Potato

fert

ilisa

tion

Potato FertilisationInformation to cultivation

The Authority in potassium and magnesium

180

160

140

120

100

80

n=2 n=2 n=10 n=13K2O (kg/ha)

31.2t/ha

31.8t/ha

38.5t/ha

37.8t/ha

0 107 213 300 0 102 198 300 0 98 199 300 0 127 221 311

rela

tive

yiel

din

crea

se(%

)Yield and qualityare nutrient dependent

Potatoes requiregreat amounts of K.K deficiencysignificantly reducestuber yield.

Yield and quality dictate the profitability ofpotato production and fertilisation plays amajor role in determining these parameters.Therefore, it is vital that fertiliser programmesare optimised. Of all nutrients, it is potassium,which is absorbed by the potato crop in thegreatest quantities.

Potassium

is a major determinant of yield and quality.

has a very positive effect on the production,translocation, conversion and storage ofcarbohydrates through the activation of theplant’s enzyme systems.

regulates the osmotic turgor of the cells andthe water balance. Crops grown with ade-quate K availability use less water per unitweight of plant biomass and are thereforebetter able to survive periods of drought.

secures economic yields.

improves nitrogen efficiency.

K soil content

very low

K soil content

low

K soil content

sufficient

K soil content

high

2

Nutrient uptake of potatoes(kg/ha)

tuber yield (t/ha)40 50 (incl. tops)

N 140 175 (225)

P22O55 55 70 (90)

K22O 240 300 (430)

MgO 35 45 (70)

S 12 15 (25)

Yield increase in potato as influenced by Potassium supply(Control = 100%)

3

Potassium

is involved in the activation of the mostimportant metabolic processes and thushas a major influence on tuber quality.

reduces the susceptibility of the tuber todiscolouration (internal bruising, black spot,discolouration of the raw tuber and after-cooking discolouration).

increases the content of both citric acid andvitamin C.

Potassium for crop quality

improves resistance to harvesting/handlingdamage and storability by allowing tubersto fully mature.

minimises the content of reducing sugarsthereby ensuring that tubers are bettersuited for processing (crisps, chips).

has an influence on the starch content.

Under potassium defi-ciency the potato topsdie off prematurely, therefore the assimilati-on is reduced and theyield potential cannotbe fully exploited.

Yield increase in potato as influenced by Potassium supply(Control = 100%)

4

K deficiency symp-toms initially begin at the older leaves,followed by the spread to the younger leaves.

With a sufficient K supply the content ofreducing sugars can be reduced, ensuring a better processingquality of crisps andchips potatoes.

Sufficient K content in leaves (i. DM)

bud stage 4.5– 7.0 % Kstart of flowering 4.0– 6.4 % Kend of flowering 3.7– 6.1 % Ktuber formation 3.5– 5.7 % K

Where K is deficient

plant growth is stunted.

initially the oldest leaves turn palegreen/yellow beginning at the leaf margins.Brown necrotic spots then develop, followedby the spread of these symptoms to theyounger leaves.

the foliage and haulms die off prematurely,thereby shortening the growing season andreducing assimilative efficiency and yieldpotential.

quality is reduced as the susceptibility tointernal and external damage increases significantly (enzymatic browning, bruising)and the shares of small tukers increases.

Leaf analysis indicates the nutritional state of the crop

Red

ucin

g su

gars

(% o

f FM

)

Fructose Glucose

0.3

0.2

0.1

00 300 600 900

K2O (kg Patentkali/ha)

Influence of K supply on reducing sugar content in tubersGermany 2002

5

Potassium improves yield and quality

high yields require, as a minimum, an adequate soil K supply which should bemaintained by correct fertilisation.

significant yield losses occur where soil Klevels are low.

in addition to soil analysis the plantsnutrient status can be monitored by leaftissue analysis.

the K fertilisation programme should be tailored to the quality requirements of thecrop.

early applications of K fertiliser prior toplanting or latest pre-earthing up, increasesyield.

