N. Dal Ferro

Bio: N. Dal Ferro is an academic researcher from University of Padua. The author has contributed to research in topics: Environmental science & Soil water. The author has an hindex of 10, co-authored 16 publications receiving 438 citations.

Soil macro- and microstructure as affected by different tillage systems and their effects on maize root growth

Abstract: Tillage practices are critical factors for the sustainability of cropping systems by modifying the soil properties and affecting root growth. In this study we compared conventional (CT) and no tillage (NT) practices to evaluate their effects on soil structure and maize root morphology and dynamics during a two-year transition period. Pore size distribution and morphology-related parameters were analyzed with a combination of X-ray microtomography (microCT) (54–2250 μm) and mercury intrusion porosimetry (MIP) (0.0074–100 μm) within the 0–40 cm soil profile. The network model PoreXpert was applied to MIP pore distribution curves to identify subtle structural changes as affected by tillage. Root samples were collected down to 1-m depth with the core method during 2005 and 2006, 40 and 114 days after sowing, in order to quantify their mass, length and diameter. Results suggested that tillage practices affected the soil macroporosity (54–750 μm) while the micropores, detected with MIP, did not show significant differences between treatments. Conventional tillage, disrupting the macropore structure and enhancing the pore class in the range 54–250 μm, improved the soil loosening. Bulk density measurements, achieved in the last date (day 114, 2006), were negatively correlated with root growth indicators. Nevertheless, root growth was weakly affected by tillage since the soil structure did not reach a new architecture after the introduction of NT. In spite of the experiment being conducted in the short-term and the soil structure still being unpredictable, microCT analysis proved its ability to predict subtle structure changes as affected by conventional and no tillage practices.

Coupling X-ray microtomography and mercury intrusion porosimetry to quantify aggregate structures of a cambisol under different fertilisation treatments

Abstract: The description of soil structure is primordial to determine the effects of management practices on soil environment. Different techniques were developed to determine the pore structure, each with its own limitations. In this study mercury intrusion porosimetry (MIP) and X-ray microtomography (micro-CT) were used to study the total porosity and pore size distribution of soil aggregates (5–6 mm) treated with different fertilisations (organic, mixed and mineral). The network model Pore-Cor was applied to pore distribution curves to highlight subtle structural properties affecting the aggregates. The combination of these techniques highlighted that: (1) MIP was fundamental to reveal the small pores that were not detected by micro-CT and that represented up to 70% of total porosity; (2) micropores (30–6.25 μm) detected by MIP were underestimated with respect to micro-CT (−9.4%) probably due to the “ink bottle” effect, whereas meso- and macropores were overestimated; (3) only micro-CT highlighted the effects of organic amendants on pore morphology. These outcomes were compared with modelling results of the network model Pore-Cor that proved its ability to predict the pore structure organisation and the differences between fertilisations. Further improvement of micro-CT will allow to cover a wider range of pores, but at present the integration with different techniques is still fundamental.

Investigating the effects of wettability and pore size distribution on aggregate stability: the role of soil organic matter and the humic fraction

Abstract: Soil organic matter (SOM) is an important factor influencing aggregate stability. Interactions between SOM and soil structure are widely studied, although the subtle relationship between SOM content, pore size distribution and aggregate stability is not fully known. Here we investigate such a relationship by means of a long-term experiment established in 1962 in northeastern Italy, which considers different fertilizer practices (organic, mineral and mixed) applied to a continuous maize crop rotation. We measured wet stability of 1–2 mm aggregates subjected to different pretreatments. Both soil physical properties (such as pore size distribution and hydrophobicity) and chemical properties (soil organic and humic carbon content) affecting aggregate stability were considered. The chemical structure of humic substances was characterized by thermal and spectroscopic analyses (TG-DTA, DRIFT and 1H HR MAS NMR). The Pore-Cor network model was then applied to evaluate the contribution of hydrophobicity and porosity to aggregate wetting. Our study suggests that SOM and its humic fraction can affect aggregate wetting and consequently slaking by modifying the pore size distribution with a shift from micropores (5–30 µm) and mesopores (30–75 µm) to ultramicropores (0.1–5 µm); hydrophobicity was also increased as a result of different humic composition. Spectroscopic analysis showed that hydrophobic compounds were mostly associated with complex humic molecules. Models of fast wetting dynamics, however, suggest that the contribution that hydrophobicity makes to aggregate stability, especially to soils with large carbon inputs, may not be the most significant factor.

