Chicory root yield and carbohydrate composition is influenced by cultivar selection, planting, and harvest date.
Optimum chicory root yields were achieved in Belgium when seed was sown in April, at a depth of 0.5 to 1.0 cm and at a spacing of 9 cm within the row, to achieve a plant density of 150 000 plants [ha.sup.-1] (Baert and Van Bockstaele, 1993). If the crop was sown in March, certain cultivars of chicory bolted and diverted carbohydrates away from root development. In Belgium, root yields were 30% greater when chicory was sown 14 April compared with sowing dates in early to mid-May (Baert, 1997).
Chicory roots were harvested in Belgium in the fall with optimum harvest date defined as the moment the maximum yield of extractable fructan per hectare was met (Baert and Van Bockstaele, 1993). From mid-September to mid-October, chicory root yield increased from 60 to 70 Mg [ha.sup.-1]; from mid-October to mid-November, root yield increased an additional 3 Mg [ha.sup.-1] (Baert, 1997). As the harvest season progressed and soil temperatures declined, the carbohydrate content of chicory roots changed (Baert, 1997). The content of free fructose and sucrose increased and the content of free glucose and fructans decreased with harvest date. The occurrence of the first frost (0[degree]C) in fall, and not daylength, was the critical factor in initiation of long chain-length fructan breakdown to short chain-length fructan in chicory roots (Van den Ende et al., 1996). A high root yield, high fructan content, high percentage of long-chain fructans, and low free-sugar content are preferred by the European chicory industry (Baert, 1997).
Because chicory has not been extensively grown in the USA for root production, there is limited information available on crop production. To better understand the influence of planting and harvesting date and cultivar on chicory production, we conducted the following field experiments to assess (i) the influence of planting and harvesting date, and cultivar on root yield, and (ii) the effect of these cultural practices on the levels of free sugars and fructans in chicory roots at various harvest dates in the fall.
MATERIALS AND METHODS
A series of three fie]d experiments were conducted near Scottsbluff, NE: the first in 1995 and 1996, the second in 1997 and 1998, and the third from 1999 through 2002. Experiment 1 was designed to determine optimum planting and harvesting dates and potential chicory cultivars adapted to Nebraska. The experimental design was a split-split plot. The main plots consisted of four planting dates, the subplot of four chicory cultivars, and the sub-subplot of three harvest dates (Table 1). Each treatment in the experiment was replicated six times, sub-subplots were two rows spaced 56 cm apart by 15.2 m long, and the study was conducted in 1995 and again in 1996. Experiment 2 examined additional chicory cultivars harvested during a longer time period. The experimental design was a split plot with the main plots consisting of five chicory cultivars and subplots of six harvest dates with treatments replicated six times (Table 2). Subplots were three rows spaced 56 cm apart by 15.2 m long, and the study was conducted in 1997 and again in 1998. Experiment 3 continued the study of chicory root development from the first of September through mid-November. The experimental design was a randomized complete block. Treatments were six harvest dates, replicated four times, and the experiment was repeated each year from 1999 through 2002. Individual plots were two rows spaced 56 cm apart by 15.2 m long. The experiments were located in different fields each year on a Glenberg silt loam (coarse-loamy, mixed, superactive, calcareous, mesic Ustic Torrifluvents), pH 7.8 to 8.0, and 0.8 to 1% organic matter. The crop the previous year was corn (Zea mays L.).
The seedbed each year was prepared in early spring by moldboard plowing followed by one pass with a seedbed conditioner (Franz Kleine, Salzkotten, Germany). The herbicide trifluralin was applied at 0.56 kg [ha.sup.-1] and incorporated with a second pass of the seedbed conditioner. Chicory seeds were sown with a Hege 95B System Kleine vacuum planter (Hege Equipment, Inc., Colwich, KS). Seeds were sown at a depth of 0.6 cm in rows spaced 56 cm apart at a rate of four seeds per 30 cm of row (Baert and Van Bockstaele, 1993). In Exp. 1, planting date varied, but in Exp. 2 and 3, chicory was planted in mid-April. In Exp. 3, the chicory cultivar Orchies (Florimond Desprez, Cappelle-en-Pevele, France) was planted each year. Chicory was irrigated with either an overhead sprinkler or by furrow 2 d after planting and continued for approximately 10 d after planting to ensure the soil surface remained moist. Beginning in late June, plots were irrigated with 25 mm of water per week through the end of September. Plots were cultivated and hand-weeded when chicory was in the two-leaf growth stage, and weeding continued throughout the season. Plots were fertilized with N (urea-ammonium nitrate, 28-0-0 N-P-K) to bring the soil nitrogen content to 145 kg [ha.sup.-1] in the surface m of soil. Nitrogen was applied adjacent to the crop row once the chicory plant reached the four-leaf growth stage.
