The effect of nitrogen fertilization and no‐till duration on soil nitrogen supply power and post–spring thaw greenhouse‐gas emissions
Bibliographic record
Abstract
Abstract With a world population now > 7 billion, it is imperative to conserve the arable land base, which is increasingly being leveraged by global demands for producing food, feed, fiber, fuel, and facilities ( i.e. , infra‐structure needs). The objective of this study was to determine the effect of varying fertilizer‐N rates on soil N availability, mineralization, and CO 2 and N 2 O emissions of soils collected at adjacent locations with contrasting management histories: native prairie, short‐term (10 y), and long‐term (32 y) no‐till continuous‐cropping systems receiving five fertilizer‐N rates (0, 30, 60, 90, and 120 kg N ha –1 ) for the previous 9 y on the same plots. Intact soil cores were collected from each site after snowmelt, maintained at field capacity, and incubated at 20°C for 6 weeks. Weekly assessments of soil nutrient availability along with CO 2 and N 2 O emissions were completed. There was no difference in cumulative soil N supply between the unfertilized long‐term no‐till and native prairie soils, while annual fertilizer‐N additions of 120 kg N ha –1 were required to restore the N‐supplying power of the short‐term no‐till soil to that of the undisturbed native prairie soil. The estimated cumulative CO 2 ‐C and N 2 O‐N emissions among soils ranged from 231.8–474.7 g m –2 to 183.9–862.5 mg m –2 , respectively. Highest CO 2 fluxes from the native prairie soil are consistent with its high organic matter content, elevated microbial activity, and contributions from root respiration. Repeated applications of ≥ 60 kg N ha –1 resulted in greater residual inorganic‐N levels in the long‐term no‐till soil, which supported larger N 2 O fluxes compared to the unfertilized control. The native prairie soil N 2 O emissions were equal to those from both short‐ and long‐term no‐till soils receiving repeated fertilizer‐N applications at typical agronomic rates ( e.g. , 90 kg N ha –1 ). Eighty‐eight percent of the native soil N 2 O flux was emitted during the first 2 weeks and is probably characteristic of rapid denitrification rates during the dormant vegetative period after snowmelt within temperate native grasslands. There was a strong correlation ( R <?h.3> 2 0.64; p < 0.03) between measured soil Fe‐supply rate and N 2 O flux, presumably due to anoxic microsites within soil aggregates resulting from increased microbial activity. The use of modern no‐till continuous diversified cropping systems, along with application of fertilizer N, enhances the soil N‐supplying power over the long‐term through the build‐up of mineralizable N and appears to be an effective management strategy for improving degraded soils, thus enhancing the productive capacity of agricultural ecosystems. However, accounting for N 2 O emissions concomitant with repeated fertilizer‐N applications is imperative for properly assessing the net global warming potential of any land‐management system.
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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 | 0.000 |
| 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".