Effects of biochar on the dynamics of aggregate stability in clay and sandy loam soils

Abstract: SUMMARY: Recent advances suggest that organic substances of different origins might have different aggregate stability dynamics. We investigated the extent to which contrasting soil types affect the dynamics of aggregation after the addition of crop residues (R) and of biochar at two doses (BC20, 20 Mg ha⁻¹; BC40, 40 Mg ha⁻¹) in a 2‐year experiment. To evaluate disaggregation, we measured a set of physical–chemical and structure‐related properties of clay and sandy loam aggregates sieved to 1–2 mm, including wet aggregate stability after different pretreatments combined with laser diffraction analysis. The electrochemical properties of the colloidal suspension were also analysed to identify changes in soil chemistry affected by organic inputs. Different amounts of added biochar and soil types produced contrasting effects on wet aggregate stability. In sandy loam, the increased soil surface area from added biochar (at either dose) offset the initial small soil organic carbon (SOC) content and subsequently promoted SOC‐controlled aggregation. Conversely in clay soil, the larger biochar dose (BC40) strengthened the repulsive forces between particles with the same charge and monovalent cations, which led to chemical perturbation and some aggregate breakdown not found with BC20. Pore structure also changed in clay aggregates. A shift towards more micropores (30–5 μm, + 29% more than in the control) and ultramicropores (5–0.1 μm, + 22% more than in the control), which contributed to aggregate stabilization, resulted when biochar was added, but not for residue. Our results suggest that biochar promotes aggregate stability, which, in turn, improves the physical fertility of soil, especially if it has a coarse texture and small organic carbon content. Further study is needed of the physical–chemical interactions between added biochar and surface‐charged clay‐rich soils. HIGHLIGHTS: Aggregate dynamics are poorly understood because of complex interactions between organic inputs and soil type. A multidisciplinary approach was used to study aggregation dynamics. Large biochar input changed soil chemical properties that weakened stability in clay aggregates. Aggregate stability depended on biochar dose and soil type.

The contentious nature of soil organic matter

Abstract: Instead of containing stable and chemically unique ‘humic substances’, as has been widely accepted, soil organic matter is a mixture of progressively decomposing organic compounds; this has broad implications for soil science and its applications. The exchange of nutrients, energy and carbon between soil organic matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil organic matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent ‘humic substances’ in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds. We discuss implications of this view of the nature of soil organic matter for aquatic health, soil carbon–climate interactions and land management. Soil organic matter contains a large portion of the world's carbon and plays an important role in maintaining productive soils and water quality. Nevertheless, a consensus on the nature of soil organic matter is lacking. Johannes Lehmann and Markus Kleber argue that soil organic matter should no longer be seen as large and persistent, chemically unique substances, but as a continuum of progressively decomposing organic compounds.

Biochar stability in soil: Meta-analysis of decomposition and priming effects

Abstract: The stability and decomposition of biochar are fundamental to understand its persistence in soil, its contribution to carbon (C) sequestration, and thus its role in the global C cycle. Our current knowledge about the degradability of biochar, however, is limited. Using 128 observations of biochar‐derived CO2 from 24 studies with stable (13C) and radioactive (14C) carbon isotopes, we meta‐analyzed the biochar decomposition in soil and estimated its mean residence time (MRT). The decomposed amount of biochar increased logarithmically with experimental duration, and the decomposition rate decreased with time. The biochar decomposition rate varied significantly with experimental duration, feedstock, pyrolysis temperature, and soil clay content. The MRTs of labile and recalcitrant biochar C pools were estimated to be about 108 days and 556 years with pool sizes of 3% and 97%, respectively. These results show that only a small part of biochar is bioavailable and that the remaining 97% contribute directly to long‐term C sequestration in soil. The second database (116 observations from 21 studies) was used to evaluate the priming effects after biochar addition. Biochar slightly retarded the mineralization of soil organic matter (SOM; overall mean: −3.8%, 95% CI = −8.1–0.8%) compared to the soil without biochar addition. Significant negative priming was common for studies with a duration shorter than half a year (−8.6%), crop‐derived biochar (−20.3%), fast pyrolysis (−18.9%), the lowest pyrolysis temperature (−18.5%), and small application amounts (−11.9%). In contrast, biochar addition to sandy soils strongly stimulated SOM mineralization by 20.8%. This indicates that biochar stimulates microbial activities especially in soils with low fertility. Furthermore, abiotic and biotic processes, as well as the characteristics of biochar and soils, affecting biochar decomposition are discussed. We conclude that biochar can persist in soils on a centennial scale and that it has a positive effect on SOM dynamics and thus on C sequestration.

Agriculture and rural development

Abstract: Although most countries in the world are rapidly urbanizing, the majority of the global population – particularly the poor – continue to live in rural areas. This Handbook rejects the popular notion that urbanization should be universally encouraged and presents clear evidence of the vital importance of rural people and places, particularly in terms of environmental conservation. Expert contributors from around the world explore how global trends, state policies and grassroots movements affect contemporary rural areas in both developed and developing countries.