Chicory density in two rows of each plot for a distance of 15 m was recorded in early June. Leaf area index was estimated with a plant canopy analyzer (LI-COR, Inc., Lincoln, NE) in mid-July and early August (Wilson, 1999). Bolted chicory plants were recorded in each plot in late August. The number of plants bolted was divided by the number of plants in each plot to determine the percentage of bolted plants. Chicory leaves were removed with a mechanical topper and roots were harvested with a mechanical two-row harvester. A random subsample of 10 roots per plot was washed, weighed after drying at room temperature, and sectioned longitudinally into quarters with a knife. Each quarter from each of the roots was combined and run through a juicer (Omega Products, Inc., Harrisburg, PA). A portion of the juice was analyzed for soluble dry matter with a refractometer (Atago, Tokyo, Japan). The total sugar content of the sample was estimated from the refractometer reading by the procedure developed by Van Waes et al. (1998). A 0.3-g sample of juice was diluted with high performance liquid chromatography-grade water to a final volume of 100 mL. A 10-mL aliquot of the diluted sample was filtered with a 0.45-[micro]M filter (Advantec MFS, Inc., Pleasanton, CA) and analyzed by high performance anion exchange chromatography-pulsed amperometric detector with a Dionex 500 system (Dionex Corp., Sunnyvale, CA) with the procedure described by Wilson et al. (2001). Glucose, fructose, sucrose, and fructans were reported as a percentage of total sugar content. Fructans were further grouped into three categories: DP 3 to 10 fructans (short chain-length fructans), DP 11 to 20 fructans (medium chain-length fructans), and DP > 20 fructans (long chain-length fructans).
Results were analyzed by ANOVA, followed by comparison of means by a Fisher's protected LSD at the 0.05 level of significance. In Exp. 1 and 2, there was a harvest date x year interaction for the variables root yield and total sugars, but the size of the interactions relative to the average treatment effects was small and the ranking of the treatments across years was similar. Therefore, the ranking of treatments across years was expected to be stable, and data were combined across years (Gomez and Gomez, 1984). Means from data collected in Exp. 1, 2, and 3 were combined and analyzed with a nonlinear correlation analysis to measure the degree of nonlinear association between chicory root yield and harvest date with the SAS procedure NLIN (SAS Institute, 1990).
RESULTS AND DISCUSSION
The results from Exp. 1 showed that planting date influenced plant stand, leaf area, bolting, and root yield (Table 1). Plant stands declined as planting dates changed from mid-April to the first of May, to mid-May. Air temperatures in May were 5.5[degrees]C warmer than in April and even though rainfall was greater in May and fields were irrigated it was difficult to keep the soil moist at the 1-cm depth and chicory seedlings died. The reduction in plant stand and the shorter growing period that accompanied the later plantings was reflected in leaf area measurements taken in mid-July. Chicory planted in mid-April had a leaf area that was 133% greater than chicory planted the first of May. This trend was still evident the first of August when leaf area was recorded.
Chicory is considered a biannual and plants must be subjected to a cold period before flowering will occur (Baert, 1997). Where chicory is grown as a root crop, it is not desirable to have the plant bolt and divert energy into flowering. Planting date did have an influence on bolting, with the percentage of plants bolting greatest with the first of April planting and decreasing as planting was delayed to mid-April (Table 1). Although bolting did occur, the percentage of plants bolting was 1% of less.
Root yields were similar when the crop was planted on 1 or 15 April, but declined 35% when the crop was seeded in mid-May (Table 1). The reduction in root yield was influenced by the shorter growing season and by the decrease in plant stand. Planting date did not influence the total sugar content of roots. The fructose content of roots decreased from the 1 April planting compared with the 15 May planting.
Chicory cultivar influenced plant stand, leaf area development, bolting, root yield, total sugar content, and the distribution of carbohydrate in roots (Table 1). Crop stand in mid-June was greater in areas seeded with 'Cassel' (Florimond Desprez) and 'Rubis' compared with 'Bergues' and Orchies. The leaf area in mid-July and early August was greater for Rubis compared with the other cultivars. In early August, Orchies had the smallest leaf area. The incidence of bolting was greatest with Cassel. Root yields were greater for Cassel and Rubis compared with Bergues and Orchies. Orchies had the greatest total sugar content (189 mg [g.sup.-1] fresh weight) and a greater percentage of fructans in the DP 11 to 20 and DP > 20 categories than the other cultivars.
