The benefits of soil organic input on crop yields have long been discussed, yet details of their relationship remain controversial. This study considers the effects of different residue management on ...crop performance as assessed by yield and nitrogen use efficiency (NUE). Three residue management (residue removal, residue incorporation, and residue incorporation + added poultry manure), combined with five levels of N application, were studied in a long-term experiment starting in 1966. Crop residue incorporation improved maize yield by 12% (nutritional effect) and sugar beet yield by 16% (non-nutritional), and the combination of crop residue incorporation with added poultry manure increased both winter wheat and sugar beet yields by 8% (nutritional effect). The NUE values of mineral fertiliser were almost three-fold those of residues and the combination of residue with poultry manure, except in sugar beet and maize, where NUE of mineral fertilizer approached those observed for residues (0.44 vs 0.45, on average). In wheat, NUE for residue incorporation with added poultry manure was nearly double the NUE for residues alone. Residue management effects depended on crop type; spring-sown crops showing stronger effects than those sown in autumn. Residues primarily produced a nutritional effect, suggesting that they decomposed within 1 year. While residue use offers little potential for soil improvement, it does reduce the need for fertilisers.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•Conservation agriculture management system affected the SOC depth distribution.•C accumulation was observed in conservation agriculture only in the first 30cm.•C accumulation was affected by mineral ...clay composition.•Conservation management led to higher polycondensed humic molecules content.•Soil tillage management did not affect microbial C and N contents.
Conservation agriculture is one of the agro-environment measures promoted by the Veneto Region (North-eastern Italy) to regulate and support many ecosystem services. This study compared conventional and conservation agriculture management systems in order to evaluate their effects on both SOC stocks and quality i.e. humic C and its molecular weight fractions, microbial C and N. The experiment was set up in 2010 on three farms in Veneto Region. In order to improve the monitoring procedures, a massive soil sampling programme was conducted in 2011 and 2014 in ca. 150 positions, considering the SOC stratification within a 0–50cm profile.
Results suggested that conservation agriculture practices affected SOC distribution rather than its total amount. The retention of crop residues on the soil surface and the absence of tillage operations drove SOC dynamics in the top layer (0–5cm) of the conservation system, while residues incorporation with ploughing was responsible for SOC accumulation at the 30–50cm depth in the conventional one. SOC stock variation in the conservation treatment was also influenced by root C input, which was identified as a major factor able to promote SOC accumulation in the 0–30cm profile. The role of clay on SOC dynamics was not uniform in the three farms since it depended both on the clay amount and its mineral composition. The strong interactions existing between management systems and local soil conditions were also confirmed by the C quality analyses.
This research did not demonstrate the benefits of conservation practices on SOC sequestration during the transition period. However, SOC sequestration is only one of the numerous ecosystem services provided by conservation practices. Some of these depend on the C content and quality in the top layers that, as demonstrated in our work, were strongly affected by the C stratification processes triggered by conservation agriculture.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Sustainable land management (SLM) practices, aimed at balancing competitive agricultural production and environmental protection, have been encouraged throughout the EU through policy and ...subsidisation. Adoption of SLM practices that regulate biogeochemical cycles requires further study, especially given the effects of local pedo-climatic variability. Conservation agriculture (CA) and cover cropping (CC) as opposed to conventional agriculture (CV), were carried out in field experiments and evaluated with modelling studies in order to mitigate the loss of soil organic carbon (SOC) and water and air pollution. All experimental treatments utilised a three-year crop rotation (maize, soybean, and wheat), and crop residues remained either atop the soil surface (CA) or were incorporated with tillage operations (CC and CV). As of March 2016, 17-month recordings from three soil-water monitoring stations per treatment (9 in total) were combined with climatic data to estimate water and N fluxes in the 0–60 cm layer. Carbon fluxes were quantified considering SOC and biomass contents. The biogeochemical model DeNitrification DeComposition (DNDC) was employed to evaluate long-term (105-yr) C dynamics and quantify greenhouse gas (GHG) emissions as affected by SLM practices and climate conditions. Experimental results showed significant differences in crop production between treatments, with lower average yields in CA (5.4 Mg ha−1) than in CC (7.9 Mg ha−1) and CV (8.5 Mg ha−1). Continuous soil cover in CA and CC determined the soil-water balance through increased evapotranspiration and reduced percolation (−30%) relative to CV. On the other hand, CC and CV tillage operations significantly affected NO3-N concentrations, with higher soil solution concentrations in tilled (CV = 74.6 mg l−1; CC = 58.1 mg l−1) than in untilled (CA = 14.0 mg l−1) systems. Model results emphasised that SLM practices responded differently in the short and long terms due to initial inertia to C changes and lower N2O fluxes, followed by higher SOC sequestration, and increased N2O emissions. These results demand time–dependent studies that weigh agro-environmental benefits provided by SLM practices against management alternatives to find a suitable compromise for stakeholders.
