Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    We will mail you new results for this query: keywords==Aggregate stability
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Interrill erodibility in relation to aggregate size class in a semi-arid soil under simulated rainfalls
Vaezi, Ali Reza ; Eslami, Seyedeh Fatemeh ; Keesstra, Saskia - \ 2018
Catena 167 (2018). - ISSN 0341-8162 - p. 385 - 398.
Aggregate stability - Interrill erosion - Rainfall intensity - Saturated hydraulic conductivity - Semi-arid region

Interrill erodibility can be affected by soil aggregates, especially by those aggregate size classes that are dominant in the soil. In the Water erosion Prediction Project (WEPP) model, interrill soil erodibility (Ki) is estimated using very fine sand content. Despite that some studies have indicated an effect of aggregate stability on the Ki, information on the relationship between the aggregate size class and Ki and factors controlling it, particularly in semi-arid region is limited. This study was conducted to determine the variation of Ki for different aggregate size classes under various rainfall intensities and evaluation of the WEPP model in estimating the Ki for different aggregate fractions. Five aggregate size classes (0.25–2, 2–4.75, 4.75–5.6, 5.6–9.75 mm, and 9.75–12.7 mm) were separated from a sandy clay loam soil sampled in an agricultural land and put in laboratory flumes of 100 cm × 50 cm. The flumes were placed on a 9% slope and exposed to ten sequential rainfall simulations varying from 10 to 60 mm h−1 for 30 min. The Ki of each aggregate size classes was determined using the interrill sediment delivery rate and compared this with the values estimated using WEPP. All physicochemical properties were also determined in the aggregate size classes. Organic matter content in the aggregate size classes was very low (0.65–0.73%) and didn't show strong relationships with the aggregate stability and hydraulic conductivity, whereas clay was major factor controlling determining these properties for the different aggregate fractions. Significant differences were found among the aggregate size classes in clay content (P < 0.05), aggregate stability measured using both wet-sieving method (P < 0.05) and water drop test method P < 0.05, saturated hydraulic conductivity (Ks), and measured Ki (P < 0.05). The measured Ki was about 34 and 90 times bigger than the estimated Ki for the fine aggregates and coarse aggregates, respectively. The fine aggregates showed higher susceptibility to interrill detachment with increasing rainfall intensity as compared with the coarse aggregates. Significant decrease was observed in the measured Ki with increasing the aggregate size which was associated with increases in clay content, aggregate stability and Ks. The stability of aggregates against raindrop impact (CND) was an important indicator describing the effect of aggregate size on the interrill erodibility in semi-arid soils. Therefore, this indicator can be taken into account as a soil structure measure to develop a proper equation for estimating interrill erodibility (Ki) for agricultural lands. The minimum use of tillage practices is essential to prevent aggregate breakdown and control interrill erosion in semi-arid regions.

