IPIBulletin 15

International Potash InstituteBasel/Switzerland 1996

IPI-Bulletin No. 15

Aspects of Fertiliser Usein Modern, High-YieldSugar Beet Culture

Dr. A.P. DraycottAshfield Green FarmWickhambrook - NewmarketSuffolk CB8 8UZGreat Britain

BInternational Potash Institute

P.O. Box 1609CH-4001 Basel/Switzerland

LT~y 1996

Contents

page

1. Introduction ...................................................................................... 5

2. Increasing world sugar requirement .......................................... 62.1. World sugar production .................................................................. 72.2, World beet sugar production ......................................................... 82.3. Sugar beet in Europe ...................................................................... 92.4. Origin and distribution of sugar beet ............................................ 102 .5 . T h e seed ........................................................................................... 1I2.6. The plant - its growth and development ........................................... II2.7. Components of high beet performance ....................................... 13

3. Nutrient uptake, removal and demand byhigh yielding sugar beet .............................................................. 14

3.1. Uptake, removal and demand ....................................................... 143.2. High yielding sugar beet ............................................................. 143.3. Major nutrients ................................................................................. 153.3.1. Nitrogen ........................................................................................ 15

Introduction ................................................................................. 15Nitrogen uptake ................................................................................ 15Nitrogen removal ......................................................................... 17Nitrogen demand ........................................................................ 17Nitrogen deficiency ...................................................................... 18

3.3.2. Phosphorus and sulphur ................................................................ 19The two macronutrient anions ..................................................... 19Uptake and concentration of phosphorus ..................................... 19Demand and offtake of phosphorus ............................................ 20Phosphorus deficiency ................................................................ 20Sulphur ........................................................................................ 21

3.3.3. Potassium and sodium .................................................................. 21Potassium uptake and demand .................................................... 22Effect of potassium on growth and yield .................................... 23Potassium deficiency .................................................................... 23 te

Sodium uptake and demand ........................................................ 24

3

Effect of sodium on growth and yield .......................................... 24Soil sodium concentration and sugar-beet yield ........................ 24

3.3.4. Calcium and magnesium ............................................................. 25Calcium and soil reaction (pH) .................................................. 25Calcium as a plant nutrient ......................................................... 26Magnesium ................................................................................... 26Uptake and demand ................................................................... 26

3.4. M icronutrients or trace elements ................................................ 273.4.1. Boron ............................................................................................ 273.4.2. M anganese ................................................................................... 283.4.3. Iron, copper and zinc ................................................................... 29

4. Fertiliser management in relation to nutrient requirement ....... 304.1. Nitrogen fertiliser requirement .................................................... 324.1.1. Effect of nitrogen on root quality ................................................ 334.1.2. Effect of nitrogen on yield ........................................................... 354.1.3. Soil type and nitrogen fertiliser requirement .............................. 35

Predicting nitrogen fertilizer requirement by soil analysis ......... 364.2. Effect of phosphorus fertiliser on yield ....................................... 374.2.1. Soil analysis for available phosphorus ....................................... 374.2.2. Phosphorus balance ..................................................................... 38

4.3. Potassium and sodium fertiliser requirement .............................. 384.3.1. Sodium ......................................................................................... 40

4.4. Use of magnesium fertiliser ......................................................... 41

4.5. Importance of boron application .................................................. 42

4.6. M anganese application ............................................................... 434.6.1. Soil analysis for available manganese ......................................... 43

4.7. Other trace elements ................................................................... 43

4.8. The dangers of excess fertiliser .................................................. 44

5. Worldwide use of nutrients for sugar beet and returns ......... 445.1. Does it pay? ......................................... . .. . .. . .. . .. .. . .. .. .. . .. .. . .. .. .. . .. . . . 47

6. Acknowledgements ................................................................... 48

7. References .................................................................................. 49

8. Profile of the author ................................................................... 52

4

1. Introduction

Sugar (the common name for sucrose) is produced from only two crops,cane and beet. Cane sugar has been produced in large quantities in the tropicalregions for several centuries. It continues to dominate the world supply ofsugar.

Beet sugar, in contrast, is a relatively new crop, appearing during the 19thcentury in the temperate regions. This century beet has increasinglycontributed to the world's insatiable demand for sugar. Last year (1994/5) totalworld production of sugar was 116m t, 35 of which was from beet (30%) and81 from cane (70%).

There is little doubt that beet sugar will continue to contribute about a thirdof the world requirement, both political and market forces ensuring a future forbeet. This means that in tonnage terms, production will need to increase. Partwill come from expansion in the area grown and part from improvements insugar yield per unit area. An example of the former is the new factory inPortugal due to open in 1997, a country never having grown beet before. Anexample of the latter is the near linear increase in sugar yield per unit area overthe last 70 years in UK (Draycott, 1972) and several other European countries(Figure 1).

50

40

30

20

0

10

1920 1940 1960 1980 20D1

Fig. I. Trend in average root yield over 70 years.

5

The main object in writing this monograph is to help ensure that themomentum for increased production goes on apace. Fundamental to high yieldis a sufficiency of all the nutrients and the following pages review the state ofknowledge of each element. With some an excess is harmful to white sugarproduction so this too is reviewed.

2. Increasing world sugar requirement

Following the trend seen throughout the 20th century sugar consumptioncontinues to increase by one to two million tonnes per year. Table I showsworld requirements over the past five years with current consumption beingabout 11 5m tonnes. What of the future? There is scant evidence to suggest thatsuch trends will not continue provided worldwide economic stability alsocontinues. Indeed with the dramatic increase in population could a more rapidrise be envisaged?

Table 1. World sugar consumption (in million t).

1990/91 1991/92 1992/93 1993/94 1994/95

110 111 112 113 115

Two main factors have influenced and will continue to influence per capitaconsumption - dietary and economic. Until the 1970s few questioned thevaluable role played by white sugar in the human diet. It was regarded as animportant energy source in addition to increasing the palatability of manyfoods and drinks with which it was mixed.

Over the past 20 years some scientists have associated sugar with severalnon-infectious diseases, in particular heart diseases. This implication, whethertrue or false, has stabilised or decreased per capita consumption in Europe andN America, as shown in Table 2.

Table 2. Sugar consumption per head of population (in kg).

1990 1991 1992 1993 1994

Europe 40 39 38 37 37N. America 38 38 38 38 37S. America 40 43 42 42 42Africa 15 14 14 14 13Asia 12 12 13 13 13

6

In Africa and Asia economic rather than health grounds determineconsumption, only 13 kg per person being the norm. Clearly if such risingpopulations could afford more sugar, per capita consumption would have a

dramatic positive impact on world sugar requirement. Currently such changes

look unlikely. Overall the world consumption looks set to continue to rise by

about Im tonnes per year for the foreseeable future.

2.1. World sugar production

Figure 2 shows total production of sugar from cane and beet over the past

50 years. Total production will soon be 120m tonnes, having risen almost

linearly since 1945. More sugar has always been produced from cane than

beet. During the period 1945-65 production of both rose in parallel. Over the

past 30 years (1965-95) cane production has risen much more rapidly than

beet due to complex social, political and economic considerations.

120

108 Beet . . . .

Cane ..........96

Total -

84

72

600

48

24 -*-. - - - -

12 -

1945 1955 1956 1975 1985 1995

Fig. 2. World sugar production.

7

2.2. World beet sugar production

Table 3 shows the amounts of sugar obtained from beet during the 1994/5harvest. Total production was 35m t. North Africa and South America eachproduce about m t from beet, being mainly cane producers. North Americaproduces over 4m t, mostly in USA. Asia is a major producer with 4Am t,most of this coming from China, Iran, Japan, Syria and Turkey. All theseamounts are dwarfed by Europe which now produces almost 30m t sugarannually from beet.

Table 3. World beet sugar production (harvest 1994/95).

1000 tEgypt 130Morocco 412Tunisia 20Africa 562Canada 182USA 4127N. America 4309Chile 548Uruguay 0S. America 548

Afghanistan IChina 1087Iran 678Iraq IJapan 640Lebanon 20Pakistan 20Syria 113Turkey 1895Asia 4455World (excluding Europe) 9874World (including Europe) 35077

Data from Licht (1995).

8

2.3. Sugar beet in Europe

Detailed statistics about many aspects of beet sugar production are

available for Europe (Licht, 1995). Table 4 shows averages for 1989-94.

Table 4. Sugar beet in Europe (averages 1989/94).

Area Roots Sugar Root Sugarprocessed production yield yield

1000 ha 1000 t 1000 t t/ha t/ha

Western EuropegAustria 51 2636 462 51.4 9.0

Belgium/Lux. 107 6364 1027 59.6 9.6

Denmark 66 3432 521 51.7 7.9Finland 33 1071 165 33.2 5.1

France 428 24931 4527 58.3 10.6

Germany 565 27219 4342 48.2 7.7

Greece 45 2810 336 62.8 7.5

Ireland 33 1375 229 41.5 6.9

Italy 278 12777 1717 45.7 6.2

Netherlands 121 7484 1209 61.9 10.0

Portugal 1 26 3 49.0 5.1

Spain 172 7648 1090 44.6 6.4

Sweden 48 2347 375 48.3 7.7

United Kingdom 177 8476 1432 48.0 8.1

EU, total 2125 108596 17435 51.1 8.2

Switzerland 15 915 144 63.9 10.1

Ex-Yugoslavia 124 4922 621 37.9 4.7

Western Europe, total 2264 114433 18200 50.5 8.0

9

Table 4. Continued.

