CONTROL OF MEAN ROOT WEIGHT IN CARROTS (DAUCUS-CAROTA) BY VARYING WITHIN-ROW AND BETWEEN-ROW SPACING

Results are reported from four carrot experiments (1987/88) to measure edge effects in crops of different ages grown in beds. A wide range of cultivars, densities and contrasting row-spacing systems was used to determine how effectively these edge effects could be eliminated by increasing the seeding rate in the outer rows relative to that in the inner ones. Edge effects were first significant between 50 and 100 days after sowing. Where each row was sown with the same quantity of seed, carrots in the outer rows were 1.5 to 2.0 times heavier than those in the inner rows. Increasing the seeding rate in the outer rows to between 1.5 to 3.0 times that in the inner rows, whilst holding the overall density constant, resulted in equal mean root weight in all rows. There was no evidence of alternate large and small plants in successive rows across the bed, as has been suggested in the literature. A previously published spacing model gave large systematic deviations when fitted to these data, but this was rectified by a simple modification to the model, which did not entail the incorporation of more parameters.