|Authors: ||G.M. Coetzer, H.J. Fouché, M.F. Smith|
|Keywords: ||rainfall, temperature, accumulated heat units, fruit thinning|
The adaptability of a cactus pear cultivar to a specific environment is primarily a function of fruit yield.
The fruit yield of local cultivars were very variable over a period of 10 years, and the objective of this study was to investigate the role of climatic factors in fruit yield.
Data were collected from a cactus pear orchard with 42 cultivars that was laid out as a randomized complete block design with two replicates of five data plants each.
Twelve cultivars were identified as potential fruit-producing cultivars for the local and export markets.
Fruit-yield data were collected over a period of 10 years and compared with rainfall, accumulated heat units and average monthly maximum temperature data.
Data analysis showed that cultivars differed significantly in their stability, and cultivar-by-season interactions played an important role in fruit production.
Cultivar ‘Van As’ was the most consistent yielding cultivar over all 10 seasons.
Seasons 4 and 5 were the highest yielding seasons, when fruit thinning was done during the first five production years, and cultivars ‘Morado’, ‘Meyers’, ‘Zastron’, ‘Van As’ and ‘Gymno Carpo’ yielded the most fruit.
These cultivars also ranked the best when no fruit thinning was done, during the next five years.
A high correlation between fruit yield and total rainfall from October to November (84.8%) existed for the first five seasons, which was not the case for heat units or maximum monthly temperature.
From season 6, when no fruit thinning was done, a high correlation existed between fruit yield and total rainfall for the period October to December (94.0%) and between average monthly maximum temperatures for October (73.2%), November (51.2%) and December (82.4%). The total rainfall for seasons 6, 8 and 10 was 311.0, 244.8 and 247.7 mm, respectively, compared with 78 and 137.3 mm for seasons 7 and 9, respectively, for the period October to December.
Our results indicated that rainfall distribution played a major role in fruit yield, and not only the total rainfall for the season.
Early summer rainfall (October-November) had a more significant effect on fruit yield than spring (July-September) or late summer (January) rainfall.
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