View of The role of fertilization practices in the yield and quality of carrot (Daucus carota L.)

Journal of Agricultural Science in Finland Maataloustieteellinen Aikakauskirja Vol 61:323—360

THE ROLE OF FERTILIZATION PRACTICES IN THE YIELD AND QUALITY ^{OF CARROT}

(Daucus carota L.)

Selostus:

Lannoitusmenetelmien vaikutus

porkkanan satoon ja

sisäiseen laatuun

AINO-MAIJA EVERS

Kemira Oy, Espoo Research^Centre Luoteisrinne 2,02270 Espoo,Finland

Academic Dissertation

TOBE PRESENTED. WITH THE PERMISSION OF THE FacultyofAgricultureand^Forestryof the University_ofHelsinki,for^public criticism inAuditorium12,Unioninkatu34,Helsinki, on^{November nth 1989,}at12 o’clocknoon

SUOMEN MAATALOUSTIETEELLINEN SEURA ^• HELSINKI

Preface

This research was carried out at Kemira Oy’s Espoo Research Centre during 1985—1989. I ^amdeeply gratefultomy teacher andsupervisor, Professor Erkki Kau- kovirta, Head of theDepartmentofHorticulture, University ofHelsinki,for hissup- port and most valuable instructions and advice during every stage of this study.

I am most grateful to Professor Eero Varis and Professor Antti Jaakkola for reading the manuscript and for their useful suggestions. I wishto express mywarmest gratitudeto Professor Anna-Liisa Varis for her kind support and guidance. I owe my deepest gratitudetoDr. Heikki Rosenqvist, Headtothe Espoo ResearchCentre, and ^to Kemira Oy for providing excellent working facilities.

The encouraging attitude of Dr. AriLokio, former Head of the Espoo Research Centre,decisively contributedtothestartof my postgraduate studies andtothis thesis.

1 would like to express my sincere appreciation to him.

My special thanksareduetoMiss Oili Uusitalo for excellent technical assistance.

Without her intelligence, greatdiligence and organizing ability the project wouldnot have been carriedout in this form. I amalso deeply gratefultoMrs.KirstiKarhunen for creatingafriendly working environment and for smooth cooperation,to Marina Niemi,^Lie. Phil., for her interest in mywork, ^forencouragement and forconstruc- tive criticism of the manuscripts, andtoKatri Tiittanen, M.Sc.,for introducing me into scientific writing, and for warminterest in my work and never-failing support.

I am gratefulto Ulla and Uljas Lehtonen for providingme withtwo organically cultivated fieldareas andcarrots grown onthem. Our discussions weremost stimu- lating, and they broadened my points of view. I also wishtothank all my collabora- tors, especially Mrs. Ann-MarieKorhonen for skilful typing and for her patience with thecorrections, ^Markku Yli-Halla,Lie. Agr., for constructive criticism of the manuscript, Dr. Pauli Seppänen for valuablediscussions, Börje Björkqvist, M.Sc., for advice concerning organic analyses, Veli-MattiTaavitsainen, ^Lie.Phil., ^{for ad-} vice concerning statistical analysis, and the personnel of the Kemira Espoo library for providingmewith all the necessary information. I also thank Sevastiana Kuusa- mo, M.A.,for revision of theEnglish text of the articles and this thesis.

My dearest thanks I owe tomy husband likka for hisencouraging attitude, lov- ing _care and never-failing sympathy, and to my parents and brothers with families for their benevolent care and encouraging ^support of all my attempts throughout the years, which I greatly appreciate. I feel special ^respect and gratitudeto myschool teacher Väinö Voutilainen for his imposing native language lessons and for his last- ing impact on my academic career.

This workwasfinancially supported by the Academy of Finland and Kemira Oy, which is gratefully acknowledged. Finally, I would liketothank the Scientific Agricul- tural Society of Finland for including ^my study in their journal.

Espoo, September 1989

Aino-Maija Evers

List of original articles

The original articles summarized here are:

1 Effects of different fertilization practices on the growth, yield and dry matter content of carrot. J. Agric. Sci. Finl. 60: 135—152.

II Effects of different fertilization practiceson the carotene content ofcarrot. J.

Agric. Sci. Finl. 61: 7 —14.

11l Effects of different fertilization practices on the N0₃-N, N, P, K, Ca, Mg, ash and dietary fibre ^contents of^carrot. J. Agric. Sci. Finl. 61: 99—111.

IV Effects of different fertilization practiceson the glucose, fructose, sucrose, ^taste and texture of carrot. J. Agric. Sci. Finl. 61: 113—122.

V Effects of different fertilization practicesonthe quality of storedcarrot. J. Agric.

Sci. Finl. 61: 123—134.

References tothese articles are made in the text by citing the appropriate Roman numerals.

Contents

ABSTRACT 329

LIST OF ORIGINAL ARTICLES 326

L INTRODUCTION 331

1.1. Vegetable qualitycriteria ³³¹

1.2.Fertilization practices 331

1.2.1. Broadcast vs. placementfertilization 331

1.2.2. Fertirrigation 332

1.3. Effects of fertilization on carrot quality 333

1.4.^Backgroundand aim of thepresentinvestigation 334

2. ^MATERIALS AND METHODS 335

2.1. Field experiments 335

2.2. Fertilization practices 335

2.3. Carrot samples 336

2.4. Soil samples 337

2.5. Weather conditions ³³⁷

2.6. Statistical analyses 337

2.7. Organically cultivated carrots 338

3. RESULTS 340

3.1. Effects of fertilization practices on carrot growthand quality 340

3.1.1. Growth, yield and dry matter content 340

3.1.2. Carotene 341

3.1.3. Nitrate-nitrogen 342

3.1.4. N, P, K, Ca, Mg and ash 342

3.1.5. ^Dietary fibre 343

3.1.6. Glucose, fructose and sucrose 343

3.1.7. Taste and texture 343

3.1.8. Quality of stored carrots 343

3.2. Organically cultivated carrots 344

4. DISCUSSION 346

4.1. Growth and quality criteria influenced by fertilization practices 346

4.1.1. Placement fertilization 346

4.1.2. Singlevs.split application 347

4.1.3. Fertirrigation 348

4.2. ^Quality criteria not oronly slightly influenced by fertilization practices 349

