Liming Enhances Soil Phosphorus Cycling in Long‐Term Agricultural Fields
Bibliographic record
Abstract
ABSTRACT Liming enhances both organic phosphorus (P) mineralization and the precipitation of inorganic phosphates with calcium (Ca) cations. To better understand how P storage and cycling in soil profiles are regulated by the interaction of long‐term P fertilization and liming, we collected soil samples from three German arable long‐term field experiments in Berlin‐Dahlem (Albic Luvisol; sandy topsoil [0–30 cm], and loamy subsoil [> 30 cm]), Dikopshof (Haplic Luvisol; silty‐loamy topsoil, and clayey‐loamy subsoil), and Thyrow (Albic Luvisol; sandy soil). Treatments within each of these experiments had received mineral fertilization with NKPCa (N: nitrogen; K: potassium; P: phosphorus; Ca: calcium, referring to liming), NKCa, NKP, and NK or no fertilizer application (none) for at least 60 years. Soil P stocks down to 100 cm depth were assessed by Hedley sequential P fractionation and the oxygen isotopic composition of 1 M HCl‐extractable phosphate (δ 18 O P ) was analyzed as an indicator of the degree of microbial P cycling over the decades of experimental duration. We found that mineral P fertilization increased soil total P stocks in all P fractions regardless of differences in soil clay content among the different experiments. Liming significantly decreased NaHCO 3 ‐Pi (Pi: inorganic P) and NaOH‐Pi stocks by up to 50% across the three experiments and soil depths, but tended to increase Po (organic P) stocks in these fractions by up to 40%, reflecting enhanced P uptake into plant and microbial biomass when acidic soil conditions were improved by lime application. Soil HCl‐Pi stocks in treatments with long‐term P fertilization and liming were larger by a factor of up to 1.8 compared to the unfertilized control plots, while especially the plots without P fertilization showed smaller δ 18 O P values of 11‰ in the subsoil. These results indicate that, on the one hand, biological P cycling was enhanced in fertilized treatments, but on the other hand, soluble Pi was precipitated as secondary Ca–P minerals into stable P fractions. These changes occurred both in the topsoil and upper subsoil (30–50 cm). We conclude that the combined application of long‐term P fertilization and liming to the surface soil also increased the utilization of subsoil P.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".