Area Roots Sugar Root Sugarprocessed production yield yield

1000 ha 1000t 1000t t/ha t/ha

Central/Eastern EuropAlbania 7 117 12 17.0 1.7Bulgaria 24 447 37 16.8 1.5Czech Republic 115 4016 571 35.2 5.0Slovakia 44 1477 163 33.4 3.8Hungary 108 3813 494 34.5 4.5Latvia 13 269 31 21.2 2.4Lithuania 30 745 82 24.8 2.8Poland 397 13062 1825 32.8 4.6Romania 164 3432 344 20.5 2.1Russia 1358 26278 2543 19.1 1.9Ukraine 1545 37439 4497 24.1 2.9Other CIS 190 4504 502 24.2 2.7

C./E. Europe, total 3995 95599 11101 23.7 2.8Europe, total 6259 210032 29301 - -

The area devoted to sugar beet is about 61Am ha, producing 210m t roots. Itis interesting that W. Europe has 2.3m ha under sugar beet and producesalmost 20m t sugar whereas E. Europe has nearly 4m ha but produces onlyI Im t sugar. Thus yield of sugar per unit area in W. Europe is three times thatin E. Europe.

There are many reasons for the higher production in the West. Just one ofthese is the nutrition of the crop. The following pages attempt to identifyoptimum conditions for the crop to produce at least 10 t1ha sugar.

2.4. Origin and distribution of sugar beet

Sugar beet is a specialised type of Beta vulgaris which was first developedin Europe at the end of the 18th century from white fodder beet. It is a biennialplant which stores up reserves in the root during the first growing season sothat it is able to over-winter and produce flowering stems and seed in thefollowing summer.

10

The plant can be cultivated successfully in a wide range of climates onmany different soils. Most is grown at latitudes between 30 and 60'N, as asummer crop in maritime, prairie and semi-continental climates. It is alsogrown as a winter or summer crop in Mediterranean and semi-arid conditions,and with supplementary irrigation in regions where low rainfall previouslyprevented its cultivation. Tables 3 and 4 list the countries where it is currentlygrown.

2.5. The seed

Throughout last century and the first half of 20th century the crop wasgrown from multigerm 'seed'. Such 'seed' was in fact the natural fruit of theplant, containing several germs which gave rise to a cluster of plants. Tocultivate the crop successfully entailed hand-thinning to leave one plant ateach station.

The great break-through was when genetic monogerm seeds werediscovered (Savitsky, 1952). These obviated the need for the hand-thinning.Coupled with selective herbicides, developed more or less at the same time,the modem crop is entirely mechanised. A fuller history of sugar beetdevelopments has been reported by Winner (1993).

2.6. The plant - its growth and development

Most modem, high-yielding crops are grown from monogerm seeds, sownto a stand using precision drills, to produce 80-100,000 plants/ha which meanssowing 100-120,000 seeds/ha. Seedlings emerge after about five days in idealmoist, warm conditions. This can extend to five weeks in very cold and excessi-vely dry or wet conditions, too often experienced in the European spring!

At this very early stage the seedlings should have a large pair of healthycotyledons and about two weeks later a pair of true leaves. Again warmth,moisture and an adequate but not excessive supply of nutrients are essential forrapid early growth, as will be shown in later pages. In fact in this area, morework is needed to identify optimum soil concentrations of major, minor andmicro nutrients so that there is no limitation to leaf expansion.

With the appearance and expansion of the second pair of true leaves theplant becomes entirely reliant on its root system to obtain nutrients for growthfrom the soil. Thus from this stage and for the whole of the remainder of thegrowing season a deep, spreading and healthy root system is vital for high

II

final yield. Such a root system should extend to more than two metres deep byharvest. Thus water and nutrients from the subsoil of sugar-beet fields play amuch more important role than with many other crops, as detailed in later pages.

At six weeks from emergence a crop on course to produce a high yieldshould have at least 10 true leaves. Up to about leaf 14 mature leaves grow toa larger and larger area but usually from leaf 15 onwards leaves never reachthe size of leaf 14. Leaves die in the order they were produced, a normalprocess as further leaves expand to form what should become a 100% leafcanopy in conjunction with the plant's neighbours. Leaves appear and expandin a linear relation with thermal time (Milford, 1973; Scott el aL, 1974)provided neither water nor nutrients are limiting. It is a period when a largesupply of nitrate-nitrogen, potassium and other nutrients must be readilyaccessible to the roots to satisfy a sudden and rapidly increasing demand.

From the 8-10 leaf stage till harvest the leaves and the tap root grow inparallel, the tap root making up an increasing percentage of dry matter (Fig 3).

100Leaf

0E Stem + petiole

- 60 -

4o-

200

a-

May June July Aug Sept Oct Nov

Fig. 3. Distribution of dry matter in high yielding sugar beet.

It is now firmly established that there are no separate vegetative andripening periods as thought by earlier workers (e.g. Ulrich, 1955). Nutrient andwater uptake continues and provides for leaf growth and sugar storage untilharvest. Fig. 4 shows that much potential is lost due to poor light interceptionin Western Europe.

12

600

ElAmount intercepted

o400

.0

0

0

o~ 2oo

April May June July Aug Sept Oct Nov

Fig. 4. Poor light interception during the early stages of growth results in

reduced yield potential.

2.7. Components of high beet performance

In simple terms, sugar beet should be grown so that 100% leaf cover isachieved as soon as possible after sowing. In this way maximum use is madeof the sun's radiant energy. Scott and his co-workers have shown that yield is

proportional to radiation interception (Scott and Jaggard, 1985). Full cover ofhealthy leaves (without excessive leaf production) then needs to be maintaineduntil harvest.

Such a crop will produce maximum root dry matter which is the basictarget. However, nutrients should not be in excess of that required for thisgrowth pattern because sugar percentage and root quality will be reduced by

any excesses as shown in later sections.

13

3. Nutrient uptake, removal and demand by high yielding sugar beet

3.1. Uptake, removal and demand

These three terms are often used loosely and confusingly, sometimessynonymously. In the following text, uptake is defined as the quantity (kg/ha)of nutrient present in the crop at a particular time in the growing cycle, notnecessarily at harvest. It is the product of the dry matter yield and the nutrientconcentration. Removal is the quantity of nutrient taken from the field atharvest. Demand is nutrient uptake per unit time (kg/ha/day) as summarised inTable 5.

Table 5. Summary of expected uptake, removal and demand of nutrients byhigh yielding sugar beet.

Uptake Removal in roots Maximum demandkg/ha kg/ha kg/ha/day

N 200 80 5P20 5 75 40 1K20 400 100 14CaO 250 80 3MgO 65 35 1Na 100 15 8.5S03 50 25 2B 0.25 0.11 0.01Fe 2 1 0.1Mn 1 0.6 0.03Zn 0.9 0.03 0.02Cu 0.4 0.2 0.015

Note: The above quantities vary widely with soil type and climate and are ageneral guide only to production of 10 t/ha sugar crops.

3.2. High yielding sugar beet

This is much more difficult to define. High yield to one farmer might beconsidered low yield to his neighbour! Similarly high yield in one region orcountry could be regarded as low yield elsewhere. In common with all crops,the presence of adequate water and nutrients, and the absence of weeds, pestsand diseases are pre-requisites of high yield.

14

Current monogerni sugar beet has the potential to (and sometimes does)produce yields in excess of 100 t/ha fresh roots of high sugar percentage andquality. Such yields are the rarity rather than the rule in the varied climateswhere the crop is grown. A realistic and achievable target yield in many of thecountries known to the author is 10 t/ha total sugar, or 62.5 ttha roots at 16%sugar. In the following pages this is the standard high yielding sugar beet, andis so defined.

3.3. Major nutrients

3.3.1. Nitrogen

Introduction

In common with most crops, nitrogen is the most important element of all,because few soils contain sufficient in an available form, i.e. as nitrate or ammo-nium, to provide for maximum growth. Where the element is in short supply,yield is drastically reduced, and may even be halved on some soils. Nitrogenhas a remarkable effect on the appearance of the crop, most noticeably by impro-ving the colour and vigour of the leaf canopy. This has led to a widespread

over-use of nitrogen, which decreases both sugar percentage and juice quality.Over the past 20 years, progress has been made towards optimising the use

of nitrogen through a better understanding of the crop's requirement undervarying conditions of soil and climate. Since 1945 there has been a rapidannual increase in the average application rate in many countries, reachingamounts which were clearly excessive in the 1960s and 1970s (van Burg et aL,1983). During the last decade, largely as a result of detailed research and

development work, there has been a change to more realistic quantities, whichis to the advantage of producers and processors alike.

Much work remains to be done, particularly in the area of understandinghow to compensate for a shortage in the soil whilst leaving little excess. Notonly does the excess decrease root quality but it is often in a form which canbe leached into drinking water. Such environmental problems must be solvedfor sugar beet because ploughed-in tops also release nitrogenous compoundsas they decay.

