The effects of ridging, row-spacing and seeding rate on carrot yield Sanna-Liisa Taivalmaa Agricultural Research Centre ofFinland, Institute ofHorticulture, Hyrköläntie 122, FIN-32810 Peipohja, Finland, currentaddress: Ministry ofAgriculture and Forestry, PO Box 232, FIN-00171 Helsinki, Finland, e-mail: sanna.taivalmaa@mmm.fi Heikki Talvitie Agricultural Research Centre ofFinland, Institute ofHorticulture, Hyrköläntie 122, FIN-32810 Peipohja, Finland Cool, wet spring weather often delays the early growth of carrots (Daucus carota L.) in northern Europe. This effect may be partly obviated by sowing in ridges. Many types of ridges are used, but the most suitable for carrot cultivation under the conditions prevailing in northern Europe has yet to be determined. The effects of ridging, seeding rate and sowing system on the yield and visible quality of carrots were therefore studied in the field during three years. The highest yields were recorded for carrots sown in double rows on a narrow ridge. The effect of sowing system on mean root weight differed depending on the ridging regime. The mean weight of roots was higher for carrots cultivated on broad ridges than in other systems. Seeding rate had the most significant effect on mean root weight. For industrial purposes it is recommended that carrots be cultivated on broad ridges in double rows at low seeding rates with irrigation. The optimal cultivation technique for carrots destined for the fresh vegetable market would be narrow ridges sown in double rows at high seeding rates. The ridging system, seeding rate and row spacing did not appear to affect the external quality of roots. More detailed studies should be carried out to establish the effects of abiotic growth factors under different ridging regimes. Key words: ridge, seeding rate, sowing Introduction A change in practice among vegetable produc- ers, carrot producers in particular, from flat bed to ridge cultivation, has become commonplace in Finland. The seeding rate and the sowing sys- tem depend on the end-use requirements for car- rots - the fresh market favours small carrots and the food industry larger ones. There is a signifi- cant correlation between plant density and car- rot size. © Agricultural and Food Science inFinland Manuscript received July 1997 363 Voi 6 (1997): 363-369. AGRICULTURAL AND FOOD SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=5mkIYnbjFENWeWGU.mwqlDtbFqXUOIFSmnDZnYg.BybhKylV0AbKq2Xy0rFrXZBTN2u6xfjIAAsfCrawHYf55L3JkGlSfPbsvbbSrIlw1jR-SLw7JAqdH_xRZVE__APKIFqOz9gZ1Yjzzv8fJi3eqq2_D8EIviT9KxD3JW_INGBxcOZAUDMBoDnOtEQCIYmevgjTyFqvO0Y_EcvB4EiGBTfMEhmx7yxTRUfPMepZqPveGFfJnFG6Sq6YFC6-kxl1d9DgJsU9aKJ4VRSmqClK1qk3Vgv5xt4SZ_AM7MGSUD7sg5203BAGiFtNDG2akYEvBOnAs3w6TVsA8U4 Taivalmaa , S.-L. c£ Talvitie , H. The effects of ridging, row-spacing and seeding rate on carrot yield Low soil temperatures and wet soil in spring often delay the germination and early growth of carrot plants. Radke (1982) and Mahrer and Avis- sar (1985) noted that ridged soil dried faster than non-ridged. The soil temperature is also poten- tially higher in ridges than on the flat (Gupta et al. 1990), and small ridges counteract slaking to a certain degree (Schoneveld 1990). Accord- ing to Tisdall and Hodgson (1990), the better aeration characteristic of soil in ridges promotes higher yields than cultivation on the flat. A change in soil surface configuration from un- ridged to ridged would therefore allow earlier sowing and promote earlier growth of carrot plants in the northern European climate. Carrot yields are heavily dependent on plant density; in general the higher the plant density, the higher the yield (Kepka et al. 1978, Salter et al. 1979, Salter et al. 1980. Mack 1980, Drag- land 1986, McCollum et al. 1986). Benjamin (1982) reported that high plant density magni- fies any variation already present in the seed- ling population. Mean root weight (Hole et al. 1984,Schoneveld 1990) and the mean length and diameterof marketable roots decreased with an increase in plant density (McCollum et al. 1986). Row arrangement has been shown to affect total carrot yields (Kepka et al. 1978, Salter et al. 1979, Salter et al. 1980, Benjamin 1984) but not the length and diameter of marketable car- rots. (McCollum et al. 1986). There is limited knowledge about the most suitable cultivation technique for carrots grown in ridges in Finland. A wide range of ridge