Variation in potassium and calcium uptake with time and root depth
Bibliographic record
Abstract
McGonigle, T. P. and Grant, C. A. 2015. Variation in potassium and calcium uptake with time and root depth. Can. J. Plant Sci. 95: 771–777. Root uptake of calcium (Ca) and potassium (K) with depth in soil and through time are of interest not only as fundamental processes of plant physiology but also for the practical application of crop management. For K specifically, depth of band placement for fertilizer should be optimized for crop uptake. Environmentally rare strontium (Sr) and rubidium (Rb) are used as root activity tracers for Ca and K, respectively. We applied Sr and Rb to field micro-plots at depths 0–5 cm, 5–10 cm, and 10–15 cm. Tracer application throughout the entire rooting volume for a given depth interval eliminated confounding effects of age-related lateral root spread seen with point application. Soil analyses confirmed there was no within-profile movement of amendments. Maize (Zea mays L.) shoot Sr concentration was greatest at 16 d of growth for amendment to 0–5 cm, in keeping with expected restriction of Ca uptake to root tips. In contrast, maximum shoot Rb concentration was at 24 d and with amendment to 5–10 cm, indicating more proximal root uptake of K. Uptake of Sr and Rb was sustained for a longer period from 5 to 15 cm than from 0 to 5 cm, so that most of the Ca and K in shoots likely comes from this greater depth interval. Soil pasteurization reduced colonization by arbuscular mycorrhizal fungi but had no impact on tracer uptake, indicating these fungi do not influence uptake of Ca and K. Studies on maize root activity using Sr and Rb should apply tracers in the 5- to 15-cm depth interval and harvest shoots between 3 and 7 wk after planting. Based on Sr uptake, determination of soil Ca levels to predict early-season uptake by maize should focus on the 5- to 15-cm depth interval. Based on Rb uptake, banded application of K fertilizer is expected to be most effective to promote early-season growth when band placement is within 5- to 15-cm depth.
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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 | 0.001 |
| 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 | 0.001 | 0.001 |
| 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 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".