Considerations for flooded corn and soybean
The rate of field drying after a flooding event also plays a large role in soybean survival (Sullivan et al, 2001). Also, researchers have found yield reductions to be much greater on flooded clay soils than on silt loam soils when flooded for the same period of time (Scott et al, 1989). At the V4 stage, these researchers reported yield losses of 1.8 bu/ac per day of flooding on a clay soil and 0.8 bu/ac per day on a silt loam soil. The effects of flooding are even more detrimental during the reproductive phases of development. For example, flooding at the R1 stage caused yield losses of 2.3 and 1.5 bu/ac per day on clay and silt loam soils, respectively. Even larger yield losses would be expected in soybeans at the R3 to R5 stages.
Some of the main indirect effects of flooding on soybean yields are: 1) root diseases, 2) N deficiency, 3) and other plant nutrient imbalances. Caring for recuperating soybean stands should focus on reducing crop stresses where possible. For example, cultivation should be considered to increase soil aeration and herbicide stress should be minimized or postponed where possible.
Flooded and wet soil conditions increase risk of corn and soybean seedling diseases
Seedling diseases of soybean and corn may be significant problems in many fields. Favorable conditions for seedling diseases include wet and compacted soils, slow plant emergence and growth, crusted soil, and poor seed quality. Seedling diseases can reduce plant and root growth, plant population, and ultimately yield. Non-lethal infection at the seedling stage may cause damage that persists through the growing season. The soilborne pathogens that cause these problems are widespread and persistent in Minnesota fields, and can cause damage when conditions develop that favor them. Several different pathogens and diseases can be problems. Wet and flooded soils are especially favorable for the soilborne, moisture-loving pathogens Pythium and Phytophthora. Pythium appears to cause most damage to seedlings of soybean or corn, and Phytophthora can damage soybean seedlings or start infections in the early summer that may develop and kill soybean plants later in the summer. For more information on soybean and corn diseases, please refer to the Minnesota Crop News article, Soybean and corn seedling diseases increase with flooded and wet soil conditions or visit the Minnesota Crop Diseases web site (http://www.extension.umn.edu/agriculture/crop-diseases/).
Ritchie, S.W., J.J. Hanway, and G.O. Benson. 1997. How a corn plant develops. Iowa State Univ. Coop Ext. Serv. Spec. Rep. 48. Iowa State Univ., Ames.
Scott, H.D., J. DeAngulo, M.B. Daniels, L.S. Wood. 1989. Flood duration effects on soybean growth and yield. Agron J. 81:631-636.
Sullivan, M., T VanTooai, N. Fausey, J. Beuerlein, J. Parkinson, A. Soboyejo. 2001. Evaluating on-farm flooding impacts on soybean. Crop Sci. 41:93-100.
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