Nitrogen uptake

High yielding sugar-beet crops are generally thought to need to take up

about 200 kg/ha N in total to give maximum sugar yields. Few mineral soils in

15

continuous arable cropping can provide more than 60 kg/ha of nitrogen eachyear without regular additions of fertiliser. Thus the crop obtains part of itsnitrogen requirement from applied fertiliser and part from soil reserves (mainlyfrom decaying organic matter plus a small amount from unused fertiliser givenfor previous crops). The nitrogen dynamics in a 'typical' UK sugar beet fieldare shown in Fig. 5.

Crop Uptake2002t Fertilisers

Organic manures 120and crop residues

50

Soil Mineral NNH +

- NO2 -NO-

1 4 160

Organic matter I Leaching4000 35

Fixed NH4300

Fig. 5. Nitrogen in typical arable soil (kg/ha N).

The amount of fertiliser applied before sugar beet greatly influences theamount of nitrogen present in the crop at harvest. Without any fertiliser, cropsmay contain as little as 25 kg/ha when grown in soil with small reserves ofnitrogen and 100 kg/ha when grown on relatively fertile soil. With correctfertiliser, crops producing maximum sugar yields contain about 200 kg/ha N.With an excessive supply of fertiliser and/or residues in the soil, there arereports of the crop taking up more than 400 kg/ha N.

In the spring, young plants contain 5% N in leaf dry matter and 3% inroots, these concentrations falling rapidly as the season progresses. In cropsproducing maximum sugar-beet yields, the tops contain about 3.0% N in drymatter at harvest and the roots about 0.8%.

16

Recent work w ith 15N in several countries has helped the understanding of"

nitrogen uptake by sugar beet. Ilaunold (1983) in Austria show ed that, with anormal application of feriliser, 50% of the nitrogen was taken up by the crop,20% was left in the soil and 30% disappeared, presumably by de-nitrificationor leaching. Similar studies by Lindemann et al (1983) in France over a five

year period on various soils showed that 50-80% was taken up by the crop,and that the soils themselves contributed 100-215 kg ha. Broeshart (1983)

placed I5N at intervals down to 120 cm and Found that sugar beet took it up

effiectively from all depths, particularly during later stages of development.

X t Ze~r/ ttnovcl

Where roots only are removed from the Field and tops ploughed in a y ield

of I t/ha sugar can be expected to remove about 80 kg/ha N. Ihis varies

widely with the amount of available nitrogen in soil prior to harvest. growth

stage and soil water. Leaves, petioles and crowns together contain about 120

kg ha N, with the same provisos as for roots. Crops containing more than these

amounts often produce no more than 10tha sugar and roots may be low in

sugar percentage and high in impurities.In contrast there are reports (Jourdan et aL. 1992) of very high yielding

crops removing less nitrogen. They grew a crop producing 85 t/ha roots at

18.7% sugar (100 tlha at 16%) which removed only 165 kgha N. Ihis

outstanding crop had the benefit of well-distributed rainlIll. plus irrigation and

near optimum temperatures fbr growth.

Viarogcn demand

Fiigure 6 shows an idealised uptake curve for a crop to produce at least I0

t/ha sugar. I)emand is greatest during June and JOIN. Uptake over 50 days at

this stage is 150 kg ha N. Demand is thus at least3 kg hvda> . much more ifgrowth of the canopy is vet great during the second half of June.

Prerequisites to satisfy this demand for nitrogen are a sufficiency of nitrate

present in the soil where there are roots growing. plus water at near field

capacity. Ihe fertiliser program me to fIllt-H this detnand is dealt with later.

17

2te

z

I 100-

50845 30

ii

Apn May June Juty Aug Sept

Fig. 6. Nitrogen uptake pattern required to produce 10 tiha sugar.

\iroge, deficieocy

When tile crop is welI supplied with nitrogen, it has a dark green leaf asshow~n in Plate I. This crop is approaching 100% cover and rapidly laking upthe necessary 200 kgha N. When the supply falls shorl of this requirement forany reason, the leaves take on a paler look, verging on a yellowing. IIme"er,there are no symptoms which can be used to identiy niitrogen deficiency withcertainty (c.f. for example, magnesium or boron deficiencies below).

Ila'tc No ,.Sugar beet supplied i% ithall (he nutrients to produce a

'high yield, in particular anadequate but not excessiveaInt of iirogen

3.3.2. Phosphorus and sulphur

The two macronutrient anions

The phosphorus requirement of sugar beet has been well researched overmany years but relatively little is known about the other macronutrientelement, sulphur. The two elements are taken up in similar quantities, as thephosphate and the sulphate anions respectively. Work on the former haspredominated because, in the past, soils have contained little phosphorus butsufficient sulphur to allow crops to yield fully.

Cultivated soils usually rely on additions of phosphorus in fertilisers,organic manures and crop residues to replace that removed at harvest. Fewsoil-forming minerals contain phosphorus, so little is released duringweathering, in contrast to other nutrients such as potassium, calcium andmagnesium. In recent times phosphorus concentrations in the soil have tendedto increase each year, because little if any is lost by leaching and also becausemore is applied as fertiliser than is removed at harvest, even with the greatlyincreased yields of cereals, sugar beet, potatoes, and other crops.

Sufficient sulphur to allow full yield is normally deposited in rain in theindustrialised countries of the world. The main origin of this sulphur is the com-bustion of fossil fuels (such as coal, gas and petroleum) which contain variablequantities of the element. This position is changing with increasing interest inclean air. More and more effluent gases are being 'scrubbed' to decrease atmos-pheric pollution, and, as a result, less sulphur will be deposited on the land.Also, most modem fertilisers (e.g. urea, ammonium nitrate, and triple super-phosphate) contain no sulphur, in contrast to ammonium sulphate and singlesuperphosphate which do contain sulphur but are now used less frequently.

Uptake and concentration of phosphorus

In sugar-beet crops, about half the phosphorus is in the roots and half in thetops. In crops grown without any additions of the element for many years thecrops take up very little, e.g. 5 kg/ha P20 5. The phosphorus dynamics in atypical sugar-beet field are shown in Fig. 7, where regular applications offertilizer have been made.

The concentration of phosphorus in all plant parts decreases from soonafter emergence to harvest. Typical concentrations for seedlings in April are1.6% P20 5 in top dry matter and 0.9% in root dry matter, decreasing to 0.9and 0.7% respectively in August. At harvest in November these concentrationsare typically 0.8 and 0.5%.

19

Total Uptake75

Plant available Organic<2.5 35DX)<2.5 (70%)I

Mineral1500 - Adsorbed(30%) 45

(1%)

Fig. 7. Phosphorus in typical arable soil (kg/ha P20 5).

Demand and offlake of phosphorus

Demand during the period of rapid growth is about 0.8 kg/ha/day P20 5 tosatisfy uptake by tops and roots. During the period August to November rootsmust take up 0.15 kg/ha/day. There appears to be little redistribution of theelement between tops and roots.

Offtake by a crop producing 10 t/ha sugar is typically 40 kg/ha P20 5 in theroots, tops at this stage containing 35 kg/ha.

Phosphorus deficiency

Phosphorus deficiency symptoms are rarely seen on mature sugar-beetplants and appear only where the concentration of available soil phosphorus isextremely small (e.g. on plots in the classical experiments at Rothamsted andSaxmundham where no fertiliser has been applied for many years). Symptomsare more common on seedlings, especially where other factors such as soilacidity, pests, diseases or herbicides have damaged the root systems andinhibited nutrient uptake.

Irrespective of the age of the plant, phosphorus deficiency is typified bydark green leaves and stunting of the whole plant. Leaves have a characteristicpurple-red coloration when severely deficient (Plate 2) and this may develop

20

into browning and death. tap-root growth is also retarded by shortage ofphosphorus, and a mass of fibrous secondary roots is olen produced.

I'lwc ,\t. 2.

Ty pical purple colour ofphosphorus deficienc\

Sulp/ur

I'he requirement of" this major plant nutrient by, sugar beet has had little

attention. Nox that responses to sulphur b% other crops (e.g. oilseed rape) have

been reported nex work on sugar beet is in progress. Most industrialisedcountries hase rapidly decreased sulphur emissions and therefore deposition.I iis source of sulphur was often suflicient to satisfy crops' requirement but

this may no longer be the case. Deposition rates at Rotham sted have fallen

fiom ', k2g'ha in 1980 to less than 10 kg/ha/year of sulphur as S in I 995.

Sulphur is taken up rapidly- into the tops of sugar beet fromt May to August,

peaking at about 50 kg/ha SO, (20 kg/h a S). Ihe amount in roots increases

throughout the gro'%.ing period, about 15 kg'ha So 3 (6 kg ha S being the

ofitake in November.

3.3.3. Potassium and sod iurn

The two monovalent cations potassium and sodium are normally

considered together when planning the nutrient requirements of sugar beet

because it has long been known that they can partly replace each other. In

classical field experiments testing increasing doses of each in the presence and

absence of the other, sields show a signiticant negative interaction (Adams.196I). More detailed studies, described beloN. indicate that too i11L0

elphasis has been placed on the interchangeability of potassium and sodiun

tertilisers. Best performance is nowk known to result from sugar beet grosn in

soil with an adequate supply of both elements.

