Zero-tillage induces significant changes to the soil pore network and hydraulic function after 7 years

Abstract

Zero-tillage and ploughing are highly contrasting soil management practices that have distinct roles in generating soil porosity. Ploughed systems employ anthropogenic perturbation to manage weed pressure and ensure optimal conditions at time of sowing. Whereas zero-tillage maintains minimal disturbance, which allows the development and persistence of a more biologically driven porosity throughout multiple seasons. However, the effects on pore geometry and associated hydraulic behaviour between these practices are unclear. Here, using X-ray Computed Tomography in combination with solute breakthrough, we demonstrate the ways in which imaged pore network structures and their impact on preferential transport differ between zero-tilled and ploughed soil using undisturbed soil columns. In zero-tilled soils, the thickness and connectivity density of the largest macropore cluster was smaller, there was a higher proportion of thicker pores, a higher degree of preferential transport and a longer period of diffusive transport. We conclude that the thicker pores in zero-tilled soils provided preferential flow paths enabling more rapid vertical transport of the solute during breakthrough, allowing bypass of the bulk soil, and limiting opportunities for diffusion. These outcomes have important implications for the transport and fate of agrochemicals applied to soils.