Effects of Short-term Tillage of a Long-term No-Till Land on Quantity and Quality of Organic C and N in Two Contrasting Soil Types
Bibliographic record
Abstract
<p>Pre-seeding tillage of long-term no-till soil may alter soil quality by changing some properties, but the magnitude of change depends on soil type and climatic conditions. Effects of short-term (2 or 3 years) tillage (hereafter called reverse tillage [RT]) of land previously under long-term no-till (NT, 29 or 30 years), with straw management (straw removed [S<sub>Rem</sub>] and straw retained [S<sub>Ret</sub>]) and N fertilizer rate (0, 50 and 100 kg N ha<sup>-1 </sup>in S<sub>Ret</sub>, and 0 kg N ha<sup>-1 </sup>in S<sub>Rem</sub> plots) were determined in autumn 2011 on total organic C (TOC) and N (TON), light fraction organic C (LFOC) and N (LFON), and mineralizable N (N<sub>min</sub>) in the 0-7.5, 7.5-15, or 15-20 cm soil layers at Breton (Gray Luvisol [Typic Cryoboralf] loam) and Ellerslie (Black Chernozem [Albic Argicryoll] loam), Alberta, Canada. Short-term RT following long-term NT had no significant negative effect on TOC and TON in soil at both sites, although these parameters tended to be slightly lower in the 0-7.5 cm soil layer with RT compared to NT. For the zero-N treatment, S<sub>Ret</sub> had greater TOC and TON compared to S<sub>Rem</sub> in both soil layers at both sites. On average, over both sites, TOC and TON in the 0-15 cm soil increased by 2.08 Mg C ha<sup>-1</sup> and 0.216 Mg N ha<sup>-1</sup>, respectively. Application of N fertilizer increased TOC and TON in both soil layers, up to the 50 kg N ha<sup>-1</sup> rate at Breton (by 7.96 Mg C ha<sup>-1</sup> and 0.702 Mg N ha<sup>-1</sup> in the 0-15 cm soil) and up to the 100 kg N ha<sup>-1</sup> rate at Ellerslie (by 5.11 Mg C ha<sup>-1</sup> and 0.439 Mg N ha<sup>-1</sup> in the 0-15 cm soil). In both RT and NT treatments, the effects of N rate on TOC and TON were similar for S<sub>Ret</sub> and S<sub>Rem. </sub>There was greater LFOC and LFON in the 7.5-15 cm soil layer with RT than NT at both sites. In the 0-15 cm soil layer, averaged over both sites, RT increased LFOC by 66 kg C ha<sup>-1</sup> and LFON by 4.0 kg N ha<sup>-1</sup>. In both 0-7.5 and 7.5-15 cm soil layers, LFOC and LFON increased with S<sub>Ret</sub> compared to S<sub>Rem.</sub> Averaged over both sites, the increase in LFOC and LFON in the 0-15 cm soil was 97 kg C ha<sup>-1</sup> and 3.5 kg N ha<sup>-1</sup>, respectively. Mass of LFOC and LFON increased dramatically in both soil layers with application of N fertilizer up to the 100 kg N ha<sup>-1</sup> rate at both sites, with an average increase of 866 kg C ha<sup>-1</sup> and 45.5 kg N ha<sup>-1</sup>. In the zero-N treatment, LFOC and LFON increased with S<sub>Ret</sub> compared to S<sub>Rem</sub> under RT at Breton and under NT at Ellerslie. On average, tillage had no effect on N<sub>min</sub> in soil, but S<sub>Ret</sub> increased N<sub>min </sub>in soil in both RT and NT, with an average increase of 4.8 kg N ha<sup>-1</sup>. Application of N fertilizer increased N<sub>min</sub> in the 0-20 cm soil up to 50 kg N ha<sup>-1</sup> rate at Breton (by 13.7 kg N ha<sup>-1</sup>) and up to 100 kg N ha<sup>-1</sup> rate at Ellerslie (by 18.6 kg N ha<sup>-1</sup>). In conclusion, RT had no effect on TOC, TON and N<sub>min</sub> in soil, but LFOC and LFON increased with RT compared to NT in the 7.5-15 cm layer at one site. S<sub>Ret</sub> and N fertilization usually had dramatic positive effects on TOC, TON, LFOC, LFON and N<sub>min</sub> in soil compared to the corresponding treatments.</p>
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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 | 0.001 |
| 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 | 0.000 |
| 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".