Selection for Drought Tolerance Increases Maize Yields across a Range of Nitrogen Levels

It is not known whether selection for improved tolerance to a specific abiotic stress leads to correlated changes in performance under other stresses. Drought and N deficiency are important constraints to production in the tropics. We examined the effect of selection for drought tolerance on performance of tropical maize (Zea mays L.) under a range of N levels. Original and advanced selections of four populations, improved for tolerance to midseason drought for two to eight recurrent selection cycles each, were evaluated in two experiments under severe N stress, one experiment under medium N stress, and two well‐fertilized experiments. Nitrogen accumulated in the aboveground biomass at maturity averaged 52, 63, 105, 151, and 163 kg N ha−1 in the five experiments, and grain yields of 3.0, 2.9, 5.2, 6.0, and 6.5 Mg ha−1 were obtained. Selection for tolerance to midseason drought stress increased grain yields by an average of 86 kg ha−1 yr−1 with nonsignificantly larger gains under severe N stress (100 kg ha−1 yr−1). Drought‐tolerant selections had increased biomass and N accumulation at maturity, the changes being largest under severe N stress. Additionally, drought‐tolerant selection cycles were associated with delayed leaf senescence and an increased or unchanged N harvest index, indicating that leaf N was used more efficiently for grain production. Selection for tolerance to midseason drought stress appears to increase grain yield across a range of N stress levels and may lead to morphological and physiological changes that are of particular advantage under N stress.