Soil aggregation and soil organic matter in conventionally and organically farmed Austrian Chernozems
Sandén, Taru ; Lair, Georg J. ; Leeuwen, Jeroen P. Van; Gísladóttir, Guorún ; Bloem, Jaap ; Ragnarsdóttir, Kristín Vala ; Steffens, Markus ; Blum, Winfried E.H. - \ 2017
Bodenkultur 68 (2017)1. - ISSN 0006-5471 - p. 41 - 55.
Aggregate hierarchy - Aggregate stability - Organic matter dynamics - Particulate organic matter (POM) - Solid-state 13C NMR spectroscopy
In order to study the soil aggregate distributions and soil organic matter (SOM), we sampled top- and subsoils in four intensively farmed croplands (two organic (Org-OB and Org-LA), and two conventional (Con-OB and Con-LA)) on Haplic Chernozems located in Marchfeld in the east of Vienna (Austria). Soil structure and SOM quantity, quality and distribution between free and occluded particulate organic matter and aggregate size fractions (<20 μm, 20-250 μm, 250-5000 μm) were studied by following a density fractionation procedure with low-energy ultrasound treatment. Te relation of the soil physicochemical (e.g., particle size distribution, pH, organic carbon, total nitrogen) and biological properties (e.g., fungal biomass, active fungi) with stable soil aggregate size fractions and SOM was studied. Te mean weight diameter (MWD) showed no significant difference between all studied sites and was between 3.8 mm and 10.0 mm in topsoils and between 6.7 mm and 11.9 mm in subsoils. In topsoils, the contents of calcium-acetate-lactate (CAL)-extractable P, active fungal biomass, dithionite-extractable Fe and sand were significantly positively correlated with the amount of the macroaggregates and with the MWD. We observed that most soil organic carbon, depending on soil texture, was stored in the microaggregate size classes <20 μm and 20-250 μm.
Contribution of raindrop impact to the change of soil physical properties and water erosion under semi-arid rainfalls
Vaezi, Ali Reza ; Ahmadi, Morvarid ; Cerda Bolinches, Artemio - \ 2017
Science of the Total Environment 583 (2017). - ISSN 0048-9697 - p. 382 - 392.
Aggregate stability - Crust formation - Infiltration rate - Runoff - Semi-arid region
Soil erosion by water is a three-phase process that consists of detachment of soil particles from the soil mass, transportation of detached particles either by raindrop impact or surface water flow, and sedimentation. Detachment by raindrops is a key component of the soil erosion process. However, little information is available on the role of raindrop impact on soil losses in the semi-arid regions where vegetation cover is often poor and does not protect the soil from rainfall. The objective of this study is to determine the contribution of raindrop impact to changes in soil physical properties and soil losses in a semiarid weakly-aggregated agricultural soil. Soil losses were measured under simulated rainfalls of 10, 20, 30, 40, 50, 60 and 70mmh-1, and under two conditions: i) with raindrop impact; and, ii) without raindrop impact. Three replications at each rainfall intensity and condition resulted in a total of 42 microplots of 1m×1.4m installed on a 10% slope according to a randomized complete block design. The contribution of raindrop impact to soil loss was computed using the difference between soil loss with raindrop impact and without raindrop impact at each rainfall intensity. Soil physical properties (aggregate size, bulk density and infiltration rate) were strongly damaged by raindrop impact as rainfall intensity increased. Soil loss was significantly affected by rainfall intensity under both soil surface conditions. The contribution of raindrop impact to soil loss decreased steadily with increasing rainfall intensity. At the lower rainfall intensities (20-30mmh-1), raindrop impact was the dominant factor controlling soil loss from the plots (68%) while at the higher rainfall intensities (40-70mmh-1) soil loss was mostly affected by increasing runoff discharge. At higher rainfall intensities the sheet flow protected the soil from raindrop impact.
Plant diversity and root traits benefit physical properties key to soil function in grasslands
Gould, Iain J. ; Quinton, John N. ; Weigelt, Alexandra ; Deyn, Gerlinde B. De; Bardgett, Richard D. ; Seabloom, Eric - \ 2016
Ecology Letters 19 (2016)9. - ISSN 1461-023X - p. 1140 - 1149.
Aggregate stability - biodiversity - grasslands - root traits - soil physics

Plant diversity loss impairs ecosystem functioning, including important effects on soil. Most studies that have explored plant diversity effects belowground, however, have largely focused on biological processes. As such, our understanding of how plant diversity impacts the soil physical environment remains limited, despite the fundamental role soil physical structure plays in ensuring soil function and ecosystem service provision. Here, in both a glasshouse and a long-term field study, we show that high plant diversity in grassland systems increases soil aggregate stability, a vital structural property of soil, and that root traits play a major role in determining diversity effects. We also reveal that the presence of particular plant species within mixed communities affects an even wider range of soil physical processes, including hydrology and soil strength regimes. Our results indicate that alongside well-documented effects on ecosystem functioning, plant diversity and root traits also benefit essential soil physical properties.

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