21

P,',1> / I U1s V( I, AC; ; Ih ,> t e~ it ~ f u4 I

Polassill is taken Lip rapidl bx sugar-beCt crops noni June to Augus.LIhe mt present in loots and tops throughout tire year ot a crop >ieldinrI0 t/ha sugar is shown in Pig. 8. The amount in toots reaches a maximlumn at

harvest (around 100 kg ha KO): tihe amount in tops is greatest in lateSeptember-earl) October. after which it decreases as leaves die and fall off theplants, At its peak the total uptake approaches 4W0 kgha K). Lager cropsmn lake up more. e. an 85 t'ha crop of roots it I8,7t, sugar grown inFiance took itp over 450 ksg/ha K20 (Jourdan c /a<- 1992) Peak uptake of thiscrop "as on 20 July because leax es senesced from that date onwards

4004

300

0-

ct

2CC

//

June Jl, Ag Setp <Ot N.o

Fig. 8. Potassium uptake by high yitelding sugar bet.

-lie authors drew attention to tihle deuand during June and July. up to15 kgb haday K(). Thi crop removed 150 kg ha K.) in roots at ham est I hecrop wias not given any sodinm iv tiliser, so part of the large uptake could havebeen reduced. probably without loss of yield.

II the rapid demand lor potassium (and sodium) as the canopx is expandingis not satistied by soil and fresh fertiliser vield will he depressed. Fig. 9 showsThat relativel little of the soils background supply is in solution, less in factdian tolal uptake. Implieations lor Iet rtiliser requirement are dealt wv ith later.

12

Total Uptake400

1Potassium in solution

350(<1%)

Organic Fixed5000 35000(13%) (86%)

Fig. 9. Potassium in typical arable soil (kgha K O).

/frect o/potassium on growth and yield

Potassium is very mobile in plant tissues and is found throughout the plant.It is important to photosynthesis. and the sugar which is produced relies on

potassium for movement to the storage root. At harvest, plants givenpotassium (and sodium) have a significantly greater sugar percentage thanthose given none. This has important financial implications because, for agiven weight of sugar produced. growers are often paid commnensurately more

for high sugar percentage roots. In addition, costs are decreased because, for agiven weight of sugar, less weight of roots has to be harvested and transported.

Potassium also inproves performance by increasing leaf area in May-August. this allows the crop to intercept more radiation (particularly in thespring when a large proportion falls on bare soil) giving proportional increasesin sugar yield (Figure 4).

Pots ium de/iciencv

"hen the plants are extremely short of potassium, the outer mareins of the

older leaves take on a bronze colour. The worst affected areas die as shown in

Plate 3. A yellowing and then browning spread down between the leaves as theseason progresses.

2-,

IPlat" N. o3Potassiurn defic ienc49W '0 Inls 5On ai imaltrx Ileaf

Sdiu i/tJplal and domancpd

Sugar beet was selected rom %kild beet types grow ing on the shores of theMeditenanean and, nor surprisingly therefore, requires sodium chloride to beMutritionally complete. The fact that it takes up and uses a large quantity ofsodium makes it unique amongst crops.

For a beet crop producing 10 Lha sugar, total uptake is typically about 100kg'ha Na (around 12 kg/ha in roots and 85 kg/ha in tops at harvest).Concentration in root drx matter ranges form 0.04 to 0.1 I1 i ald in top dr_matter from 0.9 to 1.7% in crops given normal fertiliser applications. Iyp calaverage values for roots and tops are 0.08 and 1.4% respectively.

1-A/W, 0/8 1(1/uP) oP gPoYawth L,IJVdi

Sodian fertiliser affects growth and \ild in a similar wlax to potassium. Itincreases leaf expansion early in the growing season, increases the proportionof root to top dry-matter production. and improves sugar concentration in rootsat harvest (Draycott and Farley, 1971). Some of the mechanisms for theseimprovements were investigated in controlled environments by Nilford ,t al{1977), xho found that, besides increasing the area. thickness and succulenceof the leaves, sodium chloride increased the water capacity of the % hole plant.Ihe, suggested that the greater water capacity of treated plants buffered themagainst conditions of moderate water stress. All of these beneficial effects arereflecled in sugar yield responses to sodium fertiliser, vhich are shown later.

Sod/,yodii, .oncenftrotion a)V id Smur(, heeit yWi/

In arid and semi-arid climates, sodium concentrations in the soil are oftentoo high for satisfactory crop growth. In contrast, soils of northern Europe are

24

P, pIjj Oudmnu

In 11 a l111 1 %I;i IlI

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m p " l n qNr0 w , ,W m d

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o lmuI >.( j }><pp Si. doII %.ILLII I m OipiLL pimi 211 Alm 11111q II n$ L1>{I~f IlI

(l"' ' I/ I '! md, '

(ro- It on chiaIk- oltininu, sotIl uptakc h. a (i tha t of) CLI It appiOlidch 5(00k (',i C I (Jotrdan V/ d. 199)1. Nhicv not mal i\ total 1upAc is .!0 kuih;t

t) \hoiii two III Is ill the Clc >Lv ind One thlid ill the root, t ltI'leQ'ti) ,I t k> ha hbade ( tO

N\IlegiI l I, a Jke ctincnt in the chlorophlln oiectle mnd a shililriee IatII "ild iha s sc 11111 COMNLICyIce> lot stlell lliQt heel othci ctothtp

I li t I - LL 1f 1 LiLit'( 1ill d l'icietic\ in "t ar beet I, flc lpp lu tic otitt Stiic, l iLAt>, 1-2 nj ii dilmcetr oln te distal tar m i n> < lto flt id )Ia

H it i, ltiik occti lll t in ili or August.I.iFllowing a di pmiod Iissue intile tkftcd IceT ol Oie ci al Cr 1bn ormall> , ,Iad h) i cdl-e oft lh ICALecOitt fluted tile iilitt i, I> stend mOwn hlell tie \In> 111d t in ltei\ t,'k,, blconule ncctolic bCe"innine at the eCg of thlthItA I lhc necroticISit i, culK brown ojI black fll %x% i ittle. o that it b;aks 1.ai> wlen

iouthed o etles tilt diii poitlloi hAks oft" and tht i0 '" heeontcsrl~taacid %sticalil tncltcd Plate d sholts tm pcal irtid-season sl ptolll. TiLT

minci u concenrtion in Icit" (1\ mntilcr I IOl health plaI/ iSs s usull] illthI rn"t c f (ill the "pling) to it (n tilhe lte suimt4I} tII \vs \wtnh thei tI icilS I llt I I cd i i d tellabot e ustiall conitii I botiot 0. -0 ' 0I,.

7 r.11, 4.17 i7fi~~i i <Ni litze iltn d flciecv in

It ed - dsolea in

lie tops lake tp inagnesitll rapidl tip to tile time of conplete leatco\ er andthen contain aboutl 20 k'a itg(). Roots [like up the clcment right up to harvest.(.f lake is about I3 keIla M Ut Iaxinum demn and is 0.65 kg ha daN %e()

3.4. Micronutrients or trace elements

In addition to the Miajor nutrient elements described so far, sugar beet, inCommon wih other crops. needs very small amounts of other elements. I heseIcron t rieats, or trace elements, essential for plants are boron, chlorine,cobalt. copper, iron, manganese. molybdenum and zinc. Other elements suchasgermanium, nickel, rubidium, selenium and vanadium are recognised asbeing essential br some plants but their importance in sugar beet nutrition hasnot been in lesti rated.

In most soils, the requilements of sugar beet for aticronutrients are,upplied trom soil reserves, weathering of minerals, rainfall, lime, fertiliser

Lnd organic mianture. One dressing of fann-ard niannire supplies more of mosticrLutrients than a sugar-beet crop removes. Ilowever. ol soils where

natural supplies are snW all and ",'here farmin g practice depletes reseryes, someelements need to be applied for sugar beet to yielt] fully. In Host countries.bolon and malganese are the onkl tvo of importance. Localised areas nashIow sporatdic s xiplons ot rol deficiencx and some crops mayk be short ot

copper antid ine but these deficiencies appear, at present, to be of liittleeconomic sienificance. (See survey of current practice belo,,).I lowever, asyields continue to increase and farming practices change, applications oftbee

iiicronu trien ts nlav beconlie inore important.

3A, I. Boron

Boron is by far the most in]portant of the trace elements needed by sugarbeet because, 'vi thout an adequate supply. tihe yield and quality of roots issecre i depresed. A shortage causes tvpica I symptoms to appear not ondI\ in]the leaves (as is tie case xx ith most other element de Iciencies) but also in tIlepetioles. cro\xns and roots. (Plate 5). Brandenburg (193 I) first showed thatboron deltcienc. wias the cause of heart rot' and 'dr' rot'. leart rot is tile termapplied when tile growing point becomes blackened and dies. Dry rotdescribes tihe synmploms on the tap root shoulders Nkhich appear subsCquentlIA full description of all tiIe s ,i'ptons is gi'xen by )ray cott (1972).

