Investigating the efficacy of LimeX in the

reduction of common scab in potatoes.

Richard Cogman

National LimeX Manager

Welsh Potato Day, February 2nd 2018.

LimeX: Reducing severity of common scab.

• Background to LimeX

• Background to the project

• 2012 -2015 trial results

• 2016 strip trials results

• Conclusions

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Background to LimeX

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Background to LimeX

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Background to LimeX

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Project background and objective:

• LimeX : clubroot and cavity spot

• Calcium and scab

• Investigate the basis of the relationship

• Common scab caused by Streptomyces scabies, has detrimental effects on appearance and therefore

marketability of potatoes, resulting in a low grade produce. It is considered a disease of major

economic importance and it has become a problem in many regions worldwide with varying severity.

The mode of action of these bacteria has not yet been clearly understood and infestations are typically

attributed to irrigation, potato variety, soil pH and other soil related characteristics.

• Much of the myth and negativity stems from tissue and peel analysis that shows in cases of severe

common scab (streptomyces scabies) the peel has an elevated Ca content. However, is this the cause

of scab, or is this a plant reaction to repair the damaged tissue? – More recent studies and opinion

would now support the latter.

• The aim of the trials was to evaluate anecdotal evidence that LimeX can reduce of the incidence of

common scab (S. Scabies).

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Research Partner

Study Director: Dr Apostolos Papadopoulos – ‘Tolis’

Address: Crop Intellect Ltd, University of Lincoln

Key Functions:

• Review of recent research papers relating to the interaction of calcium and

S.scabies

• Research proposal for field and glasshouse research in conjunction with BS

• Support establishment and completion of field trials 2012-2016

• Completion of data analysis, collation of results and trial reports

• Investment > £70K

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What we did…2012-2015

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2012 Field trial: Wragg Marsh, Spalding cv Maris Piper:

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Treatment # Description Details

T1 Control No application of LimeX

T2 LimeX at 3 tn/ha Application of LimeX prior to planting to equivalent rate

T3 LimeX at 5 tn/ha Application of LimeX prior to planting to desirable rate

T4 LimeX at 7 tn/ha Application of LimeX prior to planting

Block 1 Block 2 Block 3 Block 4 Block 5 Row 1 Row2 Row 1 Row2 Row 1 Row2 Row 1 Row2 Row 1 Row2

T4 T1 T3 T2 T3

T2 T4 T1 T4 T1

T1 T3 T2 T3 T2

T3 T2 T4 T1 T4

Field trial: Wragg Marsh, Spalding cv Maris Piper:

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May 2012

Final harvest assessments

• 5 plants x 2 rows

• Stems, tuber no, sizing and yield

• Washed and assessed for common scab

• 0%, >0 & <5%, >5 & <20%, >20%

• Assessed for scab @ <45mm, 45-65mm and >65mm

• Comparisons for skin and tuber calcium

• Additionally take field samples from strip trials

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Visual impact

Scab No Scab Scab No Scab

Control LimeX 7 t/ha

Visual impact

Scab No Scab Scab No Scab

Control LimeX 7 t/ha

Final harvest results: field trial – incidence of scab

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Total yield With Scab No Scab Scab Affected Extra marketable yield (%)

t/ha % t/ha

Control 64.3 27.2 37.1 42.3 - -

LimeX 3t/ha 63.2 19.0 44.2 30.0 12.3 7.8

LimeX 5t/ha 68.3 20.5 47.8 30.0 12.3 8.4

LimeX 7t/ha 63.2 16.3 46.9 25.8 16.5 10.4

0

10

20

30

40

50

60

70

80

90

Control LimeX 3t/ha LimeX 5t/ha LimeX 7t/ha

Pe

rce

nta

ge (

%)

Common scab affected yield (%)

no scab with scab

Final harvest results: glasshouse – Subclinical scab levels

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2013 Field trials: the role of calcium

4 sites with Maris Piper:

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% scab v total yield: Silt, sand and black fen T1 = UTC, T2 = 5t/ha, T3 = 7.5t/ha, T4= 10.0/tha

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T1 T2 T3 T4 T1 T2 T3 T4

T1 T2 T3 T4 T1 T2 T3 T4

pH @ final harvest: Silt, sand and black fen

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Ca @ final harvest: Silt, sand and black fen

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2015 strip trial results @ 7.5t/ha

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0

10

20

30

40

50

60

70

80

90

100

Swaton - Swaton +

Yiel

d [

%]

Swaton FarmPercentage of Scab/no scab

scab no scab

0

10

20

30

40

50

60

70

80

LimeX - LimeX +

Yiel

d [

%]

Gosberton FarmPercentage of Scab/no scab

scab no scab

Summary of all data: 2012-2015 (@95% probability)

• 12 replicated trials, all Maris Piper across a range of soil types

• Results • Most consistent treatment – 7.5t/ha LimeX70 pre planting incorporated

• Yield not significantly increased

• Marketable yield improvement – > 6.0t/ha (ie >10%)

• This is worth:

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Average Potato Yield (graded out/ha) 50

Average price per 1st grade tonne £250.00

Average price per 2nd grade tonne £150.00

LimeX £/t delivered and applied £15.00

Rate of LimeX (tn/ha) 7.5

% Increase in Marketable Yield 10

Additional Marketable Tonnes 5

Added Marketable Value £500.00

Cost of LimeX (Inc. Haul + Spread) £112.50

Net gain from LimeX application £387.50

Cost:Gain Ratio 444%

Strip Trials: Long Sutton 2016

Control

LimeX @ 7.5t/ha

Colsterworth 2016

46.0 45.416.0 24.50

10

20

30

40

50

60

Control LimeX

Yie

ld [

t/ha

]

Yield (t/ha)

with Scab without Scab

69.962.0

Frampton 2016

The average percentage of dry matter is shown above.

