Spatial Patterns and Cross-Correlations of Temporal Changes in Soil Carbonates and Surface Elevation in a Winter Wheat-Fallow Cropping System

Abstract

Soil erosion and deposition impact the sustainability of agricultural lands within the semiarid Great Plains in the United States. Temporal differences between high-resolution digital elevation maps provide physical estimates of spatial erosion or deposition, and the depth to a calcic horizon is a chemical indicator. We hypothesized that soil surface layer CaCO3 concentration is inversely correlated with the change in surface elevation (Δz). We studied a 109-ha field in northeastern Colorado under winter wheat (Triticum aestivum L.)–fallow rotation in alternating strips perpendicular to the prevailing wind. Soil samples (top 30 cm) collected from 185 landscape positions in 2001 and 2012 were analyzed for CaCO3 using a modified pressure-calcimeter method. The change in CaCO3 (ΔC) was significantly correlated with large-scale erosional and depositional areas (west and east blocks, respectively) and with soil units, whereas Δz was correlated with management strips and blocks. The west block had an average ΔC of 3.2 g kg−1 with 2.0 cm of erosion, whereas the east block decreased by 4.4 g kg−1 with 4.2 cm of deposition. Summit positions had the highest CaCO3, and toeslope positions had the lowest. We found inverse relationships between Δz and ΔC in summit and toeslope positions at both erosional (Δz < −5 cm) and depositional (Δz > 5 cm) areas, but Δz was not correlated significantly with ΔC overall. High values of CaCO3 (>100 g kg−1) decreased with time. A high-resolution map of Δz showed complex spatial patterns across scales, which inferred water and wind erosion and deposition affected by terrain and management.