Anisotropy of soil hydraulic properties induced by repeated machinery traffic in a Typic Argiudoll of the Argentinean Pampas Region

The increase in heavy machinery traffic due to crop sequence intensification under no-tillage (NT) management can lead to soil compaction, modifying the soil pore configuration, with negative effects on water dynamics. The objective of this work is to evaluate the residual effects of repeated machinery traffic under different soil water contents on the anisotropy of soil hydraulic properties. The residual effect of repeated machinery traffic under different soil moisture conditions (partially dry, PD, and wet, W) on soil compaction was evaluated and compared with the control treatment (no traffic, T0). Field infiltration using tension disc infiltrometer was carried out, and in laboratory, in order to analyse the anisotropy of soil hydraulic properties infiltration experiments were carried out on vertical and horizontal undisturbed soil samples. No significant differences in field soil hydraulic conductivity K(h) were observed between treatments. The W treatment showed a decrease on the transmission and storage pores in the vertical direction, as compared to T0. Anisotropic behavior of soil hydraulic properties was observed for the compacted treatments. The W treatment showed an increment in the transmission porosity in the horizontal direction. In addition, the W treatment presented higher values of transmission and storage pores in the horizontal direction as compared with the vertical direction. From laboratory infiltration experiments, it was observed a strong reduction on the hydraulic conductivity measured at 0, - 3 and - 6 cm water pressure heads (K0, K3 and K6) in the vertical direction under W treatment. An anisotropic behavior for both compacted treatments was observed, with higher values of K0 in the vertical direction under the PD treatment and higher values of K0 and K3 in the horizontal direction under the W treatment. These results show that machinery traffic under wet conditions causes a disruption in soil porosity, not only with a reduction of the pore space, but also with a change in its configuration.