The relative importance of some different sources of plant-weight variation in drilled and transplanted leeks

Abstract

SummaryIn six experiments the effects of various factors on plant-weight variation (sum of squares of deviation from the mean shoot weight) at harvest were examined. These factors were seed size, sowing depth, time of seedling emergence, size at different stages of development, within-row spacing, density and row position within a bed.In a drilled experiment, up to 25% of the variation in mature leek size could be attributed to variation in time of seedling emergence. Similarly, in the experiments which used transplants, 15% of the variation in the mature crop could be associated with variation in size shortly after seedling emergence from peat blocks.Variation in row position within a 4-row bed never accounted for more than 11% of the weight variation at harvest, and variation in within-row spacing never accounted for more than 4% of weight variation. However, the coefficient of variation (c.v.) of leeks growing at 22 plants/m2 was 44% whereas the c.v. of those growing at 50 plants/m2 was 61%.Using large seeds or sowing deeply gave a quicker emergence and a higher percentage emergence than using small seeds or sowing shallowly. However, these factors each never accounted for more than 7% of the weight variation in mature leeks.Most of the plant-weight variation could not be attributed to any of the measured factors in any of the experiments. The c.v. of leeks which had emerged on a specific day and had been grown in a uniform environment, was between 50 and 66%, which was similar to the c.v.s observed in the transplant and drilled experiments. However, selecting for large transplants reduced the c.v. to 28% in one experiment; this effect was only partly attributable to the greater mean plant size resulting from this treatment.