The effects of ridging, row-spacing and seeding
rate on carrot yield
Sanna-Liisa Taivalmaa
AgriculturalResearch CentreofFinland,Institute ofHorticulture,Hyrköläntie 122,FIN-32810Peipohja, Finland,currentaddress: MinistryofAgriculture andForestry,POBox232,FIN-00171 Helsinki,
Finland,e-mail:sanna.taivalmaa@mmm.fi Heikki Talvitie
AgriculturalResearch CentreofFinland,InstituteofHorticulture,Hyrköläntie 122,FIN-32810Peipohja, Finland
Cool, wetspringweather oftendelays theearly growth of carrots (Daucus carota L.) innorthern Europe.This effect may be partly obviated by sowing in ridges. Manytypes ofridges areused, but the most suitable for carrot cultivation under the conditionsprevailing innorthernEuropehas yet to be determined. The effects ofridging, seedingrateandsowing systemontheyieldand visiblequality of carrotsweretherefore studiedinthe fieldduringthree years. The highest yieldswererecorded for carrotssown indoublerows on a narrowridge. The effect ofsowing systemon meanroot weight differeddepending ontheridging regime.Themeanweightof rootswashigherfor carrots cultivated onbroad ridges than inother systems. Seedingrate had the mostsignificanteffect on meanroot weight.For industrial purposes it is recommended that carrots be cultivatedonbroadridges indouble rowsat lowseeding rates with irrigation.Theoptimalcultivationtechnique for carrots destined for the freshvegetable market would be narrowridges sown in doublerows athigh seeding rates. The ridging system, seeding rate and row spacingdid not appear to affect the external qualityof roots.
More detailed studies should be carried out to establish the effects of abioticgrowthfactors under differentridging regimes.
Keywords:ridge, seedingrate,sowing
Introduction
A change in practice among vegetable produc- ers,carrotproducers in particular, from flat bed
toridge cultivation, has become commonplace
in Finland. The seedingrateand the sowing sys- temdependonthe end-use requirements forcar- rots- the fresh market favours smallcarrotsand the food industry largerones.There is asignifi- cant correlation between plant density and car- rotsize.
©Agriculturaland FoodScience inFinland Manuscriptreceived July 1997
Voi 6(1997):363-369.
Low soiltemperaturesand wetsoil in spring often delay the germination and early growth of carrotplants. 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 thanon the flat (Guptaet al. 1990), and small ridges counteract slaking toacertain 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 yieldsareheavily dependentonplant density; in general the higher the plant density, the higher the yield (Kepkaetal. 1978, Salteret al. 1979, Salter etal. 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 etal.
1984, Schoneveld 1990)and themeanlength and diameter of marketablerootsdecreased with an increase in plant density(McCollumetal. 1986).
Row arrangement has been shownto affect totalcarrotyields (Kepka etal. 1978, Salter et al. 1979, Salteretal. 1980, Benjamin 1984)but
not the length and diameter of marketablecar- rots. (McCollum etal. 1986).
There is limited knowledge about themost suitable cultivation technique forcarrots grown in ridges in Finland. A widerangeof ridgetypes, seed densities and sowingsystems arecurrently used,but little attention has been paidtothe fact that the cultivation method in fact depends on whether thecarrotsaredestined for industrialor fresh markets.
The aim of this study was toinvestigate the effect of ridging (flatbed, narrowridge and broad ridge), seedingrate(target plant densities 40, 50, 60 and 70 roots/m2)and sowing system (single row, doublerow and band) onthe quantity and external quality ofcarrotyield.
Material and methods
The field experiments were conducted at Satakunta experimentalstation, westernFinland (61°17’N,22°14’E) during 1990, 1991 and 1992.
The experimental designwas asplit-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/m2) and the sub- subplots three sowing systems(single row,doublerowand band). The single row-broad ridge combinationwas omitted, because it isnot aneconomically viable alternative in ridge cul- tivation owing tothearea it requires in relation tothe amount ofcarrotsgrown.