•None of the three tested management practices outranked the other two in all evaluated ecosystem services.•All three tested management practices affected biogeochemical cycles differently in the short and long term.•Short time frame to cultivate cover crops negatively affected their performances.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Conservation agriculture (CA) and conventional tillage (CV) were compared•Root parameters in maize-soybean-winter wheat rotation cycle were studied•CA increased root length density at 0–10 cm owing ...to increased nutrients•The yield gap between CA and CV may have been due to weed control
Conservation agriculture (CA) is a farming system that promotes minimum soil disturbance, maintenance of a permanent soil cover, and diversification of plant species and was introduced also in the Veneto region of north east Italy. CA is not always viewed as a win-win solution for sustainable production because of the increase in soil strength and compaction that may negatively impact root growth and crop production. In this study, our aim was to analyse root length density (RLD), mean diameter (MD), and root distribution to 90 cm at the flowering stage, following a maize-soybean-winter wheat rotation cycle under CA and conventional tillage (CV) at four farms. Root traits were related to soil physical properties (gravimetric water content, bulk density, and electrical resistivity) and to existent critical limits of penetration resistance (PR), and the degree of compactness (DC). CA management was not detrimental to root development and positively affected the RLD of maize (+70 %), soybean (+121 %) and winter wheat (+20 %) at 0–10 cm most likely because of increased nutrient availability. No specific physical limitations of soil were highlighted for the crop root apparatus in three (silty soils) out of four farms. Farm 3 (sandy soil) with a hardpan below 35 cm caused lateral root development in winter wheat, but not in maize or soybean. The yield gap between CA and CV (-3.9 t ha−1 for maize, -0.4 t ha-1 for soybean and -0.7 t ha-1 for winter wheat) may have been due to other agronomic factors, notably insufficient weed control in CA. Critical limits of PR (2 or 33.5 MPa) and DC (87 %) did not seemed to impair root traits, irrespective of the tillage system, suggesting that further studies on soil-specific mechanisms between soil compaction and root apparatus are warranted.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•HGs improved the macroporosity > 828 µm.•Natural-derived HG causes less soil structure disturbance.•Commercial HG observed greater soil shrinkage.•Natural-derived HG might improve soil structure.
...Superabsorbent hydrogels are three-dimensional macromolecular compounds that can absorb and retain large amounts of water. One benefit of amending soils with hydrogels includes better soil structure (i.e., pore network), which can lead to an increase in the retention of water and nutrients, and thus improve crop yield. The objectives of this study were to 1) evaluate the effect of superabsorbent hydrogels on the specific porosity and pore size distribution of three soils and 2) estimate soil swelling from HG application. Two hydrogels (polyacrylate “CI” and cellulose-based “H30”) were used in a randomized complete block design with three soil types (sand (S), sandy loam (SL), and clay (C)), three treatments (CI, H30, and CTRL (control)), with three replicates each. Specific porosity and pore size distribution were measured with three techniques (gas adsorption, mercury intrusion porosimetry, and x-ray computed microtomography) measuring a pore diameter range from 0.4 nm to 2163 µm. Our results showed that while not always significant, HG amended soils had an overall increased porosity >12% regarding macroporosity (i.e., pores >828 µm) compared to the CTRL treatment. Both HGs caused soil volume change from −37% (shrinkage) to 6% (swelling); however, H30 caused significantly lower rates compared to CI, possibly due to soil-like substances incorporated into the H30 structure. Because of this, further studies investigating the interaction between different moisture contents and H30 should be conducted to determine if H30 helps to maintain soil structure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Automated optical methodologies can provide in depth analysis of particle size and shape.•Lased diffraction is in better agreement with automated optical methodologies than sedimentation methods ...are.•A comparative study shows that traditional techniques present limitation for particle size analysis.•Confirmation of the offset between sedimentation and laser.
