Adopting zero tillage management: Impact on soil C and N under long-term crop rotations in a thin Black Chernozem
Bibliographic record
Abstract
Society’s desire to sequester C in soils, thereby reducing the net loss of CO 2 (a greenhouse gas) to the atmosphere, is well known. It is also accepted that the choice of appropriate agricultural management practices adopted by producers will affect this goal. However, quantification of the extent and rate at which it can be achieved is uncertain. A crop rotation experiment that was initiated in 1957 on a thin Black chernozemic clay soil at Indian Head, Saskatchewan, was managed using conventional tillage until changed to zero tillage in 1990. Soil was sampled (0- to 7.5- and 7.5- to 15-cm depths) in May 1987 and 1997 to determine the effects of treatments on soil organic C (SOC) and total N. The rotations were: fallow-wheat (Triticum aestivum L.) (F-W), F-W-W, continuous wheat (Cont W), legume green manure (GM)-W-W, and F-W-W-hay (legume-grass)-hay-hay (F-W-W-H-H-H). The monoculture cereal rotations were either fertilized with N and P based on soil tests or unfertilized, while the legume systems were both unfertilized. There was also a F-W-W (N+P) treatment in which the straw was baled and removed. When the experiment was changed to zero tillage management in 1990, the fertilizer protocol was changed to satisfy the “moist soil” criteria. Consequently, higher rates of N and P were added thereafter to the fallow crop, resulting in a positive yield response of wheat grown on fallow, where before there was no response to fertilizer. Over the 10-yr period (1987-1997) fertilized soil gained C and N, but unfertilized soil did not. For example fertilized F-W, F-W-W and Cont W gained about 4, 5 and 2 Mg C ha –1 in the 10-yr period. During this period, C emissions from manufacture and transportation of N fertilizer was 0.28, 0.53 and 0.90. Mg ha –1 for these three rotations, respectively. These results suggest that without adequate fertility, conversion to zero tillage may not always result in an increase in soil C or N. By 1997, fertilizer increased soil C and N in F-W-W and Cont W, and soil C and N were greater in F-W-W-H-H-H than in GM-W-W and lowest in F-W-W (all unfertilized). Straw removal had no significant effect on C or N. The analysis showed that C inputs from crop residues was the main factor influencing SOC changes. Key words: C sequestration, crop rotation, fertilizer, grain yields, total N, tillage
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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 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".