The influence of seed type and plant density on variation in plant size of red beet (Beta vulgaris L.) crops

Abstract

SUMMARYIn each of three experiments, five seed lots, representing multigerm, monogerm, open pollinated and hybrid types, were grown at three plant densities and the time of seedling emergence, uniformity of within-row spacing, the weight of individual shoots and roots at four occasions were recorded.Seedling emergence was more rapid in a May-sown experiment than in a March-sown experiment. The monogerm seed lot had a lower standard deviation of emergence time in the May-sown experiment and in all experiments had a more uniform within-row spacing than the other seed lots, but there was no consistent relationship between these two attributes and uniformity of root weight.The mean weight of shoots and roots increased rapidly until 600 day °C above 6 had accumulated. The yield of shoots then remained constant at about 30 t/ha at 47 plants/ m2 and at about 40 t/ha at 188 plants/m2. The weight of roots increased throughout the experiments and yields of over 100 t/ha were achieved. The monogerm seed lot gave a ceiling shoot yield about 20% less than that of the other seed lots, whereas there were no large or consistent differences in root yield between the different seed lots. Shoot yield increased with plant density, especially at very early harvests, whereas root yield showed a variable response to density. At early harvests in all experiments, root yield increased with increasing density; at late harvests in one experiment, yield de-creased with density, but in another there was no marked response to density.Coefficient of variation (c.v.) of root weight was only about 30% in young unthickened roots, but in older thickened roots was between 70 and 117% at 47 plants/m2, and in-creased to over 180% at 188 plants/m2. The c.v. of root weight of the monogerm seed lot was approximately 20% less than that of the other seed lots.In a fourth experiment, plots were thinned to leave within each row either a uniform or a clumped distribution of seedlings of either uniform or variable size. Uniformity of spacing had no effect on variation in root weight 126 days after sowing, but selecting for seedlings of uniform size reduced the c.v. of root weight by approximately 20%.