Spatial variability in soil compaction properties associated with field traffic operations

Abstract

Current agricultural practices using heavy machinery are associated with soil compaction.This study was carried out to determine the effects of field traffic operations on the changes in spatial variability of soil aggregate stability (AS), bulk density (BD), total porosity (TP), penetration resistance (PR) and volumetric moisture content (VMC) in the various soil depths as indicators of soil compaction. Soil samples to determine AS, BD and VMC were collected and field measurements of PR at 0–10, 10–20 and 20–30cm depths were taken, respectively from geo-referenced intersections with 25×20m intervals before and after traffic operations. Total porosity was calculated using bulk and particle density values. Both disturbed and undisturbed soil samples were taken from each depth (0–10, 10–20 and 20–30cm) of the intersection points of the grid system, before and after traffic operations. As a total 360 soil samples were taken. Kriging analysis was performed to create spatial variability distribution maps of AS, BD, TP, PR and VMC with 1×1m intervals within the field. Results showed that the AS, BD, TP, PR and VMC were significantly influenced by traffic operation and depth. More significant effects on the AS, BD, TP, PR and VMC were produced at the 0–10cm depth than at the 10–20 and 20–30cm depths. For 0–10, 10–20, and 20–30cm depths, while BD increased in the rates of 14.5, 5.3 and 6.7% it caused a decrease in TP at the rates of 12.1, 5.5 and 6.6%, respectively. Averaged across depth, while the initial AS was 54.1% it decreased to 41.9% with traffic operation. Averaged across depth, the BD (8.6%), PR (43.3%) and VMC (12.7%) increased, with an associated decrease in AS (22.6%) and TP (8.9%) after traffic operation, as compared to their initial values measured before traffic operation. Spatial distribution patterns of AS, BD, TP, PR and VMC values following traffic operation showed significant differences compared to those values of before traffic operation. Among the indicators of compaction, the AS and PR was greatly affected by the traffic operations as compared to BD, TP and VMC. Knowledge on the spatial distribution can be used for development management options that minimize production risks and the harmful impact of traffic.