4.2.1. Carotene 349

4.2.2. Glucose, fructose and sucrose 350

4.2.3. Quality of stored carrots 351

4.3. Organically cultivated carrots 351

5. SUMMARYAND CONCLUSIONS 353

REFERENCES 356

MaataloustieteellinenAikakauskirja Vol. 61:329—360, 1989

The role of

fertilization

practices in the yield and quality of carrot (Daucus carata ^L.)

AINO-MAIJA EVERS

Kemira Oy, Espoo Research Centre Luoteisrinne 2, 02270 Espoo, Finland

Abstract.The influence of different fertilization practicesonthe growth, yield and inner quality of carrot (Daucus^carolaL.)was studied. The field experimentswerecarried outin SouthernFinland,onthe experimental farm ofKemira Oy,in 1985and 1986.Unirrigatedand irrigated placement and broadcast fertilization,NPKfertirrigations withoutorwith basic fer- tilization,and PKplacementwithNfertirrigationswerecompared.Placement and broadcast

fertilizationswere carried out by single application, whereas NPK orNfertirrigations were performed assplit applications.

The highest yieldswereobtained when the total phytomass productionwashigh.The yield increased by the placement ofNPK fertilizer ascompared tobroadcast fertilization, and by the placement ofP andK ascompared to treatmentswherePandK werebroadcastedorfer- tirrigated.ThePKplacementwith Nfertirrigationsincreased the root dry matter contentas compared toNPKfertirrigations.The lowest NO_s-Ncontents of rootswereobtained by unir- rigated placementfertilization. NPK fertirrigationscaused higher root NOr^Ncontentsthan anyother fertilization practice, and irrigation^assuch increased the NO,-N contents.^{Root N} andPcontentswereincreased by placement ofPK or NPK fertilizers, but fertilizationprac- tices had noeffectsonK, Mgand Ca contents. Single application increased ash and dietary

fibre contents^ascompared to split applications.In conclusion,the placement ofNPK orPK fertilizers had positive effectsonthe above mentioned quality criteria and yield, and thus in future research andincommercial vegetable production^thesefertilization practices should be utilized.

Fertilization practices had no oronly slighteffectsonthe carotene andsugarcontents, taste, texture and the quality of stored carrots. Carotene content increasedasthe growing sea- son progressed, andwas 41 ^%higherinthe climaticallymorefavourable year 1986 thanin

1985.Totalsugarcontentswerehigherinthe climatically less favourable year1985andinun- fertilized treatments than in 1986andinfertilized treatments. Itwashypothesizedthat carrot sugar contentsarerelated to growth and total phytomass production. The indicative results showed^thatthe NPKfertirrigationswithout basic fertilization had^aslightpositiveeffect^on carrot tasteand textureascompared to placementfertilization but, onthe otherhand,the NPKfertirrigationswithout basic fertilization showedatendency to impairthestorageability ascompared to single application.In conclusion,caroteneandsugarcontentsarestronglyin-

fluenced bygenotypeand climate and thus it is logical that the effects of fertilization practices remained slight. The results of carrot taste do not allow^anyfinal conclusions to bedrawn;

further investigationon the subject is needed.

Index words: fertilization practices, carrot, quality, yield, dry matter, carotene,nutrients, nitrate, ash,dietaryfibre, sugars, sensoryevaluation, storage

JOURNAL OFAGRICULTURAL SCIENCEIN FINLAND

1. INTRODUCTION

1.1. Vegetable quality criteria

Modern vegetable cultivation aimsto even and high-quality products. Quality can be classified ^{as to outer} quality (size, form, colour) and inner quality (nutritionally impor- tant factors, nutritionally negative factors,

tasteand texture). The quality classification is modified case by case, according to each specific purpose for which the vegetables are produced.

The criteria ofouterqualityare defined in national and international quality and grad- ingstandards,and the vegetable marketabili- tyand tradeare based mainlyonthese stand- ards. Lack of rapid, inexpensive and relia- blemeasurement technology has made it im- possible toclassify and price the productsac- cording toinner quality. The nutritionally im-

portant inner quality criteria include nutri- tional fibre, sugars, proteins and essential aminoacids, minerals, vitamins and provi- tamins,^organicacids, essential fatty acids and aromacompounds. The nutritionally negative quality criteria include nitrate content, pesti- cide residues, heavy metal and radioactivity contents, oxalic acid, free amino acids and aromacompounds that giveabadtaste,mak- ing e.g. the carrot bitter _or harsh.

Alternativecultivation methods emphasize the quality criteria differently, and the inner quality is given high priority (Schuphan 1974). Some of the quality factors can be measured by methods known to the natural sciences, but othersare more difficultto de- fine andarecharacterised by aholistic,non- analytical view of _nature (Dlouhy 1981).

The quality of vegetables is influenced ^by genotype,climate and soil aswell asby culti- vation practices, harvest, storageand market-

ing. Different plant species have different op- timal growing conditions, and thus the pro- duction of high-quality vegetables is an op- timization task. Some of the variablescanbe influenced byagrower,someby plant breed- ers and _some by nature.

