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

Abstract

Conservation 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.

Influence of Tillage and Crop Rotations in Organic and Conventional Farming Systems on Soil Organic Matter, Bulk Density and Enzymatic Activities in a Short-Term Field Experiment

“…We argue that the decrease of bulk density (Table 4), which could be a signal of enhanced porosity, was the consequence of conventional and light ploughing that broke down the superficial layer after the no cultivation period. A slow reaction to improve soil structure properties in similar silty soils with low organic carbon content was also observed in previous studies, [53], suggesting that long-term strategies to increase the chemical and physical soil fertility are required.…”

Assessing the long-term effects of zero-tillage on the macroporosity of Brazilian soils using X-ray Computed Tomography

“…The opposite was observed by Pires et al (2017) for a Brazilian Rhodic Ferralsol of clay texture under long term ZT, using X-ray CT with an image acquisition resolution of 20 μm. Using a combination of mercury intrusion porosimetry and X-ray CT, Piccoli et al (2017) concluded that a conservation agricultural system comprised of no-tillage, cover crops and residue retention in silty soils in the Veneto Region in Italy did not significantly change macroporosity (>26 μm), but increased ultramicroporosity (0.1–5 μm), compared to conventional intensive tillage after five years of implementation. The authors attributed the slow reaction to conservation agriculture in macroporosity to poor aggregate stability and low soil organic carbon content in the studied soils.…”

Examining conservation agriculture soil profiles: Outcomes from northeastern Italian silty soils combining indirect geophysical and direct assessment methods

“…It was previously postulated that the limited amount of non‐complexed OC available for interaction with clay minerals and the low ratio between clay and silt particles could prevent the formation of a resilient structure in silty soil in the Veneto region (Piccoli, Schjønning, et al, 2017). On the other hand, after 3 to 5 years of CA, an enhanced humification process produced more polycondensed humic substances (Piccoli et al, 2016) and was concurrently associated with an increase in ultramicroporosity, for instance, 0.1–5.0 μm (Piccoli, Camarotto, Lazzaro, Furlan, & Morari, 2017), which is strictly linked to SOC physical protection (Lugato, Morari, Nardi, Berti, & Giardini, 2009; Simonetti et al, 2017). These results suggested that a virtuous cycle between SOC and soil structure was initiated in the CA system, leading to soil C pool stabilization, well‐developed macropore systems and, in turn, enhanced soil functions and related ecosystem services in the longer term.…”