western free state cultivar trial under irrigation at bultfontein in

• CHIPS • Maart/April 2016

Western Free State cultivar trial under irrigation at Bultfontein in

2014 and 2015

The Western Free State currently produces about 17% of the national potato production which makes it South Africa’s second largest potato production region in terms of volume only to be surpassed by Limpopo. The region cultivates seed potatoes, fresh market and processing. The region’s contribution to the South African processing industry amount to 4%. The standard cultivars planted for the fresh and processing markets are Mondial (69%), Up-to-date (17%) and Sifra (13%). The Western Free State production region (Bultfontein) (Figure 1) is regarded as summer rainfall area with a temperate climate and receives an average annual rainfall of between 369 to 549 mm

/ annum. Summers are moderate to very hot summers (warmest January), whilst the winters are cold with severe frost (from April). Potatoes are primarily planted from end October to middle February, and harvested and marketed from April to October. The trial at Bultfontein was conducted on a site with sandy loam soil and was planted in a random complete block design with three replications. Additional technical information regarding the trial site and lay-out is summarised in Table 1.

Growing period is an important factor to take note of since it can influence the yields of cultivars. Growing period is

Chantel du Raan and Attie van den Berg (Potatoes South Africa)

Bedryfsdienste • Industry Services

CHIPS • March/April 2016 • Page 67

Figure 1: Location of Bultfontein in the Western Free State production region.

1. Summer rainfall, temperate

2. Summer rainfall, tropical

3. Dry continental

4. Winter rainfall

Bultfontein

Figure 1: Location of Bultfontein in the Western Free State production region.

Table 1: Summary of technical information regarding trial site and layout.

Farm Oasis

Farmer Mr Izak Cronjé

Planting date 7 January 2014 and 9 January 2015

Harvesting date 11 June 2014 and 18 August 2015

Irrigation / Dryland Irrigation

Double or single row Double rows

Foliage die-off Natural

Between-row spacing 2.00 m

Within-row spacing 0.25 m

Trial plot area per cultivar: 20 m2

Plant population 40 000 plants / hectare

Fertilizer program

Application timing: Nutritional value

N (kg/ha) P (kg/ha) K (kg/ha)

Total 301 142 106

defined as the number of day from emergence up until the foliage die-off naturally, depending on the season. The exact timing of these four growth phases depend, amongst various other factors, on the environment and the management practices which vary between localities and cultivars as a result of different growing periods. The cultivars included in the workgroup trial during 2014 en 2015 are indicated in Table 2.

Temperature, photoperiod (daylight length) and soil moisture are the most important abiotic factors that influence the growth pattern, yield and quality of potatoes. To determine the ability of new cultivars to adapt to the Bultfontein area, it is important to take note of these factors into account when he performance of the different cultivars are evaluated. It is also important that cultivars are evaluated for a number of season because climate differs from season to season.


1 General guidelines and categories (days from emergence to natural foliage die-off, depending on the season):Short = 70-90 days; Short to Medium = 80-100 days; Medium = 90-110 days; Medium to Long = 90-120 days; Long = 90-140 days2 Plant readiness of seed tubers1 – Fresh; 2 – Slightly fresh; 3 – Plant ready; 4 – Slightly old; 5 – Old.

Table 2: Characteristics in respect of growing period, plant readiness, population (%) and haulm count for everycultivar included in the trial in 2014 and 2015.