Harvest date influenced root yield, total sugar content, and the distribution of carbohydrate in roots (Table 1). Root yields and total sugar content increased as harvest date was delayed. From mid-September to late October, root yield increased 25% and total sugar content increased 8%. Harvest date also influenced fructan distribution. In mid-September, the percentage of fructans present as DP 3 to 10 was lowest and the percentage present as DP > 20 was highest compared with the 1 and 21 October harvest dates. As the harvest season progressed into late October, the percentage of fructans present as DP 3 to 10 increased and the percentage present as DP > 20 decreased. At the same time, fructan polymerization changed the percentage of carbohydrate present as sucrose increased from 2.6% in mid-September to 6.6% in late October. The changes in fructans observed in this study are similar to those reported by Baert (1997) that occurred in Belgium during fall harvest.
Fructose polymers are synthesized from sucrose by the combined activity of sucrose: sucrose 1-fructosyl transferase (1-SST, EC 22.214.171.124) and fructan: fructan 1-fructosyl transferase (1-FFT, EC 126.96.36.199) (Van den Ende and Van Laere, 1996). The 1-SST enzyme catalyzes the production of a trisaccharide from sucrose, and 1-FFT performs chain elongation (Edelman and Jefford, 1968). Depolymerization in fructans are triggered by the occurrence of the first frost in the fall (Van den Ende et al., 1996). After the first frost, the activity of fructan 1-exolydrolase (1-FEH, EC 188.8.131.52) increases and leads to the breakdown of fructans in chicory roots.
The first frost (-3[degrees]C) in 1995 occurred on 21 September and in 1996 on 29 September. After the occurrence of the first frost we would anticipate depolymerization of fructans. Observations made on 1 and 21 October indicated that breakdown of mid- (DP 11 to 20) to high-DP (DP > 20) fructans had begun.
Results from Exp. 2 indicated that chicory cultivar influenced root yield, total sugar, and carbohydrate distribution (Table 2). The chicory varieties, Cassel, 'Madona' (Chicoline, Warcoing, Belgium), and Orchies produced a greater root yield than Rubis or 'Katrien' (Chicoline) when averaged across harvest dates. Total sugars were greatest for Katrien followed by Orchies. Katrien and Cassel had a greater percentage of fructans in the DP 11 to 20 category than Rubis of Orchies. Cassel also had more fructans in the DP > 20 category than Rubis of Orchies.
Harvest date influenced root yield, total sugar content, and distribution of carbohydrates in roots (Table 2). The greatest root yield was achieved from the 1 November harvest date. From 1 September to 1 November, root yield increased 29.8 Mg [ha.sup.-1]. During this same time period, concentration of total sugars present in roots increased from 172 mg [g.sup.-1] fresh weight on 1 September to 197 mg [h.sup.-1] fresh weight on 1 November. Allowing chicory roots to overwinter in the field led to a 33% reduction in root weight and a 22% reduction in total sugar content. Most of the loss both years could be attributed to root deterioration caused by the fungus Sclerotina sclerotiorum (Lib.) de Bary (Baert and Van Bockstaele, 1993). The first frosts occurred on 9 October in 1997 and 17 October in 1998. Fructan measurements taken on 1 November reflect the effects of the October frost with decreased concentrations of fructans in the DP 11 to 20 and DP > 20 categories and the increase in DP 3 to 10 fructans and sucrose. The maximum amount of fructans in the DP > 20 category were achieved with a 1 October harvest (Table 2). The maximum amount of fructans in the DP 11 to 20 category were achieved with a 15 September harvest date, while the maximum amount of fructans in the DP 3 to 10 category was achieved by allowing roots to overwinter and harvest in mid-March. Overwintering of roots caused a dramatic decrease in fructans in the DP > 20 and DP 11 to 20 categories and an increase in fructans in the DP 3 to 10 category, and an increase in free sugars glucose, fructose, and sucrose. Harvest date played an important role in determining the DP of fructans in chicory roots and root yield.
Experiment 3 showed trends similar to those observed in the previous experiments, that harvest date was a key factor in determining root yield, total sugar content, and carbohydrate distribution (Table 3). During the 4-yr period from 1999 to 2002, the mid-November harvest date produced the greatest root yield with an increase in root yield of 26.7 Mg [ha.sup.-1] from early September to mid-November. The total sugar content was greatest on 1 November and began to decline if harvest was delayed until mid-November. The first frost (-3[degrees]C) in 1999 through 2002 occurred on 28 September, 25 September, 5 October, and 22 September, respectively. There was a trend for the greatest concentration of fructans in the categories DP 11 to 20 and DP > 20 to occur on 20 September. Following the first frosts, the concentration of fructans in the categories DP 11 to 20 and DP > 20 declined and fructans in the category DP 3 to 10 increased.