Boron deliciencv is widespread throughout the sugar beet regions of tieworld and the sym ploms are similar in all countries It usually occurs in cropsuroxx a in soils Mviich possess certain features in coimon: as well as havin'glow. concentrations of available boron they tendto be alkaline, sand,, and drx'.

27

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r i,

KI iC c lit ugar-h111 oa :11140lr> l 2+ipp\ 111 IIlia I " l d ,I a ode( an1t(5 om ius YvmLZV 0 I I pll huL n <o0141(1 h 1 i Np 1K i A

WIN Y Lo' Iv t >11100 ; 10 . I ll in %%l co-idnth io , A 0 l k hollo lWto. crnmnl mhih olkn hills "kh! ",w Inc rh vll o ncco " a!' y i;: lore

IHld Ic leal <-04 [0, I IC C Im ini >Ol IOS , d uo A h ; o1, d th e LI K, of LL ( I

al fl, tloo 0141 t 301avaleo of 11 ON an 1101 hin. KIII C al H.11 KINAB YAW=I "OrnI iclm III puBlt dal0kw n h p11 > rs, hI e ppa moro No A II 01 II ' lol

t 0111 i ll ILoUM II". ttln 112 i0 and h oo id U jaiheI, loi J L I LI -> > tLon K<Litta ii

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t LtIT .My (e q. in pcu oi l H twaulded Ws Manllctn . ',? [)H Ill e~ %1( m\I' I l bh ;ojlrlvmlF hi1 ct)uaLI,d wt nIuni, odl Me]( oiho' mi lanum ' imw w okarI'~t i v "'tIl lt O nc}

halo b2i doscrihcl [ iN ovo. 1110 OlCho -llSIV (i re1il4 .111<, < l I ,oil i, OCVIpliOx andl

2 1l8 l Falk undo'lood I he "dlolc dlte of I la ld scc atll 1I1 0, ht

availability and a soil containing a large amount of total manganese oftencontains little that is available to plants because it is not in the divalent form.

Not" c Na 6.Manganese deficiency.

l.eaves of plants with deficiency symptoms in mid-season usually contain10-12 ppm Mn whereas leaves from healthy plants of the same age contain 50-200 ppm. Radioactive tracer studies showed that the element does not move

from leaf to leaf (lienkens and Jongman, 1965). Thus, when treated with foliarsprays of manganese, only the sprayed leaves have increased concentrations:

newly formed leaves do not benefit from sprays given earlier. Total uptake ofmanganese is about I kg/ha Mn.

3.4.3. Iron, copper and zinc

Most soils contain huge amounts of iron and a deficiency is rare. When it

does occur the leaves of plants show typical bright yellow symptoms (Plate ?).Often this is on highlx calcareous soils where presumably iron is immobilized.Sugar beet usually takes up to about 2 kgha fe by harvest. approximately

evenly distributed between tops and roots. There are reports of much largeruptakes ( 12 kg/ha) vs here soils contain large quantities of available iron.

Shortage of copper is not seen in field grown sugar beet but can beartificialy produced in nutrient culture (Plate 8) Sandy and organic soils

sometimes contain too little copper for maximum growth lptake by a high-yielding crop is about 0.1 kgha Cu.

Zinc deficiency is very rare, most soils containing sufficient for sugar beet.

At harvest the crop may contain about 0.4 kg ha Zn,

29

Iron dcticienc%

Plate V), s.Artificially induced copperdeficiency in nutrientculture.

4. Fertiliser management in relation to nutrient requirementSection 3 above has outlined the amounts of each nutrient which sugzar beet

must take up to produce high yield. This section nov, deals with theirapplications because in common With other crops, sugar beet usually satisfiesonl part of its need for each nutrient from the soil: the remainder must beobtained irom fi liliser, organic manure or foliar spray applied b\ the grower.Not surprisingly, most of the questions which are asked of crop researchersand advisers are about which elements need to be applied in a given soilsituation and how much of each is required for optimum yield. The need toanswer these questions has led to literally thousands of field experimentsworldwide. This amount of work has been considered necessary largelybecause of the wide range of climates and soils in which the crop is grown.

'3t

The climate plays a part in the nutrition of the crop because it sets limits onthe likely yield and therefore the uptake of nutrients. Indirectly, the climatealso affects the amounts of nutrients needed because it determines, to a largedegree, the soil characteristics through leaching and other soil formationprocesses. The other dominant factor which decides which and how muchnutrient is needed at a particular site is the physio-chemical make-up (orlithology) of the parent material from which the soil is formed. In practice, thesugar-beet grower has to manage his particular soil through additions ofnutrients to allow the crop to make maximum use of the climatic resources athis location.

Without doubt, the greatest step forward in sugar-beet nutrition in the past20 years has been the widespread adoption of soil analysis as the basis for anutrient application programme. This approach, which contrasts markedly withthe earlier method of simply applying an average quantity to all fields, givesscientific answers to both of the questions 'which' and 'how much'.Internationally agreed methods of analysis have been introduced which arereliable, repeatable and, most important, which accurately determine the plant-available nutrient concentration of a given soil. These have gained rapidacceptance in many countries, and have persuaded growers thatrecommendations for each crop's nutrient requirement can safely be based onsoil samples. Interestingly, several of these methods, e.g., those for phosphorus(Olsen et al., 1954) and magnesium (Draycott and Durrant, 1970), have beenworked out using sugar beet as the test crop and have since been shown to beapplicable to many other common crops. These methods allow the cost ofunwarranted fertiliser to be saved on fertile fields and enable nutrientdeficiencies to be made up on others.

Comparisons of the concentration of plant-available nutrients present insoils where sugar beet is grown show wide variability from region to region.Some soils, e.g., in parts of Spain, North Africa and the Middle East, havegrown sugar beet and other crops intensively for only a few years, oftenfollowing the provision of irrigation. Many others, e.g. in northern Europe,have been in arable cultivation for centuries and have many features incommon, particularly their ability to supply the major nutrients needed bysugar beet and other crops.

Nitrogen is in short supply in nearly all arable soils and is the mostimportant element applied to sugar beet in fertiliser form wherever the crop isgrown. When virgin soils are brought into intensive farming, phosphorus isusually the first element needed; however, the continued use of fertilisers

31

containing this element has meant that many old arable soils now contain largereserves of phosphorus, and fresh applications given little or no increase insugar-beet yield. Consequently, in the past 20 years most of the research efforthas been directed towards understanding nitrogen requirements, whereasresearch on phosphorus has declined. Work has continued on the othermacroelements, particularly the cations potassium, sodium and magnesium forwhich sugar beet has a high requirement compared with other common crops.The gradual shift of sugar beet to lighter soils, brought about by mechanisationof sugar-beet growing, has increased the need for these three elements whichare often in short supply on such soils.

The macronutrient requirement of the sugar-beet crop is now fully satisfiedon many fields, resulting in greater interest in the micronutrient requirement.The uptake of microelements has increased in parallel with increasing yields,causing the need for additions where, previously, the soil's natural supply wassufficient.

Not only must the macro and micro elements be available to ensure a highyield but, in commercial practice, the lift in performance must be economic inrelation to nutrient costs. Last but not least, additions of nutrients which havean adverse effect on root processing (particularly nitrogen) must also beconsidered on an economic basis so that growers' and processors' requirementsare harmonized as far as possible.

4.1. Nitrogen fertiliser requirement

In addition to improving the colour of the leaves, nitrogen fertilisernoticeably increases their size and number. Early in the season, therefore,nitrogen increases dry matter production per unit area, mostly from leaves andpetioles. Later in the season, nitrogen maintains this increase in leaf and

petiole dry matter and also increases root dry-matter production. This isreflected in greater sugar production per unit area.

Armstrong et al (1983) showed that nitrogen fertiliser did not affect theconversion of intercepted radiation to dry matter but greatly increased the

amount intercepted. In practical terms, fertiliser nitrogen applications need to

be planned to boost the early growth of the leaf canopy, to maintain it throughthe period until harvest but to avoid excess which inevitably depresses rootquality. The following sections show what progress there has been towardsachieving these objectives.

32

4.1.1. Effect of nitrogen on root quality

Figure 10 shows the typical effect of nitrogen fertiliser on yield, sugarpercentage and juice purity. In soils which contain a large concentration ofavailable nitrogen the addition of only a small amount of fertiliser causes a

rapid decline in both characteristics of quality. Much of the effect on sugarpercentage results from increased water retention by the tap root. The drop in

juice purity largely reflects increasing concentration of amino compoundscaused by excessive uptake of nitrate late in the season.

12-

9-

I I I I

18

b

017-

a

16-

6- ------------

-95-

2

94 -

50 100 150 20

Noge appfllotlon (kglhc N)

Fig. 10. The effect of nitrogen fertiliser on sugar yield, sugar concentrationand juice purity on a mineral soil.

33

Dutton and Bowler (1984) found that, on average, an increase in aminonitrogen concentration in roots of 100 mg N/100g sugar decreased sugarpercentage by about 0.8%. For optimum returns for grower and processor theysuggested that the aim should be to set an upper limit of 150 mg N/100g sugarfor mineral soils and 200 mg N/100g sugar for organic soils. The percentagereductions in net crop value (i.e. the value of the beet less the cost of thenitrogen fertiliser) at greater levels in the UK are shown in Table 6.

