Recent Rain Creates Stress on Crops

Recent intense rainfall events have caused flooding, ponding, and soil saturation in many of our corn
and hay fields. What are the prospects for these crops?

Corn Fields

Corn plants can turn pale green to yellow because they have not been able to absorb enough nitrogen.

Corn plants can turn pale green to yellow because they have not been able to absorb enough nitrogen.

Beautiful and dry spring weather allowed most folks to get corn planted in a timely fashion. We’ve seen corn around the state that is just about knee high and ready for nitrogen topdress! The recent rain, however, has caused some fields to become flooded, ponded or saturated with water. Flooded or ponded soil can create risks for corn. Soil oxygen becomes depleted after about 48 hours of soil saturation. Without oxygen, corn cannot perform critical life functions (i.e. nutrient uptake, root growth inhibited). Corn that is at the 5th leaf stage and younger still has its growing point below ground and it is directly subject to the stress of oxygen depleted conditions. The likelihood of crop injury is less where the flooded and ponded conditions last less than 24 hours. To confirm plant survival, check the color of the growing point and look for new leaf growth 4 to 7 days (with 70 degree weather) after the water drains from the field. Healthy growing points will be firm and yellowish white, not mushy and discolored.

Even if ponding and saturated soil do not kill the plant outright, it can have a negative impact on the crop performance. Excess moisture can retard root growth and plants may become more susceptible to drought stress later in life. Saturated soils can also result in significant losses of nitrogen through denitrification and also leaching. A pre-sidedress nitrate test taken just prior to nitrogen topdress can help you understand how much additional nitrogen will be needed to growth a high yielding corn crop.

Hay and Pasture Fields

Forage plants (other than perhaps wet site-tolerant reed canary grass) can survive for several weeks in saturated soils, but the lack of oxygen in the root zone will adversely affect their growth. These plants do not take up soil nutrients normally, an increasing part of the root system deteriorates, and legumes cease “fixing” nitrogen. They appear stunted and yellowish-green in color. If the soils drain quickly, plants begin to recover.

Flooded forages may contain fine silt, fungus spores, bacteria that are bad for you and your animal’s health. Forage that has been flooded with silt and debris can cause health problems, production problems, and/or reproduction problems in livestock. To be safe, avoid making silage out of it. However, if you do, keep it separate from the rest of your unflooded silage. It may spoil and it could contaminate adjacent silage. If you ensile these flooded crops, you may find that once the silo is opened, they spoil faster than other silage. Generally, you should avoid feeding this material if possible. However, if you haven’t already done it, try to get this standing material off the field as soon as possible to encourage regrowth. If hay fields were flooded, remember to wear a dust mask when harvesting. Grazing animals can be exposed to clostridial organisms that can lead to some serious diseases. The safest approach would be to clip the contaminated pastures and then wait to graze the regrowth. But don’t graze it too closely – avoid letting your livestock get down into the old dead material. Watch your livestock closely. If any of you animals appear sick, call your vet immediately.

If you have any questions, please give our office a call or email cropsoilvt@gmail.com.

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