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Phytolith is widely known as a silica structure in numerous silicon (Si) accumulator plants, e.g., rice, and it contains various nutrients and other beneficial elements. When rice straw is returned to paddy fields, the silica structure of phytolith can be dissolved, thereby releasing its occluded nutrients. While the intrinsic characteristics and dissolution properties of phytoliths under the effect of solution chemistry have been intensively studied, the effect of gas phases, especially CO2, on phytolith stability and the implications for nutrient release are not fully known. Here, dissolution properties of phytolith ashes obtained from dry ashing of rice straw at 400, 600 and 800 °C were investigated by quantifying Si release together with other nutrients under two atmospheric conditions, i.e., without and with CO2 support (aeration). In a time span of 6 days, the releases of nutrients (K, P, Ca, Mg) showed high dependence on the overall dissolution of the phytolith ashes. CO2 significantly reduced the dissolution rate of the phytolith ashes but increased the release rates of cationic as well as anionic nutrients. The aeration of CO2 shifted the carbonate equilibrium (H2CO3, HCO3− and CO32−) towards H2CO3, reducing solution pH, thereby decreasing the dissolution rate of phytoliths. Following this, intensification of H+ exchange promoted nutrient releases from the phytolith ashes. This indicates contrasted responses of phytoliths and their occluded nutrients to CO2, and provides a better insight on the fate of soil phytoliths and the tendency of nutrient budgets from rice straw phytoliths in soils. [ABSTRACT FROM AUTHOR]

Arsenic (As) contamination has been identified as a tangible risk related to soil and land degradation, and identifying pristine regions is, therefore, important for the long‐term safety considerations of humans. The Red River Basin is among the largest cultivation regions in Southeast Asia that provides rice for local consumers as well as for exports. While the lowland part of the Red River Delta (RRD) has been recently identified as an area suffering from As risk, little is known about the upland terrace part. In this study, terraced paddy was found to be an ecosystem with a lower accumulation of As. The median As value, x~, in the terraced paddy soil was 2.22 mg kg−1, while almost no As was detected in the rice grain. The content of soil As of the RRD (x~= 6.12 mg kg−1) was equal to the global average and led to a significant accumulation of As in rice grain (x~ = 221 μg kg−1). Among the soil properties, soil water‐soluble silicon (SiH2O) appeared to be the most effective factor for reducing As translocations to rice. As the diminution of available Si can narrow the arable land that produces non or low‐As rice, this is likely an emerging factor that affects land degradation. With its low‐As rice status, the terraced paddy can be highlighted as a pristine part for rice growing. The fact that As accumulates in rice at different levels between terraced and lowland paddy regions can be considered in developing As mitigation strategies or rice repricing. [ABSTRACT FROM AUTHOR]

Xanthophyceae (Stramenopiles) are common microalgae in soil habitats, but not commonly known from maritime sandy habitats. Here we studied the genetic diversity of nine new isolates of Xanthophyceae from coastal habitats using two chloroplast-encoded markers. The isolates exhibited only three morphotypes. The sequence comparisons uncovered a respectable phylogenetic diversity, including novel infraspecific genotypes, among the isolates. The phylogenetic analyses of full rbcL gene sequences identified eight of the isolates to five named species based on monophyletic origins and short genetic distances with defined taxonomic reference strains. One strain, representing a coccoid species, was within a so far unrecognised lineage of Xanthophyceae. In four clades of the rbcL phylogeny, the coastal isolates were most closely related to strains from Antarctic soil habitats. Comparisons of the psbA/rbcL spacer region sequences, a highly variable molecular marker, uncovered a fine-scale structuring within a species which was consistent with habitat preferences. The new maritime isolates exhibited genotypes distinct from those of the same species from other habitats. It suggests that the environment selects for specific genotypes in these pioneering algae. [ABSTRACT FROM AUTHOR]

The polyphasic approach has been widely applied in cyanobacterial taxonomy, which frequently led to additions to the species inventory. Increasing our knowledge about species and the habitats they were isolated from enables new insights into the ecology of newly established genera and species allowing speculations about the ecological niche of taxa. Here, we are describing three new species belonging to three genera that broadens the ecological amplitude and the geographical range of each of the three genera. Cyanocohniella crotaloides sp. nov. is described from sandy beach mats of the temperate island Schiermonnikoog, Netherlands, Oculatella crustae‐formantes sp. nov. was isolated from biological soil crusts of the Arctic Spitsbergen, Norway, and Aliterella chasmolithica originated from granitic stones of the arid Atacama Desert, Chile. All three species could be separated from related species using molecular sequencing of the 16S rRNA gene and 16S–23S ITS gene region, the resulting secondary structures as well as p‐distance analyses of the 16S–23S ITS and various microscopic techniques. The novel taxa described in this study contribute to a better understanding of the diversity of the genera Cyanocohniella, Oculatella, and Aliterella in different habitats. [ABSTRACT FROM AUTHOR]

Recently, low input agriculture has been encouraged because of its sustainability and environmentally friendly vision. Conversion of biomass into control‐released materials is one of the approaches to upcycle biomass and nutrients. This study aims at examining the dynamics of K release from Si‐rich biochars formed from various pyrolysis strategies with the findings expected to be applicable to develop new refinery strategies for biomass nutrients. A Si‐rich fern species [Dicranopteris linearis (Burm.f.) Underw.] was selected to prepare biochars under various pyrolysis conditions (e.g., temperature, N2 supported). It was found that K was re‐located during pyrolysis and occurred as free K+ ions, associated with organic matter and occluded in silica structure. Pyrolysis can be strategically applied to alter either the organic phase or the silica phase in the biochars in term of porosity and chemical reactivities, whereby controlling K release kinetics. The maximum level of released K was at 600 °C (5.4 g kg−1) which was about one order of magnitude higher than the minimum level of released K at 200 °C (0.55 g kg−1). This discrepancy in the release rates of K suggests that adjusting pyrolysis temperature can be a strategical practice to control K release and to develop biochar‐based K fertilizers. [ABSTRACT FROM AUTHOR]