Maataloustieteellinen A ikakauskirja Vol. 60: 93—100, 1988 Herb yield and essential oil of dill (Anethum graveolens L.) at different locations S. HÄLYÄ', R. HUOPALAHTI2 , CH. FRANZ 3 and S. MÄKINEN4 ' Dept, of Horticulture, University of Helsinki, SF-00710 Helsinki, Finland 2 Dept, of Chemistry and Biochemistry, University of Turku, SF-20500 Turku, Finland 3 Inst, for Vegetable Growing, Technical University of Munich, 8050 Freising, West Germany present address: Inst, for Botany and Food Science, Linke Bahngasse 11, A-1030 Wien, Austria 4 Dept, of Nutrition, University of Helsinki, SF-00710 Helsinki, Finland Abstract. A study on the effect of growing site on the growth of the dill herb at three locations (Helsinki, Sahalahti, Inari) in Finland and at Freising, West Germany, was carried out in 1985. The growing medium was fertilized peat of the same quality at each location. Dill (’Dura’) was sown twice, in early spring and 2—3 weeks later at all growing sites. The herb crop was harvested just when the first flower buds had developed. The later sowings gave significantly larger yields than the earlier ones. The herb yields were largest at the most southern location. The fresh yield was the larger the more rain there was, and the warmer the growing season was. The significantly highest oil contents were recorded in the herb of the later sowings at Freising and Sahalahti. Otherwise, no differences in the oil content were recorded. The corre- lation between the oil content and degree days was positive. The total amount of components responsible for the aromavaried between 4.5 and 7.9 mg/g dry weight.The amount of essential oil and that of a typical aroma compound in dill, 3.6-dimethyl-2,3,3a,4,5,7a-hexahydro- benzofuran, were not significantly affected by the location. Index words: anethofuran, essential oil, dill herb, growing site, 3,6-dimethyl-2,3,3a,4,5,7a-hexahydrobenzofuran Introduction Dill (Anethum graveolens L.) is one of the most important herb plants in the Nordic countries. It is mostly used as a fresh or dried herb. The seed production, on the other hand, is not successful in the north, and thus there is no wider use of seeds for flavouring in Fin- land. It has been claimed that in aromatic herbs the odour and taste are the stronger the farther north they grow. The main ecological differ- ences between the latitudes are the tempera- 93 JOURNAL OF AGRICULTURAL SCIENCEIN FINLAND https://www.c-info.fi/en/info/?token=8OpEi3PI0zvC_5EZ.cUx_59mxCxUZSzTh2NnBrg.pRA-U5H3fTYppYMad3fPATC9-ZvmBBD05dI_0h8BA2-_zL1zKwvSmaafv334Cqc9aP17oGdV0YgVm-mVfz5Kw3JvRz7m1H1uZAbepWQpPnMMhilMlWTWH-Xpl0TlsiLh3MqH2cJNY41a6Fb4jZToP3IbBbh86ou3OS62P5RGo_8FXx7UotyhCQwyp6ywE8wuEubEKB7yXI0pvggnTDNJ1C_ghmjRcbJvOL4moqR-fw ture and the day length (Härdh and Härdh 1972, Härdh 1975, Franz et al. 1984). Thus the possible differences in the aroma are probably due to these two factors. Besides, according to Huopalahti (1984), the essential oil content in the dill herb is dependent on the degree days, i.e. the sum of daily temperatures > +5°C. The earliest investigations on the effect of growing site on the quality of vegetables in the northern countries have been conducted by Lamprecht (1929) and Dragland (1969). The effect of day length, intensity and composi- tion of light, and temperature on the quality of various vegetable crops, including dill, was studied in the beginning of the 70’s in the Nordic countries (Härdh et al. 1977, Härdh 1978). The highest contents of aroma com- pounds were reported in dill grown farthest north. The result is supported by Huopalah- ti (1984). Otherwise the investigations on this subject are few. Recent studies report partly conflicting re- sults on the effects of growing site. Yliaho (1981) found no clear differences in the total content of essential oil in the roots of angelica (Angelica archangelica L.) grown on similar soils and at different locations in Finland. Franz et al. (1984, 1986) investigated the essential oil content of peppermint (Mentha X piperita L.) and chamomile (Chamomilla recutita (L.) Rauschert) grown at different locations in Europe, the chamomile also in Finland. The oil content of peppermint was not affected by the growing site, and no qualitative changes were found in the oil com- position of chamomile grown at different locations. Certain quantitative differences were, however, observed between the northern and southern locations (Franz et