Reclamation of Alkali Soils: Influence of Amendments and Leaching on Transformation and Availability of Phosphorus
Notice bibliographique
Résumé
Abstract Phosphorus (P) availability to plants in reclaimed alkali soils was the main objective of this study, which was also focused on P transformations, decrease in Olsen‐P content, and magnitude of P lost in leachate in course of amendment application and leaching. Liquid sodium bicarbonate (NaHCO3) was added to nonalkali soils to set up four ESP (exchangeable sodium percentage) levels (viz., 2.9, 25.0, 50.0, and 75.0), but actual ESP levels obtained were 2.9, 24.6, 51.2, and 75.3. Amendments (viz., gypsum and pyrites) and P treatments (viz., 0 and 50 mg P Kg−1) were mixed with dry, sieved soil before filling into PVC (polyvinyl chloride) drainage columns, which were then compacted to uniform bulk density and leached with deionized water for 30 days. Results indicated that the pH and electrical conductivity (EC) of the soils increased with increase in ESP level of the soil but decreased with amendment application. Phosphorus addition to alkali soils decreased the pH on day 30, but it could not affect the EC of the soils. Successive increase in the ESP level of the soil increased the pH and EC off the leachate. Gypsum‐amended soils exhibited lower pH and EC values than pyrite‐amended soils. The EC of the leachate decreased sharply with time in amended soils, but the pH decreased slowly. Phosphorus addition affected the leachate pH earlier than the soil pH. Cumulative volume of leachate decreased with increasing ESP levels, but it increased with amendment and phosphorus application. Leaching of P increased with increase in ESP levels, and the maximum cumulative loss of P was 11.2 mg Kg−1 in the 75.3 ESP soil. Cumulative P lost in the pyrite‐amended soils was higher than the gypsum‐amended soils. Phosphorus leaching in the gypsum‐amended soils stopped at day 10 and beyond, but it continued until day 30 in the pyrite‐amended soils. Part of the applied P in alkali soils was also lost along with the native P, whereas it was protected in the nonalkali soils. OlsenP increased with increasing ESP levels, and alkali soils invariably contained higher Olsen P than nonalkali soils. At day 30, alkali soils contained much higher Olsen P (12.6 mg Kg−1) than nonalkali soils (5.9 mg Kg−1). In general, there was a decrease in the Olsen P with both of the amendments, but it decreased more with pyrites than with gypsum. Phosphorus added through monopotassium phosphate (KH2PO4) remained extractable by Olsen's extractant up to day 30. Results also indicated that percent distribution of ammonium chloride (NH4Cl)‐P, calcium (Ca)‐P, and unknown P increased with rising ESP levels but iron (Fe)‐aluminum (Al)‐bound P and residual P decreased. Percent distribution of Ca‐P and unknown P exhibited an increase with time also. Unamended alkali soils contained more NH4Cl‐P than amended ones. Iron and Al‐ bound P and residual P increased more with pyrites, whereas formation of Ca‐P and unknown P was enhanced with gypsum. Applied P tended to convert more into NH4Cl‐P, Ca‐P, and residual P than to Fe‐Al‐bound P or unknown P fractions. Models developed to estimate Olsen P and P concentration in leachate, through pH or EC, have application value for P management in alkali soils that are leached after application of amendments. Keywords: Exchangeable sodium percentagephosphorussalt Acknowledgements S.M.Misra express his deep sense of gratitude to the Director, Indian Grassland and Fodder Research Institute, Jhansi, for granting the study leave for completion of the project and to the Indian Council of Agricultural Research, New Delhi, for awarding the senior research fellowship to meet the contingent requirements. S.M.Misra is also indebted to Biplav Misra for his involvement in the project from the very beginning and his assistance in data‐management procedures and model fitting and for critical reading of the manuscript.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,003 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».