Weather-dependent relationships between topographic variables and yield of maize and soybean

Weather and topography are two important drivers of spatial variability in crop yield, but interactions between these two factors remain poorly understood. To elucidate how spatial yield variability shifts in response to precipitation, we collected data from published literature that examined the yield response of maize (Zea mays L.) or soybean (Glycine max (L.) Merr) to elevation, slope, planar curvature, or profile curvature. From these studies, we extracted correlations between yield and topographic variables for 86 site-years. We assessed the response of yield–topography correlations to the spring and total growing season precipitation of each site-year. Averaged across all site-years, maize yield was negatively correlated to elevation and planar curvature while soybean yield was negatively correlated to slope. For maize, the correlations between yield and elevation, slope, planar curvature, and profile curvature increased from negative to positive with increasing growing season precipitation, whereas for soybean the correlations between yield and elevation and between yield and slope became more negative with increasing growing season precipitation. Spring precipitation was a better predictor of yield–topography correlations than growing season precipitation for soybean but not for maize. We conclude that maize and soybean generally yield higher in low-elevation and low-slope landscape positions, respectively, but the yield–topography relationships vary with precipitation.