Comparative effects of summer and winter conditions on the growth of six species of pasture legumes subjected to various nutrient levels

Abstract

The results of a series of water culture experiments is reported in which the comparative effects of summer or winter conditions respectively on the growth of subterranean clover (Trifolium subterraneum L. var. Dwalganup), red clover (T. pratense L. certified), white clover (T. repens L. 'mother strain' certified), cluster clover (T. glomeratum L.), suckling clover (T. dubium Sibth.), and barrel medio (Medicago tribuloides Desr. strain 173), in a complete nutrient solution and in solutions deficient in either potassium, phosphorus, or magnesium were studied. In the complete nutrient solution, the mean daily increment in dry weight (T+R) for each species was less in winter than in summer. Rates of growth (T+R) of red clover, white clover, cluster clover, and suckling clover were each reduced more by winter as compared with summer conditions than was that of barrel medic, while a similar comparison also showed that white clover and suckling clover were more affected than subterranean clover. For subterranean clover and barrel medic (T+R) differed little as between the summer and winter tests respectively, but (T+R) for red clover, white clover, cluster clover, and suckling clover was significantly depressed under winter conditions. Significant season X species interactions occurred. Differences in seasonal conditions had no effect on the percentage top of five of the species when grown in the complete nutrient solution, but in the sixth species (barrel medic) winter conditions when compared with summer conditions favoured top growth at the expense of root growth (i.e. increased percentage top). Within any species there was no significant seasonal effect on the depression in (T+R) caused by a deficiency of either potassium, phosphorus, or magnesium. Between species certain significant effects were unrelated to seasonal conditions for potassium or phosphorus deficiencies, but with magnesium deficiency significant species x season interactions occurred for (T+R). Within species, the mean effect of potassium deficiency in reducing percentage top in all tests was significant for white clover, barrel medic, and suckling clover, but the season x potassium level interaction was significant for cluster clover only. There were no significant differences between species. Phosphorus deficiency caused a significant reduction in percentage top within all species under both summer and winter conditions, but no significant season x phosphate level interaction occurred. The percentage top of white clover was reduced more than that of subterranean clover in summer, but not in winter. Magnesium deficiency produced a significant reduction in the percentage top of white clover and barrel medic in winter, but not in summer. The season x magnesium level interaction effect was significant for white clover. Several significant species x magnesium level interactions for percentage top were also recorded.