Phytolith‐associated potassium in fern: characterization, dissolution properties and implications for slash‐and‐burn agriculture

Abstract

In recent time, phytoliths (silicon deposition between plant cells) have been recognized as an important nutrient source for crops. The work presented here aims at highlighting the potential of phytolith‐occluded K pool in ferns. Dicranopteris linearis (D. linearis) is a common fern in the humid subtropical and tropical regions. Burning of the fern D. linearis is, in slash‐and‐burn regions, a common practice to prepare the soil before planting. We characterised the phytolith‐rich ash derived from the fern D. linearis and phytolith‐associated potassium (K) (phytK), using X‐ray tomographic microscopy in combination with kinetic batch experiments. D. linearis contains up to 3.9 g K/kg d.wt, including K subcompartmented in phytoliths. X‐ray tomographic microscopy visualized an interembedding structure between organic matter and silica, particularly in leaves. Corelease of K and Si observed in the batch experiments confirmed that the dissolution of ash phytoliths is one of major factors controlling K release. Under heat treatment, a part of the K is made available, while the remainder entrapped into phytoliths (ca. 2.0–3.3%) is unavailable until the phytoliths are dissolved. By enhanced removal of organic phases, or forming more stable silica phases, heat treatment changes dissolution properties of the phytoliths, affecting K release for crops and soils. The maximum releases of soluble K and Si were observed for the phytoliths treated at 500–800 °C. For quantitative approaches for the K provision of plants from the soil phytK pool in soils, factors regulating phytolith dissolution rate have to be considered.

Encapsulation of lead in rice phytoliths as a possible pollutant source in paddy soils

“…Soluble Pb content in the aqua regia solvent decreased from 0.74 to 0.09 mg g −1 , while it was maintained at less than 0.1 mg g −1 in DI water, H2O2 and Na2CO3 solution following treatment over the entire temperature range from 400 °C to 1000 °C. At temperatures above 500 °C, lower contents of Pb were released when using aqua regia as solvent, which suggests that some Pb might be tightly entrapped in the phytolith structure and is not accessible by the aqua regia solvent Dissolution of phytolith silica has been reported as a control factor for the release of occluded substances (Nguyen et al, 2015;Tran et al, 2018;Trinh et al, 2017). However, no obvious evidence relating the release of Si and Pb was confirmed in this work.…”

pH-dependent silicon release from phytoliths of Norway spruce (Picea abies)

“…Several studies have been done on the dissolution properties of silicon and phytoliths. Authors investigating this theme, however, used different extraction methods and different test subjects to describe silicon turnover, thus making it difficult to compare results between studies, and with our results (Cabanes et al 2011;Cabanes and Shahack-Gross 2015;Haynes and Zhou 2018;Tran et al 2018). Dissolution of ''in situ'' silicon, which is integrated into the tissues of needles, may be bound in several organic forms.…”

“…For example, aluminum content may affect solubility (Bartoli and Wilding 1980;Bartoli 1985), but at the same time, Fraysse et al (2009) reported that aluminum had no effect on phytolith solubility. Additionally, phytoliths with different elemental contents would be sources for these elements, and phytolith dissolution could thus affect the biogeochemical cycles of these elements (Tran et al 2018). As Osterrieth et al (2009) suggested, the degradation process of phytoliths usually starts with the initial destruction of plant tissues.…”

Carbonization and H3PO4 activation of fern Dicranopteris linearis and electrochemical properties for electric double layer capacitor electrode

“…In many remote regions, this fern is burned to fertile soils (slash-and-burn agriculture) or used as a material for covering soil surface or earlier it has been an important fuel for local minorities. More recently, D. linearis has been more intensively studied and the findings suggested this fern species as a potential material for biochar production 5 or soil improvement 6,7 . This encourages more research works to get the advantages from this type of species economically and efficiently [5][6][7][8][9][10] .…”