Multicropping increases water scarcity and irrigation demand in Brazilian croplands

Agricultural areas are expected to experience more intense rainfall variability in the coming decades, with critical implications for global food production and climate resilience. In Brazil, the world's largest producer of soybean, more than 90% of cropland is rain-fed, making the nation susceptible to shortening rainy seasons, drought and intensifying climate extremes. The Brazilian government plans to expand irrigation to mitigate these risks to its large agricultural sector. Simultaneously, Brazil is incentivizing farmers to grow multiple crops per year in the same tract (multicropping) to ostensibly increase national agricultural output without additional land conversion or deforestation.

Here, we use remote sensing and a crop water model to evaluate how these land-use changes affect evapotranspiration (ET), green water scarcity (an imbalance between rainfall-derived water availability and crop water demand ), and blue water requirements (BWR, the additional water required via irrigation to fulfill crop water requirements not met rainfall) across Brazilian soybean-safrinha maize systems. We find that increasing cropping intensity substantially increases annual ET and irrigation requirements relative to single-cropped, rain-fed systems. As a result, precipitation alone is increasingly insufficient to meet crop water demand, particularly under intensified production and future climate change. We further identify regions where irrigation is most frequently needed and evaluate water resource sustainability under CMIP6 climate projections by estimating monthly blue water scarcity (when human consumption exceeds renewable blue water availability after accounting for environmental flow requirements). The largest increases in BWR and BWS occur in MATOPIBA, an agricultural frontier where agricultural conversion is resulting in rapid biodiversity loss, which may be exaggerated by unsustainable irrigation practices.

Our results highlight a fundamental trade-off between intensification-driven productivity gains and growing pressure on regional water resources. Quantifying these interactions is essential for evaluating the sustainability of irrigation expansion and multicropping as climate adaptation strategies in Brazil’s major agricultural regions.