The soiltype wasfine sand with pH 5.9. The soilwasformed intonarrowridges (width ofbase 49 cm, height 23 cm)and broad ridges (width of base 75 cm, height 29 cm) usinga Rumpts- tadrotary tiller with soil former. The peak of both types of ridge was 15cmbroad. Plots with flat beds and narrow ridges measured 3.2 m2, and those with broad ridges 4.9 m
2.
The carrots, cv. Fontana BZ, were sown in early May each year with apneumatic sowing machine (Gaspardo). The seedingratewasbased on 70% emergenceto produce 40, 50, 60or70 plants/m2. The width of the band and interrow space in the doublerow system was7cm. Sow- ing depthwas 1-1.5cm.Before sowing, granu- lar compound NPK fertilizer(10-7-14 withtrace elements) was applied atarate of80 kg N/ha, 56 kg P/ha and 112 kg K/ha. At the beginning of August 20 kg N/hawas applied and the earth- ing-up was done. Weeds were controlled with Gesagard (prometryn 500 g/kg) or Lurox (linuron 500 g/kg)once ayearaccordingtoman- ufacturers’ instructions and later by hand-weed- ing. Insects werecontrolled with applications of Malasiini (malathion 513 g/1) and Ripcord (sy- permetrin 100 g/1, 3-5 times year).
Taproots were hand-harvestedatthe begin- ning of October every year. The size of the har- vestedarea for flat beds and narrowridges was 2.5
m 2 and
for broad ridges 3.8 m2.
The taprootsTable 1.Total and marketableyieldsof carrots under various managementregimes.Means(+S.E.)Marked with the sameletter do not differ (P<0.05). Mainplots(soil surfaceconfiguration), subplots (target plantdensities) and sub- subplots (sowingsystem)weretested within each year.
Yields (t/ha)
1990 1991 1992
Treatments Marketable Total Marketable Total Marketable Total D.F.
Soilsurface
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 narrowridge 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+2.1la 56.6±1.18a 66.2+1.29b 30.1±1.47a 38.9±1.53c Target plant density1 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
1plants/m2
2Thesinglerowsowingsystemwasnotincludedinthe statistical contrast examination of thesowingsystem because the combination “broadridge-single rowsowing system”waslacking.
wereweighed individually and classified accord- ingtocommercial criteria. The marketable yield included taproots weighing atleast 40 g with no external defects.
Therewerelarge differences in weathercon- ditions at seedling emergence time during the study period. The coldest year was 1991, when the heatsum was only 175 degrees by the mid- dle ofJune,whereas it was321 and 376 in 1990 and 1992,respectively. The cumulative precipi- tation from I May until 10 Junewas also high- estin 1991,58mm,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 warmand fairly damp in 1990 and 1992.
The total yield, marketable yield, mean weight ofrootsand proportion of branched car- rots were subjected to split-split plot analyses of variance(Steeland Torrie 1981, Rantaetal.
1991, SAS Institute 1985)using the GLM pro- cedure. Treatment means were compared using Tukey’s HSDtestandcontrastexamination. The
differences betweentreatmentmeans were con- sidered significant atP<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 narrowridges giving the highest yield in both years. Marketa- ble yieldwas notaffected 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 withanincrease 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- creasein seedsownresulted ina 1.05-1.2 -fold Vol.6(1997):363-369.
increase in yield. The increase in yields was greatest between target densities of50 and 60 plants/m2in 1990 and 1992, but between 40 and 50 plants/m2in 1991. The highest average plant populations were obtained when double rows were sown. The targetplant populations, as- sessed during seedingon the basis of70%emer- gence,were reached only in 1991, when condi- tions during seedling emergence were very damp.
The sowingsystem affected marketable and total yields each year (P<0.01). The doublerow sowing system improved the yield in each soil surface configuration(Table 1).Therewerealso statistically significant interactions between soil forming and sowing systemin marketable yield
and total yield in 1990 and 1991 (P<0.04) (Fig. 1).The difference in yields between dou- blerow and band sowing systems was small in ridges in 1991 and 1992; in all years singlerows sownin ridges gave the smallest yield.