A nonlinear regression equation with an [r.sup.2] value of 0.95 describes the change in root yield from the first of September through mid-November (Fig. 1). From 1 September to 1 October root yield increased 14.7 Mg [ha.sup.-1], and from 1 October to 1 November root yield increased 9.2 Mg [ha.sup.-1]. The harvest season for the crop could run from the first of September through mid-November. If the grower is paid only on tonnage, it is more desirable to harvest in late fall. If the grower is paid on the content of fructans with the greatest DP, an early- to mid-October harvest is desirable. It is therefore important for the grower and processor to have a contract that considers tonnage, total sugar content, and degree of fructan polymerization.
[FIGURE 1 OMITTED]
In summary, the results of 7 yr of research indicated that chicory could be successfully grown in western Nebraska. Planting date was important with a mid-April planting date optimum. Chicory cultivar selection was also a significant factor in determining root yield and total sugar content. The cultivar Orchies had a combination of low percentage of bolting, good root yield, high total sugar content, and percentage of long chain-length fructans. A mid-October harvest date produced root yields that ranged from 46 to 54 Mg [ha.sup.-1] and provided a good compromise between root yield, total sugar content, and percentage of long chain-length fructans.
Abbreviations: DP, degree of polymerization.
Table 1. Experiment 1: effect of planting date, cultivar, and harvest date on chicory growth at Scottsbluff, NE, in 1995 and 1996. Leaf area Plants Plant stand boiling in Treatment 15 June 17 July 1 Aug. late Aug. Plants LAI [m.sup.-1] % [ha.sup.-1] ([double dagger]) Planting date (main plot) 1 April 116 400 2.2 3.4 0.8 15 April 118 100 2.0 3.2 0.5 1 May 112 800 1.5 2.9 0.3 15 May 71 000 0.8 1.6 0.2 LSD (0.05) 4 400 0.1 0.1 0.2 Chicory cultivar (subplot) Cassel 109 700 1.6 2.8 1.0 Bergues 99 800 1.6 2.8 0.2 Raids 107 100 1.8 3.1 0.4 Orchies 101 600 1.5 2.5 0.2 LSD (0.05) 4 400 0.1 0.1 0.2 Harvest date (sub-subplot) 15 Sept. 105 300 1.6 2.8 0.4 1 Oct. 103 100 1.6 2.7 0.4 21 Oct. 105 300 1.5 2.8 0.4 LSD (0.05) ns ns ns ns % of carbohydrate as Root Treatment yield Total sugars Glucose Fructose mg [g.sup.-1] Mg [ha.sup.-1] FW ([section]) % Planting date (main plot) 1 April 55.1 182 7.0 11.2 15 April 55.7 182 7.3 10.9 1 May 52.5 181 7.2 10.8 15 May 36.0 181 7.2 9.5 LSD (0.05) 1.9 ns ([paragraph]) ns 1.2 Chicory cultivar (subplot) Cassel 52.2 183 7.7 9.6 Bergues 47.1 178 6.9 11.5 Raids 52.6 175 7.5 13.2 Orchies 47.4 189 6.7 8.1 LSD (0.05) 1.9 2 ns 1.2 Harvest date (sub-subplot) 15 Sept. 43.6 174 10.6 11.3 1 Oct. 51.5 183 7.1 9.6 21 Oct. 54.4 188 4.0 10.9 LSD (0.05) 1.6 2 0.9 1.1 % of carbohydrate as Fructans ([dagger]) Treatment Sucrose DP 3-10 DP 11-20 DP > 20 % Planting date (main plot) 1 April 4.4 35.8 22.1 15.0 15 April 4.1 35.3 22.4 15.2 1 May 4.4 36.2 22.6 14.7 15 May 4.8 34.1 25.4 15.6 LSD (0.05) ns ns 1.1 ns Chicory cultivar (subplot) Cassel 4.6 35.3 23.3 16.4 Bergues 3.5 36.9 22.6 13.7 Raids 5.3 34.5 21.9 13.9 Orchies 4.1 32.5 25.8 19.5 LSD (0.05) 0.6 ns 1.3 