Evaluating the effect of compaction on soil hydraulic properties

Abstract

Soil compaction is commonly viewed by agronomists as an undesirable consequence of intensive agricultural activities arising from heavy machinery or livestock trampling. However, deliberate compaction of the furrow bottom has been considered as a potential water management practice to reduce deep percolation losses and improve furrow irrigation efficiency. Therefore, understanding how such compaction affects soil hydraulic properties and overall soil quality is essential before its long term adoption. As such, this study aimed to investigate the impact of compaction on soil hydraulic properties. Thirty undisturbed clay textured soil samples were collected from a depth of 15 cm in Koga irrigation scheme, Ethiopia, and subjected to five compaction levels: control (0%), 5%, 10%, 15%, and 20% volume reduction, each with six replicates. Saturated hydraulic conductivity was measured using the KSAT apparatus with the falling head technique, while water retention and unsaturated hydraulic conductivity were measured using the HYPROP (hydraulic property analyzer) system based on the modified evaporation method. Compaction reduced water retention and hydraulic conductivity, particularly in the wet and moist range up to −1000 cm matric suction. Saturated hydraulic conductivity decreased by 9%–78% with increasing compaction. Compaction also increased bulk density (8%–40%) and relative field capacity (4%–10%) and decreased total porosity (6%–33%), macroporosity (28%–82%), air capacity (25%–61%), and plant available water content (3%–17%). The findings of this study emphasize the need for sustainable soil water management to improve crop yield and soil resilience through controlled compaction.