1.2. Fertilization ^practices

1.2.1. Broadcastvs. placement

fertilization

Broadcast fertilization is themostcommon fertilization practice applied in vegetable cul- tivation inFinland, though placement fertili- zation has been shown in many agricultural studies (Aura 1967, Kähäri and Elonen 1969, ^{Pessi etai.} 1970,Varis and Lannetta 1974, Varis 1975,^Lyngstad 1977, ^{Esala and}

Larpes 1986

a, 1986

^{b) to} increase the yield and the efficiency of fertilizer. Broadcast fer- tilization for row^cropsiseasy toperform in spring before sowingorplanting, but after the foliage has grown, each timeatractor drives through the field some photosynthetasing leaves are damaged. And with common dis- tribution practices, it isnoteasytoaccomplish an even distribution_so that every plant ob- tains an equal amount of nutrients.

Techniques whereasolid fertilizer is placed under the soil surfacearecalledrow applica- tion, banded fertilizationorplacement fertili- zation. In these techniques, thefertilizergran- ulesareplaced inabandat varying depthsun- der the soilsurface, where the moisturecon- ditions remain optimal for granulestodissolve over a longer period of time than in broad- cast fertilization. In addition, placement fer-

tilizationcan increase the fertilizer efficiency, it provides an economical and convenient operation for precise and even distribution, and considering the distance from fertilizerto

seedsorplants, itcan preventsalt damage dur- ing germination _orearly growth (MacLeod et al. 1975).

Various nutrientsaredifferently suitable for broadcast vs. placement fertilization. Both ammonium and nitrate nitrogen applied tothe surface ofloam, silt, silt clay, and fine sand clay soils have been shown to remain in the topinch foraconsiderably long period in dry conditions (Kaila and Hänninen 1961), but in irrigated plots the nitrate nitrogen moves downwards (Aura 1967). This is^an obvious phenomenon, as N0₃-N is unreactive with anyionretaining complexes of soil, it is^read- ily mobile in the soil solution, ^{and it moves} primarily vertically assoilwater moves.Am- monium nitrogen reacts with the cation ex- change complex, becoming absorbed on the surface of soil particles. Mobility is thus diminished (Randall et al. 1985). Conse- quently, the effect of placement fertilization varies from yeartoyear and isclosely related toprecipitationor irrigation and to nitrogen application (Aura 1967, ^{Lyngstad 1977).}

it is generally accepted that orthophosphate in soilreactsrapidly with cations, ^hydrousox- ide coatings,orcations in solution^toform in- soluble compounds, therefore making themo- bility of phosphorus insignificant. Thus broadcasted phosphorus concentrates in the surface soil, is susceptible to loss by erosion (Timmonsetal. 1973), and may influence the surface water quality (Young et al. 1985).

The plantroots growin deeper, moist soil lay- ers, and thus the efficiency of broadcasted phosphorus is poor. The placement of phos- phorus has been showntoincrease the uptake of phosphorus (MacLeod etal. 1975,^Mulkey

etal. 1979) and the efficiency of phosphorus (Pearsonand Kirkham 1980,Peterson etal.

1981). Placement of phosphorus has been reported tobemosteffectiveatlow soil phos- phorus levels (Fox and^Kang 1978, Peterson et al. 1981), in dry soil conditions (Chaud-

hary and Prihar 1974, ^{Ekeberg 1986), at} low soiltemperatures (Gingrich 1964, ^Power

etal. 1964),and with granular phosphorus fer- tilizer(Engelstad and Terman 1980).

It is well established that potassiumas a ca- tion is absorbed _to cation exchangesurfaces and becomesavailable ^toplants from soilso- lution and bycontactexchange. Potassium is relatively immobile in soil, having a moder- ate cation exchange capacity, but in coarse soils it canbe leached downwards by rain or irrigation. Potassium in most casesdoesnot react to become unavailabletoplants. In dry conditions,broadcasted potassium isnottak- en upby plants, but in moist conditions plants can utilize it if the roots come into contact with it. Calcium and magnesium areslightly mobile in the soil. They bind tothe exchange complex of the soil and act very much like potassium. The plant uptake mechanismsare similar to those for potassium.

1.2.2. Fertirrigation

The application of fertilizers in irrigation water is called fertirrigation or fertigation.

The advantages of this methodare the low costs of energy, labour and equipment,great flexibility in thechoiceof time andrate of fer- tilizer application, precise application and dis- tribution of nutrients withsome low-pressure systems, and reduced leaching losses of mo- bile nutrients if the proper application tech- niquesare used. The potential disadvantages arethat fertilizer distribution is determined by water distribution; precise application _rates are not always possible withsomeof thewa- ter application equipment in current use;

fertilizers can be lost in runoff ^water; nitro- gen may be lost by volatilization from NH₄⁺-containing fertilizer ^applied to the sur- face of calcareoussoils, stratification on the soil surface orlocalized concentrationnear the emitter of immobile nutrients (e.g. phospho- rus, potassium and some micronutrients)are observed, and precipitation problems mayre- sult when some forms of nutrients are in- troduced into irrigation waters high in Ca²⁺,

Mg²⁺ and bicarbonate ^HC03

~ (Randall ^et al. 1985). In spite of disadvantages, the fer- tirrigation is becoming increasingly popular in the USA (Randall et al. 1985).In the Mer-

die countries this fertilizer application meth- od isnot widely used, mainly because of the variable weatherconditions, the need for ir- rigation varying from yearto year and from month to month. Also the irrigation equip- ment now in use is not especially good for maintaining _{an even}distribution(Gregersen 1978). Aura (1983) has proposed that in Finnish conditions fertirrigation ismostsuit- able for plants havinga long growing period and taking up nutrients relatively late. Thus vegetables andpotatoes grownon coarsesoils can produce good yields if fertirrigation is used.

