Abstract:
Four strains of subterranean clover were grown in swards and mown regularly until the beginning of flowering. During the period of flowering and seed development, the swards were irrigated as required to prevent moisture stress. Watering was then continued to keep the burrs and seeds moist for a further 5 months. Depending on the strain, seed yields reached a peak between 74 days and 86 days after the onset of flowering (late August-early September). Then followed a sudden and marked decline in both the amount and number of seeds present in the four strains. By the end of February less than 20% of the seeds produced were still present in the soil. Seed germination accounted for less than 50% of the seed losses. The remainder (unrecovered seed) was presumably lost as a result of attack by pathogenic microorganisms in the soil. The results suggest that it may be difficult to obtain maximum seed yields in swards of subterranean clover. Even a relatively small (3 weeks) decrease or increase in the period for which moisture is available, compared with the optimum, can lead to markedly reduced seed yields.