Conservation Agriculture Had a Poor Impact on the Soil Porosity of Veneto Low‐lying Plain Silty Soils after a 5‐year Transition Period

Abstract

AbstractConservation agriculture practices have been proposed as a set of techniques for improving soil structure properties and related ecosystem services. This study compared conservation agriculture (CA) practices (no‐tillage, cover crop and residue retention) and conventional intensive tillage system in order to evaluate their effects on total porosity, pore size distribution, pore architecture and morphology. The experiment was set up in 2010 on four farms of the low‐lying Veneto Region plain characterized by silty soils. Almost hundred soil samples were collected in 2015 at four depths down to 50‐cm layer and investigated for porosity from micrometre (0·0074 μm) to macrometre (2·5 mm) by coupling mercury intrusion porosimetry and X‐ray computed microtomography (μCT). Indices of soil morphology and architecture were derived by analysing 3D images and mercury intrusion porosimetry pore size curves. Results suggested that silty soils of Veneto plain are microstructured because much (82%) of the porosity ranged between 0·0074 and 30 μm. CA practices positively influenced the ultramicroporosity class (0·1–5 μm) (1·86E‐01 vs 1·67E‐01 μm3 μm−3) that is strictly linked to soil organic carbon stabilization while no effects were observed in X‐ray μCT porosity domain (> 26 μm). Silty soils of Veneto plain showed a slow reaction to CA because of the poor aggregate stability and low soil organic carbon. However, the positive response of the ultramicropore fraction indicates that a virtuous cycle was initiated between soil organic carbon and porosity, hopefully leading to well‐developed macropore systems and, in turn, enhanced soil functions and ecosystem services. Copyright © 2017 John Wiley & Sons, Ltd.