24. YIELD AND QUALITY OF FORCED CHICORY (Chicorium intybus L.) cv. ‘Goriški’
Jože OSVALD, Dragan ŽNIDARČIČ
Agronomy Department, Biotechnical faculty, University of Ljubljana, Slovenia (E-mail: )
Introduction
One of the most important economic uses of chicory is the forcing of its mature root to obtain the etiolated, vegetative apical bud, known as chicon. Forced chicory is an expensive vegetable to grow as it is a two-stage crop. Firstly, the seed is direct-sown in the field to produce suitable parsnip-type roots. These are then dug up and re-grown under special conditions to produce the chicons (Burt, 2001). In Europe chicons were traditionally grown in winter in darkened sand-covered beds at a constant temperature and humidity (Hill, 2000). Chicons can be harvested about three weeks after the forcing is started (Vertreget et al., 1989). Chicons are graded according to their length and firmness. Loose, open heads do not present well on the market and they will not be packed ready (Burt, 2001).
An autochthonous population of chicory (cv. 'Goriški'), has been cultivated for a century in Slovenia (Osvald, 1999). Although the production of this cultivar has had a long tradition in Goriška region, no earlier reports have been found clearly specifying the influence of root size on chicon yields. The aim of the research was to determine weather the root diameter (RD) has an effects on chicon yields as well as on morphological characteristics of chicons.
Materials and methods
The experiment was conducted at the Experimental Station of the Biotehnical Faculty in Ljubljana. Pre-plant herbicide and fertilizer applications consisted of the following: the herbicide Kerb 50-WP at 3 kg ha-1 was applied in end-June. At the same time, 350 kg ha-1 of 15-15-15 fertilizer was applied, whereas 80 kg ha-1 of N was applied twice during growing season. The field was prepared for sowing using a rotary harrow.
Chicory seeds , cv. 'Goriški' were sown on 15 July, 1999 and 1 July 2000 in a heavy clay loam soil, using a pneumatic seed-drill. Seeds were planted approximately 1 cm deep. Plants were thinned to a density of nearly 65.000 plants ha-1 in rows 0.6 m apart. Weeds were controlled by hoeing as required.
Plants were dug up by hand-fork on 18 November, 1999 and 27 November, 2000. After harvest, the undercut roots were left to wilt on the field for 5 days according to the traditional method. Before the roots were placed for forcing the leaves were cut about 2 cm above the root crown. The roots were trimmed to the length of 15 cm and sorted by diameter into four groups: 10, 20, 30 and 40 mm. The roots were placed in upright position on a few centimetres of sand in chicory-forcing boxes. These boxes were of metal construction, 0.15 m deep with dimensions of 2.5 x 1.2 m and covered with a black plastic sheet. The boxes were arranged in a glasshouse with one box per plot and one plot of each treatment randomised in each of four blocks. Air temperature was maintained at 10 oC during the first forcing period and was gradually increased to 15 oC during the second period. After 28 days chicons were harvested.
Samples of 30 plants were taken from each plot to determine the most important yield parameters.
Analyses of variance were performed for each plant characteristic. Character means were evaluated by least significant differences (LSD, P ≥ 0.05).
Results and discussion
Table 1: Effect of RD on chicon yields (1999-2000 mean)
Root diameter (mm) / Total weight of yield/chicon (g) / Net weight of yield/chicon (g) / Discarded yield(%) / Root productivity
10 / 6.33 / a / 4.20 / a / 33.7 / a / 0.50 / a
20 / 39.03 / b / 27.80 / b / 28.8 / b / 0.83 / d
30 / 74.01 / c / 46.60 / c / 37.1 / c / 0.69 / c
40 / 106.61 / d / 72.57 / d / 32.0 / ad / 0.59 / b
Means / 56.49 / 37.79 / 33.2 / 0.65
Means followed by the same letter are not significantly different at P ≥ 0.05.
RD had a rather strong affect on chicon yields. In general, chicon yields increased in proportion to RD. Significant differences among RD were shown in the total weight. An increase in the total weight of chicons depended on an increase in RD. The data concerning the net production were more important. Also as far as chicon weight is concerned a very significant difference exists between the RD. The differences established the range from 4.20 g (10 mm RD) to 72.57 g (40 mm RD).