types, seed densities and sowing systems are currently used, but little attention has been paid to the fact that the cultivation method in fact depends on whether the carrots are destined for industrial or fresh markets. The aim of this study was to investigate the effect of ridging (flat bed, narrow ridge and broad ridge), seeding rate (target plant densities 40, 50, 60 and 70 roots/m2 ) and sowing system (single row, double row and band) on the quantity and external quality of carrot yield. Material and methods The field experiments were conducted at Satakunta experimental station, western Finland (61°17’N,22°14’E) during 1990, 1991 and 1992. The experimental design was a split-split plot of four replicate blocks. The main plots comprised three soil surface configurations (flat bed, nar- row and broad ridge), the subplots four target plant densities (40, 50, 60 and 70 roots/m 2) and the sub- subplots three sowing systems (single row, double row and band). The single row-broad ridge combination was omitted, because it is not an economically viable alternative in ridge cul- tivation owing to the area it requires in relation to the amount of carrots grown. The soil type was fine sand with pH 5.9. The soil was formed into narrow ridges (width ofbase 49 cm, height 23 cm) and broad ridges (width of base 75 cm, height 29 cm) using a Rumpts- tadrotary tiller with soil former. The peak of both types of ridge was 15 cm broad. Plots with flat beds and narrow ridges measured 3.2 m 2, and those with broad ridges 4.9 m 2. The carrots, cv. Fontana BZ, were sown in early May each year with a pneumatic sowing machine (Gaspardo). The seeding rate was based on 70% emergence to produce 40, 50, 60 or 70 plants/m2 . The width of the band and interrow space in the double row system was 7 cm. Sow- ing depth was 1-1.5 cm. Before sowing, granu- lar compound NPK fertilizer (10-7-14 with trace elements) was applied at a rate of 80 kg N/ha, 56 kg P/ha and 112 kg K/ha. At the beginning of August 20 kg N/ha was applied and the earth- ing-up was done. Weeds were controlled with Gesagard (prometryn 500 g/kg) or Lurox (linuron 500 g/kg) once a year according to man- ufacturers’ instructions and later by hand-weed- ing. Insects were controlled with applications of Malasiini (malathion 513 g/1) and Ripcord (sy- permetrin 100 g/1, 3-5 times year). Tap roots were hand-harvested at the begin- ning of October every year. The size of the har- vested area for flat beds and narrow ridges was 2.5 m 2 and for broad ridges 3.8 m 2. The tap roots 364 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Table 1.Total and marketable yields of carrots under various management regimes. Means (+ S.E.) Marked with the same letter do not differ (P<0.05). Main plots (soil surface configuration), subplots (target plant densities) and sub- subplots (sowing system) were tested within each year. Yields (t/ha) 1990 1991 1992 Treatments Marketable Total Marketable Total Marketable Total D.F. Soil surface configuration flat 56.2±2.08a 69.3±2.66a 60.6±1.96a 74.4±2.09a 30.1±1.72a 41.3±1.92b narrow ridge 54.0±3.31a 66.7±3.31a 61.7±2.08a 74.5±2.36a 32.1±1.40a 45.0±1.65a 6 broad ridge 56.7±2.34a 68.6+2.1 la 56.6±1.18a 66.2+1.29b 30.1±1.47a 38.9±1.53c Target plant density 1 40 47.9±3.05c 60.7±3.10c 57.9±2.36a 70.4±3.01a 26.9±1.45a 38.7±1,86a 50 52.3±3.35a 65.9±3.21b 60.8±2.03a 72.8±1.99a 30.3±1.89a 40.5±1.96a 60 59.9+2.49ab 71.9+2.65a 60.8±2.26a 72.7±2.47a 33.3±1.75a 43.5±1.89a 27 70 62.1±3.07ab 74.0±2.97a 60.6±2.40a 73.6±2.67a 33.7±1.93a 45.6±2.42a Sowing system2 single 49.7+2.31 62.0+2.29 54.1+1.98 66.5+2.09 29.7±1.86 41.2±2.2 double 68.2±2.17a 80.4±2.16a 65.4±1.78a 77.5±2.26a 32.7+1.53a 43.9±1.69a 72 band 46.8±2.27b 59.9±2.26b 58.5±1.63b 71.1±1.81b 30.2±1.40b 40.9±1.64b 1 plants/m2 2 The single row sowing system was not included in the statistical contrast examination of the sowing system because the combination “broad ridge-single row sowing system” was lacking. were weighed individually and classified accord- ing to commercial criteria. The marketable yield included tap roots weighing at least 40 g with no external defects. There were large differences in weather con- ditions at seedling emergence time during the study period. The coldest year was 1991, when the heat sum was only 175 degrees by the mid- dle of June, whereas it was 321 and 376 in 1990 and 1992,respectively. The cumulative precipi- tation from I