For many years papers have been published showing differences between sedimentation-based methods against laser diffraction. Differences were found especially in the fine texture ranges and regression equations were presented to convert data obtained between different methods. In this paper we aimed at understanding which method is closer to an independent measurement of particle size. We selected a new, automated image analysis technique as a reference method. Since with this new method each individual particle is photographed, its pixels counted and its shape analysed, we assumed this method as the reference method against which test the accuracy of sedimentation methods and laser diffraction. Comparison showed that laser diffraction was in better agreement with the independent optical methods, indicating that the sedimentation methods tend to largely overestimate the finer fractions of the distribution. Considering the results presented in this research, and the methodological disadvantages of sedimentation methods, we propose to employ laser diffraction as a standard method for particle size analysis in soils.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Scale is a key issue in soil studies. The idea that a sample must be of adequate size to embody a specific physical property comes from the representative elementary volume (REV) concept that defines ...minimum sample size for consistent results. Other approaches to describe soil spatial heterogeneity rely on the fractal dimension concept (FDC), which assumes structure changes with scale continuously, and the discrete hierarchy concept (DHC), which assumes change occurs discretely. This study considered using gas transport measurements combined with X-ray computed micro-tomography (μCT) for multi-scale analyses. Specifically, 24 large (“L cores”, 628.3 cm3) core volume samples were collected from two farms and two soil depths (3–11 cm and 20–28 cm) in northeast Italy. Gas transport parameters, such as air-filled porosity, air permeability, and gas diffusivity, were measured on the original cores and on successively sub-sampled medium (“M cores”, 100.4 cm3) and small (“S cores”, 4.7 cm3) cores. X-ray μCT–derived porosity indices were calculated for the two smaller scales. Soil core sub-sampling resulted in reduced soil gas transport property measurements, especially in the deepest depth when related to large and continuous bio-pore decreases in root channels and wormholes. In small core volumes, the pore network was dominated by small isolated pores, which might obstruct gas diffusion at that scale. All three concepts named above could be reconciled with our data. The limited numbers of samples and observation scales hindered identifying which model described soil spatial heterogeneity best. Finally, our results suggested the importance of considering scale effects on soil physical properties and their measurement consistency.
•Sub-sampling operations reduced soil porosity and functionality in the deepest layer.•In small core volumes, the pore network was dominated by small isolated pores.•Limited samples and scales hindered creation of a soil spatial heterogeneity model.•Sampling with larger volumes decreased the gas transport measurement's variability.•Scale-invariant soil physical properties were observed below 100 cm3 soil volume.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Poor soil gas transmission properties were observed independently from agronomic management.•Critical values were reached for soil aeration.•CA practices significantly affected pore network ...properties in the coarser soil.•Poor SOC content could prevent the exploitation of conservation practices.•Different soil water dynamics occurred in field compared to the laboratory conditions.
Soil air exchange is one of the most important soil functions that directly impacts on crop productivity and environment. Generally, conservation agriculture (CA) practices are expected to provide improved soil aeration but contrasting texture-related effects were found in the literature. The aim of this study was to evaluate the effect of CA practices on gas transport characteristics in the silty soils of the Veneto Region (North-Eastern Italy). In 2010, a field experiment comparing CA practices (no-tillage, cover crop and residues retention) to conventional intensive tillage (IT) system was established in four farms located in the Veneto low plain. In fall 2015, 144 undisturbed 100cm3 soil cores where collected at two different layers (3–6.5cm and 20–23.5cm) and analysed for air-filled porosity, air permeability, gas diffusivity and soil structure indices derived.
Gas transport measurements highlighted low transmission properties of the silty soils independently from agronomic management. Both air permeability and relative gas diffusivity showed poor aerated conditions being generally <20μm2 and <0.005, respectively.
CA treatments affected the transmission properties only in the coarsest soil studied causing a reduction of air permeability in the deeper layer and relative gas diffusivity in both layers. The CA-induced reduction was related to the tillage effect on soil bulk density and suggested that CA not only affected the air-filled porosity but also continuity and tortuosity characteristics.
The poor structural stability of Veneto soils, particularly the poor soil organic carbon content, could prevent the exploitation of CA practices firstly on soil structure and in turn on gas exchanges. For these reasons further studies elucidating the mechanisms improving soil structural conditions for silty soils as those examined in this study are required.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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