There was a significant difference between the Control &

LimeX treated plants with LimeX treated plants having a

larger percentage of dry matter compared to the control .

Spalding 2016

The LimeX treated plants had a significantly

greater yield of tubers without scab compared to

the Control (t(14) = -2.92, p = 0.011), with an

average of 9.3t/ha more potatoes compared to the

control treatment.

There was a significant difference between

the Control and LimeX treated plants with

LimeX treated plants having a higher

percentage of dry matter compared to the

control.

Conclusions:

• LimeX and common scab

• Peer review

• CUF, AHDB, AHDB Potato, ADAS, AIC

• RB209 revision - tbc

• Commercial reality

• Good science into practice

• Delivering confidence and real grower benefit

• Soil analysis

• pH, avail Ca, P, K & Mg

• Post storage benefits yet to be evaluated

• What else?.... black dot, black leg, dehydration…

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Calcium and potatoes:

• Auxins in the new foliage signal for calcium to be absorbed, which bypasses tubers. As this calcium

doesn’t move back to the tubers, stolons and tubers should be exposed to available calcium.

• Calcium is not re-translocated via the phloem from the aerial shoot tubers and main (basal) roots.

• Calcium is transported to the developing tuber via the xylem and the roots on the stolon associated

with the tuber supply water.

• The main root system does not supply calcium to the tuber.

• Calcium is not transported across the periderm to the interior tuber tissue.

• Transpirational demand is a significant determinant of calcium distribution within the plant.

• Long stolon varieties and those taken to a larger size i.e. bakers have a higher Ca requirement.

• Calcium reduces tuber abortion and strengthens the cell walls reducing internal disorders, bruising,

and bacterial attacks while maintaining quality (cell integrity), weight (water loss) and reduced rotting

during storage.

• Providing consistently available Ca in the tuber zone during growth and development significantly

reduces the incidence of hollow heart and internal browning.

• Many researchers have found up to 10 fold concentrations of Ca in infected peel which has been

wrongly attributed to calcium applications – these concentrations occur even without supplying Ca.

• Research suggests that adding lime to soil with already high pH is most effective for controlling

common scab. When the pH is over 7.5 this will supress scab - levels of 80% have been measured to

reduce to 10% incidence.

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Signalling, Transport, Demand, Benefits, Research

Summary of all data: 2012-2015 (@95% probability)

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Year Field Site Soil

type

start

pH C

End

pH C

End pH

7.5t/ha

Soil pH Soil av. Ca Stem # Tuber # Yield Change in

marketable yield

Best

treatment

Second best

treatment

2012 G Hay Farms Calcare

ous

coarse

silt

7.6 8.2 7.8 increased increased n/s n/s n/s 9.75 t/ha LimeX 7t/ha LimeX 3t/ha

2013 G Hay

Farms

Calcare

ous

coarse

silt

7.9 7.8 8.0 n/s increased n/s n/s n/s 6.5 t/ha LimeX 7.5t/ha -----

Bannister Farms Calcare

ous

coarse

silt

7.5 7.1 7.4 increased increased n/s n/s n/s 7 t/ha LimeX 7.5i

t/ha

LimeX

7.5t/ha +10i

J Davis Holme

Fen

Peaty

soil

5.7 5.3 5.7 increased n/s n/s n/s n/s n/s ----- -----

P Johnson

Diss

Fine

loam

over

clay

6.1 5.9 7.0 increased increased n/s n/s n/s 8.3 t/ha LimeX 7.5i

t/ha

LimeX10i

t/ha

2014 Bannister Farms Calcare

ous

coarse

silt

7.5 7.8 8.0 increased increased n/s n/s n/s 6.4 t/ha LimeX10+

t/ha

LimeX 7.5

t/ha

JGrant Fen Peaty

soil

6.8 6.8 6.9 n/s n/s n/s n/s n/s 11 t/ha LimeX5+ A Cal

Abrey Farms Sandy

Loam

7.5 7.9 8.0 increased increased n/s n/s n/s 9.20% Limex 7.5 t/ha A Cal

2015 Bannister Farms Calcare

ous

coarse

silt

7.8 7.9 8.5 increased increased n/s n/s n/s 2.2 t/ha LimeX 5t/ha LimeX 10t/ha

J Grant Fen Peaty

soil

6.5 6.6 6.8 increased increased n/s n/s n/s 0.5 t/ha LimeX 5t/ha LimeX 7t/ha

` Abrey Farms Sandy

loam

7.5 8.1 8.1 increased increased n/s n/s n/s n/s ------ -------

G Hay Farms Calcare

ous

coarse

silt

7.5 7.9 8.1 increased increased n/s n/s n/s n/s ------ --------

Average approx. 6.5 t/ha Best Treat.

Value £845/ha LimeX 7.5 t/ha

Background to LimeX

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