Planting Date Influences on Growth, Yield and Nutrient Status of Fodder Radish Under Rainfed Conditions in South Africa

Abstract

Ranked 30th globally in dryness, South Africa faces severe challenges in ensuring fodder security, which is worsened by climate change impacts on agriculture. However, there is still limited knowledge about optimising fodder radish cultivation under shifting climatic conditions. This study investigated the effects of planting dates (December to March), cultivars (Nooitgedacht, Line 2 and Endurance) and seasons (2020/21 and 2021/22) on growth, yield, and crude protein (CP) and mineral concentrations under rainfed conditions. Seasonal variation significantly (p < 0.05) influenced emergence, relative growth, and flowering across planting dates. Fresh tuber yield was highest when Nooitgedacht was planted in December (2052 and 2102 kg ha−1). In contrast, January planting enhanced aboveground biomass and crude protein (CP) yield, with Endurance recording the highest biomass (1260 and 1157.95 kg ha−1 DM) and tuber CP yield (19.2 and 18 kg ha−1). December planting favoured tuber production, whereas January planting optimised biomass, CP yield, and persistence. Planting date and cultivar significantly affected leaf and tuber mineral concentrations. December–January plantings generally enhanced leaf P, K, and Zn concentrations. Endurance and Nooitgedacht accumulated higher micronutrients than Line 2, particularly under early planting. The late flowering of Endurance extended the grazing period, aligning with late-winter forage demand under rainfed conditions. Overall, this study offers practical guidance for improving the quantity and quality of fodder radish in diverse agricultural settings. Future work should evaluate these cultivars across more sites to confirm performance stability under variable rainfall patterns.