Soil temperature appears to be more critical than air temperature, when irrigating during mid-summer. Alfalfa was flooded and then allowed to recover before yields were measured. Alfalfa yields after 3 weeks of recovery from flooding showed that while top growth may have been normal for some time during the flooding treatment, the plants were nevertheless being damaged by the flooding from the beginning. All flooded plants at all temperatures showed yield loss compared to non-flooded plants at 3 weeks after drainage. Alfalfa growth rate 3 weeks after flooding, compared to growth rate of unflooded plants at the same temperature.
All values are a percentage of unflooded plant growth.
Flooding did not appear to kill the alfalfa directly. However, flooding did reduce plant vigor so as to make the plants susceptible to other disturbances. This is approximately the first day of yellowing of plant leaves during flooding. Leaf yellowing which appears while the plant is still flooded is indicative of eventual stand loss. Several things can be done to minimize the potential damage caused by long duration flooding.