Seed And Seedling Survival In Flooded Conditions
Seeds and seedlings, regardless of crop type, are living organisms and need oxygen to live and within 48 hours of being oxygen-deprived (estimate), chances of survival are limited.
If there is oxygen in the soil and early flooding doesn't kill plants outright, it may still have long term negative impacts on crop performance. For example, excess moisture in early crop stages reduce early root development, which reduces the ability of the plant to access subsoil water if summer weather turns hot/dry.
After the water is gone, plants can be assessed by examining the color of the growing point of the seedlings (if present). The stem germinating out of the seed (radicle and coleoptile) should appear white or cream coloured. If no germination has occurred, seeds can be cut in half to determine if turgor pressure is still present. If the seed is extremely soft and does not hold form, it probably won't survive. Surviving plants will resume growth within three to five days after the water recedes.
Response Of Crop Type, Development Stage To Flooding Duration
Sensitivity and injury will depend on crop species, plant stage, duration of flooding and the air/soil temperatures. If temperatures are cool during flooding, survival could be better as plants are growing slower and don't need as much oxygen, but plants are at a higher risk for disease development for pathogens that thrive in cool/wet conditions. To combat excess water and disease, drainage within one to two days will increase the chances of survival.
Most annual crops can withstand 24 to 48 hours in waterlogged conditions and up to 7 days. In general, grasses are more tolerant than legumes. In cereal crops, oats are the most tolerant, then wheat, and then barley. In legumes; faba beans, followed by soybeans are most tolerant with field beans and peas considerably less tolerant.
Management After Flooding Completed
Careful assessment of damage needs to occur before replanting. Rotted seed or damped-off seedlings will reveal probable crop losses. Evaluate plant population and uniformity and weigh out what the crop stand left will potentially yield vs. a replanted crop at this later date.
An additional nitrogen application may be necessary in fields that show signs of yellowing or uneven growth. A late test for nitrate can determine if more nitrogen is needed.
Maintain a good weed control program so that crop plants are not robbed of nutrients and moisture later in the season.
