Kaolinite formation from palygorskite and sepiolite in rhizosphere soils
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Bibliographic record
Abstract
Abstract Palygorskite and sepiolite are fibrous clays that occur mostly in agricultural soils of arid regions. Although many investigations have examined the environmental conditions for the formation and stability of these clays, information on the transformation of these clays in the root zone (or rhizosphere) of agricultural crops is limited. In this study, changes in palygorskite and sepiolite within the rhizosphere of selected agricultural crops were determined and the ability of plants to extract Mg from these minerals compared. Alfalfa, barley, and canola were cultivated in pots under controlled conditions in a growth chamber using growth media that consisted of a mixture of Ottawa sand and clay-sized Florida palygorskite (PFl-1) or Spanish sepiolite (SepSp-1). After 100 days of cultivation, the biomass of plant roots and shoots were determined and Mg uptake measured by inductively coupled plasma analysis of the plant biomass after microwave oven digestion. The clay fraction in each pot was separated from the sand and analyzed using X-ray diffraction (XRD) and examined using transmission electron microscopy (TEM). The XRD reflection at 0.718 nm clearly indicated kaolinite in the rhizosphere after growth of the three crops. Furthermore, hexagonal kaolinite particles were observed, using TEM, and the amount of Mg extracted by the three crops was significantly greater for sepiolite than for palygorskite. Palygorskite and sepiolite kaolinization in the rhizosphere was apparently due: (1) to high acidity in the rhizosphere caused by root activity and organic matter decomposition; and (2) to fibrous clay destabilization caused by Mg uptake by plants. This study shows that kaolinite in agricultural soils of arid and semi-arid regions might be partly due to neoformation after fibrous clay dissolution and not entirely inherited from parent materials, as has been suggested in earlier literature.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it