Surface reactivity of the natural metal (hydr)oxides in weathered tropical soils

Earthworms affect reactive surface area and thereby phosphate solubility in iron-(hydr)oxide dominated soils

“…Therefore, the small fraction of crystalline Fe-(hydr)oxides compared to the total pool of metal-(hydr)oxides was ignored in our further calculations. Presently, no specific proxy with a consistent set of parameters for the CD model is available for natural Al-(hydr)oxides, but according to recent work with Al-(hydr)oxide-dominated weathered tropical soils, Fh was an adequate proxy in the CD modelling (Mendez et al, 2022). Therefore, Fh was chosen as reference oxide for soils S3 and S4.…”

“…However, those authors noted that the NOM surface loadings required to explain the observed PO 4 concentrations in casts were very high compared to the typical NOM loading of Dutch agricultural soils (Hiemstra et al, 2010b;Hiemstra et al, 2013). Another reason to question these results is the use of goethite as a proxy for the natural metal-(hydr)oxide fraction in the model approach, while ferrihydrite (Fh) particles may be responsible for most of the reactivity towards PO 4 (Mendez et al, 2020;Mendez et al, 2022).…”

Soil carbon stocks in stable tropical landforms are dominated by geochemical controls and not by land use

“…Due to their environmental boundary conditions and their extensive weathering history, most tropical soils are dominated by end member minerals such as 1:1 clays (e.g., kaolinite) as well as highly crystalline Fe oxyhydroxides and Fe oxides, which have a lower potential for the sorption of organic matter (Barré et al, 2014; Doetterl et al, 2018; Ito & Wagai, 2017; Six, Conant, et al, 2002). Thus, the reduced mineral reactivity of tropical soils (Doetterl et al, 2018; Mendez et al, 2022) compared to temperate soils leads to a lower potential to store C despite higher inputs in natural (tropical forest) ecosystems.…”

Models for predicting nutrient availability in soils from sub-Saharan Africa

“…We showed that K transfer functions were significantly different between temperate and tropical soils, which we attributed to clay mineralogy. Although not tested for P, differences in the transfer functions between temperate and tropical soils are also expected, given the effect of climate and weathering on soil properties such as Al-oxides (Mendez et al, 2022).…”