Assessing environmental impacts of agricultural water table management: A global meta-analysis
Bibliographic record
Abstract
Global climate change intensifies the need for adaptive water management in agriculture, particularly as extreme rainfall and drought events jeopardize yield stability and water quality. This study provides a comprehensive global meta-analysis comparing controlled drainage (CD) and controlled drainage with subirrigation (CDSI) against free drainage (FD), based on 84 publications encompassing 52 sites (1788 paired site-years). Overall, both CD and CDSI significantly reduced subsurface drainage discharge and nutrient losses (NO₃⁻, TN, DRP, TP) compared to FD, while improving crop yields. CD had no significant effects on surface runoff or surface NO₃⁻ loss, and CDSI increased both. Neither practice significantly influenced subsurface NH₄⁺, PP, or DP losses, and CDSI showed only limited evidence for CH₄ reduction, with no consistent effects on other greenhouse gases. Significant differences between CD and CDSI were observed only for subsurface NO₃⁻, TN, and TP losses, with CDSI achieving greater reductions in NO₃⁻ (CD: 59.4 %, CDSI: 72.5 %) and TN (CD: 16.3 %, CDSI: 55.9 %), whereas CD was more effective in reducing TP (CD: 56.8 %, CDSI: 28.6 %). Moderator effects revealed notable patterns. Crop types influenced subsurface drainage discharge under both CD and CDSI, with small grain crops producing the largest reductions (CD: 68.1 %, CDSI: 83.6 %). Under CDSI, drainage responses were further shaped by N input rate, with higher inputs associated with greater reductions (77.3 %). For CD, subsurface NO₃⁻ loss was strongly affected by precipitation and soil texture, with wetter years (79.2 %) and medium-textured soils (63.6 %) offering the greatest reduction potential. This study presents the first comparative assessment of the environmental impacts of CD and CDSI, highlighting their context-dependent nature and providing insights to inform more informed drainage management decisions. • First comparative assessment of impacts and moderators for controlled drainage and controlled drainage with subirrigation. • Both practices reduced subsurface drainage and nutrient losses relative to free drainage, while also improving crop yields. • Controlled drainage with subirrigation cut nitrate and total nitrogen most; controlled drainage cut total phosphorus most. • Crop types affected subsurface drainage under both ; nitrogen input affected drainage under controlled drainage with subirrigation. • Precipitation and soil texture shaped subsurface nitrate loss under controlled drainage.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".