Cultivar Growing period(Days)1

Plant readiness2

Stand (%) Haulms per plant

Haulms per hectare

2014 2015 2014 2015 2014 2015 2014 2015

Almera Short (85) 2 3 100 100 3.4 3.4 136 000 136 000

Destiny Medium (110) 3 3 95 85 3.2 3.5 128 000 140 000

Electra Short to medium (100) 2 3 90 100 3.2 3.4 128 000 136 000

Elmundo Short to medium (90-100) 3 - 100 - 3.4 - 136 000 -

Eos Medium (90-110) 2 3 80 70 3.0 3.2 120 000 128 000

Everest Short to medium (90-100) 3 - 95 - 3.8 - 152 000 -

Fianna Short to medium (112) - 2 - 100 - 3.4 - 136 000

Fontaine Short to medium (120) - 2 - 95 - 3.2 - 128 000

Golf Medium (90-110) - 2 - 100 - 3.6 - 144 000

Kikko Medium (90-110) 2 - 95 - 3.2 - 128 000 -

Konsul Medium (110) 2 - 90 - 3.2 - 128 000 -

Labadia Short to medium (100) 2 - 95 - 3.6 - 144 000 -

Lady Alba Short to medium (95-100) 1 - 95 - 4.0 - 160 000 -

Lady Sara Medium (110) - 2 - 85 - 3.8 - 152 000

Lanorma Short (80-90) 3 2 100 80 3.6 3.4 144 000 136 000

Marimba Short (85) 3 3 95 80 3.6 3.4 144 000 136 000

Markies Medium (110) 3 3 90 100 3.6 3.4 144 000 136 000

Melanto Medium (90-110) - 3 - 100 - 3.4 - 136 000

Monati - - - 3 - 90 - 3.4 - 136 000

Mondial Short to medium (95-100) 2 3 100 100 4.0 3.8 160 000 152 000

Navigator Short to medium (100) - 3 - 90 - 3.6 - 144 000

Nectar Medium (90-110) 2 - 100 - 3.4 - 136 000 -

Panamera Medium (90-110) 2 3 95 100 3.6 3.4 144 000 136 000

Savanna Medium (90-110) 2 2 90 100 3.4 3.6 136 000 144 000

Synergy Short to medium (100) 2 3 100 100 4.0 3.8 160 000 152 000

Sifra Short to medium (90-100) 2 3 95 90 3.6 3.4 144 000 136 000

Taysiya Short to medium (100) - 3 - 100 - 4.0 - 160 000

Triomf Short to medium (110-120) - 3 - 100 - 3.6 - 144 000

Valor Medium (100-110) 3 3 100 100 3.2 3.4 128 000 136 000



0

50

100

150

200

250

300

January February March April May June July August

Rain

fall

(mm

)

Date

Total rainfall per month 2014 Total rainfall per month 2015 Long term average rainfall

Cumulative rainfall 2014 Cumulative rainfall 2015 Long term cumulative rainfall

20142015

-20

-10

0

10

20

30

40

01-Ja

n 09

-Jan

17-Ja

n 25

-Jan

02-F

eb

10-F

eb

18-F

eb

26-F

eb

06-M

ar

14-M

ar

22-M

ar

30-M

ar

07-A

pr

15-A

pr

23-A

pr

01-M

ay

09-M

ay

17-M

ay

25-M

ay

02-Ju

n 10

-Jun

18-Ju

n 26

-Jun

04-Ju

l 12

-Jul

20-Ju

l 28

-Jul

05-A

ug

13-A

ug

21-A

ug

29-A

ug

Tem

pera

ture

(°C)

Date

Maximum temperature 2014 Minimum temperature 2014 Maximum temperature 2015 Minimum temperature 2015 Long term average maximum temperature Long term average minimum temperature

2014 2015

Figure 2: Rainfall during the growing seasons (2014 and 2015) as well as the long term average rainfall.

Figure 3: Minimum and maximum temperatures (°C) during the growing seasons (2014 and 2015) as well as long term.


WEATHER DATA FOR THE 2014 AND 2015 GROWING SEASON

The measured rainfall during the 2014 growing season followed the same pattern as in previous years with the exception of February, March and April which was higher compared to the long term average rainfall (Figure 2). On the other hand, the measured rainfall in respect of the 2015 trials was significantly lower than the norm throughout the growing season (Figure 2). The maximum temperatures (Figure 3) for the 2014 and 2015 growing seasons were fairly in line with the norm with the exception that the 2015 growing season experienced very high maximum temperatures during February and August. A lower than usual minimum temperature during 2014 and a higher than usual minimum temperature during 2015 were also conspicuously evident from June. Temperatures below freezing-point (0ºC) during the 2014 growing season were observed from end April and continued until the end of the season. In respect of the 2015 trial the minimum temperatures were in general higher compared to the long term average data and temperatures below freezing-point were only experienced by middle June. There was also big differences in the maximum and minimum temperatures during the 2014 and 2015 seasons (Figure 3). These extreme weather conditions could have negatively affected

the yield and quality of the cultivars.

