Long-term effects of liquid hog manure on the phosphorus status of a silt loam cropped to corn
Bibliographic record
Abstract
Repeated application of animal manure or mineral P fertilizer can significantly increase soil P content and enhance the risk of water contamination. The objectives of this study were to evaluate the long-term (8 yr) effect of liquid hog manure (LHM) applied at high rates and its timing of application on the soil P status and on the risk index of water contamination by P. Spring (S), fall (F), or spring + fall (SF) applications of LHM on a silt loam (Humo Ferric Podzol) were compared to recommended application rates of mineral fertilizer (MF) in a continuous corn (Zea mays L.) system. Total P applied ranged from 7 to 34 kg P ha-1 yr-1 in the MF treatment and from 106 to 150 kg P haP ha-1 yr-1 in the LHM treatments. Soil samples were collected to 1.0-m depth after one, six and eight annual applications. Applying high rates of LHM for 8 consecutive years resulted in a significant (P ≤ 0.10) enrichment in total soil P content relative to MF at the 0- to 20-cm soil depth. The effects of LHM on labile P forms (water soluble P, Pw and Mehlich-III extractable P, M3P) were also restricted to the 0- to 20-cm depth with values as high as 11 mg kg-1 for Pw and 241 mg kg-1 for M3P in the LHM plots. The degree of soil P saturation, evaluated as Pox/(Alox+Feox), increased to 15% in the 0- to 20-cm depth after 6 to 8 yr of LHM application. Saturation values of 12 to 15% were also found at the 80- to 100-cm depth in some LHM plots. The P index rating was always medium (109 to 216) in soil receiving MF but was high (217 to 432) after 6 to 8 yr of heavy LHM applications, which indicates a high potential risk of soil P transfer to surface water. The results of this study showed that timing of application had little influence on long-term soil P status. Overall, applying LHM at high rates greatly increased total soil P, the degree of soil P saturation, and the labile P forms in the surface horizons but had little effects below 20 cm. Key words: Hog manure, soil P, long-term effects, labile P, P saturation
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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 | 0.000 | 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 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".