Understanding the Impacts of Crop Rotation on Soil Microbial Dynamics and Carbon Cycling
Bibliographic record
Abstract
Soil organic matter (SOM) is the largest terrestrial C sink on the planet and plays a key role in C storage. The quantity and forms of SOM storage in agricultural soils are an indicator of soil health, function, and fertility in cropping systems. Canola, wheat, and corn, considered staple cash crops across Canada, have recently been grown with increasing frequency within crop rotations. However, little is known about the impact of short rotation cropping systems on SOM and the formation of different SOM functional pools. The objective of this research was to assess crop frequency impacts on microbial communities through measurement of phospholipid fatty acids (PLFA), on enzyme activities, and on soil C storage in particulate organic matter (POM) and mineral-associated organic matter (MAOM) functional pools. Soil samples were collected from long-term AAFC rotational studies including a multi-site canola frequency study (est. in 2008), a continuous wheat vs. rotation wheat study at Swift Current, SK (est. 1987), and a continuous vs. rotation corn study at Harrow, ON (est. 2001). For all soils, we measured total C and organic C content of physically fractionated POM and MAOM and PLFA. Beta-glucosidase (BG), N-acetyl-glucosaminidase (NAG), phosphatase (PHOS), phenol oxidase (PHN.OX), and arylsulfatase (ARYL) enzyme assays were performed on the canola rotation study while the cereal rotation samples were assayed for ß-D-cellobiohydrolase (CBH), ß-Xylosidase (BX), and PHN.OX activity. Canola and corn grown continuously vs. in rotation had inconsistent impacts on microbial community composition and appeared to respond more strongly to the time of sample collection than crop rotation. Extracellular enzyme activity was impacted greatest by location, sampling time, and crop growth stage rather than crop rotation. There were no differences found in soil organic C (SOC) storage in either POM or MAOM C pools in response to long-term crop rotation practices indicating that although continuous monocropping is not recommended as a best practice agronomically, it does not impact the quantity of C stored in the functionally-relevant pools. The amount and proportion of MAOM C (mg C g-1 soil) was consistently greater than POM C content across all crop rotation systems and field sites. From these results we determined the dominant driving factors to microbial dynamics and SOC storage in our studies were soil moisture and edaphic soil properties, as moisture levels are key determinants of microbial activity, community dynamics and SOM turn over. Although these experiments had been ongoing for many years, the studies analyzed in this work may not be long enough in length to assess changes in SOM C storage in agricultural soils. While changes in SOM have been observed over time in response to land management practices, these changes are slow and gradual. In our studies the change implemented was one management factor, rotation, where the length of time our observations occurred over may not be long enough for the rotational practices tested in our studies to impact SOM C storage.
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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 | 0.001 | 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 | 0.001 | 0.001 |
| 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".