Soil organic matter conservation in no-tillage Zea mays L.
Bibliographic record
Abstract
Usually, no-tillage (NT) crop production conserves more soil organic carbon (SOC) than conventional tillage (CT). The objective of this thesis was to measure the annual input and distribution of crop residue C in NT and CT (moldboard plow) treatments of a long-term tillage experiment with maize ('Zea mays' L.). Since the field plots were 18 years-old, SOC dynamics should reflect long-term, if not steady-state, conditions. The experiment was located at Elora, Ontario, on a Conestoga silt loam (Gleyed Melanic Brunisol, Aquic Hapludalf) with 500 g kg-1 silt, 200 g kg-1 clay, and pH 7. Maize was exposed to 14CO2 nine times over the growing season to obtain 14C-labeled shoots and roots. Their decomposition in the NT and CT soil was followed for the next 2.5 years. 14C-root residues were first sampled seven weeks after grain maturity. By that time, labile compounds had mineralized, and over the next 2.5 years, the remaining 14C-root residues mineralized too slowly to measure. The total 14C-root residues in the 0-20 cm depth of NT and CT soil were not significantly different ('P' < 0.05): the root residue C was 294 (250, 345) [mu]g C cm-3 soil (95% confidence limits), or 0.8 (0.7, 0.9) g root-C/g shoot-C (grain+stover). In NT, 32, 33, 21, and 14% of 14C-root residue was found in the 0-5, 5-10, 10-15, and 15-20 cm depths, respectively. After one year, rapid mineralization of ground 14C-stover residues was complete. The residual 14C-stover in stable organic matter (0-20 cm depth) of NT and CT soil was not significantly different ('P' < 0.05): in two separate experiments, 14C-stover remaining in stable SOC was 41.7 ± 3.9% (±SE) and 30.8 ± 4.4%. In both NT and CT, there was little vertical movement of 14C-stover residue. After one year in NT, 27.6, 3.8, 2.2, 1.1, and 0.5% of the initial 14C-stover was found in the 0-2.5, 2.5-5, 5-10, 10-15, and 15-20 cm depths, respectively. After 18 years, the field plots contained 7.1% more SOC in NT than CT even though NT averaged a 12.7% lower yield than CT. Conservation of SOC in NT than CT was due to slower decomposition of stable SOC, and not more efficient stabilization of crop residue C into SOC.
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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) | 0.001 | 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".