Heat units are also an important factor to take into account because the development of the plant is primarily based on the accumulating heat units. It is consequently accepted that a plant must accumulate a specific number of heat units to complete the development phase. The heat units of the 2014 growing season were lower than the norm the heat units of the 2015 growing season were higher than the norm as indicated in Figure 4.

YIELD DATA

The yield data collected from the trials was statistically analyzed using the statistical program GenStat® and the means were seperated using the Tukey LSD test at the 5% level. The cultivar effect for the 2014 trials (Figure 5) and the 2015 trials (Figure 6) was both statistically highly significant (p<0. 01) in respect of yield while the coefficient of variation was very low (2014 = 10.6%, 2015 = 9.5%). This indicates that the trials were well executed and the results are trustworthy. The trial average of all the cultivars is taken as 100%. The yield of the individual cultivars is then divided by the trial average and the yield performance of each cultivar are expressed as a percentage of the trial average (yield index).

-200

0

200

400

600

800

1000

1200

1400

1600

January February March April May June July August

Heat

uni

ts

Month

Total heat units per month 2014 Total heat units per month 2015 Long term average heat units

Cumulative heat units 2014 Cumulative heat units 2015 Long term cumulative heat units

20142015

Figure 4: Heat units during the growing seasons (2014 and 2015) as well as long term average.



74.1 75.5

78.5 82.2 83.1

92.7 97.4

99.6 99.9

103.5 104.0 105.1

106.8 110.2

111.2 111.7 112.3

116.4 116.4

119.3

0 20 40 60 80 100 120 140

Lady Alba Nectar

Valor Almera Destiny

Savanna El Mundo

Labadia Synergy Everest

Marimba Eos

Markies Sifra

Lanorma Panamera

Mondial Kikko

Konsul Electra

Yield and marketing index as percentage of the trial average (%) for 2014

Culti

var

Yield index (%) Marketing index (%)

p < 0.01 LSD = 21.17 CV% = 10.6

2014

57.6 66.0

75.6 76.3 77.4 78.4

87.4 90.2

95.7 101.0 102.6 102.7 102.8

111.8 116.7 117.4 118.8

120.5 123.6 124.0 125.0

128.4

0 20 40 60 80 100 120 140 160

Eos Destiny

Lady Sara Fianna

Marimba Fontane

Golf Savanna

Sifra Lanorma

Navigator Triomf

Markies Electra

Mondial Melanto

Almera Valor

Monati Panamera

Taisya Synergy

Yield and marketing index as percentage of the trial average (%) for 2015

Culti

var

Yield index (%) Marketing index (%)

p < 0.01 LSD = 20.8 CV% = 9.5

2015

Figure 5: Total yield and marketing index per cultivar for 2014 as percentage of the trial average.

Figure 6: Total yield and marketing index per cultivar for 2015 as percentage of the trial average.

*Values followed by the same letter do not significantly differ from one another.

*Values followed by the same letter do not significantly differ from one another.

2 • CHIPS • Maart/April 2016


0

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20

30

40

50

60

70

80

Size

dist

ribut

ion

(t/h

a) fo

r 201

4

Cultivar

Baby Small Medium Large medium Large

62.7 t/ha

Trial average 2014

0

10

20

30

40

50

60

70

80

Size

dist

ribut

ion

(t/h

a) fo

r 201

5

Cultivar

Baby Small Medium Large medium Large 2015 Trial average

55.1 t/ha

Figure 7: Size distribution of each cultivar during the 2014 final harvest.

Figure 8: Size distribution for each cultivar during the 2015 final harvest.



0

10

20

30

40

50

60

70

80

Grad

ing

(t/h

a) fo

r 201

4

Cultivar

Rejected Class 3 Class 2 Class 1

62.7 t/ha

Trial average 2014

Figure 9: Grading of each cultivar during the 2014 final harvest.

0

10

20

30

40

50

60

70

80

Gra

ding

(t/h

a) fo

r 201

5

Cultivar

Rejected Class 3 Class 2 Class 1 Trial average 2015

55.1 t/ha

Figure 10: Grading of each cultivar during the 2015 final harvest.


