Edible fynbos plants : a soil types and irrigation regime investigation on Tetragonia decumbens and Mesembryanthemum crystallinum

Fynbos’ rich biodiversity has been a source of much economic activity with its beautiful wild flowers and world-famous Proteas. Additionally, the medicinal and health benefits of rooibos and honey bush have enormous market value all over the world. Despite the importance of Fynbos as a biome, the value of its edible species as agronomic resources has been neglected. A two-part study having an agronomic and social component was conducted at the Welgevallen Experimental Farm (WEF, Stellenbosch University) and the Sustainability Institute (SI, Lyndoch, Stellenbosch), respectively. The aim of the agronomic study was to determine the performance of Tetragonia decumbens (dune spinach) and Mesembryanthemum crystallinum (sout slaai) in relation to soil type and watering regime trials. A completely randomised design was used for the water trial having four treatments (no watering as a control, 25 %, 50 % and 80 % pot water holding capacity) and the soil trial having three treatments (dune sand from Kommetjie beach as a control, sandy soil from the SI, and loamy soil from WEF). Though the water treatments had no significant effect (p > 0.05) on the agronomic performance of dune spinach and sout slaai, the results suggested that the 25 % and 50 % water treatment levels are sufficient for growth of dune spinach and sout slaai when grown in the soil in which they naturally occur. Results from the soil regime trial indicated significant increases in agronomic performance of dune spinach and sout slaai among soil treatments, except the number of dune spinach runners and sout slaai leaf pairs. It was concluded that agronomic performance can be improved significantly when dune spinach and sout slaai are planted in more fertile sandy soils and well aerated loamy soils. For the social study, an indigenous food tasting event was organised at which a survey was administered to 24 respondents that primarily assessed their acceptance of the two edible fynbos species as alternative vegetables and nutrition sources. A cooked and raw version of each vegetable was tasted by each participant. The cooked version (smoortjie) of dune spinach, elicited a statistically significant median increase in acceptability compared to the, dune spinach salsa, exact p = 0.035. The sout slaai smoortjie did not generate a statistically significant median increase in acceptability compared to the sout slaai salsa, exact p = 0.092. It was found that the ‘overall acceptance of dune spinach vegetable’ was positively correlated to the ‘overall acceptance of sout slaai vegetable’, r(23) = 0.504, p = 0.01. There was no association between consumption intent and overall acceptance of the two indigenous vegetables, r(23) = 0.362, p = 0.082. However, there was a strong positive association between the respondent’s overall acceptance of the two indigenous vegetables and their purchasing intention, r(23) = 0.698, p < 0.001. The most important reason for purchasing these indigenous vegetables that emerged was the frequency of general vegetable shopping and desire to eat the vegetables. These reasons were closely followed by the availability on the market and price of the dune spinach and sout slaai. ii Stellenbosch University https://scholar.sun.ac.za