LAUSR

Abstract Drought frequency and severity analysis during the growing period of maize was carried out by means of the Standardized Precipitation Evapotranspiration Index (SPEI) based on climatic data from seven weather stations (1975–2014). The index was aggregated at different time scales following three consecutive planting dates (October, November and December), relative to the average start of the rainy season in the area. Temporal analysis of droughts was conducted and trends were evaluated using the non-parametric Spearman's Rank Correlation test. The relative frequency distributions of the different drought categories were plotted for each growth stage of maize, with respect to the three planting dates. Results revealed an average drought occurrence of once every two seasons. The 1991/92 drought was identified as the most extreme drought during the analysis period; and generally there were no significant trends across the catchment, except for weak increasing SPEI at Levubu, Lwamondo and Thohoyandou with Spearman's ρ values of 0.4. This implies that the severity of drought decreased over time in these regions following the respective planting dates. The study further revealed that planting a 120-day maturing maize crop in December would pose a high risk of frequent severe-extreme droughts (SPEI -1.5 to ≤ −2) during the flowering to grain-filling stage at the high and moderate rainfall regions, while results at the low rainfall region indicated this risk following planting in October.