Western Free State cultivar trial under dryland conditions at Kroonstad in 2014 and 2015

Transcription

1 Western Free State cultivar trial under dryland conditions at Kroonstad in 214 and 215 Chantel du Raan and Attie van den Berg (Potatoes South Africa) The Western Free State currently produces approximately 17% of the total national potato production which, after Limpopo, is the second highest potato production in South Africa. The region produces 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%). Although potatoes are produced under irrigation in most parts of the Western Free State, dryland production is possible, for example in die Kroonstad area. Kroonstad (Figure 1 ) falls in a summer rainfall area with a temperate climate and receives an average annual rainfall of between 468 to 6 mm / annum. Summers are moderate to very hot summers, whereas winters are cold with severe frost (June and July). Potatoes are primarily planted from end of November to end of January, and harvested and marketed from April to September. The trial at Kroonstad 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 layout 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 defined as the number of day from emergence up until Page 54 CHIPS Maart/April 216

2 Bedryfsdienste Industry Services 1. Summer rainfall, temperate Kroonstad 2. Summer rainfall, tropical 3. Dry continental 4. Winter rainfall Figure 1: Location of Kroonstad in the Western Free State production region. 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 214 en 215 are indicated in Table 2. Yield and tuber size distribution are also influenced by the number of haulms per area and consequently by the amount of seed tubers planted and the number of haulms per seed tuber. The number of haulms, on the other hand, depends on the number of eyes per tuber, the number of sprouts per eye and the number of haulms per sprout. The number of eyes per tuber is cultivar dependent, whereas the number of haulms per tuber are influenced by the size and plant readiness of the seed tuber. It is important to note that these characteristics vary between cultivars. The plant readiness, population (%) and haulm count of cultivars Table 1: Summary of technical information pertaining to the trial site and layout. Farm Grootkuil Farmer Mr Kobus Crous Planting date 8 January 214 and 8 January 215 Harvesting date 11 July 214 and 3 July 215 Irrigation / Dryland Dryland Double or single rows Single rows Foliage die-off Natural Between row spacing 1.75 m Within-row spacing.35 m Trial plot area per cultivar: 18 m 2 Plant population plants / hectare Fertilizer program: Application timing: Nutritional value N (kg/ha) P (kg/ha) K (kg/ha) Ca (kg/ha) Mg (kg/ha) S (kg/ha) At planting Emergence Tuber initiation 14 2 weeks after tuber initiation weeks after tuber initiation Total CHIPS March/April 216 Page 55

3 Table 2: Characteristics regarding growing periods, plant readiness, population (%) and haulms counts for each cultivar included in the trial in 214 and 215. Growing period (Days) 1 Plant Stand (%) Haulms per readiness 2 plant Haulms per hectare Almera Short (85) Destiny Medium (11) Electra Short to medium (1) Elmundo Short to medium (9-1) Eos Medium (9-11) Everest Short to medium (9-1) Fianna Medium to long (112) Golf Medium (9-11) Kikko Medium (9-11) Konsul Medium (11) Labadia Short to medium (1) Lanorma Short (8-9) Marimba Short (85) Markies Medium (11) Melanto Medium (9-11) Monati Mondial Short to medium (95-1) Navigator Short to medium (1) Nectar Medium (9-11) Panamera Medium (9-11) Savanna Medium (9-11) Sifra Short to medium (9-1) Synergy Short to medium (1) Tiasiya Short to medium (1) UTD Medium to long (9-12) Valor Medium (1-11) General guidelines and categories (days from emergence to natural foliage die-off, depending on the season): Short = 7-9 days; Short to Medium = 8-1 days; Medium = 9-11 days; Medium to Long = 9-12 days; Long = 9-14 days 2 Plant readiness of seed tubers 1 Fresh; 2 Slightly fresh; 3 Plant ready; 4 Slightly old; 5 Old. Page 56 CHIPS Maart/April 216

4 Bedryfsdienste Industry Services 35 Total rainfall per month 214 Total rainfall per month 215 Long term average rainfall Cumulative rainfall 214 Cumulative rainfall 215 Long term cumulative rainfall 3 Rainfall (mm) January February March April May June July Month Figure 2: Rainfall during the growing season (214 en 215) as well as the long term average rainfall. 5 Maximum temperature 214 Minimum temperature 214 Maximum temperature 215 Minimum temperature 215 Long term average maximum temperature Long term average minimum temperature 4 Temperature ( C) Jan 8-Jan 15-Jan 22-Jan 29-Jan 5-Feb 12-Feb 19-Feb 26-Feb 5-Mar 12-Mar 19-Mar 26-Mar 2-Apr 9-Apr 16-Apr 23-Apr 3-Apr 7-May 14-May 21-May 28-May 4-Jun 11-Jun 18-Jun 25-Jun 2-Jul 9-Jul 16-Jul 23-Jul 3-Jul Plant Date Harvest Figure 3: Minimum and maximum temperatures (ºC) during the growing seasons (214 and 215) as well as long term. CHIPS March/April 216 Page 57

