Growth of subterranean clover when subirrigated from water tables at different depths

Abstract

Subterranean clover plants were grown in a glasshouse with sub-irrigation from water tables maintained at depths of 0.30 m, 0.60 m, and 0.90 m. The depth of water table had little effect on the weights of the above-ground parts; there was a non-significant trend towards greater weights with deeper water tables. However, there were striking effects of treatment on root growth. Active root extension occurred while soil moisture content of the soil was between about 25 and 15%. With the deeper water tables, the zones of active root growth moved downwards as the soils dried out, i.e. out of the zones where, through increasing plant intake of water, demand exceeded supply from the water table. By the third harvest (about flowering time of the clover plants) the greatest root density with all treatments was between 0.20 m and 0.30 m above the water table. For the soil type used, this was apparently the height above the water table at which plant intake and upward movement of water from the water table were in equilibrium.