The percentage of the discarded yield was determined after the chicons were cleaned and it amounted to 28.8 and 37.1. No consistent influence of RD on the amount of discarded yield could be observed. The higest rates were obtained at the RD of 30 mm.
An important efficiency index of chicory forcing is the productivity, which is determined by the ratio of the net head to root weight (Babik, 1998). Babik (2000) showed that the productivity of forced chicory was significantly connected with the weight of roots, and was inversely proportional to the root weight. Almost identical relation was recognised with RD in our trials. Root productivity was in significantly inverse proportion to increasing RD, only plants which had reached a minimum RD size, showed a tendency to minimum productivity.
Table 2: Effect of RD on morphological characteristics of chicon (1999-2000 mean)
Root diameter (mm) / Chiconheight (mm) / Chicon diameter
(mm) / Number of leaves in the chicon / Width of leaves in the chicon (mm)
10 / 105.16 / a / 45.22 / a / 6.63 / a / 9.62 / a
20 / 132.20 / b / 72.31 / b / 11.68 / b / 9.58 / a
30 / 156.68 / c / 93.50 / c / 14.48 / c / 10.34 / a
40 / 162.79 / cd / 103.90 / d / 17.17 / d / 10.86 / a
Means / 139.20 / 78.73 / 12.49 / 10.10
Means followed by the same letter are not significantly different at P ≥ 0.05.
A special aspect of the production of forced chicory is head uniformity (Babik, 1998). The ability to grow leaves during forcing does not mean the ability to form high quality heads (Babik, 1996). Especially the height of the chicon should neither be too great nor too small in order to obtain good quality chicons (Lips et al. 1989). RD had a rather strong influence on chicon morphological characteristics. Generally, the results showed that an increase in RD meant an increase in chicon sizes (Table 2). The only exception was the average width of chicon leaves, which did not vary according to the RD.
Conclusion
Most parameters considered in this experiment were significantly influenced by root diameter. The response to RD were almost generally linear for the most important yield parameters measured:
- Total weight, as well as net weight of chicon were gradually increased in proportion to RD.
- Discarded yields varied independently of RD.
- Root productivity decreased in proportion to RD, except at minimum RD size.
The morphological features of chicons (chicon height, chicon diameter and number of leaves) were improved with RD. The exception was the leaf width, which was not directly influenced by RD.
As mentioned before, to obtain the maximum chicon production the roots 40 mm in diameters are optimal. Generally, our studies have shown that the plants which had the greatest RD, also had the highest yields of good quality chicons.
Literature
Babik, J. (1998): The influence of root size and water temperature during forcing on growth of witlof chicory (Chicorium intybus L var. Foliosum).- Vegetable Crops Research Bulletin, 49: 35-40.
Babik, J. (2000): Estimating optimum root weight of witloof chicory (Chicorium intybus L var. Foliosum) in hydroponic forcing, as affected by oxigen contents and fertilizers applied.- Vegetable Crops Research Bulletin, 53: 5-16.
Babik, J. (1996): Effects of harvest time, storage conditions and largeness of roots of chicory witlof for their usefulness to forcing.- Dr. Thesis, Instytut Warzywnictwa, Skierniewice, Poland, 112 p.
Burt, J. (2001): Growing witlof chicory.- Farmnote 83,99: 1-3.
Hill, D., E. (2000): Yield and quality of witloof chicory (Belgian Endivie) grown using weighted insulation.- The Connecticut Agricultural Experiment Station, New Haven, Bulletin 967: 1-8.
Lips, J., Cappelle, W. and Moermans, R. (1989): Pre –cooling or an artificial stimulation of the maturation process of witloof-roots (Chicorium intybus L.) for early forcing.- International Symposium on Postharvest Handling of Fruit and Vegetables. Acta Horticulturea, 258: 31-36.
Osvald, J. (1999): Chicory variability (Chicorium intybus L.) var. Goriški.- Research Reports, Biotehnical Faculty, University of Ljubljana, 73, 195-200.
Vertreget, N., Van Kruistum, G. (1989): Redistribution of dry matter and carbohydrates in chicory during forcing.- Scientia Horticulturae, 39: 271-278.