Quality of yield
Themeanindividualroot weight ofcarrotswas 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). Seedingrate hadasignificant effecton mean root weight in 1990 and 1991 (PcO.OI).
The lowest seeding rate resulted in the highest meanroot weight each year: 190 g, 123 g and 126 g in 1990, 1991, 1992, respectively. The mean root weights at the highest seedingrate were 139 g, 89 g and90gin 1990, 1991, 1992, respectively.
The sowing system affected the mean root weight only in 1990, when the highest meanroot weight wasrecorded for band sowing, 183 g; it was 173 g in single and 143 g in doublerows (P<0,001). There was a statistically significant interaction between soil surface configuration and sowingsystemeach year (P<0.02) (Fig. 2).
Theaverageamountofbranchedcarrotswas 160 kg/ha, 80 kg/ha and 150kg/ha in 1990, 1991, 1992, respectively. There were only minor dif- ferences betweentreatmentsin thisproperty. The amount of branchedcarrots was not analysed statistically. The drymatter contentoftaproots ranged from 9.7to 11%andwaseach year high- estin thecarrots grownon narrow ridges.
Discussion
Each soil surface configuration requires itsown cultivation technique for the optimal production ofcarrots.In this experiment the highest yields were obtained with narrow ridges and double rows.With the exception of the size oftap roots, Fig. I.The interaction between soil surfaceconfigurations
and sowing systems for marketable yield in a) 1990 (P=0.002), b) 1991(P=0.03).
the effects of the factors studiedon the quality of yieldwere small.
One of the main factors affecting yield was the weather during seedling emergence and its effecton emergence. Good emergence resulted inagood yield, suggesting that good emergence is vital for all cultivation techniques. It seems thatwet weather does not favour cultivation in broad ridges, whereas theuse ofnarrowridges apparently provides a suitable environment for carrotdevelopment, irrespective of the weather.
However, irrigation is becoming increasingly popular among vegetablefarmers, enabling op- timal soil moisturetobe maintained during seed- ling emergence.
The doublerow systempromoted good car- rotyields under all conditions, although there- sults of Salteretal.(1979), Salteretal. (1980) and Mack(1980)suggested thatrow spacing had little effect onroot yields in experiments made on the flat. Kepka etal. (1978) considered band sowing themostsuitable method forcarrotgrow- ing. The usefulness of this method is, however,
impaired by a reduced ability to maintain soil moisture, mostlikely due to differences in the width of the roller wheel in sowing machines;
that of the doublerow sower being narrow and thereforemore inclined topress the seeddeep into moist soil than the broad roller wheel used during band sowing. Our studywas made in fine sand, without irrigation. The effect of soil sur- face configuration may differ fromonesoiltype to another. On the basis of the results of these experiments doublerow orband sowingcan be recommended for ridge cultivation.If, however, the soil is dry during seedling emergence, band sown carrotsshould preferably be irrigated. With flat beds evensinglerows can give satisfactory yields.
The mean root weight ofcarrots was influ- encedmosteffectively by changing the seeding
rate - the higher the seedingrate, the smaller theroots and the higher the yields. This effect of seedingrate on themean root weight ofcar- rotsis consistentwith previously reported results (McCollum etal. 1986, Schoneveld 1990),but Fig. 2.The interaction between soilconfigurationsandsow- ingsystems formeanrootweight ina) 1990(P=0.003), b)
1991(P=0.002), c) 1992(P=0.02).
Vol.6(1997): 363-369.
in general, the effect of seedingrate on yields was small, being significant only in 1990. This finding supports the results of Benjamin and Sutherland (1992), who noted that atenfold 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 werenot significantly different, therewas asignificant difference when yieldswere classi- fied by size.
The effect of sowing system on meanroot weight differed between soil surface configura- tions. Themeanrootweight ofcarrotscultivated in flat beds andnarrowridges was similar in all years, but it was higher for carrots grown on broad ridges. The mean root weight correlates with the size ofcarrots, eventhough the correla- tion is not perfect.
