Previous PageTable Of ContentsNext Page

Study of some factors affecting carrot taproot size uniformity

A.J. Gracie and P.H. Brown

Tasmanian Institute of Agricultural Research, GPO Box 252-54, Hobart, TAS.


Though carrot crops in Tasmania are high yielding it is not uncommon for packout to be low (e.g. approximately 60%) for fresh market carrots. One of the major causes of low packouts in carrot crops in Tasmania is lack of size uniformity, that is, carrots failing to meet the stringent premium market size range. This study found that seed quality in terms of uniformity of embryo size has a large influence on uniformity of seedling establishment, and is directly correlated with uniformity of carrot size 40 days after sowing. Between seedling establishment and harvest, competition appears to be the main factor influencing uniformity of taproot size. While evenness of spacing of the carrot seedlings at establishment did not influence the %CV of taproot sizes at harvest it did affect other important shape characteristics for marketing. With increasing stand density there was an increase in %CV of taproot size and a decrease in mean taproot size at harvest.

Key Words

Carrot, Daucus carota, taproot, uniformity, %CV.


A large proportion of carrot taproots produced in Tasmanian crops fall outside the stringent size requirements of Japanese markets. An increase in the proportion of carrots within the premium size range would substantially increase profit margins to both exporting companies and growers. This paper reports trials assessing the effects of seed quality, plant density and evenness of spacing on carrot taproot uniformity at harvest.

Materials and Methods

Trials were conducted on ferrosol soils near Devonport on the north west coast of Tasmania. The carrot cultivar Koyo 2 was planted on beds 1.2 metres wide in 3 double rows using a Stanhay precision air seeder.

The effect of seed quality was examined by grading a commercial seed lot on the basis of size and density and the resultant seed lots characterised using International Seed Testing Association (ISTA) procedures (1). Embryo size was assessed using the methodology of Gray (3). Carrots were harvested in all trials during the establishment phase (approx. 40 days after planting) and at commercial harvest (approx. 120 days after planting). Embryo length was a measure of embryo size, seedling weight was a measure seedling size and taproot weight was a measure of taproot size at harvest. Size variability was expressed as the coefficient of variation (CV).


The results for three graded seedlots, designated high, medium and low embryo size variability (2) were tested. Reduced embryo size variability resulted in a more uniform crop at the seedling establishment (40 days after sowing) stage of development but had less effect on uniformity at harvest (Figure 1a).

Since seed grading influenced seedling size variability, but had less effect on variability at maturity, it was hypothesised that competition between plants after establishment has a greater impact on uniformity at harvest than variability of crop establishment. While sowing density did not influence the total yield of taproots it did effect the %CV (Figure 1c) and the mean carrot taproot weight (Figure 2). The decrease in weight obtained at higher densities was consistent with the taproots being both shorter in length and having a lower shoulder diameter (Data not shown). A more even intra row spacing did not significantly lower the %CV (Figure 1c) of harvested carrots, but did reduce the proportion of misshapen carrots to zero (Figure 3).


The finding that seed quality in terms of uniformity of embryo sizes is directly correlated with uniformity of seedling sizes at establishment is consistent with previous findings (2). However, uniformity of plant sizes at establishment did not continue through to the entire growth of the crop indicating that competition has a large impact on the final harvest uniformity. This is also evident by plants planted at higher densities have a higher variability at harvest and a lower mean taproot weight. While evenness of intra row spacing did not have a large impact on uniformity of mature taproots, important shape characteristics for marketing were improved.


This work was funded by HRDC and the AusVeg levy. The support of Field Fresh Tasmania, Harvest Moon and Serve-Ag Pty Ltd is also acknowledged.


1. ISTA 1999. Seed science and technology rules. ISTA, Zurich

2. Gray, D. and Steckel, J.R.A. 1986. J. Hort. Sci. 61(1), 71-80.

3. Gray, D. and Steckel, J. R. A. 1983. Ann. Appl. Biol. 103, 327 – 34.

Previous PageTop Of PageNext Page