Soil oxygen and the growth of white clover

Abstract

Abstract The response of mature plants of white clover to different levels of oxygen in the soil was tested in four pot trials. Gas mixtures containing various proportions of air and nitrogen were flushed continuously through the pores of the soil in which the plants grew. Depressions of shoot growth attributable to oxygen deficiency occurred only where the mean flux of oxygen to platinum electrodes inserted in the root zone was less than 1.0×10-7 g cm-2 min-1 for all or part of the treatment period. Where the mean flux was 1.5×10-7 g cm-2 min-1, growth did not differ significantly from the growth at higher levels of soil oxygen. These figures are similar to the flux of oxygen required for optimum growth of ryegrass, and lower than the flux required for crop plants. The mechanism by which the growth of clover was reduced appeared to be one of root functioning rather than of limitation to root extension, as the reductions of root growth were smaller than those of shoot growth and were not significant.