The sowing system didnot affect theexter- nal quality ofroots. Only in 1990was there a difference inmean rootsize between bandsow- ing and doublerow sowing. This finding attrib- utedtothe plant population atharvest,whichwas clearly smaller for band sowncarrots thancar- rots sown in doublerows, presumably as a re- sult of poor emergence. Kepkaetal.(1978)found more split and branched carrots in singlerows, butwe notednosuch effect inour experiments.
Fresh marketcarrots arebest produced by a cultivation technique that requires a high seed- ingrate ondoublerowsandnarrowridges, since a large number of small tap roots are needed.
The optimaltargetplant density in thiscase isat least 60-70 roots/m2 Dragland (1986) likewise recommended70 plants/m2,whereas therecom- mendation of Kepka etal. (1978) was twice as high (150 plants/m2).
Carrots grown for industrial processing are best cultivatedonbroad ridges, in doublerows and atlower seedingrates thancarrotsused for fresh market purposes. Thetargetplant density should be50 roots/m2(or less) dependingonthe variety. Themean root weight ofcarrots grown on ridges is high. Moreover, in the experience of growers, carrots grownon broad ridges tend tobe longer and larger than those grown in oth- ersoil surface configurations. These longroots arenot suitable for packing in small plastic bags butareideal for industrial purposes.
Future studiesare neededon abiotic growth factors, temperatureand moisture in particular, in different soil surface configurations and on different soil types.We also lack basic knowl- edge of the abiotic conditions that prevail in ridg- es of different types. The effect of ridging on the internal quality ofcarrots should also be in- vestigated.
Acknowledgements. We thank Martti Linnainmaa, Jari Pärssinen,HelenaPalo, RaunoKauppila and TerttuKaup-
pila for their excellent technical assistanceduringtheex- periments.We also thankDrAino-MaijaEvers for her val- uable commentson the manuscript.Weareparticularly grateful toDrJonathan Robinson for his comments and for revisingthe text.
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SELOSTUS
Maan muotoilun, kylvötavan ja siementiheyden vaikutus porkkanan satoon
Sanna-Liisa Taivalmaa ja Heikki Talvitie
Maatalouden tutkimuskeskus
Tutkimuksella selvitettiinmaanmuotoilun (tasamaa, pieni jaiso harju), kylvötavan (yksirivi,kaksirivi ja nauha) sekäsiementiheyden(40,50, 60ja 70taimea/
m 2) vaikutustaporkkanan sadonmäärään jaulkoiseen laatuun. Jokainenmaanmuotoilutapavaatiioman vil- jelytekniikan, jonkavalintaan vaikuttaasemihintar- koitukseenporkkanoita viljellään. Taimettumisenon- nistuminen oliyksitärkeimmistä sadonmääräänvai-
kuttavistatekijöistä. Suurin satosaatiinpienestä har- justa. Kaksoisrivikylvö olisopivin kylvötapakaikil- la maanmuotoilutavoilla.
Porkkanan juurenkokoon vaikutti eniten siemen- tiheys; mitä suurempi tiheys, sitäpienempiä juuria.
Maanmuotoilu,kylvötapa tai kylvötiheys eivät vai-
kuttaneet haarautuneiden ja haljenneiden juurten määrään,Viljeltäessä porkkanoita tuorekäyttöönha- lutaan paljonkooltaan melkopieniä porkkanoita.Täl- löin sopivin maanmuotoilutapa on tasamaa taipieni harju ja taimitiheys tulisi olla60-70 porkkanaa/m2. Pieneen harjuun paras kylvötapa onkaksirivikylvö, mutta myös nauhakylvölla saadaan hyvä sato, jos maaperäon taimettumisaikanatarpeeksi kostea. Ta- samaalla myösyksirivikylvöllävoidaan saadatyydyt- tävä sato.Isoissaharjuissa porkkanoiden keskipaino on suurempi kuin muilla maanmuotoilutavoillavil- jeltyjen porkkanoiden, joten iso harju sopii hyvin teollisuusporkkanan tuotantoon.Tällöinsopivataimi- tiheystulisi olla40-50 porkkanaa/m2.
Vol.6(1997): 363-369.
