Scale‐Dependent Relationship between Wheat Yield and Topographic Indices

Topography can have a significant influence on crop yield, thus a better understanding of the effects of topographical parameters on crop yield is important—especially for site‐specific soil management. The objective of this study was to determine whether topographical indices developed for hydrological studies could be used as indicators of crop yield using a wavelet approach. The effects of soil curvature, upslope length, and a wetness index on wheat grain yields in a hummocky terrain were investigated along a transect on a clay loam Black soil (Blaine Lake Association) in Saskatchewan, Canada. A wavelet approach was used to elucidate the processes underlying the relationships between crop yield and topographical parameters. Wheat grain yields had significant correlations with upslope length ( R 2 = 0.60) and the wetness index ( R 2 = 0.46), whereas soil surface curvature explained only 15% of the variations in grain yield. Wavelet analyses revealed that significant variations occurred at scales <160 m for wheat grain yield, 280 m for upslope lengths, and 110 m for the wetness index. The cross wavelet analysis indicated that significant covariance existed at scales <180 m between wheat grain yield and upslope lengths and at scales <140 m between wheat yield and the wetness index, at a 99% confidence level.