K deficiency increa-ses the susceptibilityof the tuber to discolouration.Particularly the blackspot incidence isreduced with a goodpotassium supply.

Potassium deficiency in leaves causes discolourationto pale green/yellow beginning at the margins.Continued severe deficiency causes that the tissue dies off subsequently.

with Patentkali without Patentkali

before after storage

80

60

40

20

00 102 205 307

blac

k sp

ot in

cide

nce

(%)

K2O(kg/ha) as sulfate

Influence of K supply on black spot incidence(means of 9 trials on light soils in North Germany)

6

Bargfeld 1993 Langwedel 1997 Langwedel 1998 Langwedel 1999 Langwedel 2001

60

50

40

30

200 300 300 0 200 200 0 200 200 0 200 200 0 200 200

beforeControl after planting

tub

er y

ield

(t/h

a)

K2O (kg Patentkali/ha)

5mg K2O3mg Mg

7mg K2O4mg Mg

10mg K2O6mg Mg

6mg K2O 3mg Mg

4mg K2O (CAL)4mg Mg (CaCl2)

The K applicationbefore planting leadsto yield advantages.

Tuber yield dependent on K supply(different sites in Germany)

7

Quality requirements vary greatly depending onthe target market. Potatoes produced for theprocessing market (crisps, chips) require a me-dium starch content whereas those destined forstarch production require a high starch content.

K deficiency inhibits the formation andtranslocation of starch to the tuber. Thestarch content of tubers can be raised sig-nificantly on low K availability sites by theaddition of moderate levels of K fertilisers.

... for processing and starch production

Quality requirements differ

Tuber starch content is also influenced bythe form of potassium applied, i.e. chlorideor sulphate form. High levels of chloride inthe plant restrict the formation and translo-cation of starch to the tuber. On average, K fertilisers based on the sulphate form produce approximately 1% higher starchcontent than the chloride form.

Even when chloride form K fertiliser isapplied early, e.g. 4–12 weeks pre-planting,the chloride may still affect tuber productionas it may not have been leached to a suffi-cient depth to be unavailable to the plantroots. A re-ascent in the capillary water intothe rooting zone increases further the risk ofan excessive off-take of chloride by theplant resulting in a decreasing starch con-tent.

Therefore: Sulphate based K fertiliserproduces significantly higher starchyields, which fully justify the higher financial input involved.

K fertilisers on sulphate base improvethe profitability of processing potato.

tub

er y

ield

(t/h

a)

star

ch c

onte

nt (%

)

turn

ove

r 100

0 €

/ha

45

40

35

30

25

20

chlorid. fertiliser

+ 2.4 t /hatuber

205 € /ha profit

Patentkali

2.75

2.5

2.25

2.0

20

19

18

17

16

+ 0.7%starch

Comparison of chloridic and sulfatic K supplyGermany, 200 kg K2O/ha

8

Quality parameter NutrientN P K Mg Ca

tuber yield ++ + ++ + +

starch content – + +/– + +

protein content ++ ++ +

citric acid ++

asorbic acid + + ++

ripeness – +

shell strength – +

storage attributes – + +

taste – + +

Resistance to

tuber damage – + + +

black spot incidence – ++ +

after cooking discoloration ++

brown discoloration ++

+ = positive influence ++ = very positive influence – = negative influence

... for potatoes for fresh consumption

Potatoes for human consumption ideallyshould be free from skin damage and disease, should peel easily, not disintegrateduring cooking, look good on the plate andhave a pleasant taste.

Discolouration in any form should be minimised i.e. internal bruising, black spot, discolouration of the raw tuber and after-cooking discolouration.

Thus the objective of the fertiliser program-me should be to produce a high tuber yieldof optimum dry matter content for the vari-ety grown and the target market.

High inputs of K are thus required to produce a crop having a high percentage of marketable sized tubers, good storageattributes and minimal discolouration duringpreparation. Potassium thus improves thesevaluable quality parameters and mostimportantly, taste.

