Intra-seasonal rainfall patterns and extremes drive maize productivity and nitrogen use in sub-humid Zimbabwe
Abderrahim Bouhenache, Gwenaëlle Lashermes, Hugues Clivot, Sylvie Recous, Régis Chikowo, Armwell Shumba, Hope Mazungunye, Emmanuel M. Matimba, Gonzague Alavoine, Olivier Delfosse, Gatien N. Falconnier, François Affholder, Marc Corbeels, Rémi Cardinael
Abstract
Background and purpose Increasing intra-seasonal rainfall variability poses a major challenge to the sustainable intensification of rainfed maize systems in sub-Saharan Africa. This study investigates how intra-seasonal rainfall patterns and extreme dry and wet events affect maize productivity and nitrogen (N) use, particularly under crop residue mulching—a practice widely promoted to improve soil water and N availability. Methods A maize field experiment with manipulated rainfall conditions was conducted over two cropping seasons (2022–23 and 2023–24) in sub-humid Zimbabwe. The factorial design combined three rainfall treatments (ambient, 30 % reduced rainfall, and heavy rainfall with two additional artificial events of 100 mm day −1 each), with or without mulch (0 vs. 6 t DM ha −1 ) and N fertilization (0 vs. 80 kg N ha −1 ). Measured variables included aboveground biomass, plant N accumulation, grain yield, yield components, and harvest indices. The relative influence of rainfall variability and management practices was assessed. Results The two seasons showed contrasting rainfall: 2022–23 was near-normal, while 2023–24 (an El Niño year) was drier, with uneven rainfall distribution. Intra-seasonal rainfall patterns and extremes explained 78 % of maize yield variability. Poor rainfall distribution significantly decreased maize productivity and N use, despite adequate total seasonal rainfall. Rainfall reduction decreased yield by 22 % in 2022–23 but increased it by 20 % in 2023–24. Heavy rainfall, especially with N fertilization, doubled grain yield in 2023–24. Mulching provided no buffering effect and reduced maize biomass and N uptake by about one-third in 2023–24. Conclusions Intra-seasonal rainfall patterns and extremes were the dominant factors affecting maize productivity and N use, far outweighing the effects of mulch and N fertilization. These findings highlight the need for cropping strategies that better account for intra-seasonal rainfall variability to improve the resilience and sustainability of rainfed maize systems in sub-Saharan Africa.