By John Brien, CCA, AgriGold Hybrids, Eastern Regional Agronomist
Unevenness is the best description for all corn fields in the Eastern Corn Belt. Driving up and down the road uneven corn fields can easily be spotted. Some corn fields are yellow, stunted and uneven, while other corn fields are green, knee high and still uneven.
The unevenness in all the corn fields has been caused by the difference in rooting environments. The current corn crops rooting environment has been affected by planting date, planting conditions, soil types and most severely the amount of rainfall since planting started. The difference between rooting environments can easily be seen by plant height and plant color. Good rooting environments produce green, fast growing corn plants, while poor rooting environments produce stunted, yellow and slow growing corn plants.
What is the difference in the rooting environment that has caused the huge unevenness in corn fields? The difference between rooting environments is the amount of oxygen present in the root zone. Corn plants are oxygen dependant organisms and when oxygen is limited, corn growth is limited. Therefore much of the poor rooting environment is due to a lack of oxygen in the soil. With the over abundance of rainfall keeping the soil moist or saturated, oxygen has been driven out or used up in the soil and has not been able to be replaced. A prime example demonstrating differences in oxygen levels are tile lines. In many fields the tile lines are green, lush and fast growing, while in between the tile lines the corn in short, stunted and yellow. The tile has drained the water and has allowed oxygen to be put back into the soil, while between the tile lines soils are depleted of oxygen.
The lack of oxygen in the soil can lead to several severe problems:
1. A reduction in root growth. Roots cannot grow where there is no oxygen. Wet, oxygen depleted soils have shallow root systems that are stunted. With the smaller root systems plants cannot pull in the nutrients that a growing corn plant needs.
2. A wet or saturated soil can also cause a decrease in soil temperature, thus further reducing root growth.
3. A low oxygen environment increases undesirable microbial growth which can cause the formation of sulfides and butyric acid that are toxic to plants. Add a small root mass surrounded by toxins and the corn plant can be severely stressed.
4. Increases the potential for root diseases. The main disease that is affecting the current corn crop is seedling blights. Seedling blights can kill small corn plants by killing the seedling roots. Seedling blights can also stunt corn plants by injuring the root system and causing the plant to be delayed and ultimately stunted.
The unevenness in corn fields can easily be blamed solely on too much water, but in reality the real damage is caused by a lack of oxygen in the soil. Many corn fields will have a difficult road ahead of them due to the early stress placed upon them. The end results will depend on the amount of stress the corn plant is exposed to from today forward. Due to limited root growth, the corn plant may not be able to thrive in stressful conditions. Harvest will inevitably show UNEVENESS as well, therefore remembering where and why the corn field was under stress early will help explain the yield unevenness in the fall.
Source: Irmak, Suat & Rathje, William. “Plant Growth and Yield as Affected by Wet Soil Conditions Due to Flooding or Over-Irrigation. December 2008.