Cessation of storage root growth of carrot in autumn

SummaryOptimization of the timing of harvest requires information on effects of harvest time on the quantity and quality of yield. The relation of calendar and thermal times to the increase of fresh- and dry-matter yield of carrot storage roots was studied at an experimental site and on farms for two years. Usually cessation of yield increase occurred at the beginning of October, regardless of the yield level. Gradual senescence of the foliage and frost injuries in 1996 did not prohibit the increase of fresh yield, but frost injuries and dry soil interfered with dry-matter accumulation. The cessation of fresh- and dry-yield increase could be explained by thermal time in uninjured carrot stands. Comparison of different base temperatures (Tb:0,1,3,58C) for calculating temperature sums revealed that low values of Tb often produced the best fit and the most consistent slope values in the regression models. Hence it is suggested that the low temperature limit for carrot root growth is lower than 58C. Slight di...