1.7 Harvest date (sub-subplot) 15 Sept. 2.6 28.4 24.9 18.2 1 Oct. 4.0 33.8 24.7 17.2 21 Oct. 6.6 42.1 20.6 12.2 LSD (0.05) 0.5 1.5 0.9 0.8 ([dagger]) DP = degree of fructan polymerization. ([double dagger]) LAI = leaf area index. (section]) FW = fresh weight. ([paragraph]) ns = not significant. Table 2. Experiment 2: effect of cultivar and harvest date on chicory root yield at Scottsbluff, NE, in 1997 and 1998. % of carbohydrates as Treatment Root yield Total sugars Glucose Fructose mg [g.sup.-1] FW Mg [ha.sup.-1] ([double dagger]) % Chicory cultivar (main plot) Cassel 45.0 176 2.1 2.8 Rubis 41.1 171 2.8 3.8 Orchies 43.1 187 2.8 4.0 Madona 43.8 179 2.6 3.7 Katrien 37.8 192 1.9 3.2 LSD (0.05) 1.9 4 0.7 0.8 Harvest date (subplot) 1 Sept. 27.8 172 3.1 2.7 15 Sept. 37.0 182 2.4 2.2 1 Oct. 45.5 188 1.8 2.4 15 Oct. 46.5 193 1.2 2.3 1 Nov. 57.6 197 0.7 3.9 15 Mar. 38.4 153 5.5 7.4 LSD (0.05) 2.1 3 0.7 0.8 % carbohydrates as Fructans ([dagger]) Treatment Sucrose DP 3-10 DP 11-20 DP > 20 % Chicory cultivar (main plot) Cassel 5.4 41.5 27.3 17.8 Rubis 6.4 42.0 25.8 16.3 Orchies 5.2 41.4 26.4 16.9 Madona 5.1 41.4 26.8 17.3 Katrien 5.7 41.3 27.4 17.3 LSD (0.05) 0.6 ns ([section]) 0.6 0.7 Harvest date (subplot) 1 Sept. 3.8 37.9 31.0 18.4 15 Sept. 3.3 35.6 31.9 21.7 1 Oct. 3.5 33.1 30.8 25.3 15 Oct. 4.8 37.4 29.7 21.4 1 Nov. 7.1 44.9 26.0 14.0 15 Mar. 10.7 60.3 11.0 1.9 LSD (0.05) 0.7 1.3 0.7 0.8 ([dagger]) DP = degree of fructan polymerization. ([double dagger]) FW = fresh weight. ([section]) ns = not significant. Table 3. Experiment 3: effect of chicory harvest date on root yield at Scottsbluff, NE, in 1999 through 2002. % carbohydrates as Harvest date Root yield Total sugars Glucose Fructose mg [g.sup.-1] FW Mg [ha.sup.-1] ([double dagger]) % 1 Sept. 31.7 186 1.7 1.0 20 Sept. 42.4 186 0.7 0.6 5 Oct. 48.6 190 0.6 1.1 21 Oct. 49.2 199 0.3 0.8 5 Nov. 55.9 201 0.3 1.5 15 Nov. 58.4 189 0.7 2.7 LSD (0.05) 1.1 3 0.3 0.3 % carbohydrates as Fructans ([dagger]) Harvest date Sucrose DP 3-10 DP 11-20 DP > 20 % 1 Sept. 8.9 35.8 27.4 20.4 20 Sept. 7.0 36.0 29.3 22.6 5 Oct. 6.6 37.2 29.0 21.5 21 Oct. 8.0 41.5 27.2 18.2 5 Nov. 8.5 42.5 26.4 16.6 15 Nov. 11.1 45.0 23.4 12.6 LSD (0.05) 0.4 1.1 0.4 1.2 ([dagger]) DP = degree of fructan polymerization. ([double dagger]) FW = fresh weight.
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Robert G. Wilson, * John A. Smith, and C. Dean Yonts
R.G. Wilson, Dep. of Agronomy, Univ. of Nebraska, Panhandle Research and Extension Center, Scottsbluff, NE 69361; J.A. Smith and C.D. Yonts, Dep. of Biological Systems Engineering, Univ. of Nebraska, Panhandle Research and Extension Center, Scottsbluff, NE 69361. A contribution of the Univ. of Nebraska Agricultural Research Division, Lincoln, NE. Journal Series No. 14067. This research was supported in part by funds provided through the Hatch Act. Received 22 April 2003. * Corresponding author (email@example.com).
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|Title Annotation:||Crop Breeding, Genetics & Cytology|
|Author:||Wilson, Robert G.; Smith, John A.; Yonts, C. Dean|
|Date:||May 1, 2004|
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