Turner (1989) reviewed the value of testing every load of beet delivered tothe factory for amino nitrogen concentration. Preliminary work started in1981, and testing has since been adopted at all factories in the UK. Individualresults are conveyed to the growers, together with advice on the implicationsof excessive nitrogen fertiliser usage. Average nitrogen applications in the UKhave declined, with benefits to both sides of the industry as a result ofdecreased fertiliser costs, increased sugar percentage and improved rootquality. It may also result in less nitrate left in the soil to be leached intopotable waters (Johnston, 1989), although recent work suggest that nitrogenresidues after sugar beet are independent of the amount of fertiliser nitrogenapplied (Allison and Hetschkun, 1990).

Table 6. Reductions in net crop value related to application levels of nitrogen.

Amino N Approximate reduction(mg/bO0g sugar) in net crop value (%)

200 1.0250 3.5300 8.5350 14.0

Marcussen (1985) described parallel experiences in Denmark where themeasurement of amino N in roots received by factories had a beneficial impacton nitrogen fertiliser use, which decreased from 190 kg/ha in 1974 to 140kg/ha in 1985. He considered that it was useful for farmers to know the valuesof amino N in readiness for the next time a field was in sugar beet.

When monogerm seed is sown to a stand, quite moderate amounts ofnitrogen fertiliser can kill some seedlings, slow emergence of others anddecrease the number of plants which establish. Certainly the crop cannottolerate the broadcast application just before or just after the sowing of thetotal amount of fertiliser necessary to give optimum sugar yield.

34

Many experiments have investigated possible solutions to this problem.Initially, various forms of placement were tested but these involved the use ofmore sophisticated and expensive equipment than that which was alreadypresent on most farms. Later work showed that a small, initial broadcast dosepermits full establishment and gives optimum early growth. Once the crop isestablished, the required balance of nitrogen fertiliser can be applied. This hasbecome universal practice during the past ten years.

4.1.2. Effect of nitrogen on yield

More experiments have been done on this subject than on any other relatedto sugar beet. The primary effect of nitrogen fertiliser is on root and top drymatter production, most of which is eventually stored in the form of sugar.Figure 10 shows a typical sugar yield response curve. On soils containing littleresidual nitrogen the sharp point of inflexion of the curve is usually in therange 100-150 kg/ha of fertiliser nitrogen. Where there are large amounts ofnitrogen already present in the soil, e.g. on organic soils or where residues arepresent from previous crops, the point of inflexion moves further to the left. Insome soils, e.g. in parts of the USA where huge amounts of residual nitrogenare present, sugar yield is maximal with no additional fertiliser, and experi-ments have even been done to discover whether yield is increased by growinga preceding crop to remove some of the residual nitrogen (Winter, 1984).

4.1.3. Soil type and nitrogen fertiliser requirement

Many investigations have been made into the nitrogen requirement ofsugar beet grown on different soils, usually classified either by texture, or bysoil group or series (Webster et al., 1977). With few exceptions, the overwhel-ming evidence is that, for a given climatic zone, neither of these classificationsis useful in predicting nitrogen requirement. Far more important are:

I. the amount of available nitrogen present in the soil before sowing the sugarbeet crop; and,

2. the amount mineralised during the growing period, as described in the nextsection.

Organic soils form a separate group which can easily be defined, e.g. byloss on ignition, and there is good evidence that little nitrogen fertiliser isneeded on some of these soils. Usually a stater dose of 35 kg/ha N is sufficientto produce maximum sugar yield.

35

Predicting nitrogen fertiliser requirement by soil analysis

In the case of organic mineral soils, crude relationships have beenestablished between total nitrogen concentrations and fertiliser requirement.However, these relationships are unreliable for mineral soils which containlittle organic matter.

Residues of mineral nitrogen, or easily decomposed remains of previouscrops, can reduce fertiliser requirement. Pests and diseases appear to have littleimpact on nitrogen requirement, with the exception of ectoparasitic nematodeswhich can increase the need for added fertiliser (Cooke and Draycott, 1971).

Allison and Armstrong (1995) have recently reviewed whether soilanalysis could be used to predict nitrogen fertiliser requirement. They studiedavailable nitrogen in the soil in spring (Nmin), available nitrogen from soilorganic matter released whilst the crop is growing (Nminealised) and thenitrogen derived from fresh fertiliser (Nirt). It was shown in Section 3 that forhigh-yielding sugar beet 200 kg/ha N needed to be taken up thus:

200 = Nmin + Nmineralised + Nfentherefore,

Nfert = 200 - (Nmin + Nmineralised)

This simple equation has been widely used throughout Europe, variousmethods of measurement of Nmin and Nmineralised being adopted to forecastNfert. Soil samples have been analysed by conventional chemical methods orby modem techniques such as EUF (Electro-Ultra Filtration). The latter hasfound favour in several countries (e.g. Ireland and Austria) and is the basis ofadvisory programmes. However, the authors found that a prediction systembased soil type, previous cropping and organic manure usage adequatelypredicted fertiliser requirement (Table 7).

The Nmin system may be useful as an additional tool when sugar beet isgrown on soil types containing large amounts of naturally occurring nitrogenand on fields with a long history of organic manure use. However, the EUFsystem was not recommended because it is expensive and found to be not veryaccurate.

36

Table 7. Optimum nitrogen applications (kg/ha N).

After cereals After peas, After lucerne, orpotatoes, beans, long leys with

etc. high N

Sandy and shallow soils 125 100 75

Deep silty soils 100 50 40

Other mineral soils 125 75 50Organic mineral soils(6-20% organic matter) 75 50 25

Peaty soils (more than20% organic matter) 40 25 0

Note: The above amounts should be decreased where organic manures areapplied, e.g. 30 t/ha cattle manure, reduce by 45 kg/ha; 7.5 t/ha chickenmanure, reduce by 75 kg/ha.

4.2. Effect of phosphorus fertiliser on yield

Phosphorus fertiliser only gives worthwhile yield increases on soilscontaining little available phosphorus. In most countries where sugar beet isgrown, the element has now been applied for many years. Even in the climateof northern Europe, phosphorus does not leach, and the amount of availablephosphorus in soils had tended to increase because more has been applied thanhas been removed in crops. Many recent experiments lead to the conclusionthat the response to phosphorus by sugar beet is usually small.

4.2.1. Soil analysis for available phosphorus

Soil analysis has become a useful tool to decide where the crop willrespond economically to the application of phosphorus in ferliliser. It is alsonow sufficiently well-researched to permit recommendations on fertiliser ratesto be based on soil concentrations of available phosphorus.

Available phosphorus is determined using soil extractants such as sodiumbicarbonate, calcium ammonium lactate, water and ion-exchange resins. Theseall give values which are more closely related to field responses than the acidextracts used previously. Olsen's bicarbonate extraction (Olsen et al, 1954)was found to be one of the best methods both in the USA (Tolman el al,

37

1956) and in the UK (Draycott el al., 1971). Table 8 summarises the optimumfertiliser requirement and the expected response by sugar beet for a range ofsoil values obtained by this method.

Table 8. Soil phosphorus extracted by sodium bicarbonate, yield response andoptimum phosphorus fertiliser application (summary of USA and UK evidence)(ppm P).

0-11 11-15 16-25 26-45 >45

Root yield increase +3.0 +0.8 +0.5 +0.2 0(t/ha adjusted to 16% sugar)Phosphorus required 150 100 50 25 0(P20 5 kg/ha)

4.2.2. Phosphorus balance

On many fields now adequately supplied with reserves of phosphorus,future fertiliser use needs to be planned ahead on the basis of nutrient offtake.Offtake can be balanced against fertiliser input, aiming to maintain soilconcentrations which are sufficient to ensure maximum yield of all crops inthe rotation. Long-term experimental work in the UK suggests that soilphosphorus extracted by sodium bicarbonate should be stabilised at 20-30 ppmP in soil for sugar-beet/cereal rotations (Last et al., 1985).

4.3. Potassium and sodium fertiliser requirement

Section 3 above showed that sugar beet needs to take up a large quantity ofboth these elements to produce a high yield. Timing of the application is alsoimportant in that the fertiliser is thoroughly incorporated in the soil, for rapiduptake to take place during June-July. Spreading on the surface before sowingsugar beet is not acceptable because much of the fertiliser would not beavailable to that crop.

Until quite recently all the fertiliser potassium (except that in kainit) was soapplied, immediately before drilling sugar beet. Following the introduction inthe early 1970s of blended fertilisers containing no nitrogen, first in the USAand then in Europe, potassium is increasingly spread during the autumn orwinter before the sugar-beet crop. This earlier application has severaladvantages:

38

I. less traffic on soil prepared for drilling;2. decreased spring workload;3. better incorporation of potassium with the soil and therefore better uptake;4. no negative effect on seed germination.

The amount of potassium for maximum performance is best determined bysoil analysis. A long-term view must be taken if high yield is to be obtainedevery year. Soils which contain small concentrations of potassium need to beimproved by gradual and careful additions of fertiliser so that an adequatesupply is in the root range during the period of peak demand (see Section 3).Care is needed to avoid excessive applications, damaging to root quality,because both K and Na are impurities in root juice as outlined below.Similarly, excess must be avoided on light soils of low exchange capacity toavoid loss by leaching.

