Comments on “No‐Tillage and Soil‐Profile Carbon Sequestration: An On‐Farm Assessment”
Bibliographic record
Abstract
4 present data on soil organic carbon (SOC) concentrations from soils managed under no-tillage (NT) or plow-tillage (PT) from samples taken from studies of paired fields at 11 (MLRA) sites in three states of the USA. The results seem to show extremely large annual changes in soil organic C stocks between NT and PT to a depth of 60 cm, ranging from +3.75 to −6.65 Mg ha−1 yr−1 (Table 2). However, these values are far greater, and not compatible with, the data displayed in Fig. 2, nor the total stocks of soil N and the C/ N ratio displayed in Tables 3 and 4, respectively. However, the data displayed taken from seven studies in the literature (a total of 16 comparisons) are correctly reported as annual changes. Table 2 should thus be corrected as shown here (Table 1). A further error in the data presentation is in the vertical scale adopted for the Fig. 4, which suggests that most soil profiles contained over 200 Mg C ha−1 to a depth of 60 cm, and that several woodlots showed soil C stocks above 500 Mg C ha−1 to this depth. These errors do not change the main conclusion of the study that “the idea that no-tillage would also enhance soil organic carbon sequestration as an additional benefit of no-tillage technology needs a careful examination.” However the data as presented grossly exaggerate the magnitude of possible gains and losses in such systems. Although the authors cite two studies from southern Brazil, in neither was the soil sampled to a depth >40 cm. Two more recent studies from the same region on the same soil type (Typic Hapludox) were sampled to depths of 100 cm or more (8; 5). In the study of 8 where a N2–fixing legume (hairy vetch—Vicia villosa) was included as a winter crop with maize (Zea mays) in summer, the soil C stocks to 30 cm under NT management was between 5.4 and 9.1 Mg ha−1 greater than under PT. When the soil was sampled to the 100-cm depth the difference in C stocks increased to 16.9 Mg C ha−1 in both rotations. In the study of 5 in two rotations maize was planted in a mixture with either lablab (Lablab purpureum) or pigeon pea (Cajanus cajan). In these rotations, the C stocks to a 17.5-cm depth increased by between 7.9 and 8.4 Mg C ha−1 under NT after a 17-yr period. When sampling was made to 107.5 cm, the increase in soil C stocks under NT were even greater at 13.1 and 21.2 Mg C ha−1 Recent results from sites in the USA (6; 7; 4), as well earlier results from Canada (2; 9), suggest that increases in soil C to depths of 20 to 30 cm under NT do not necessarily indicate that any net C sequestration occurred, as higher concentrations of C can be encountered under PT at depths below this. However, the two studies on free-draining Oxisols in southern Brazil indicate that, (i) C accumulation is highly dependent on N supply (a positive N balance from legumes– 1), and, (ii) in these cases where C accumulation was detected within the “plow layer,” deeper sampling revealed that C sequestration under NT compared with PT was much greater than was to be expected from the shallower soil sampling. Data from all sites indicate that in all sampling to assess net changes in soil C due to changes in tillage practice it is essential to sample well below the plow layer (>60 cm). Most data from temperate regions suggest that superficial sampling will overestimate possible benefits of changes form PT to NT (3), but in the case of deep free-draining soils in the tropics it may be that shallow sampling could lead to gross underestimation of soil C sequestration after adoption of NT.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.007 | 0.031 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.003 | 0.002 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.020 | 0.012 |
| Insufficient payload (model declined to judge) | 0.010 | 0.006 |
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".