5 planted in the 214 and 215 trial are indicated in Table 2. Temperature, photoperiod (day 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 the performance of the different cultivars are evaluated. It is also important that cultivars are evaluated for a number of seasons because climate differs from season to season. WEATHER DATA FOR THE 214 AND 215 GROWING SEASON The measured rainfall during the 214 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 215 trials was significantly lower than the norm throughout the growing season (Figure 2). The maximum temperatures (Figure 3) for the 214 growing season was higher than the norm during January, April and May whereas in 215 extreme maximum temperatures were experienced from January until May. During 215 higher than normal minimum temperatures were also conspicuously evident from May to July. During the 214 growing season temperatures below freezing-point (ºC) were observed from early June and continued until the end of the season. On the other hand the minimum temperatures for the 215 trial 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 huge differences in the maximum and minimum temperatures throughout the 214 and 215 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 therefore accepted that a plant must accumulate a specific number of heat units to complete the development phase. The heat units of both the 214 and 215 growing seasons were continually slightly higher than the norm the heat units of the 215 growing season were higher than the norm (long term accumulative heat units) as indicated in Figure 4. Heat units Total heat units per month 214 Total heat units per month 215 Long term average heat units Cumulative heat units 214 Cumulative heat units 215 Long term cumulative heat units January February March April May June July Month Figure 4: Heat units during the growing season (214 and 215) as well as long term average. Page 58 CHIPS Maart/April 216

6 Bedryfsdienste Industry Services Mondial Kikko Sifra Markies Lanorma Everest Panamera Synergy Konsul Labadia Savanna Electra Marimba Destiny Valor Elmundo Almera Nectar Yield index (%) Marketing index (%) p <.1 LSD = 22.1 CV% = Yield and marketing index as percentage of the trial average (%) for 214 *Values followed by the same letter are not significantly different from one another. Figure 5: Total yield and marketing index per cultivar for 214 as percentage of the trial average. Markies Mondial Panamera Melanto Lanorma Valor Monati Taisiya Golf Fianna Savanna UTD Electra Destiny Almera Navigator Sifra Marimba Eos Yield index (%) Marketing index (%) p <.1 LSD = 32.4 CV% = Yield and marketing index as percentage of the trial average (%) for 215 *Values followed by the same letter are not significantly different from one another. Figure 6: Total yield and marketing index per cultivar for 215 as percentage of the trial average. CHIPS March/April 216 Page 59

7 Baby Small Medium Large medium Large Trial average Size distribution (t/ha) for t/ha Figure 7: Size distribution of each cultivar during the 214 final harvest. Baby Small Medium Large medium Large Trial average Size distribution (t/ha) for t/ha Figure 8: Size distribution of each cultivar during the 215 final harvest. Page 6 CHIPS Maart/April 216

8 Bedryfsdienste Industry Services 5 Rejected Class 3 Class 2 Class 1 Trial average 214 Grading (t/ha) for t/ha Figure 9: Grading of each cultivar during the 214 final harvest. 45 Rejected Class 3 Class 2 Class 1 Trial average 215 Grading (t/ha) for t/ha Figure 1: Grading of each cultivar during the 215 final harvest. CHIPS March/April 216 Page 61

9 YIELD DATA The yield data collected from the trals was statistically analysed using the statistical program GenStat and the means were separated using the Tukey LSD test at the 5% level. The cultivar effect for the 214 trials (Figure 5) and the 215 trials (Figure 6) was both statistically highly significant (p<. 1) in respect of yield while the coefficient of variation was low (214 = 11.7%, 215 = 14.6%). This indicates that the trials were well executed and the results are trustworthy. The trial average of all the cultivars is taken as 1%. 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). In 214, high yields were recorded (average 34.4 t/ha) that can probably be ascribed to the good rains received compared to the long term weather data for the area. This resulted in the plants reaching their potential and the tubers bulking quicker before the frost shortened the growing season. The cultivar Mondial attained the highest yield, and which was significantly higher than the cultivars Konsul, Labadia, Savanna, Electra, Marimba, Destiny, Valor, Elmundo, Almera and Nectar. On the other hand Nectar and Almera (Figure 5) attained the lowest yields that can be ascribed to the poor plant population (5% and 65% respectively). Higher yields than the trial average (34.4 t/ ha) were attained by the cultivars Mondial, Kikko, Sifra, Markies, Lanorma, Everest, Panamera, Synergy and Konsul. The average yield (27.5 t/ha) for the 215 season was significantly lower and can primarily be ascribed to the fact that compared to the long term weather data lot less rain had fallen at the trial site during the growing season. The drought continued throughout the season which could have affected yields negatively. The plants, therefore, could not reach their full potential to initiated tuber and bulk before the frost damaged the foliage. During the 215 trials (Figure 6) the cultivar Markies attained the highest yield which was significantly higher compared to the other cultivars, excluding Mondial, Panamera, Melanto, Lanorma, Valor and Monati. On the other hand Eos that statistically did not differ from Marimba, Sifra and Navigator, had the poorest yield which can be ascribed to the poor plant population (5% and 65% respectively). Higher yields than the trial average (27.5 t/ha) were attained by the cultivars Markies, Mondial, Panamera, Melanto, Lanorma, Valor, Monati and Taisiya. 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 group distribution and grading, gives the marketing index (Figure 5). The cultivar Lanorma attained the highest marketing index during the 214 growing season and Sifra during the 215 growing season that can be ascribed to both 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 is therefore important to take into account to ensure an optimum economically marketable yield. In Figures 7 and 8 the size distribution are indicated and in Figures 9 and 1 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 five year data is indicated in respect of the cultivar trials in the Kroonstad production area. It appears that the cultivar Lanorma has shown the least variation for the Kroonstad 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 214 growing season only the cultivars Lanorma and Markies complied with the chip colour norm of >5 for processing. However, a slight discolouration was found with the cultivar Valor after cooking. In respect of specific gravity (SG) the cultivars Destiny, Labadia, Lanorma, Markies, Nectar, Panamera, Savanna and Valor complied with the norm of The low SG values can possibly be ascribed to the environmental conditions, such as the temperatures below freezing point that caused foliage damage and therefore affected photosynthesis negatively, and extremely high temperatures that cause excessive respiration and inhibited starch accumulation. As far as internal defects are concerned the cultivars Destiny, Labadia, Lanorma, Markies, Nectar, Panamera, Savanna and en Valor showed evidence of brown spot. In addition, the cultivars Everest (1%), Lanorma (1%), Marimba (3%), Markies (3%), Nectar (1%) and Savanna (2%) showed evidence of hollow heart. As far as the 215 growing season s specific gravity (SG) is concerned, the cultivars Destiny, Fianna, Golf, Mondial, Panamera, Up-to-Date and Valor complied with the norm of The low SG values can possibly be ascribed to the environmental conditions, for example high temperatures Page 62 CHIPS Maart/April 216

