Global synthesis of drought effects on cereal production

Abstract:

Cereal grains remain as the most important source of calories for the majority of human population. Yet drought has adversely affected their production which co-varies with factors such as crop species, phenological phases and agro-ecosystem. The extent to which those factors affect the vulnerability of cereal agriculture to drought, however, remains unclear. Using a meta-analysis approach, this study aims to better characterize the effects of these factors and to provide critical information on minimizing yield loss. We collected data from peer-reviewed publications between 1980 and 2015 which examined cereal yield responses to drought using field experiments. We performed unweighted analysis using the log response ratio to calculate the bootstrapped confidence limits of yield responses and calculated drought sensitivities for different species (i.e., maize, wheat, rice, barley, sorghum, millet), phenological phases (i.e., vegetative, reproductive, and throughout growing season), soil texture (i.e., fine, medium, coarse), and agro-ecosystems (i.e., dryland vs non-dryland). Our result showed that yield reduction varied with species, with wheat having lower sensitivity and yield reduction (20.6%) compared to maize (39.3%) at approximately 60% water reduction. Millet had the lowest yield reduction compared to other cereal species while rice showed a sharp decline in yield with greater than 50% of water reduction. Drought that occurred during crop reproductive phase caused greater yield reduction (30%) than that occurred during vegetative phase (20%). Maize was particularly sensitive to yield loss when drought occurred during reproductive phase while other cereal species tended to have similar sensitivity to drought during vegetative or reproductive phase. We also found that cereal cultivation in the drylands was more prone to yield loss than in the non-dryland regions, but no difference was observed among different soil textures.