May until 10 June was also high- est in 1991,58 mm, whereas in 1990and 1992 it was only 18 and 8 mm, respectively. The grow- ing season following emergence was cold and wet in 1991, but warm and fairly damp in 1990 and 1992. The total yield, marketable yield, mean weight of roots and proportion of branched car- rots were subjected to split-split plot analyses of variance (Steel and Torrie 1981, Ranta et al. 1991, SAS Institute 1985) using the GLM pro- cedure. Treatment means were compared using Tukey’s HSD test and contrast examination. The differences between treatment means were con- sidered significant at P<0.05. Results Total and marketable yield The effect of soil surface configuration on car- rot yield was statistically significant in 1991 (P=0.02) and 1992 (P=0.05), with narrow ridges giving the highest yield in both years. Marketa- ble yield was not affected in any year (Table 1). The average marketable yields were 55.7 t/ha, 59.6 t/ha and 30.7 t/ha in 1990, 1991 and 1992, respectively. Carrot yield increased with an increase in the seeding rate each year, but the difference was significant for marketable (P=0.009) and total (P=0.01) yields only in 1990. The 1.75-fold in- crease in seed sown resulted in a 1.05-1.2 -fold 365 Vol. 6 (1997): 363-369. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Taivalmaa, S.-L. & Talvitie, H. The effects ofridging, row-spacing and seeding rate on carrot yield increase in yield. The increase in yields was greatest between target densities of 50 and 60 plants/m 2 in 1990 and 1992,but between 40 and 50 plants/m2 in 1991. The highest average plant populations were obtained when double rows were sown. The target plant populations, as- sessed during seeding on the basis of70% emer- gence, were reached only in 1991, when condi- tions during seedling emergence were very damp. The sowing system affected marketable and total yields each year (P<0.01). The double row sowing system improved the yield in each soil surface configuration (Table 1). There were also statistically significant interactions between soil forming and sowing system in marketable yield and total yield in 1990 and 1991 (P<0.04) (Fig. 1). The difference in yields between dou- ble row and band sowing systems was small in ridges in 1991 and 1992; in all years single rows sown in ridges gave the smallest yield. Quality of yield The mean individual root weight of carrots was 161 g, 106 g and 107 g in 1990, 1991, 1992, re- spectively. The soil surface configuration influ- enced mean root weight each year (P<0.02) (Fig. 2). Seeding rate had a significant effect on mean root weight in 1990 and 1991 (PcO.OI). The lowest seeding rate resulted in the highest mean root weight each year: 190 g, 123 g and 126 g in 1990, 1991, 1992, respectively. The mean root weights at the highest seeding rate were 139 g, 89 g and 90 g in 1990, 1991, 1992, respectively. The sowing system affected the mean root weight only in 1990, when the highest mean root weight was recorded for band sowing, 183 g; it was 173 g in single and 143 g in double rows (P<0,001). There was a statistically significant interaction between soil surface configuration and sowing system each year (P<0.02) (Fig. 2). The average amount of branched carrots was 160 kg/ha, 80 kg/ha and 150kg/ha in 1990, 1991, 1992, respectively. There were only minor dif- ferences between treatments in this property. The amount of branched carrots was not analysed statistically. The dry matter content of tap roots ranged from 9.7 to 11 % and was each year high- est in the carrots grown on narrow ridges. Discussion Each soil surface configuration requires its own cultivation technique for the optimal production of carrots. In this experiment the highest yields were obtained with narrow ridges and double rows. With the exception of the size of tap roots, Fig. I. The interaction between soil surface configurations and sowing systems for marketable yield in a) 1990 (P=0.002), b) 1991 (P=0.03). 