When the going gets tough: Performance of stress tolerant maize during the 2015/16 (El Niño) and 2016/17 (La Niña) season in southern Africa

The 2015/2016El Niño was the most severe on record in southern Africa and was associated with drought and heat stress. To help farmers to cope with such extreme production constraints the International Maize and Wheat Improvement Centre (CIMMYT), has been developing maize varieties through a rapid-cycle breeding strategy to deliver a steady stream of incrementally improved varieties with tolerance to multiple stresses. Performance of stress tolerant maize germplasm in an El Niño year was evaluated using two types of trials. The first one comprised a regional on-farm trial with forty maize varieties (20 early-intermediate and 20 intermediate-late varieties), planted across 30 locations in four countries in southern Africa. The second set comprised a multi-locational evaluation trial with six hybrids that were tested under conventional ridge tillage (CP) and conservation agriculture (CA) using a randomized block design with each farm as replicate in nine extension planning areas (EPA), across two years. In the regional on-farm trial, analysis of variance on grain yield showed significant differences (P < 0.001) in both early-intermediate and intermediate-late varieties. Stress tolerant varieties such as CZH142020 (5.6 t ha −1) and CZH131008 (4.8 t ha −1), had significantly higher yield advantage over commercial control varieties (<4.5 t ha −1) in both maturity groups, respectively during the El Niño year. Furthermore, stress tolerant hybrids had larger grains and smaller ear uniformity index (EUI) (calculated as among plots ear size variance); compared non-stress tolerant varieties. In the CA/CP evaluation trial, varieties under CA yielded ≥0.7 t ha-1 more grain compared to those under CP. Stress tolerant maize in combination with CA led to higher yield gains compared to non-stress tolerant maize planted under CP. Therefore, combinations of climate-smart agriculture technologies are required to mitigate negative effects of extreme events like El Niño and increase resilience of low-input farming systems.