Benchmarking soil potassium extraction methods and establishing critical thresholds for wheat production in Inceptisols
Bibliographic record
Abstract
Accurate assessment of plant-available potassium (K) in soils is crucial for optimizing crop nutrition and enhancing the efficiency of fertilizer use. This study systematically benchmarked ten widely used soil K extractants, Calcium Chloride (CaCl 2 ), Ammonium Acetate (NH 4 OAc), Ammonium Bicarbonate-Diethylenetriaminepentaacetic Acid (AB-DTPA), Morgan's extractant (Morgan), Calcium acetate lactate extractant (Ca-AL), Kelowna extractant (Kelowna), Olsen extractant (Olsen), Modified Kelowna extractant (Kelowna-2), Nitric Acid (HNO₃), and Sodium Tetraphenylborate (NaTPB) to identify the most effective method for quantifying available K and defining critical thresholds for wheat production in Inceptisols. Pot trials were conducted on soils from twenty Inceptisol series in the Gangetic alluvial plains of Eastern India using five K fertilizer rates that simulates the wide K variability in real field situations. Among the tested methods, NaTPB emerged as the most reliable extractant, showing the strongest correlation (R 2 = 0.83, P < 0.05) with Bray’s percent yield (BPY) and a critical K threshold of 1110.3 kg ha −1 . CaCl 2 also demonstrated high accuracy (R² = 0.82). Multivariate analysis revealed that NaTPB-extractable K was significantly influenced by soil clay content and electrical conductivity, which together explained 76.9 % of its variability. Furthermore, NaTPB effectively captured K from multiple pools, including water-soluble, exchangeable, and non-exchangeable pools, providing a more comprehensive index of plant-available K. A critical K concentration of 0.35 % in wheat grain was identified as the threshold for optimal yield, offering a practical benchmark for site-specific K management. By integrating chemical extraction, crop response modeling, and soil property analysis, this research presents a novel and scientifically robust framework for assessing K fertility. With the successful implementation in Eastern India, the findings have benchmarked broader applicability to Inceptisols in other agroecological regions, providing a scalable diagnostic approach for sustainable nutrient management. This study makes a significant contribution to precision agriculture and global efforts to optimize fertilizer recommendations through the development of improved soil testing methodologies.
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How this classification was reachedexpand
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 | 0.004 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| 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 teacher head, 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".