Production evaluation of Opuntia robusta and O.ficus-indica cultivars in the central Free State
English: The search for appropriate plant species able to produce with sustainably in arid and semi-arid areas, has been a concern for some farmers living in such harsh environments. Unfortunately there is a lack of information concerning the adaptability of different cactus pear cultivers under a range of environmental conditions. This includes the cultivation for both fodder and fruit production. Cactus pear could be introduced with great success on land presently deemed marginal for other crops. A study was therefore conducted to evaluate the production potential of ten cultivars of the green pad cactus pear species (Opuntia ficus-indicaï and one blue pad cultivar of O . robusta over three growing seasons (2001/02 to 2003/04). The cultivars of O. ficus-indica included Algerian, Gymno Carpo, Morado, Nudosa, Roedtan, Sicilian Indian fig, Tormentosa, Van As, X28 and Zastron. The species O. robusta was represented by the cultivar Monterey. The experimental layout was a randomised block design with three treatments (fodder, fruit and scozzolatura), consisting of 11 cultivars replicated twice on 66 plots. Each plot consisted of 20 plants, of which 10 were used as data plants, planted in two rows. During the study vegetative, reproductive and laboratory measurements were evaluated for the different treatments and cultivars. It was evident from this study that young cactus pear plants could be killed by a combination of frequent successive nights of temperatures below the freezing point (as low as -9°C) and water stress. Shortage of soil nutrients could also influence both fruit and fodder production in young cactus plants. Mechanical weeding near the cactus plants could damage the shallow and widespread roots thus reducing the ability of plants to cope with harsh drought. Therefore, chemical control of weeds is encouraged. This limited study has revealed that Roedtan is the best cultivar for both fodder and fruit production while Morado is also ideal for production of both fodder and fruit. Other promising cultivars (although not as outstanding) for fodder production are Algerian, Gymno Carpo, Nudosa, Van As and Zastron. The same cultivars, except Zastron, can produce promising results in fruit production. Monterey, Sicilian Indian fig, Tormentosa and X28 can produce satisfactory results in terms of fodder production. The same cultivars except Monterey can produce satisfactory results in terms of fruit production. The study has proved that Zastron and Monterey should be discouraged for fruit production. However, more in-depth research should be carried out to provide more information about the cultivars in the different arid environmental conditions of southern Africa. In the minimum descriptor list for Opuntia species for fruit production, only Tormentosa qualifies to be categorised as having very few seeds « 100), while most of the other cultivars have few seeds (101 - 200). The study has demonstrated that all other cultivars except Monterey are easy to peel. It needs to be established by research if there is a difference between young and mature cactus pear cultivars in terms of number of seeds produced per fruit. The limited information obtained from this study could benefit both commercial and subsistence farming communities living in drought threatened areas.