1.3. Effects of fertilizationoncarrot quality The carrot root dry matter content is un- affected by increasing amounts of nitrogen (Habben 1972,^Dragland 1978, Aura 1985, Vuorinen and Takala 1987), potassium (Habben 1972), organic _orinorganic fertiliz- er (Nilsson 1979), or by irrigation (Aura

1985, Vuorinen and Takala 1987). A drought period before harvest increases (Dragland 1978) the carrot root dry matter contentand placement fertilizationdecreases it (Ekeberg 1986), and the differences be- tweenyears have beengreaterthan the differ- ences between fertilization treatments (Dragland 1978, Aura 1985, Vuorinen and Takala 1987).

In the literature there are contradictory reports of the influence of macronutrientson the carotene content. An increasing nitrogen amount eitherincreases ^thecarotene content (Freeman and Harris 1951, Habben 1972), hasno effect(Dragland 1978),or it may de- crease the carotene content (Southards and Miller 1962). An increasing amount of potassium has no influence on the carotene content (Gallagher 1966, Habben 1972) or increases it (Southards and Miller 1962).

The fertilizer ^{level or theuse} of organic vs.

inorganic fertilizers has_noeffecton thecaro- tene content (Nilsson 1979).

In fertilization experiments, the N0₃-N contents (Dragland 1978, ^{Nilsson 1979,}

Lehtinen 1984) and the total nitrogen con- tents in carrots (Bishop etal. 1973, Nilsson

1979,Lehtinen 1984) have increasedsystem- atically with increasing nitrogenamounts. The phosphorus content in carrots has not in- creased with increasing phosphorus fertiliza- tion, but increasing potassiumfertilization^in- creasespotassium contentsin carrots(Bishop etal. 1973, Nilsson 1979). Reports of the ef- fect of fertilizationon the calcium and mag- nesium^contents incarrotshavenotbeenpub- lished.

The effects of fertilizationon the ash and dietary fibrecontents have been investigated only a little,but because of the vital role of dietary fibre in human health (Spiller and Freeman 1981),this subject oughtto be well understood. Increasing nitrogen fertilization decreases the dietary fibrecontentand increas- ing potassium fertilization increases the diet- ary fibre content, but the effects have been relatively small(Habben 1972).

Reports of the influence of fertilization_on carrotsugarcontentsin the literatureare con- tradictory. The carrot glucose content in- creases by increasing nitrogen fertilization (Barnes 1936,Habben 1972),decreases ^{by in-} creasing potassium fertilization ^(Habben

1972), or remains unaffected by increasing nitrogen (Dragland 1978), phosphorus (Barnes 1936) or potassium fertilization (Gallagher 1966). The _carrot fructose con- tentincreases by increasing nitrogen fertiliza- tion and decreases by increasing potassium fertilization (Habben 1972). The carrot su- crosecontent decreases by increasing nitrogen fertilization (Barnes 1936, ^Dragland 1978), the sucrose content remains unaffected by nitrogen (Habben 1972)or potassium fertili- zation (Gallagher 1966), and the sucrose content increases by increasing phosphorus (Barnes 1936) or potassium fertilization (Habben 1972). In Nilsson’s (1979) study the glucose, fructose and sucrose contents were unaffected by either thetypeof fertilizer (or- ganicvs. inorganic)ortheamountof fertiliz- er applied.

The flavour ofrawcarrotsis influenced by

genotype and environment (Simon et al.

1982). Sugarsand volatile ^{terpenoids are the}

two major components of carrot flavour (Freeman and Simon 1983), butcarrot aroma is very complex, and it is influenced by many compounds (Simon 1985). Results concerning the effects of fertilization^on carrot tasteand texturehavenotbeen found in the literature.

1.4. Background and aim of the present investigation

Thereare severalreasons why the develop- ment of fertilization practices is important.

Economists have predicted that fertilizers will undoubtly become more expensive in future due_toescalatingcostsof natural gas,labour, mining, exploration, processing andtransport (Randalletal. 1985), andthus it is very im- portant to improve the efficiency of fertiliz- ers. Trade on national and international vegetable markets requires large quantities of products ofevenquality. Atharvest,each in- dividual vegetable should be of similar size and in thesame developmental stage. More

precise dosage and application of fertilizer promotes evengrowth and supplies the plant with nutrients needed at any given time.

Growingconcernis being voiced by the pub- lic towards the impact offertilizers^{on theen-} vironment. Modern application techniques can play a significant role in preserving the quality of the environment while still produc- ing optimum crops. Techniquestoreduce en- vironmentalconcern almost always result in improved fertilizer efficiency (Randalletal.

1985). The primary aim of thepresent inves- tigationwastostudy whether the development of fertilization practices affects some of the inner ^quality criteria ^ofcarrot.

In public discussion there is increasing in- terestin human health and nutrition, ^{and of-}

ten vegetable quality is consideredto depend mainly on modern growing practices and mineralfertilizers.However, also genetic and environmental factors havea certain effecton the quality. The secondary aim of thepresent investigation was to find out which quality criteriaare mainly dependenton^genotypeand climate, and which on fertilization.

2. MATERIALS AND METHODS 2.1. Field experiments

The field experiments were carriedouton the Kotkaniemi Experimental Farm of Kemira Oy in Vihti, Southern Finland (60°22'N, 24°22'E) during the growing seasonsof1985 and 1986. Thecarrotvariety grown in thisex-

periment_{was cv.} Nantes Duke Notabene 370 Sv which is commonly grown for the food in- dustry in Finland. Coated seeds (I)were sown

1 cm deep at a row distance of 50 cm and plants were thinned later to 30 plants/m.

