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Although the semiarid and subhumid Chaco regions in northern Argentina have been traditionally considered marginal and unsuitable for cultivating grain maize for human and livestock nutrition, this crop is increasingly being adopted by local farmers. The low maize yields observed in the area suggest that climatic constraints limit productivity, while changes in genotypes and management may be useful to mitigate the effect of these constraints. We analyzed data from 792 farm paddocks with multivariate mixed models to identify and quantify the main environmental and management constraints to maize's yield. In addition, we used the crop model CERES-Maize to assess the potential of a temperate maize hybrid to overcome water constraints. Results from the mixed models identified the amount of rainfall during February as a primary determinant of maize yield and showed that tropical hybrids tended to withstand higher temperatures and heat stress better, while temperate hybrids performed better under conditions of water scarcity. CERES-Maize simulations suggested that temperate maize hybrids have the potential to increase grain yields from 18 to 21 kg ha −1 (14.5% moisture content) for every millimeter of rain during February. This report is the first to identify alternative roles of temperate and tropical maize hybrids for counteracting climatic risks in the studied subtropical regions. These findings will provide plant breeders urgently needed information to breed better adapted maize genotypes for the semiarid and subhumid Chaco.

Climatic change effects on crop yields are expected to be crop-and site specific.Here, Decision Support System for Agrotechnology Transfer models were used to evaluate climatic change effects and mitigation strategies on maize (Zea mays L.)and soybean [Glycine max (L.) Merr.] yields in soils of the subtropical and semi-arid region of Chaco. Simulations were performed for the DK747 and A8000 genotypes, calibrated for the CERES-Maize model in a previous report and for the CROPGRO-Soybean model in the present study, respectively. Both crops markedly differ in their response to climatic change and putative levels of atmospheric CO 2 concentration.The observed significant reductions in maize yields in future climate scenarios (5-42% compared with the baseline, 1986-2010) were more associated with increased temperatures that shortened the crop cycle than with water stress. Delaying the sowing date is a feasible strategy to mitigate this effect. Projected temperature increases are expected to play a secondary role in determining soybean yields. Instead, water stress will continue to be an important constraint to soybean yield in the context of global warming, but this effect is strongly affected by rainfall regimes. Responses to raising CO 2 levels were more pronounced in soybean (+10-40%) than in maize (+2-4%). Soil degradation exacerbated the negative effects of global warming on crop yields, especially on maize, which highlights the importance of soil conservation practices. The observed high interannual climatic variability and the different sensitivities of maize and soybean to climatic variables indicate that crop diversification would be the key to improve the resilience of the agrosystems under the future scenarios.