Waterlogging in the coldest months does little damage to dormant pastures. Waterlogged pastures may retain moisture for a longer period through spring. However, the extra growth that occurs may be at the expense of more valuable growth in winter and early spring. Deep roots are killed, so the plant takes up less water and nutrients. Leaching and denitrification cause nitrogen deficiency, which is seen as a yellowing of the older leaves.
Nitrogen deficiency increases plant stress.
Weeds and disease, particularly root rots, increase under these conditions. Nitrogen fixation by pasture legumes is also severely reduced. Even small amounts of salt will kill plants if the soil is waterlogged. Waterlogging reduces pasture growth in duplex soils that have a clayey subsoil within 50 cm of the soil surface. The water lies on top of the subsoil and kills the deep roots.