DROUGHT IMPACTS ON POTENTIAL MAIZE YIELD IN THE FREE STATE PROVINCE, SOUTH AFRICA

Maize (Zea mays L.) is the most-grown rainfed crop in South Africa and is consumed by most people as their staple food. However, due to recurring droughts, which are predicted to intensify in severity and occurrence, its production is challenged, leading to lower yields. In order to address this issue, the study pursued two specific objectives. Objective a) analyzed the impacts of drought on maize yield, focusing on the selected maize-producing areas (Bethlehem, Bloemfontein and Bothaville) within the Free State Province over the historical period (1990- 2020). In pursuit of this objective, the study employed widely used methodologies, including the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI), to dissect the temporal- seasonal variations in drought occurrence and severity. Additionally, the coefficient of variation (CV) was used to measure the variability in seasonal climate patterns, providing insights into erratic climate patterns. The modified Mann-Kendall trend test was applied to pinpoint drought trends in the maize growing season (at monthly and seasonal scales). The correlation between drought indices (SPI and SPEI) and maize yield was systematically explored using the Pearson correlation coefficient to evaluate drought impact. The utilization of yield loss rate further enhances the understanding of the detrimental impact of drought on maize production, highlighting the urgency of effective adaptive strategies. The study results indicated that the highest variability in rainfall, maximum and minimum temperatures was 46.62%, 5.31% and 22.66%, respectively. Based on SPI and SPEI, drought frequently occurred in Bethlehem than Bloemfontein and Bothaville, particularly during the ONDJFM season. Regarding drought severity, the moderate droughts were prevalent in Bethlehem, while severe droughts were common in both areas (Bethlehem, Bloemfontein and Bothaville) and extreme droughts in Bloemfontein. Trends indicated that significant decreasing trends (indicating drier conditions) on monthly and seasonal scales were prevalent over Bethlehem under SPI and over Bloemfontein under SPEI. The impact of drought on maize was different during different growing seasons across all areas, where a strong relationship (r = 0.82, p = 1.3e-08) was noted between SPEI and maize yield over Bloemfontein during the ONDJFM season. Regarding calculated yield loss, the highest maize yield loss recorded was -83.86% for Bethlehem, while Bloemfontein and Bothaville were -75.26% and -58.93%, respectively due to extreme drought. In tandem with these findings, the study objective b) evaluated planting dates as an adaptation strategy under changing climate for the mid-century period (2040-2069) using the AquaCrop model. The AquaCrop model, calibrated and validated with meticulous attention to detail, emerges as a robust tool for assessing the potential outcomes of adjusted planting dates. Ensemble climate projections sourced from multiple climate models under Representative Concentration Pathways (RCP) 4.5 and 8.5 were harnessed to decipher shifting rainfall and temperature patterns in the mid-century (2040-2069). These projections unveiled a complex landscape of shifting climatic conditions, with an overall increase in seasonal rainfall, except for some months with a decline in rainfall across all study areas. Moreover, the anticipated rise in maximum and minimum temperatures across the maize growing season reinforces the urgency of proactive measures. A noteworthy aspect of the study is its elucidation of projected maize yield changes under RCP 4.5 and 8.5 scenarios. The anticipated changes in yield, ranging from positive to negative, were contextualized for each study area, offering valuable insights into the intricate interplay between changing climate and agricultural outcomes. The study identified optimal planting dates for each study area and RCP scenario by analyzing model simulation outputs (i.e. yield). The study results revealed that the optimum planting dates could be 1 st November for RCP 4.5 and 15th November (conventional planting date) for RCP 8.5 in Bethlehem, 29 th December for both RCPs in Bloemfontein, and 13th December for both RCPs in Bothaville. These insights not only provide a practical roadmap for adapting maize production to changing climate conditions but also contribute to the broader discourse on sustainable agricultural practices in the face of a changing climate. In essence, this study underscores the imperative of proactive, science-driven strategies to safeguard South Africa’s maize production and food security in the years ahead.