G.M. Ceronio’s scientific contributions

The ongoing climate change, frequent and long-term droughts, and grazing land deterioration pose a threat to sustainable animal production systems in arid and semi- arid regions of South Africa. Under these adverse conditions, animal production is limited due to the scarcity of fodder. It is essential to investigate the use of a resilient, high water content crop such as cactus pear to mitigate the need for alternative fodder, especially for subsistence farmers. The potential of cactus pear as a fodder crop necessitates the investigation into the role of nitrogen fertilizer on the cladode yield of ‘Morado’ cactus pear. The response of ‘Morado’ to two nitrogen sources (urea and limestone ammonium nitrate) and four nitrogen levels (0, 60, 120, and 240 kg N ha-1 in 2017/2018 and 0, 180, 360 and 720 kg N ha-1 in 2018/2019) was investigated. A randomized complete block design with three replications was used, and each replication consisted of four data plants. Cladode number, fresh mass, and mineral content were measured during pruning. The nitrogen sources did not have a significant effect on most of the parameters measured. However, the cladode number and fresh mass were significantly increased by the two highest nitrogen levels applied in both seasons. The crude protein content of the cladodes was also significantly influenced. Overall, these findings suggest that the fertilization of cactus pear with nitrogen increases cladodes’ crude protein content, making the crop a staple fodder material in drought-stricken countries such as South Africa. Keywords: cladode yield, crude protein, limestone ammonium nitrate (LAN), mineral content, urea

AbstractCactus pear seed oil production is an important emerging industry in South Africa. The oil is classified as an essential oil containing mainly omega-6 fatty acids, vitamins and antioxidants. Although the yield of the oil is low, it is classified as a good-quality oil with good stability. As part of an initiative to promote cactus pears as a multi-functional crop, dual-purpose cultivars should be identified, and their production increased. This study forms part of an existing project aimed to increase the yield and quality of the Opuntia ficus-indica ‘Morado’ produced for its commercially viable green-coloured fruit in South Africa. The main project encompasses a trial using nitrogen (N)fertilization from three N sources and four N application rates. It was found that fruit production significantly increased with both the N source and application rate. However, the N source did not influence fruit quality. Seeds from approximately 50 fruits per treatment were extracted from the pulp, dried at room temperature and ground with a commercial coffee grinder, after which it was vacuum packed and frozen (not longer than one month). Oil was extracted using the Soxhlet method, and the fatty acids were determined by gas chromatography. Oil yield and major fatty acids content for the 2020-2021 seasons are reported and compared to published data for the 2019 season. In general, oil yield increased with increased N fertilization, as did most major fatty acids, although the main fatty, linoleic acid levels provided inconclusive results.