Spatial analysis of machine-wheel traffic effects on soil physical properties

Infiltration in irrigation furrows exhibits spatial variation from furrow to furrow within a field. One major contributing factor is the effect of multiple levels of machine-wheel traffic on soil physical properties. The purpose of this study was to determine the effect of machine-wheel traffic levels within equipment passes on a field basis. Variations in satiated hydraulic conductivity (K₅), penetrometer resistance (R_p), and bulk density (ρ_b) due to nine, eight-row equipment passes were studied in three transects, crossing 72 furrows perpendicular to crop rows, on a Hord silt loam (fine-silty, mixed, mesic, Pachic Haplustoll). Mean values, spatial patterns, and regression relationships between properties were determined. Spectral analysis was used to fit cosine curves to property data that showed significant periods at 2.7, 8.0, and 72 furrows. An additional period of 24 furrows was seen in the R_p and ρ_b data. All properties tested showed significant mean differences due to wheel traffic from equipment passes. Within the equipment passes it was possible to further separate treatment means for all soil properties. Results in wheel tracked furrows were different from all other treatments. Linear regression of log K₅ and R_p in a 72-furrow transect shows 58% of log K₅ variability is explained by changes in R_p. Predicted vs. measured log K₅ in two transects shows predictions somewhat high, although the slope of the linear regression is 0.95, nearly parallel to a 1:1 line.