10 Bedryfsdienste Industry Services that could have affected photosynthesis negatively. The incidence of brown spot and hollow heart was significantly higher in 215 as indicated in Table 3. It is known that internal brown spot bear relation to warm (especially high soil temperatures) and a dry climate as experienced during the 215 growing season. Under these conditions the nutrients and water is translocated from the tubers to the haulms which leads to weak or damaged cells in the tuber. C Yield as percentage of the trial average (%) Almera Lanorma Markies Sifra Mondial Figure 11. Performance of cultivars over five years expressed as a percentage of the trial average. CHIPS March/April 216 Page 63

11 Table 3. Cooking and processing characteristics and internal quality of yield for 214 and 215 (Conducted by ARC Roodeplaat). 214 Flesh colour Cooking Structure Discolour type 1 after cooking Chip SG 3 Brown colour 2 spot (%) Hollow heart (%) Almera Yellow SF Medium None Destiny Yellow F Medium None Electra Cream SF Medium None Elmundo Yellow SF Medium None Everest Yellow SF Medium None Kikko Cream SF Medium None Konsul Yellow F Medium None Labadia Yellow SF Medium None Lanorma Cream SF Medium None Marimba Yellow SF Medium None Markies Yellow SF Medium None Mondial Yellow SF Medium None Nectar Yellow F Medium None Panamera Cream SF Medium None Savanna Yellow F Medium None Sifra Cream NF Firm None Synergy Yellow NF Firm None Valor Cream NF Firm Slight VF Very floury to loose texture; F Floury, crumbly to loose potato; SF Slightly floury, free firm potato with fine to moderately fine texture; NF Not floury, firm potato with a fine texture. 2 Chip colour with value of >5 and without defects is acceptable for the crisps industry. 3 Specific gravity of >1.75 is acceptable for the processing industry. >Norm (Acceptable for processing) <Norm (Unacceptable for processing) Page 64 CHIPS Maart/April 216

12 Bedryfsdienste Industry Services Table 3. Cooking and processing characteristics and internal quality of yield for 214 and 215 (Conducted by ARC Roodeplaat). 215 Structure Discolour Flesh colour Cooking type 1 after cooking Chip SG 3 Brown colour 2 spot (%) Hollow heart (%) Almera Dark yellow F Medium None Destiny Dark yellow F Medium None Electra Dark yellow F Medium None Eos White SF Medium None Fianna Cream SF Medium None Golf Cream F Medium None Lanorma Cream NF Firm None Marimba Yellow SF Medium None Markies Yellow SF Medium None Melanto Yellow SF Medium None Monati Dark yellow SF Medium None Mondial Yellow SF Medium None Navigator Cream SF Medium None Panamera Yellow SF Medium None Savanna Cream SF Medium None Sifra Cream SF Medium None Taisiya Yellow SF Firm None UTD Cream F Medium None Valor White F Medium None VF Very floury to loose texture; F Floury, crumbly to loose potato; SF Slightly floury, free firm potato with fine to moderately fine texture; NF Not floury, firm potato with a fine texture. 2 Chip colour with value of >5 and without defects is acceptable for the crisps industry. 3 Specific gravity of >1.75 is acceptable for the processing industry. >Norm (Acceptable for processing) <Norm (Unacceptable for processing) CHIPS March/April 216 Page 65