The response of lucerne cultivars to levels of waterlogging

Abstract

Five lucerne cultivars were grown for 10 weeks during summer at two irrigation frequencies, specified by evaporation intervals of 38 and 76 mm. Changes in soil moisture were monitored by tensiometers installed at 15 and 30 cm depths. At the first harvest no significant difference in yield was found between treatments. At the second harvest, regrowth of all cultivars was depressed by frequent irrigation, but Du Puits was particularly affected. The yield depression caused by frequent irrigation continued for six months after the treatment ended. The reduced growth following frequent irrigation was related to low soil aeration. In this treatment air-filled pore space in the 15-30 cm horizon remained at or below 15 per cent, a critical level for plant growth. A period of waterlogging for 10 days when the temperature at 5 cm depth remained at approximately 30¦C led to reduced production and high mortality in all cultivars. Yields of Lahontan and Siro Peruvian at the end of the waterlogging period were significantly higher than yields of the other three cultivars. The possibility is suggested of increasing the tolerance of lucerne to poor aeration by natural selection on wet soils.