Weeds were sprayed with promethryn twice pergrowingseason. Sypermetrinwasused for protection againstcarrotpsyllit, Trioza^apica- lis F. The carrots were harvested manually,

and 8 kg of sample per plot in 1985 and 15 kg in 1986were stored in refrigerated storage (0...⁺I.5°C, RH 90—95 ^%)for six months and fourmonths, respectively.

2.2. Fertilization ^practices

In the field experiments, ten treatments werecompared (Table 1). In thecaseof unir- rigated and irrigatedcontrols, ^noannual fer- tilization wasapplied. In the original articles I—V these have been called unfertilizedtreat- ments.

In broadcast and placement practices (Ta- ble 1), allnutrients ^{weregivenas asingle ap-} plication in spring, beforesowing. Placement

fertilization_was done with _a fertilizer drill.

Table 1. The fertilization treatments and the total amounts of nutrients^and irrigation water.

Treatment Number and time of Macronutrient Irrigation water

fertilizer applications amounts in 1986³ amountsin 1985

kg/ha and 1986

N P K mm

Unfertilized

Unirrigated 0 0 0 0 0

Irrigation 0 0 0 0 3x10

NPK placement

Unirrigated Once before sowing 80 35 133 0

Irrigation Once before sowing 80 35 133 3x 10

NPK broadcast

Unirrigated Once before sowing 80 35 133 0

Irrigation Once before sowing 80 35 133 3x 10

NPK fertirrigations

No basic Three times during the ^{season 80 29} 160 3x 10

Half the basic1 ^Once before sowing and 80 32 142 3x 10

three times during theseason

PKplacement 2

3N-fertirrigations Once before sowing and 81 56 133 3x 10

three times during theseason

4N-fertirrigations Once before sowing and 155 56 133 4x 10

four times during theseason

' Half of the nutrients were giveninbasic placement fertilization and halfin NPK fertirrigations.

2 Phosphorusand potassium ^weregiveninbasic placement fertilization and nitrogenin fertirrigations.

' The nutrient amounts were30^{% higher} in 1985thanin 1986.

The fertilizerrowdistancewas50cm,^{and the} seeds were sownafterwards, ³ cmbeside the fertilizerrow. In the broadcastmethod the fer- tilizerwas spread onthe soil surface manual- ly and harrowed in witha rotarycultivator.

The NPK fertirrigations and PK placement with N fertirrigations (Table 1)weresplit ap- plications, in otherwords, the nutrientswere given periodically three to five times during the growing season. In NPK fertirrigations, awater-soluble fertilizerwas dissolvedⁱⁿ wa- ter,and allorhalf of the nutrientamountwas spread with aself-made boom. In PK place- ment with N fertirrigations, the phosphorus and potassium were given by the placement method with_afertilizer drill in spring before sowing, and nitrogen was given by nitrogen fertirrigations during the growing season.

All fertilized_treatmentsreceived thesame amountof nitrogenexceptPK placement with 4N fertirrigations which receiveda supraop- timalamount of nitrogen (Table 1). The PK placement treatments received a greater amountof phosphorus owingtothe phospho- rus content of the granular fertilizer used in the experiments. The amount of potassium was somewhatgreater in the NPK fertirriga- tiontreatmentowingtothe fertilizer used. The micronutrient fertilizations ^are given in the original article I. Irrigated placement and broadcast fertilized treatments received the same amounts of water as the fertirrigated treatments (Table 1).

2.3. Carrot samples

In 1985,carrot rootand shoot sampleswere collected three times during the growing sea- son (Table 2) for determination of fresh and

dry weight and N0₃-N, total N, ^{P, K,} Ca, and Mg contents. Carrot_root samples were collectedatharvest for yield, for determina- tion of carotene, glucose, fructose and su- crose, and for sensory evaluation, ^{e.g. taste} andtexture. After the storageperiod, the mar- ketable yield and weight loss were weighed, thecarotene contentwasdetermined, ^andsen- sory evaluation fortasteand^texture wasper- formed.

In 1986,carrot root and shoot sampleswere collected three times during the growingsea- son(Table 2) for determination of fresh and dry weight and NOrN content, and ^root samples were collected for determination of carotene content.Carrotroot and shootsam- pleswerecollectedatharvest for determina- tion ofN, P,K, Ca, ^{Mg and ashcontents,} and root samples for determination of yield, die- taryfibre, glucose, fructose and sucrose con- tents, and for sensory evaluation, ^{e.g. taste} andtexture.After thestorage period, themar- ketable yield and weight loss ^{were weighed,} the carotene, NOrN, N, P, K, Ca, ^Mg, ash, glucose, fructose ^{and sucrose contents} were determined, and sensory evaluation for taste and texture was performed. The sample size for yield was 8 m 2, i.e. 16row metres per plot. Other sample sizesareshown in Table 3.

Table 2. The schedule for fertilization, sowing, sampling, harvest and storage.