366 AGRICULTURAL AND FOOD SCIENCE IN FINLAND the effects of the factors studied on the quality of yield were small. One of the main factors affecting yield was the weather during seedling emergence and its effect on emergence. Good emergence resulted in a good yield, suggesting that good emergence is vital for all cultivation techniques. It seems that wet weather does not favour cultivation in broad ridges, whereas the use of narrow ridges apparently provides a suitable environment for carrot development, irrespective of the weather. However, irrigation is becoming increasingly popular among vegetable farmers, enabling op- timal soil moisture to be maintainedduring seed- ling emergence. The double row system promoted good car- rot yields under all conditions, although the re- sults of Salter et al. (1979), Salter et al. (1980) and Mack (1980) suggested that row spacing had little effect on root yields in experiments made on the flat. Kepka et al. (1978) considered band sowing the most suitable method for carrot grow- ing. The usefulness of this method is, however, impaired by a reduced ability to maintain soil moisture, most likely due to differences in the width of the roller wheel in sowing machines; that of the double row sower being narrow and therefore more inclined to press the seed deep into moist soil than the broad roller wheel used during band sowing. Our study was made in fine sand, without irrigation. The effect of soil sur- face configuration may differ from one soil type to another. On the basis of the results of these experiments double row or band sowing can be recommended for ridge cultivation. If, however, the soil is dry during seedling emergence, band sown carrots shouldpreferably be irrigated. With flat beds even single rows can give satisfactory yields. The mean root weight of carrots was influ- enced most effectively by changing the seeding rate - the higher the seeding rate, the smaller the roots and the higher the yields. This effect of seeding rate on the mean root weight of car- rots is consistentwith previously reported results (McCollum et al. 1986, Schoneveld 1990), but Fig. 2. The interaction between soil configurations and sow- ing systems for mean root weight in a) 1990(P=0.003), b) 1991 (P=0.002), c) 1992 (P=0.02). 367 Vol. 6 (1997): 363-369. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Taivalmaa, S.-L. & Talvitie, H. The effects of ridging, row-spacing and seeding rate on carrot yield in general, the effect of seeding rate on yields was small, being significant only in 1990. This finding supports the results of Benjamin and Sutherland (1992), who noted that a tenfold in- crease in density resulted in a twofold increase in yield. Our results are also compatible with those of Mack (1980), who found that although the total yields resulting from different seeding rates were not significantly different, there was a significant difference when yields were classi- fied by size. The effect of sowing system on mean root weight differed between soil surface configura- tions. The mean root weight ofcarrots cultivated in flat beds and narrow ridges was similar in all years, but it was higher for carrots grown on broad ridges. The mean root weight correlates with the size of carrots, even though the correla- tion is not perfect. The sowing system did not affect the exter- nal quality of roots. Only in 1990 was there a difference in mean root size between band sow- ing and double row sowing. This finding attrib- uted to the plant population at harvest, which was clearly smaller for band sown carrots than car- rots sown in double rows, presumably as a re- sult of pooremergence. Kepka et al. (1978) found more split and branched carrots in single rows, but we noted no such effect in our experiments. Fresh market carrots are best produced by a cultivation technique that requires a high seed- ing rate on double rows and narrow ridges, since a large number of small tap roots are needed. The optimal target plant density in this case is at least 60-70 roots/m 2 Dragland (1986) likewise recommended 70 plants/m 2 , whereas the recom- mendation of Kepka et al. (1978) was twice as high (150 plants/m 2 ). Carrots grown for industrial processing are best cultivated on broad ridges, in double rows and at lower seeding rates than carrots used for fresh market purposes. The target plant density shouldbe 50 roots/m 2 (or less) depending on the variety. The mean root weight of carrots grown on ridges is high. Moreover, in the experience of growers, carrots grown on broad ridges tend to be longer and larger than those grown in oth- er soil surface configurations. These long roots are not suitable for packing in small plastic bags but are ideal for industrial purposes. Future studies are needed on abiotic growth factors, temperature and moisture in particular, in different soil