Projecting the effect of climate change on planting date and cultivar choice for South African dryland maize production

Abstract

The anticipated climate change in South Africa is of great concern as Southern Africa appears to be warming at twice that of the global average, limiting maize production in the country and threatening food security in the region. The formulation of effective adaptation measures calls for understanding how projected changes in temperature, precipitation, and climate extremes might become misaligned with the critical maize developmental stages, which are likely to impact crop development. We conducted an analysis of the climate change impacts for dryland maize phenology in Bloemfontein and Lichtenburg, which represent major maize growing regions of South Africa. The climate projections generated by six Global Climate Models under the Representative Concentration Pathways (RCP) 4.5 and 8.5 were used. Analyses were performed for four representative planting dates: November 15 (early), December 15 (optimal), January 15 (late), and February 5 (very late). Days to maturity decreased (by approx. 5-10 days) as years progressed from baseline period (1991-2020) to the far future period (2051-2080), at both locations with higher rates projected under RCP 8.5. The results suggest a longer summer season with receding freeze dates in these regions and might provide additional flexibility for adaptive strategies. At the optimal planting dates, future climate will likely affect both vegetative and reproductive stages of maize leading to the decrease in the days to maturity. A major factor affecting maize productivity is extreme temperature, with the number of days above 35 °C expected to increase 20–30% at the optimal planting date as climate changes progresses, which will likely limit grain filling and yield. Exploring maize phenology in the future at later planting dates revealed a decrease in days to maturity trending towards the optimal number of days required for each cultivar (100–110 days) in both regions. This coupled with the projected receding freeze date at these planting dates under future climates suggests there may be opportunities to shift planting to later dates in the region.