Fertilizer experiment Organiccultivation

1985 1986 Location 1 Location 2

Basic fertilization 4 June 1985 6^June 1986 14May 1986 21 May 1986

First fertirrigationor irrigation 14 June 1985 29 June 1986 Second fertirrigationorirrigation 5 July 1985 10 July 1986 Third fertirrigationorirrigation 19July 1985 24 July 1986 Fourth fertirrigationor irrigation 2 Aug. 1985 7Aug. 1986

Sowing 8 June 1985 9 June 1986 14May 1986 21 ^May 1986

First plant sampling 20 Aug. 1985 12Aug. 1986 14Aug. 1986 14Aug. 1986

Second plant sampling 10Sept. 1985 3 Sept. 1986 I Sept. 1986 I Sept. 1986

Harvest 30 Sept. 1985 6Oct. 1986 25 Sept. 1986 25 Sept. 1986

End ofstorage 2 April 1986 23 Dec. 1987 23Feb. 1987 23Feb. 1987

Table 3. The carrot sample sizesin the experiments of 1985and 1986.

Sample size Carrots Carrots

per per

plot treatment 1985

Root and shoot fresh and dry weight N03-N

20 mm

80 20*

N, P, K, Ca, Mg 20*

Root carotene 6 12*

glucose, fructose,sucrose 10*

tasteand texture

5

10 20*

1986

Root and shoot fresh and dry weight NO,-N

20 80

20 80

N, P, K, Ca, Mg, ash 20 Root carotene

5

6 24

dietary fibre ⁵ 20

glucose, fructose,sucrose 5 taste^and texture

20 40 10

Carrotswerecollected from two blocks only.

In 1985, samples for determination of qual- ity were collected from two blocks only. A heavy rain in June 1985 caused acruston the soil surface, as aresult ofwhich the planta- tion was uneven in _twoblocks which were omitted.

The methods used toanalyse the plants are describedorreferredtoin the following origi- nal articles:

dry weight (I) carotene (11)

NOj-N, N, P, K, Ca, Mg, ash and dietary fibre (III)

glucose, fructose, ^{sucrose (IV)}

taste and texture (IV) 2.4. Soil ^samples

The soil in the experimental fieldwas fine sand with 15—30 °7o clay and a humuscon- tentof 12—20 °7o. Soil samples^werecollected acrossthecarrot rowfrom a soil layer 15^cm deep. Samples were taken two days before sowing and 6, 27, 41, 54, 76, 96 and 116 days

after sowing in 1985. In 1986, the samples weretakenoneday before sowing and 18,31, 46, 65 and 117 days after sowing. Soil ^sam- pleswerecollected and analysed asdescribed in the original article I. The chemical charac- teristics of the soil in spring before fertiliza- tion _are given in the original article I, Table 4, those during growing seasons aregiven in the original article I, Figure 5.

2.5. Weather conditions

The weather conditionswereunfavourable in June and July 1985 (I/Table 3). Themean daytemperatureand the number of sunshine hourswerelower than the long-term^averages.

On 16June, heavy raincame onlytwo days after the first irrigation, when seedlings had begun to emerge. The heavy rain caused a crust toform_onthe soilsurface,and thecrust hindered the emergence of seedlings. In Au- gustand September 1985, weather conditions were moderate, but the soil was too wet.

In 1986, Junewas very warm and sunny.

The mean day temperature and the number of sunshine hourswere above the long-term averages (I/Table 3). The precipitation was only 28 mm, and thesoil ^{was dry. Julywas} favourable for growth. August and Septem- berwerecold and rainy, and thus unfavoura- ble for growth. Altogether, 1985was a less

favourableyear for growth than 1986.

2.6. Statistical analyses

The field experiments were set up accord- ing _to the method of completely randomized blocks. Therewerefourblocks,ten treatments and thus totally 40 plots.

Theresults ^werestudied statistically bycon- trast analysis (Steel and Torrie 1980). The twoyears werestudied separately (II—V),ex- ceptin the original article I. The partitioning of treatmentsinto contrasts are presented in Table 4. The unfertilized, placement and broadcast fertilizedtreatmentswerealso stud- ied by the analysis of variance as afactorial experiment. Thefertilizationlevelswere 1)no

fertilization,2) placementfertilization, and 3) broadcast fertilization. The irrigation levels were 1)noirrigation and 2) irrigation. The sig- nificance of differences betweenmeans were tested with the Duncan ^testor with Student^- Neuman-Keul’s ^test (Steel and Torrie 1980).

The Pearson’s ^{product moment} correlation coefficients (r)werecalculatedtomeasurethe strength and direction of the linearity between the variables.

The differences were considered to be statistically significant at the5 ^% level, ^and were marked with asterisks as follows:

* significant at 5 ^% level, p<0.05

** significant at 1 ^% level, p<o.ol

*** significant at 0.1 ^% level, p< 0.001 The differences were regarded to show a tendency at the 10 ^% level, ^p<o.l.

2.7. Organically cultivated carrots

In 1986, simultaneously with the fertiliza- tionexperiment, samples fromtwoorganically

cultivated fields were collected. These were grown from the same seed material, ^{but the} geographical position, climate and soil charac- teristics were different. The aim of this_sam- plingwas^toobtain _somedataon organically cultivated^carrotsand soils,but theywerenot compared statistically with theresults of^the fertilization experiment.

Organically cultivated fieldswerelocated in Central Finland. At locationone, the field had been cultivated organically for five years, at location _two for 20 years. The field works were done manually, and they were home gardens. They were fertilized with compost (I/Table 2) and sown in May (Table 2). No herbicidesorpesticides _wereused, but Agryl clothwas spread _over the plantation topre- vent insect damage. The row distance _was 25—30 cm, and plants were thinned to 25 plants/m. Carrots were harvested manually, and a 15 kg sample was stored in the same refrigeratedstorage asthecarrots for the fer- tilization experiment. Carrot and soil samples werecollected and analysed similarlytothose

Table4.-The partitioning ^oftreatments to contrasts.