surface configurations and on different soil types. We also lack basic knowl- edge of the abiotic conditions thatprevail in ridg- es of different types. The effect of ridging on the internal quality of carrots should also be in- vestigated. Acknowledgements. We thank Martti Linnainmaa, Jari Pärssinen, Helena Palo, Rauno Kauppila and Terttu Kaup- pila for their excellent technical assistance during the ex- periments. We also thank DrAino-Maija Evers for her val- uable comments on the manuscript. We are particularly grateful to Dr Jonathan Robinson for his comments and for revising the text. References Benjamin, L.R. 1982. Some effects of differing times of seedling emergence, population density and seed size on root-size variation in carrot populations. Jour- nal of Agricultural Science 98: 537-545. - 1984. The relative importance of some sources of root weight variation in a carrot crop. JournalofAgri- cultural Science, Cambridge 102: 69-77. - & Sutherland, R.A. 1992. Control of mean root weight in carrots ( Caucus carota) by varying within- and between-row spacing. Journal ofAgriculturalScience 119: 59-70. Dragland, S. 1986. Plantetetthet og radavstand i gulrot. Forskning og forsok i landbruket 37: 139-145. Gupta, S.C., Radke, J.K., Swan, J.B. & Moncrief, J.F. 1990. Predicting soil temperatures under a ridge-fur- row system in the U. S. corn belt. Soil & Tillage Re- search 18: 145-165. Hole, C.C., Thomas, T.H., Barnes, A., Scott, P.A. & Rankin,W.E.F. 1984. Dry matter distribution between shoot and storage root of carrot, parsnip, radish and red beet. Annals of Botany 53: 625-631. Kepka, A., Umiecka, L. & Fajkowska, H. 1978. The influ- 368 AGRICULTURAL AND FOOD SCIENCE IN FINLAND ence of row spacing and plant density in rows on the yield of carrots and root quality. Acta Horticulturea 72: 217-224. Mack, H.J. 1980. Effect of row spacing on processing carrot root yields. HortScience 15, 2: 144-145. Mahrer, Y. & Avissar, R. 1985. A numerical study of ef- fects of soil surface shape upon the soil temperature and moisture regimes. Soil Science 139, 6: 483-490. McCollum, T.G., Locascio, S.J. & White, J.M. 1986. Plant density and row arrangement effects on carrot yields. Journal ofAmerican Society of Horticultural Science 111, 5: 648-651. Radke, J.K. 1982. Managing early season soil tempera- tures in the northern corn belt using configured soil surfaces and mulches. Journal of American Soil Sci- ence Society 46: 1067-1071. Ranta, E., Rita, H. & Kouki, J. 1991. Biometria. Tilasto- tiedettä ekologeille. 3rd ed. Helsinki, Yliopistopaino. 569 p. Salter, P.J., Currah, I.E. & Fellows, J.R. 1979. The ef- fects of plant density, spatial arrangement and time of harvest on yield and root size in carrots. 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SELOSTUS Maan muotoilun, kylvötavan ja siementiheyden vaikutus porkkanan satoon Sanna-Liisa Taivalmaa ja Heikki Talvitie Maatalouden tutkimuskeskus Tutkimuksella selvitettiin maan muotoilun (tasamaa, pieni ja iso harju), kylvötavan (yksirivi, kaksirivi ja nauha) sekä siementiheyden (40, 50, 60 ja 70 taimea/ m 2) vaikutusta porkkanan sadon määrään ja ulkoiseen laatuun. Jokainen maan muotoilutapa vaatii oman vil- jelytekniikan, jonka valintaan vaikuttaa se mihin tar- koitukseen porkkanoita viljellään. Taimettumisen on- nistuminen oli yksi tärkeimmistä sadon määrään vai- kuttavista tekijöistä. Suurin sato saatiin pienestä har- justa. Kaksoisrivikylvö oli sopivin kylvötapa kaikil- la maanmuotoilutavoilla. Porkkanan juuren kokoon vaikutti eniten siemen- tiheys; mitä suurempi tiheys, sitä pienempiä juuria. Maanmuotoilu, kylvötapa tai kylvötiheys eivät vai- kuttaneet haarautuneiden ja haljenneiden juurten määrään, Viljeltäessä porkkanoita tuorekäyttöön ha- lutaan paljon kooltaan melko pieniä porkkanoita. Täl- löin sopivin maanmuotoilutapa on tasamaa tai pieni harju ja taimitiheys tulisi olla 60-70 porkkanaa/m 2 . Pieneen harjuun paras kylvötapa on kaksirivikylvö, mutta myös nauhakylvölla saadaan hyvä sato, jos maaperä on taimettumisaikana tarpeeksi kostea. Ta- samaalla myös yksirivikylvöllä voidaan saada tyydyt- tävä sato. Isoissa harjuissa porkkanoiden keskipaino on suurempi kuin muilla maanmuotoilutavoilla vil- jeltyjen porkkanoiden, joten iso harju sopii hyvin teollisuusporkkanan tuotantoon. Tällöin sopiva taimi- tiheys tulisi olla 40-50 porkkanaa/m 2 . 369 Vol. 6 (1997): 363-369. AGRICULTURAL AND FOOD SCIENCE IN FINLAND