Exploiting genotype x environment x management interactions to enhance maize productivity in Ethiopia

Maize is the main staple food crop grown by smallholder farmers in Ethiopia. High variability in inter-seasonal rainfall presents the biggest risk for farmers to invest in best management practices in maize crop grown in Ethiopia. Optimising genotype (G) and management (M) of maize for different growing environments (E) could alleviate risks associated with seasonal rainfall variability and enhance reliability of yield of this crop. The objectives of this study were to quantify G x E x M interactions and identify best combinations of G and M for target maize production environments in Ethiopia. Ten genotypes, five each from early and medium maturity classes were evaluated at five planting densities, 2, 5, 6, 7 and 9 plants m(-2), across seven environments in 2013 and 2014 cropping seasons. Our study explored a range of morphological, phenological and physiological traits underpinning the yield of maize. Our results revealed that combining the appropriate G and M is more effective than relying on the choice of genotypes. The optimum plant densities identified in this study are higher than the plant densities currently used by farmers. Planting BH-546 and TH13321 at 7 plants m(-2) substantially increased yield compared with other genotypes. For instance, yield for TH13321 was higher by 48% (3.7 t ha(-1)) at 7 plants in high yielding environments compared with BH-540, the most widely grown hybrid by farmers. This indicates the need for optimising G and M and using versatile genotypes to exploit variability in weather and input-use in the country. The genotypes substantially varied for their response to radiation use efficiency, rainwater productivity and leaf orientation value at high plant density. The least response to these traits observed for BH-540 highlights the need for a reassessment of current varietal and agronomic options for maize production in Ethiopia. Information from this study could be extended to sub-Saharan African countries that are similarly using low plant density.