al. 1986). Similarly, there were no differences in the essential oil content of different dill varieties due to the locations in Finland (Hälvä 1987). The influence of latitude appears to depend on the specific plant species, too. For instance, the formation of essential oil is less dependent on ecological factors in chamomile than in peppermint (Frantz et al. 1984, 1986). The aroma characteristics and the fresh herb yield of dill grown in West Germany and at three locations in Finland were investigated in the present study. The purpose was to determine the effect of the southern and northern growing sites (latitude) on the pro- ductivity and on the content and composition of the aroma causing compounds (from here on referred to as aroma compounds) in the dill herb. Material and methods The experiment was carried out in 1985 at three locations in Finland, i.e. in Helsinki (60°14’N), Sahalahti (61°28’N) and Inari (69°04’N), and at Freising, West-Germany (48°24’N). The dill variety was ’Dura’ Sv, which had earlier given large yields with high content of essential oil (Huopalahti 1985, Hälvä 1986). The experiment was carried out in pots (5 litre) filled with peat (St 400 A2) which had received basic fertilization of 110-124-176 g NPK/pot. Dill was sown twice, 2—3 weeks apart, 50 seeds per pot in a 10-fold replica- tion at each location. The first sowing was a typical early sowing in May and the second one took place three weeks later except for Inari, where the dill was first sown in June. The later sowing was carried out after two weeks because of the shorter growing season in the north (Table 1). The plants were ex- posed to rainfall, and were irrigated during the dry periods. No fertilizers were broadcast. The height of the plants was measured and the fresh herb yield weighed when harvested, at the first appearance of flower buds. The herb was frozen, and three samples of both sowings at each location were analysed for the content and composition of essential oil. Also the dry weight was determined (+ 102—106°, 6 h). Aroma compounds were isolated by extrac- ting for six hours 50 g (fresh weight) of chop- ped dill leaves and branches with a mixture of n-pentane and diethyl ether (1; 2, v/v) by using a modified Soxhlet technique, in which 94 Table 1. Data on climatic factors during the growing period of dill herb, height of the plants at harvest, and dried yields/pot (5 I). Two sowings (dates) were carried out at four locations in 1985. Location, Rainfall Degree Hours of Radiation Growing Height/ Dried sowing mm days sunshine MJ/mJ period, plants yield/ dates °C days cm pot, g Freising May 3. 228 426 302 819 48 46 30.5 May 24. 134 464 314 852 48 46 40.7 Helsinki May 24. 195 416 342 757 46 25 14.8 June 14. 191 467 250 590 41 30 21.5 Sahalahti May 22. 184 424 287 724 49 35 17.3 June 12. 204 467 263 600 43 43 18.2 Inari June 17. 73 391 421 714 49 22 10.3 July 8. 134 436 227 470 57 37 15.7 the side tube of the regular apparatus was re- placed by a column containing glass beads to prevent the cycling of compounds. The extract was concentrated in a Widmer column, to a volume of 2 ml. A previous study showed that the extraction used in this investigation was suitable for comparative serial analysis of essential oil compounds (Huopalahti et al. 1981). The quantitative gas chromatographic analysis was performed on a Varian 3700 gas chromatograph equipped with a flame ioni- zation detector connected to a Hewlett Packard 3388 A integrator. A fused silica capillary column (0.32 mm i.d. X 25 m; film thickness 0.20 pm) coated with OV-351 was used for the separations. The oven tempera- ture was programmed from 70 to 240°C after an isothermal period of 2 min. The tempera- ture of the injection port was 245°C, that of the detector 255°C. The split ratio was 1: 30, and the flow rate of carrier gas (helium) was 1.5 ml/min. The quantitative estimation of individual components was performed using linalool as internal standard. The identification of com- pounds was carried out using a 70 eV VG Analytical 7070 E mass spectrometer. The iso- lation and identification methods are dis- cussed in detail in previous papers (Huopa- lahti 1984, 1985, 1986, Huopalahti et al. 1981, Huopalahti and Linko 1983). For statistical analysis of results the analy- sis of variance was applied. The means were tested by the Duncan, Student-Neuman-Keuls or Tukey tests (Steel and Torrie 1980). The correlations of