In addition, air temperature and temperature of the irrigation water appear to significantly affect alfalfa stand longevity. Several studies have compared the growth of roots and forage of alfalfa flood irrigated for various lengths of time and at different temperatures. This three week wait and cut period would be similar to irrigating three weeks before harvesting the alfalfa. High water tables which accompany spring thaws and exceptionally heavy rains can inhibit alfalfa growth. Wet soil conditions can reduce stand vigor and promote fungal root infection.
Periodic inundation can create short-term flooded conditions which inhibit growth.
These reduced yields are the result of direct interference with normal plant physiological processes. Soil temperature appears to be more critical than air temperature, when irrigating during mid-summer. Irrigators should avoid prolonged flooding of irrigated alfalfa, when the temperature of the irrigation water is high. There are two reasons for this. First, colder water will hold more dissolved oxygen and the cool air temperatures will keep the alfalfa demand for oxygen relatively low.