Influence of the stolonkoil surface interface and plant morphology on the survival of white clover during severe drought

Abstract

Field observations indicate that conditions at the stolen/soil surface interface are important for the survival of white clover (Trifolium repens) during drought. Mini-swards of clonal material of two contrasting white clover cultivars (Grasslands Tahora, small-leaved, densely branched; Dusi, large-leaved, tap-rooted) were established in boxes (300 x 420 x 290 mm deep) for 6 months, then subjected to a 6-week drought. Stolen/soil surface conditions were modified to have stolons either, 1) fully exposed, 2) shaded, or 3) buried. Numbers and, characteristics of surviving plants were measured. The major effect was on the number of plants surviving. More plants survived under shading (55%) than burial (25%) and full exposure (17%). Numbers of plants surviving drought was related to pre-drought plant density, hence Tahora had higher plant survival than Dusi, particularly when fully exposed. Although initially Dusi plants were 25 times heavier, with 5 times the number of stolons and roots of Tahora, surviving plants of both cultivars were small and similar in dry weight, although Tahora had higher numbers of growing points and roots thanDusi. The tap-rooted character of Dusi did not. confer any advantage during drought. It was concluded that the main factor influencing drought survival of white clover appears to be grazing management. Systems that can produce dense white clover populations and maintain high pasture density (grass) capable of providing shelter from direct solar radiation during drought stress, are superior. Keywords: drought survival, plant density, plant morphology, stolon burial, stolon shading, Trifolium repens