Centennial Fertilization-Induced Soil Processes Control Trace Metal Dynamics. Lessons from a Long-Term Bare Fallow Experiment

Abstract

Long-term bare fallow (LTBF) experiments with historical sample archives offer unique opportunities to study long-term impacts of anthropogenic activities on mineral soil fractions. In natural agro-and ecosystems, such impacts are often masked by organic matter due to its buffering action and rapid turnover. The 42-plot LTBF trial of INRA (Institut National de la Recherche Agronomique) started in Versailles (France) in 1928 to assess the impacts of prolonged application of fertilizers and amendments on the composition and properties of loamy soils. Here, we established geochemical budgets of major and trace elements on surface samples from 1929 and 2014 for four groups of treatments relevant for developed soil processes. We considered accompanying effects of soil compaction or decompaction due to changing physicochemical conditions over 85 years. Element losses from the surface horizon were quantified via fertilization-induced or -amplified soil processes: clay leaching favored by Na-or K-based fertilization, and lixiviation of major and trace elements in acidic or alkaline soil conditions. Enhanced mineral weathering was shown for acidified and nonamended plots. Conclusions on trace metal migration were confirmed by selected analyses on subsurface horizons. Additional information was provided on specific element inputs via fertilizers and/or diffuse inputs via atmospheric deposition.

Partitioning soil organic carbon into its centennially stable and active fractions with machine-learning models based on Rock-Eval® thermal analysis (PARTY<sub>SOC</sub>v2.0 and PARTY<sub>SOC</sub>v2.0<sub>EU</sub>)

“…Of these methods, only a few are reasonably reproducible and easy to implement such as the ones based on rapid thermal analysis and chemical extractions (Gregorich et al, 2015;Poeplau et al, 2013Poeplau et al, , 2018Soucémarianadin et al, 2018a). Other methods, such as size and density SOC fractionation, need to be inferred from machine-learning models or infrared spectroscopy to be implemented for large soil sample sets (Baldock et al, 2013;Cotrufo et al, 2019;Jaconi et al, 2019;Viscarra Rossel et al, 2019;Viscarra Rossel and Hicks, 2015;Vos et al, 2018;Zimmermann et al, 2007b). However, all SOC fractionation methods fail to achieve a proper separation of stable from active SOC, and the isolated SOC fractions are thus mixtures of centennially stable and active SOC (Fig.…”

Improving Yasso15 soil carbon model estimates with ensemble adjustment Kalman filter state data assimilation

“…State data assimilation (SDA) refers to Bayesian methods where state information from two or more sources is combined to create a more accurate estimation of the true state (Evensen, 2009). It has already been applied in several geophysical subjects (e.g., Elbern et al, 2000;Weaver et al, 2003;Viskari et al, 2012;Yang et al, 2019) and is a fundamental component that allows weather forecasts (Le Dimet and Talagrand, 1986). In recent years there have been efforts to also use SDA methods to better incorporate flux tower and satellite measurements (Viskari et al, 2015) to update ecological model projections.…”

Is the operationally defined fraction of soil organic matter, “GRSP” (glomalin‐related soil protein), stable in soils? Evidence from trends in long‐term bare fallow soil

“…In line with SOC, GRSP declined rapidly in the KClamended soil, indicating a similar effect of loss of physical protection. A marked loss of clay has also been reported for this treatment due to clay leaching, and SOM including protein would have been lost along with the mineral (van Oort et al, 2018). The net decline in GRSP:SOC suggests greater relative loss of GRSP, coherent with preferential adsorption of proteins on leached clay minerals.…”

“…It was found to contain 320 g C kg −1 , 14.3 g N kg −1 and 7.8 g GRSP kg −1 . A more detailed description of the trial and major results for pedogeochemical changes are given by van Oort and co-workers (van Oort et al, 2016(van Oort et al, , 2018 and for SOC changes by Barré et al (2010) and Paradelo, van Oort, Barré, Billiou, & Chenu (2016).…”