the herb yield and essential oil content were tested between different climatic factors, i.e. rainfall (including irrigation), degree days, hours of sunshineand radiation. Results and discussion 1. Herb yield It took 41—57 days for the crop to grow from sowing until the appearance of the first flower buds (Table 1). The rate of develop- ment was highest at the most southern loca- tion in Finland, especially when sown in June, at the time the days were longest. This was observed also earlier (Hälvä 1987). In the most southern location, at Freising, the rate of development was consistently 48 days. In the north, in Inari, the crop devel- oped slowly when sown as late as in July. The decrease in radiation and increase in rainfall most probably decreased the rate of develop- ment. The fresh herb yields per pot ranged from 95 74 to 261 grams. At the time of harvest there were 39 plants/pot in average. The latter of the two sowings yielded significantly (Freising and Sahalahti: p < 0.05, Helsinki and Inari: p < 0.01) larger yields (191 g/pot in average) than the earlier one (151 g/pot) (Fig. 1). The yield was smallest in the first harvest at the location furthest north, and largest in both harvests at the location furthest south, in Germany. The yields correlated positively with the height of the crop (Table 1). Dill yielded equal amounts at the locations in Fin- land when sown in June in the south, and in July in the north. On the contrary, the smaller yields of the early sowing in the north com- pared to the south resemble those reported earlier for the early crop (Hälvä 1987). The crop was decreased by the cool weather in the north, where the number of degree days remained under 400°. The number of degree days in the north was significantly (p < 0.05) lower than that in the southern locations (Duncan (2,4) = 12.3°C) and, on the other hand, during the later growing period it was significantly (p < 0.05) greater than during the earlier growing period (Duncan (2,3) = B.7°C) (Table 1). The coefficient of determination(r 2 ) of the fresh herb yield and climatic factors (rainfall, degree days, radiation and hours of sunshine) was 85.5 % (Table 1). The separate cor- relation coefficients (r) were 0.76++ +, 0.58 + + + , 0.36 + + , and —0.35 + + , re- spectively. The positive correlation between the herb yield and rainfall was strongest. The proportion of dried yield of the total fresh herb ranged from 9.5 to 15.6 %, the highest figures being recorded in the south, at Freising. The dry weight showed significant positive correlations between radiation (r = 0.66+ + + ) and the hours of sunshine (r = 0.52+ +). The radiation explains (r 2 ) 85 %of the variation. According to Härdh et al. (1977), also the dry matter content of herbs is highest in the south. 2. Essential oil 2.1. The content and composition of oil The total content of aroma components in Fig. I. Fresh yield [Tukey 0.01 (8,63) = 26.56 g], total aroma content [Tukey 0.05 (7,14) = 1.55 mg/g], and proportion of anethofuran (stippled area) in total aroma of dill herb. The two sowings (1 and II) were carried out at four locations in 1985. The bars within the item indicated by the same letters (a-d) belong to the same group of signifi- cance. Fig. 2. Correlation between the total aroma content and degree days (°C). 96 Table 2. Contents and relative proportions of the aroma compounds (means of three replications) at two sowings (1 and II) and at four locations in 1985. FREISING HELSINKI SAHALAHTI INARI i n i n i ii i n ™ey i + n Compound mg/g Vo mg/g Vo mg/g Vo mg/g Vo mg/g Vo mg/g Vo mg/g Vo mg/g Vo p < 0.05 a-Pinene 0.1 1.2 0.1 1.4 0.1 1.2 0.1 1.3 0.1 1.4 0.1 1.3 0.1 1.2 0.1 1.2 0.03 a-Phellandrene 2.1 47.5 3.5 48.0 2.2 36.8 2.9 50.0 3.1 52.7 4.1 50.8 2.9 49.8 3.1 59.3 0.97 p-Phellandrene 0.3 6.4 0.5 7.0 0.5 8.1 0.4 7.2 0.5 8.5 0.6 7.4 0.4 7.2 0.4 8.0 0.13 + Anethofuran 1.4 31.7 2.5 33.7 2.1 37.5 1.8 30.8 1.5 25.8 2.3 29.2 1.6 24.7 1.1 21.6 0.75 + Limonene 0.1 2.1 0.2 2.5 0.2 2.7 0.1 2.5 0.2 2.8 0.2 2.5 0.1 2.4 0.1 2.5 0.04 P-Pinene tr 0.0 tr 0.0 0.1 0.0 0.1 0.0 0.2 0.0 0.1 0.0 tr 0.0 0.1 p-Cymene 0.1 1.1 0.0 0.5 0.1 1.0 0.0 0.7 0.0 0.7 0.0 0.4 0.4 0.0 0.5 0.0 0.6 Thymol 0.0 0.5 0.1 0.6 0.0 0.5 0.0 0.5 0.0 0.4 0.0 0.4 0.1 0.8 0.0 0.3 Carvacrol tr 0.0 0.2 0.0 0.7 0.0 0.2 0.0 0.3 0.0 0.2 0.0 0.2 0.0 0.2 Myristicine 0.0 0.5 0.0 0.3 0.1 0.7 0.1 0.9 0.1 1.5 0.1 1.3 0.1 2.1 0.0 0.7 Terpine-4-ol 0.1 Carvon tr tr tr tr tr tr tr tr