Influence of nutrients on yield and quality charachteristics of potato tubers.

9

Magnesium is important ...

Potatoes are particularly susceptible to magnesium deficiency. Therefore it is essential to include magnesium in a balanced fertiliser programme.

Magnesium plays a primary role in photosynthesis, protein synthesis and in the activation of various enzymes.

Magnesium deficiency inhibits protein syn-thesis and is frequently accompanied byexcessive nitrate accumulation in the tubers.Growth is stunted and results in reducedyields and crop quality.

A considerable area of potatoes is grown onlight soils which are inherently low in magne-sium and therefore require Mg fertilisation.

On light soils, it is particularly advisable toapply Mg and K fertiliser in spring for agro-nomic and efficiency reasons (see figure).

Patentkali (30% K2O, 10% MgO, 42% SO3)contains the three nutrients potassium, mag-nesium and sulphur in the sulphate form,which are immediately available to the plant.

High pH soils are, in the main, low in mag-nesium availability and need additionalmagnesium fertilisation to meet potato croprequirements. Magnesium sulphate, beingcompletely water soluble irrespective of pH,is therefore ideal in high pH soils.

60

50

40

30

20site 13

site 26

site 311

Sulfat of potash200 kg K2O/ha

0 Patentkali200 kg K2O/ha + 67 kg MgO/ha

tub

er y

ield

(t/h

a)

Mg(mg/100g soil) Also at high soil MgPatentkali increasestuber yield.

Influence of sulfate of potash and Patentkali on tuber yield(3 sites in Germany)

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With a foliar fertilisation in form of EPSO Microtop temporary deficiencyof Mg, S, B and Mncan be prevented.

Trials conducted at various research insti-tutes have confirmed yield increases of4–10%, even at adequate soil magnesiumlevels, as result of foliar applications ofEPSO Top. Significant dry matter and starchcontent increases were also noted.

Foliar fertilisation with magnesium

The potato crop’s major magnesium requi-rement should without question be suppliedby soil application (40–70 kg MgO/ha).

Magnesium is taken up by the plant muchlater in the growing season than potassium.Stress factors such as cold, drought andcationantagonism can significantly reducethe uptake of soil Mg resulting in temporarymagnesium deficiencies in the sensitivepotato plant.

Applications of the foliar fertilisers EPSO Top (16% MgO, 32% SO3) and EPSO Microtop (15% MgO, 31% SO3, 1% B, 1% Mn), on their own or in combination with potato blight treatments,can prevent the damage of transient mag-nesium and trace element deficiencies.

Mg-deficiency in potatoes

70

60

50

40

301999n=4

2000n=4

2001n=14

2002n=10

2003n=14

Mitteln=46

Control EPSO Microtop

tub

er y

ield

(t/h

a)

Effect of EPSO Microtop®® foliar application on tuber yield(Foliar application with each 25 kg EPSO Microtop to bud stage and start of flowering)

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Foliar fertilisation with manganeseand boron

Manganese and boron can become unavai-lable due to soil moisture deficits and highsoil pH levels.

Potatoes remove about half as much boronas sugar beet (360 g B/ha). Despite thisfact, however, a similar leaf boron content(25–35 ppm) is required to ensure optimumhealthy growth. Consequently, the potatocrop’s boron requirement is in many casesunderestimated.

Boron is required for cell development andthe synthesis of the energy components,sugars and starch. Boron also plays a role instabilising the plant’s cell walls and tissues.

The potato while having a high demand formanganese is relatively inefficient at remo-ving it from the soil.

As manganese plays a broadly similar roleto magnesium in the plant’s metabolism, itis advisable from a nutritional and physiolo-gical viewpoint to apply both nutrientstogether.

Foliar application of EPSO Microtop supplies Mg, S, B and Mn and lowers therisk of black spot incidence.