Table 9 shows the optimum applications based on exchangeable soil Kconcentration (Potash Development Association, 1995).

Table 9. Optimum potassium application (K20 kg/ha).

Target yieldSoil K concentration Low Medium High

mg/I (ppm) 40 t/ha 50-60 t/ha 75 t/ha

Less than 40 200 260 35041- 60 175 235 31061- 90 150 210 28091-120 125 175 220121-150 100 150 185151-240 75 110 155241-400 0 60 125401 and over 0 0 90

Note: For soils less than 90 mg/I, 40 kg/ha of the above should be applied inthe seedbed. For advisory purpose, the dimension mg K/I is set equal to ppmK.

39

4.3.1. Sodium

The sodium which is readily available to plants is held in simple ionicbonding to colloids in the soil and is water-soluble. Shaking a sample of soilwith ammonium nitrate solution was shown by Tinker (1967) to extract thesodium that was available to the plant. Draycott (1969) measured soilexchangeable sodium in samples from a group of field experiments whereresponse to sodium was determined on plots given 125 kg/ha K2 0. Allsignificant responses to sodium were on soils with less than 25 ppm Na.Further work has confirmed that large responses are to be expected in soilswith 0-25 ppm Na and some smaller responses in soils with 25-50 ppm Na.

Durrant et al (1974) summarised over 200 experiments which investigatedthe amount of sodium needed on various soil types and concluded that 150kg/ha Na was optimal in mineral soils; on organic soils (>10% organic matter)only a few crops responded. Table 10 summarises optimum sodium dressingsin relation to soil and sodium concentration. On sandy soils containing verylittle available sodium the optimum application rate is around 200 kg/ha Na.

Table 10. Optimum sodium applications based on soil type and soil sodiumconcentration.

Na(kg/ha)

Soil typeSands and light loams 200Loams 150Heavy loams and silts 100Organics (>10% O.M.) 0

Sodium concentration in soil (ppm)0-25 200

25-50 75>50 0

Measurements over many years show that where sodium fertiliser is appliedapproximately every third year (i.e. before every sugar-beet crop) in theclimate of northern Europe, it does not accumulate in soil. A full application istherefore needed before each sugar-beet crop and the yield response remainssimilar on each occasion. Studies made on the physical properties of soilstreated in this way show no deterioration in structural stability or workability.

40

4.4. Use of magnesium fertiliser

Many sandy and calcareous soils contain insufficient magnesium for sugarbeet to produce maximum yield.

Early experiments were made with Epsom salts (MgSO 4 "7H 20 - 10% Mg)which is water-soluble and can be used in foliar sprays. When the work turnedto applying larger amounts of magnesium to the soil as fertiliser, Kieserite(MgSO 4 -H2 0 - 17% Mg) was used. This is less pure and soluble than Epsomsalts, but the magnesium is highly plant-available. Kainit (KC, NaCI, MgSO4

- 4.5% Mg) has long been used as an effective source of magnesium for sugarbeet.

Dolomitic limestone (MgCO 3, CaCO3 - 11% Mg) is a very inexpensiveform of magnesium, but long-term experiments showed that the magnesium inthis form is far less available in neutral and alkaline soils than magnesium inthe salts already mentioned. However, if used to correct acidity onmagnesium-deficient fields, it is an effective source of the element with lastingqualities superior to the soluble forms.

Magnesite (MgCO 3 ) is also a concentrated source of magnesium, but theelement is not plant-available in the mined form. Removal of carbon dioxideby heating results in an alkaline oxide called calcined magnesite (MgO-55%Mg). Provided the calcination is carefully controlled near to the minimumtemperature needed to expel the CO 2, the oxide is highly reactive in soil andnearly all the magnesium is plant-available (Draycott et al., 1975).

There are three broad categories of soils needing quite different treatmentwith magnesium fertiliser. By far the majority of soils worldwide need nomagnesium because sufficient is already present naturally to sustain fullproduction. Soil containing more than 50 ppm Mg exchangeable in molarammonium nitrate solution should receive no magnesium fertiliser.

Sandy soils, particularly in humid climates, frequently contain less than 50ppm exchangeable Mg. Those with less than 15 ppm require special treatmentbecause there are likely to be severe deficiency symptoms and significant yielddepression. In the range 15-50 ppm magnesium, fertiliser is also needed toimprove (15-25 ppm) or maintain (25-50 ppm) soil magnesium status andensure maximum production of sugar beet (Table 11). The nutrient balancesheet approach described for other major elements such as phosphorus andpotassium is also useful for determining magnesium requirements. For soils inthe range 0-50 ppm Mg, periodic applications of magnesium are needed toprevent decline in exchangeable soil magnesium and eventual yield depression.

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Where magnesium is in very short supply sugar beet leaves show thehighly noticeable and specific deficiency symptoms in Plate 4.

Table 11. Magnesium fertiliser required by sugar beet determined byexchangeable soil Mg.

Soil Mg exchangeable Mg applicationin molar NH 4NO3 (ppm) (kg/ha)

0-15 10015-25 7525-50 5050+ 0

4.5. Importance of boron application

Soil analysis is able to identify which fields are likely to produce sugar-beet crops with boron deficiency. Plant-available boron is extracted from soilin hot water, using boron-free glassware. Deficient crops are nearly alwaysfound on soils with less than 0.5 ppm boron and, to prevent symptomsappearing, treatment before mid-June is necessary. Due to the very patchynature of boron deficiency within a field, soils in the range 0.5 - 1.0 ppmshould also be treated (Smilde, 1970). Boron deficiency has never been seen insugar-beet crops growing in soil with more than 1.0 ppm boron.

Boron deficiency, in contrast to manganese deficiency (see below), can beeasily and entirely eliminated from sugar beet by one simple treatment. Soilapplication and foliar sprays are equally effective. Sodium borate (Na 3BO 3) isthe usual source of the element. Specially refined forms which dissolve easilyand completely in water ('Solubor') provide much of the boron used on sugarbeet. For soil application, borate is often added to major nutrient fertilisers at0.1 to 0.3% boron. These fertilisers can be applied at any time from theautumn before sugar beet to the spring, immediately before sowing, andprovide about 3 kg/ha of boron. Spraying the foliage up to mid-June shouldsupply about 2 kg/ha of boron.

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4.6. Manganese application

Many studies have shown that manganese sulphate in aqueous solutionsprayed on to sugar beet leaves can greatly increase their manganeseconcentration and, within a few days, decrease the severity of deficiencysymptoms (Draycott and Farley, 1973). The inclusion of a chemical whichspreads the solution over the leaf assists uptake (Last and Bean, 1990).

Applications of manganese to the soil as sulphate, oxide or activatedsilicate have been far less successful than foliar sprays. The application ofchelated manganese to soil, though partly successful, is not economicallyviable for a crop like sugar beet. Pelleting of sugar-beet seed with manganesehas also met with limited success.

In recent years, chelated manganese has been applied to many sugar-beetcrops as a foliar spray. However, there is no economic or scientific justificationfor this treatment. The less expensive and more effective aqueous solution ofthe sulphate often provides many times as much manganese per unit area forunit cost and penetration of the leaf by manganese in chelated form does notappear to be any better than penetration by the sulphate (Last and Bean, 1990).

Ideally, applications of 10 kg/ha of manganese sulphate together with awetting agent should be sprayed onto sugar-beet leaves at the first appearanceof deficiency symptoms. Two or three applications may be needed on severelydeficient soils where they can give root yield increases of 1-5 t/ha.

4.6.1. Soil analysis for available manganese

There are no simple tests which will measure the concentration of availablemanganese in the soil, as there are for some other elements. Because manganeseexists in many forms in the soil, laboratory extractants usually under- or over-estimate how much of the element is available. Farley and Draycott (1976)tested a range of soil analysis methods and found that normal ammoniumacetate buffered to pH 7.0 was the best extractant. It produced values whichwere weakly related to the appearance of manganese deficiency symptoms in arange of crops.

4.7. Other trace elements

Symptoms of iron defiency appear sporadically on sugar-beet plants grownin sandy, calcareous soils but there is no evidence of economic returns fromtreatments. However, in the case of copper, although a shortage of the elementdoes not produce any typical symptoms on the crop, there are reports that

43

yields can be depressed on some soils, especially light sands and peats. Onthese soils, if the soil concentration of copper is known to be low (e.g. lessthan 3 ppm), copper oxychloride at 5 kg/ha should be applied before sowingsugar beet.

4.8. The dangers of excess fertiliser

No review of nutrient application for sugar beet is complete withoutaddressing the problems of over-use. In particular, the effect on the chemicalquality of the roots for processing and increasingly, the awareness of everyoneto protect the environment. Applications should ideally fit the requirements ofthe crop for growth and high yield whilst leaving the roots in optimumcondition at harvest and the minimum residue in soil.

The chemical quality of the roots is affected most by the three nutrientelements nitrogen, sodium and potassium, because all three decrease theproportion of white sugar produced during the factory process. Thus excessesof these are particularly to be avoided. Carruthers et a! (1962) showed that theconcentrations of amino-nitrogen, potassium and sodium could be used in asimple linear regression equation to accurately predict root quality (r = 0.86).