Unfertilized Notirrigated NormalN, split Placement fertilization Placement fertilization Placement fertilization Placement fertilization Placement fertilization Broadcast fertilization Broadcast fertilization Broadcast fertilization Broadcast fertilization Single application Single application Single application Single application Irrigated single application Irrigated single application Irrigated single application Irrigated single application Unirrigated singleapplication Unirrigated single application Unirrigated single application Unirrigated single application Pand Kplacement fertilization PKplacementwith N fertirrigations PKplacementwith N fertirrigations

vs. Fertilized vs. Irrigated

vs. Big amountN, split vs. Broadcast fertilization vs. Split application

vs. NPK fertirrigations, nobasic fertilization vs. NPK fertirrigations

vs.PK placementwith N fertirrigations vs. Split application

vs. NPK fertirrigations,nobasic fertilization vs. NPK fertirrigations

vs.PK placementwith Nfertirrigations vs. Split application

vs. NPK fertirrigations, nobasic fertilization vs. NPK fertirrigations

vs. PK placementwith N fertirrigations vs. Split application

vs. NPK fertirrigations, nobasic fertilization vs. NPK fertirrigations

vs.PK placementwith Nfertirrigations vs. Split application

vs. NPK fertirrigations, nobasic fertilization vs. NPK fertirrigations

vs. PK placementwith N fertirrigations vs. Pand K, noplacement fertilization vs. NPK fertirrigations,nobasic fertilization vs. NPK fertirrigations

taken for the fertilization experiment. The soil 3—6 %in location one and of 12—20 %in in the organically cultivated fields _was fine locationtwo.Weather condition datawerenot sand moraine, with a humus content of collected.

339

3. RESULTS

3.1. Effects of fertilization practices on carrot growth and quality

3.1.1. Growth,yield and drymatter content The rootand shoot dry weights were posi- tively correlatedonall sampling dates of both years(Fig. 1). Thus theroot dry weight was high when the total phytomass productionwas great.In otherwords,the big photosynthetiz- ing apparatus provided plenty of photosyn- thates for the growing root.

The fertilization practices with_a highroot toshoot dry weightratio ^wereplacement fer- tilization and NPK fertirrigations without ba- sic fertilization. In otherwords, thesetreat- ments favoured root growth in relation to shoot growth. Unirrigated broadcast fertiliza- tion had_alowroot toshoot dry weightratio,

which indicates that thistreatmentfavoured shoot growth in relationto rootgrowth (I/Fig.

4). The calculatedroot toshootratios ^{did not,} however, correlate with yield, asthe ratio may be high even though the absoluteroot yield was relatively small,as was thecase in NPK fertirrigations without basic fertilization. This treatmenthad a highroot toshootratio,^but only _amoderate yield (I).

The highest yieldswereachieved with place- ment fertilization _as compared tobroadcast fertilization. The yields werealso high when phosphorus and potassium were applied by placement fertilization as compared to the treatmentswhere P and K were broadcasted or fertirrigated (Table 5). Thus it _can be _as- sumed that the yield increase was due to the placement of phosphorus or potassium. Be- cause granular NPK or PK fertilizers were used, ^{it is} not possible_todistinguish between the effects of phosphorus and potassium.

Table 5. The effect of different fertilization practices onthe carrot dry matter content and total yield,^aswell^as standard errors.

Treatment Dry matter content Yield

% tons/ha

1985 1986 Average 1985 1985 Average

No fertilization

No irrigation 9.4±0.1 10.710.1 10.1 36.4±3.1 47.611.5 42.0

Irrigation 9.5±0.2 10.7⁺0.1 10.1 32.0⁺3.0 45.815.4 38.9

NPK^placement

No irrigation 9.710.3 10.510.2 10.1 37.712.7 50.612.4 44.2

Irrigation 9.310.2 10.310.2 9.8 38.611.5 56.613.4 47.6

NPKbroadcast

No irrigation 9.410.3 10.6⁺0.2 10.0 37.1 12.9 48.211.8 42.7

Irrigation 9.610.2 10.310.1 9.9 25.912.6 48.214.8 ^37.)

NPK fertirrigation

No basic ^9.210,3 10.310.2 9,8 35.115.9 52.113.7 43.6

Half the basic 9.410.1 10.510.2 10.0 36.012.1 55.011.6 45.5

PKplacement

3N fertirrigation 9.610.1 10.810.1 10.2 39.812.0 48.416.5 44.1

4Nfertirrigation 9.610.2 10.5⁺0.2 10.1 37.711.8 52.612.2 45.2

Average yield 9.510.4 10.510.2 10.0 35.613.3 50.513.7 43.1

Placement fertilization increased also the phosphorus content ofcarrot roots as com- pared tobroadcast fertilization, NPK fertir- rigations withorwithout basic fertilizationor split application in 1986 (111/Table 2). The soil phosphorus levels were low in alltreatments (1/Fig. 5).

Theroot dry matter contents obtained in the present studyare in agreement with the literature in thesensethat the differences in root drymatter content were greaterbetween years than between fertilization practices, and that the nitrogen amount did not affect the root drymatter content (1). In both years, the root drymatter content washigher in the PK placement with N fertirrigation treatments than in the NPK fertirrigationtreatments(I).

Thus the placement of phosphorus andpotas- siumincreasednot only the yield but also the dry matter content of_carrots.

The parameters that correlated with root drymatter contentwere root sucrosecontent (1985r⁼0.84*), root total sugarcontent (1985 r⁼0.95**, 1986 r⁼0.39*) and shoot NOr N content (1985 r⁼ —0.71 with p<0.07, 1986 r⁼—0.32*). Carbohydrates form the major dry matter component in carrot, as Souci et al. (1979) reported that 100 g carrot fresh weight contains 88.2 gwater, 0.98 gprotein, 0.20 g lipids, 8.71 g carbohydrates, 1.05 graw fibre,and0.86 g minerals.Glucose,^fructose and sucroseaccountfor91 ^% of the totalsu- gars incarrot (Alabran and Mabrouk 1973).