Foliar applications of EPSO Microtop (15% MgO, 31% SO3, 1% B, 1% Mn) can prevent the yield losses caused by temporarysoil nutrient unavailability (see data on previousand next pages).

EPSO Top®® and EPSO Microtop®®

usage

Depending on the severity of the deficiency,a total of 25–50 kg/ha should be applied bymultiple (2–4) applications – the 1st beforeflowering or with the first potato blight treat-ment.

The concentration should not exceed 5%i.e. 5 kg product/100 l water.

Compatible with most fungicides, fertilisersand insecticides but always follow manu-facturers’ recommendations.

New field trails have proven:

12

Boron deficiency in potato tubers (right)

Micronutrient deficiency leads to yield and quality losses.

Manganese deficiency in potatoes

13

Fertiliser recommendations

Anticipated yield and target market areimportant factors in determining optimumfertiliser inputs.

To ensure adequate soil K availability for highyield (40–50 t/ha) and good quality the fol-lowing K fertiliser rates are recommended:

Potatoes for fresh consumption

and seed potatoes: 800–1100 kg Patentkali/ha

Potatoes for processing:700–800 kg Patentkali/ha

Starch potatoes:600–700 kg Patentkali/ha

The use of sulphate based K fertilisersallows both starch and tuber yields to beoptimized and avoids the negative effectsassociated with chloride based K fertilisers.The optimal starch yield is close to the maximum tuber yield.

Patentkali contains potassium and magne-sium sulphate in the ideal ratio of 3:1, satis-fying both the high K and Mg requirementsof the potato crop.

Additionally Patentkali meets the sulphurdemand of the crop. The three nutrients K,Mg and S are immediately available.

By applying 20–50 kg/ha of the foliar fertiliserEPSO Top or EPSO Microtop, split overseveral applications, temporary nutrientdeficiencies of magnesium, sulphur, boronand manganese can be prevented.

All out of the hand

14

Patentkali is a highly concentrated three-nutrientfertiliser with a potassium and magnesiumbasis especially suited to the production ofhigh quality crops. It is specifically recom-mended for use on high value crops such astobacco, vegetables, potatoes, fruits, nuts,spices and flowers.

EC-FERTILISER

Sulphate of Potash containing Magnesium Salt 30 (+10+42)30% K2O water-soluble potassium oxide10% MgO water-soluble Magnesium oxide42% SO3 water-soluble sulphur trioxide (17% S)

EPSO Microtop is a quick acting and effectivefoliar fertiliser containing magnesium, sulphur,boron and manganese. Meets the increasingrequirements for micronutrients of borondemanding crops and rapidly alleviates magne-sium, sulphur, boron and manganese deficien-cies in growing crops.

EC-FERTILISER

Magnesium sulphate with micronutrients 15+3115% MgO water-soluble magnesium oxide 31% SO3 water-soluble sulphur trioxide (12% S)

1% B water-soluble Boron1% Mn water-soluble Manganese

EPSO Top is a quick acting magnesium andsulphur fertiliser developed specifically for fertigation and foliar application. He is the idealfertiliser to cure acute magnesium and sulphurdeficiencies in agricultural and horticulturalcrops as well as in forest trees by foliar appli-cation.

EC-FERTILISER

Magnesium sulphate 16+3216% MgO water-soluble magnesium oxide 32% SO3 water-soluble sulphur trioxide (13% S)

15

Detailed information can be foundon the website of K+S KALI GmbH

www.kali-gmbh.com

or contact directly:

K+S KALI GmbHAgricultural Advisory DepartmentBertha-von-Suttner-Str. 734131 KasselFon +49 561 9301-2316Fax +49 561 9301-1416fertiliser@kali-gmbh.com

www.kali-gmbh.com

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K+S KALI GmbHAgricultural Advisory Department, D-34131 Kassel, GermanyPhone +49 (0) 561 9301-2316, Fax +49 (0) 561 9301-1416fertiliser@kali-gmbh.com, www.kali-gmbh.com

A K+S Group Company