Yield and fruit quality assessment of cactus pear (Opuntia ficus-indica (L.) Mill.) treated with natural bio-stimulants

English: In arid and semi-arid regions of South Africa, both subsistence and commercial farmers experience economic pressure due to varying prices of staple crops such as maize and wheat as well as weather uncertainties. The prickly pear, Opuntia ficus-indica, is an alternative crop that can partially offer a solution to these problems as an extra income. Further, it is capable to produce both fruit and young cladodes under rather extreme weather conditions, including severe drought. Further, its economic potential per hectare far exceeds that of maize and wheat. This supplied a rationale for investigating new ways for manipulating the crop with the aim to increase either fruit yield and quality or new cladode production or both, by applying natural bio-stimulants as foliar sprays to adult plants while standard management practices were adhered to. ComCat® (CC), a commercially available natural bio-stimulant known for its potential to stimulate yield, growth and development in some crop plants, along with SS, a prototype natural bio-stimulant still in the developmental phase, was used in this study in an attempt to reach the set objectives. Kelpak®, a commercially available bio-stimulant also known for its growth stimulating properties, was used as a positive control. Although, in the two trials conducted, the results were not consistent as far as all measured parameters are concerned and were not statistically significant in all cases, ComCat® (CC) consistently contributed to a increase in the total fruit yield expressed in ton ha-1 while the SS treatment consistently contributed to elevated new cladode production in both trials. When fruit and new cladode yield data was expressed per old cladode, a different picture arose. This prompted the need to correlate the relationship between morphological and yield data. Subsequently, multiple regression and correlation analyses were performed using morphological parameters such as fruit-, peel- and pulp mass as well as fruit diameter and length to predict fruit yield and quality. Although the linear equation models resulting from this statistical calculation did not consistently show significant prediction accuracy at the 95% probability level, it was a worthwhile exercise as definite correlations were observed at least at the 90% probability level. Prediction models resulting from multiple regression and correlation analyses of morphological, yield and quality data strongly indicated that this approach might become a handy tool for farmers assisting them in managing their orchards not only in a specific growing season but especially for the following season. More research is necessary to pursue this aspect. Finally, manipulation of fruit yield in O. ficus-indica by foliar sprays of adult plants with ComCat® and manipulation of new cladode production by treatment with SS, can become additional techniques to optimize the productivity of this crop plant.