Soil microaggregates store phytoliths in a sandy loam
(2019) Geoderma — Vol. 360, p. 114037 (2020)
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- Authors
Li, Zimin 
Delvaux, Bruno
- Abstract
- Phytoliths are finesilt-ized amorphous silicap articlesthat for min living plant tissues. Oncedeposited in soils through plant debris, they may dissolve and increase the fluxes of silicon (Si) towards the biosphere and hydrosphere, thus enhancing positive Si impacts one.g.,plant health and carbon fixation by marine diatoms. Here we analyzed the role of soil aggregates in phytolith protection against dissolution. We investigated the distribution of phytoliths in the size fractions of a sandy loam topsoil subjected to two long-term treatments: conventional(CT) and no tillage(NT).The top soil size fractions were separated through wet sieving and named, respectively: macro aggregates (250–2000µm), free micro aggregates (50–250µm), and silt+clay (<50µm). Protected microaggre gates held within macro aggregates wereextracted using ac onstantand continuous water flow process. We assessed the pool of phytoliths through heavy liquid separation and alkaline dissolution (Na2CO3), and we assessed the bioavailability of Si using CaCl2 extraction. As expected, NT generates larger amounts of aggregates than CT. Concentrations andstocks of phytoliths determined by heavy liquid separation are ten times higher than those measured byNa2CO3 in bulk soil and size fractions. Soil micro aggregates contribute for over 60% to the pool of phytoliths, which control bioavailable Si. There lease of bioavailable Si from micr oaggregate sis slower than that from the silt +clay fraction, suggesting that soil microaggregates can trap phytoliths and protect them from rapid dissolution. No-tillage and associated conservation agricultural practices may thus promote the stabilization of phytoliths in soils and decrease their dissolution rate.We propose that the entrapment of phytoliths in soil aggregates may be one of the processes favoring the persistence of phytoliths in soils and sediments. We expect that this persistence should be enhanced in strongly aggregated soils.
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Citations
Li, Z., de Tombeur, F., Vander Linden, C., Cornelis, J.-T., & Delvaux, B. (2019). Soil microaggregates store phytoliths in a sandy loam. Geoderma, 360, 114037. https://doi.org/10.1016/j.geoderma.2019.114037 (Original work published 2020)