With regard to the 2014 trials, slightly higher yields were obtained (average 62.7 t/ha) which can probably be ascribed to the favourable weather conditions that prevailed. This resulted in the plants reaching their potential quicker as well as the tubers to bulk before the frost shortened the growing season. The cultivar Electra attained the highest yield, and it as significantly higher compared to the yields of Elmundo, Savanna, Destiny, Almera, Valor, Nectar and Lady Alba. Lady Alba which did not statistically differ from Nectar, Valor, Almera, Destiny and Savanna, performed the worst (Figure 5). Higher yields than the trial average (62.7 t/ha) were attained by the cultivars Electra, Konsul, Kikko, Mondial, Panamera, Lanorma, Sifra, Markies, Eos, Marimba and Everest.

The average yield (55.1 t/ha) for the 2015 season was significantly lower than that of the previous year and can primarily be ascribed to the unfavourable weather conditions that prevailed during the growing season at the trial site. Consequently the plants could not reach their full potential to initiate tuber as well as bulk before the frost damaged the foliage. During the 2015 trials (Figure 6) the cultivar Synergy attained the highest yield, and it was significantly higher than the other cultivars except for Taisiya, Panamera, Monati, Valor, Almera, Melanto, Mondial and Electra. On the other side Eos which did not statistically differ from Destiny, Lady Sara, Fianna, Marimba and Fontane, delivered the worst yield. Yields higher than

the trial average (55.1 t/ha) were attained by the cultivars Synergy, Taisiya, Panamera, Monati, Valor, Almera, Melanto, Mondial, Electra, Markies, Triomf, Navigator and Lanorma.

In order to determine the performance of the cultivars in terms of yield and quality, the yield, size distribution and class were used to determine a marketing index based on the average market prices for the relevant day. The yield multiplied by the current price, which is determined by the size distribution and grading, gives the marketing index (Figure 5). The cultivar Lanorma attained the highest marketing index during the 2014 growing season and Panamera during the 2015 growing that

0

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40

60

80

100

120

140

Almera Electra Eos Lanorma Marimba Markies Mondial Panamera Savanna Sifra Valor

Yiel

ds a

s per

cent

age

of tr

ial a

vera

ge (%

)

Cultivar

2015 2014 2013 2012

Figure 11. Performance of cultivars over four years expressed as a percentage of the trial average.



Mondial have shown the least variation for the Bultfontein area.

Furthermore it is important to focus on the internal quality of the product in order to ensure an optimum economically marketable yield, and therefore profitability. It includes important factors such as cooking and processing characteristics, specific gravity (SG) as well as internal defects (hollow heart, brown spot and vascular discolouration) that is summarized in Table 3.

During the 2014 growing season only the cultivars Markies and Panamera complied with the chip colour norm of >50 for processing. In respect of specific gravity (SG) the cultivars Destiny, Mondial, Markies, Panamera, Labadia, Lady Alba, Synergy, Savanna, Elmundo and Valor complied with the norm of ≥1.075 for processing. The tuber formation index for 2014 is also indicated in Table 3.

With regard to the 2015 growing season’s specific gravity (SG), the cultivars Destiny, Fianna, Fontane and Golf complied with the norm of ≥1.075 for processing. The low SG values can possibly be ascribed to the environmental conditions, such as the high temperatures that could have affected photosynthesis negatively. The cultivars Destiny, Electra, Eos, Fianna, Fontane, Golf, Lady Sara, Lanorma, Markies, Navigator, Triomf and Valor complied with the chips colour norm of >50 for processing. There was no appearance of brown spot and hollow heart in 2015. C

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can be ascribed to the high percentage large and class 1 potatoes produced by the cultivars. Size distribution and grading are also factors that are used to class potatoes, and it is therefore important factors to take into account to ensure an optimum economically marketable yield. In Figures 7 and 8 the size distribution is indicated and in Figures 9 and 10 the grading of the yields of the various cultivars.

It is also important to take cognisance of the ability of

the cultivars to perform consistently, in spite of climatic fluctuations over time. In Figure 8 the four year data is indicated in respect of the cultivar trials at the Bultfontein production area. It appears that the cultivars Markies and

western free state cultivar trial under irrigation at bultfontein in

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