Over the last 30 years this and similar equations have been used in somecountries as a basis for payment for quality by processors to growers. Mostrecently M~rlander et al. (1996) have proposed a similar formula, but onewhich gives more weight to the harmful effects of nitrogen and less to sodiumand potassium. It has been adopted throughout Germany as the basis of aquality payment scheme. It brings into even sharper focus the care needed inplanning nitrogen fertiliser use. Orlovius (1996) also stresses the importanceof a correct balance between nitrogen, sodium and potassium in the nutritionof the crop. Much work is in progress in this area because there is still roomfor improvement of root processing quality and our knowledge of the subject.

5. Worldwide use of nutrients for sugar beet and returns

Table 12 shows typical examples of nutrient applications in Europe, Asia,North Africa and North and South America. Use of the three major nutrientsNPK is universal in all countries and nearly 100% of the land surface undersugar beet receives all three. Generally nitrogen is applied in the range 100 to200 kg/ha N, reductions being made in most countries for organic manure andsoil type.

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Table 12a. Worldwide use of nutrients in fertilisers, manures and sprays for sugar beet (kg/ha).

N P20 5 . K20 S Na CaO MgO B Mn

France 130 110 240 - 1000 40 2.3 -Germany 110 60 150 25 40 700 40 1.0 1.5Portugal 165 155 90 - 430 25 3.5UK 113 55 95 155 1500 40 3.0 4.0Italy 95 135 125 - 1.0 3.0Netherlands 155 117 143 - 75 330 40 - -

Denmark 110 68 115 15 60 900 33 0.7 1.0Spain Spring crop 210 140 140 - - 360 100 2.5 -

Autumn crop 200 100 50 - - - - -Ireland 160 100 220 36 64 1000 - 4.0 10.0Finland 142 95 65 13 37 - 60 1.1 6.7Hungary 78 60 116 - - - - -Turkey 159 137 20 - -Tunisia 130 90 50 - - 0.4 -Chile 180 450 120 80 - 500 20 1.3 -

Japan 170 300 160 0 60 160 70 4.5 4.3USA 158 60 34 20 - - 0.6

(Al

Table 12b. Area (%) treated with the different nutrients.

S Na Ca Mg B Mn

France - - 50 20 65 -

Germany 15 20 80 50 10 10

Portugal - - 3 7 3 -

UK - 67 32 30 17 26

Italy - - - - 10 10

Netherlands - 35 100 35 - -

Denmark 50 70 100 100 100 10

Spain Spring crop - - - 7 2.5 -

Autumn crop - - - - - -

Ireland 98 98 60 - 100 3

Finland 100 80 - 10 70 70

Hungary - - 15 - - -

Turkey - -

Tunisia - - - 15 -

Chile 100 100 100 100 -

Japan - - - -

USA 5 5

Phosphorus applications vary widely. In old arable soils, particularly inEurope, 150 years of residues from fertilizer application of this element greatlydecrease the need. Most countries report the use of soil analysis to determinerequirement of fresh fertilizer. A maintenance dressing usually suffices onthese soils. In contrast, on newly-reclaimed soils and those with a history ofsub- optimum usage, phosphorus may be the most limiting nutrient.

Potassium is available from breakdown of clay in all soils, the amountfrom this source depending on percentage of clay and the lithology of the soilsparent material. Generally throughout the world 100 to 200 kg/ha K2 0 isapplied for sugar beet. In countries with wet winters where rainfall leacheslight soils, sodium is needed in addition to potassium for maximumperformance. In UK where the need for sodium in conjunction with potassiumhas been researched extensively, 150 kg/ha Na is highly profitable.

5.1. Does it pay?This is the final question or, in the jargon, 'the bottom line'. In general,

nutrient applications are very cost-effective, but of course it depends on thenatural fertility of the field. If soil analysis, soil type, previous cropping andthe potential yield of the crop are taken into account in planning nutrientrequirement, returns will be optimised.

The nutrient shopping list is the single most important (and usually themost expensive) item in growing the crop. It is also the single most importantfactor, in the growers control, governing the yield and profitability of the crop.Climate sets the limit on yield. Variety choice, seed quality, weed, pest anddisease control are all very important but soil nutritional and physical state hasthe biggest impact on profit on most fields.

Table 13 shows typical responses by sugar beet to the major nutrientsgrown on light mineral soil with little residue of nutrients from previous crops.Currently fertilizer prices are rising rapidly but to provide a general guidecosts are given in Table 13 for average doses, together with the value of theincreased output. In the case of the minor and trace elements, the responses areones expected by crops which would otherwise show deficiency (Table 14).

Table 13. Response to major nutrient applications.

Application ResponseAmount Cost Yield of roots Value Marginkg/ha $/ha t/ha S/ha S/ha

125 N 85 +15 +900 +81550 P205 27 + 2 +120 + 93100 K20 33 + 4 +240 +207

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Table 14. Response to minor and trace element applications where sugar beetwould otherwise show some deficiency.

Application Response in root yieldkg/ha t/ha

1500 CaO +12150 Na + 5100 MgO + 3

3 B +204Mn + 2

In conclusion, it is easy to establish that correct use of the full range ofnutrients continues to make a vital contribution to the success of this crop.

6. Acknowledgements

I am grateful to the following for supplying up-to-date information onnutrient requirements in their countries:

FRANCE: R. DuvalM. Richard-Molard

SPAIN: R. Morillo-VelardeD.J. GuisasolaD. MartinA. Sanz

GERMANY: M. BurbaB. MArlanderR. MerkesK. Burcky

IRELAND: F.E. Ryan

FINLAND: M. Erjala

PORTUGAL: J.D. Amaral

TUNISIA: M.A. Ben Kharbeche

DENMARK: C. Marcussen

TURKEY: H. Inan

ITALY: G. Mantovani

NETHERLANDS: P. Wilting

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CHILE: H.G. Despouy

JAPAN: N. Takase

HUNGARY: L. Magassy

U.S.A. T.K. Schwartz

I am also grateful to Dr. A. Krauss for reading and correcting themanuscript, and to Susan Kimber for typing it and drawing the diagrams.

7. References

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Allison, M.F. and Armstrong, M.J. (1995): Can the fertiliser nitrogenrequirement of sugar beet be predicted? British Sugar Beet Review 63, No.4,6-9.

Allison, M.F. and Hetschkun, H.M. (1990): Nitrogen use by sugar beet. Reportof the Institute of Arable Crops Research for 1989, pp. 95-6.

Armstrong, M.J., Milford, G.F.J., Biscoe, P.V. and Last, P.J. (1983):Influences of nitrogen on physiological aspects of sugar beet productivity.International Institute for Sugar Beet Research. Symposium 'Nitrogen andsugar beet', pp. 53-61.

Brandenburg, E. (1931): Die Herz- und Trockenfhule der Rtlben alsBormangelerscheinung. Phytopathology 3, 449-517.

Broeshart, H. (1983): 15N tracer techniques for the determination of activeroot distribution and nitrogen uptake by sugar beets. International Institutefor Sugar Beet Research. Symposium 'Nitrogen and sugar beet', pp. 121-4.

Carruthers, A., Oldfield, J.F.T. and Teague, H.J. (1962): Assessment of beetquality. XVth Annual Technical Conference of British Sugar Corporation,pp. 1-28.

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Draycott, A.P. (1972): Sugar beet nutrition. Applied Science, London, 250 pp.Draycott, A.P. and Durrant, M.J. (1970): The relationship between

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Draycott, A.P. and Farley, R.F. (1971): Effect of sodium and magnesiumfertilizers and irrigation on growth, composition and yield of sugar beet.Journal of the Science of Food and Agriculture, 22, 559-62.

Draycott, A.P. and Farley, R.F. (1973): Response by sugar beet to soildressings and foliar sprays of manganese. Journal of the Science of Foodand Agriculture 24, 675-83.

Draycott, A.P., Durrant, M.J. and Boyd, D.A. (1971): The relationshipbetween soil phosphorus and response by sugar beet to phosphate fertilizeron mineral soils. Journal of Agricultural Science, Cambridge 77, 117-21.

Draycott, A.P., Durrant, M.J. and Bennett, S.N. (1975): Availability to arablecrops of magnesium from kieserite and two forms of calcined magnesite.Journal of Agricultural Science, Cambridge, 84, 475-80.

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Lindemann, Y., Guiraud, G., Chabonis, C., Christmann, J. and Mariotti, A.(1983): Cinq anndes d'utilisation de l'isotope 15 de lazote sur betteravessucri~res en plein champ. International Institute for Sugar Beet Research.Symposium 'Nitrogen and sugar beet', pp. 99-115.

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8. Profile of the author

Dr Philip Draycott qualified at the Universities of Cambridge, Leicesterand Leeds. His first job was in university teaching and research where hebegan work on sugar beet nutrition. He then worked for Rothamsted atBroom's Barn on factors limiting sugar production, particularly nutrients andwater. Through his writings in books and scientific papers, and lecturing inU.K. and abroad, he has established a reputation on many aspects of sugar beetproduction. Currently he divides his time between advising on sugar beetgrowing, research and development, and putting research into practice farmingnear Cambridge.

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