Fluid drilling of pregerminated carrot seed

The effects of a fluid drill system on the emergence, yield and color of three carrot (Daucus carota L.) cultivars were studied for two years (1981-1982) at Knoxville, TN. A gel of 1.5% Laponite was used as the seed carrier for dry seed and pregerminated seed, which were compared with a treatment of dry, hand-sown seed. Also studied was the effectiveness of a seed separation procedure based on specific gravity differences among seeds within a lot. This involved separating germinated from ungerminated seed in a seedlot which had been pregerminated until an average radicle length of 3.0 mm was obtained. Fluid drilling of pregerminated carrot seed decreased the time to 50% emergence the first year of the study. In the second year, the more adverse year climatologically for carrot emergence, fluid drilling of both dry and pregerminated seed decreased the time to 50% emergence compared to dry, hand-sown seed. The spread of emergence was no different either year among the seed treatments or among the three cultivars evaluated. In the first year, the cultivar 'Gold King' responded with the shortest time to 50% emergence and "Danvers 126' took, the longest time. In the second year there was no difference in time to 50% emergence among cultivars. Carrots were harvested three times each year to compare the growth duration with subsequent yields of marketable roots. After 90 days in 1981, the pregerminated seed produced the heaviest roots with the largest shoulder diameters, although by the 120- and 150-day harvests there was no difference between the ungerminated and pregerminated seeds of the two fluid-drilled treatments. The pregerminated seed treatment produced the least number of marketable roots at each harvest in 1981. In 1982, the number of marketable roots at each harvest was least for the dry, hand-sown seed. Variation between the two years was possibly attributable to different plant populations and different climatic conditions. Carrot root color, as measured on a Hunter Color/Difference Meter D25-2 and expressed by the Hunter a/b ratio, was not affected by any seed treatment. Carrot color was dependent upon the cultivar, with roots of 'Camden R80' attaining the most intense orange color, represented by a Hunter a/b ratio of greater than one. The seed separation technique utilizing a Maltrin 250 solution with a specific gravity of 1.110 was effective in separating the seed by showing differences between the top and bottom fractions. Seed from the top fraction demonstrated the greatest percentage, rate and uniformity of emergence. However, to be of practical importance, the top fraction of seed should have consisted of a greater proportion of germinated seed than was shown in this study.