Sucrose is themostabundant sugar in carrot (Alabran and Mabrouk 1973, Simonet al.

1982). Thus it is most natural that the in-

creased dry matter content depends on in- creased sucrose and total sugar amounts.

3.1.2. Carotene

Fertilization practices showedsometenden-

cy(P^<0.1)toaffect thecarrot carotenecon- tentin the less favourable year of 1985 (II).

The PK placement with N fertirrigations tendedtoyield ahighercarotene contentthan did broadcast fertilization,irrigated single ap- plication and NPK fertirrigations. There was also _atendency to a higher carotene content when P and K were placement fertilized, as comparedto treatmentswhere P and K were not placement fertilized. In the climatically more favourable ^{year of} 1986, fertilization practices had no effects or tendencieson the carotene content at harvest.

Weather conditions had _{a strong} effecton the carotene content of carrots; the average carotene content was41 ^%higher in 1986 than in 1985 (11/Fig. 1). The carotene content in- creased with advancing growing season (11/Fig. 2).

In 1985,^carotene correlated positively with root dry matter percentage (r⁼0.78*) and negatively with theroot to shoot ratio (r⁼

—0.75*). In otherwords, ^the carotene con- tentwashigh when the shoot fresh weightwas greatin relationto root fresh weight. This is in _agreement with Banga and De ^Bruyn (1964), who reported the same correlations.

They concluded that the percentage of dry mattercan be seen as an indicator of the in- tensity of photosynthesis, and itappears that

Fig. I. The correlations of root and shoot dry weightsin 1985and 1986on three different samplingdates, A two months after sowing, o three months after sowing and □ four months after sowing.

the totalcarotene contentof thecarrot roots depends highly on the intensity of photo- synthesis andonthe size oftheapparatusused for photosynthesis. In 1986, thecarotenecon- tent correlated negatively with glucose (r⁼

—o.4l**) and with fructose (r⁼—o.46**).

This may indicate that whena greater amount of photosynthateswas used forcarotenesyn- thesis, less is left in theroot in the form of glucose and fructose.

3.1.3. Nitrate-nitrogen

Fertilization practices affected the N0₃-N contents of carrots (III). In both years the highest N0₃-N contents in carrot roots were found in NPK fertirrigations without basic fertilizationtreatment,and the lowestcontents in unirrigated placement fertilized treatment (lIIa/Tables2 and 3, 111/Fig. 2a). In 1986, the irrigation increased the root N03-N content as comparedto unirrigated treatments.Thus part of the difference found between NPK fertirrigations without basic fertilization and unirrigated placementfertilization ^{may be} due

to irrigation. The relatively high N0₃-N con- tentin NPK fertirrigations without basic fer- tilizationtreatment cannotbe caused only by the nitrogen application methodorirrigation, because the N0₃-N contents were lower in both years in PK placement with N fertirri- gations. Thus the placement of P and K may have hadapositive effect _on the

NO3-N

^con-

tent ofcarrot roots. Splitapplication didnot differ from single application. The N0₃-N contents were lowas compared ^to the find- ings reported in the literature (III), and there was acleardifference between years (111/Ta- ble 2).

3.1.4. N, P, K, Ca, Mgand ash

The effects of different fertilization prac- tices on the macronutrient and ash ^contents in carrotshoots androots werestudied in 1986 (III). The mean macronutrient ^{contents de-} tected in shoots and^rootswerein good agree- mentwith those reported in theliterature,^the

only exception being the shoot Ca content whichwas lower than those reported in the literature. The fertilizationpractices affected theroot N and Pcontents,but hadno effects on the K, Ca and Mg contents (111/Table 2, 1986).Flowever, fertilizationas comparedto unfertilized treatments increased ^{the root K}

content highly significantly.

Fertilization increased the N content of roots, and the Ncontent was higher with PK placement withN fertirrigations ascompared to NPK fertirrigations without basic fertiliza- tion or ^to NPK fertirrigations (111/Tables 2 and 3, 1986). In thesetreatments,Nwasgiven by split fertirrigations; thus the N application methodcannot be thereason for the higher Ncontentin PK placementwith N fertirriga- tions. The contrast PK placement with N fert- irrigations also includes the supraoptimal N amount, which had a slightly higher root N content (111/Table 2, 1986),but thiswas not statistically significant. The placement of PK fertilizer probably hada favourable effecton N uptake.

In the Pcontentsofcarrot rootthere were manysignificant differences between fertili- zation practices in 1986 (III). From these results it canbe concluded that the placement of NPKor PK fertilizer increased the^root P contents. NPK fertirrigations without basic fertilization yielded alower Pcontentthan did any other treatmentexcept broadcast fertili- zation.

Fertilization increased the ash content as compared to the unfertilized treatments.

Placementfertilization,single application and unirrigated single application yielded a higher ash contentthan did split applications, NPK fertirrigations and PK placement with N fert- irrigations (III). In 1986, the root ash con- tent correlated with root N content (r⁼ 0.437**), root Kcontent (r⁼0.393*), root Ca content (r⁼—0.289, p⁼0.07), dietary fibre (r⁼0.340*), total sugarcontent (r⁼—0.306, p⁼0.06) root dry matter content (r⁼

—0.355*), shoot N0₃-N content (r⁼0.282,

p⁼0.08), shoot N content (r⁼o.s**), shoot