU Extension