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Date Last Edited:  08/24/2001


J. Liu and N.V. Hue

Biology and Fertility of Soils (1996) 21:264-270

Subsoil acidity is a serious constraint to crop production, and is difficult to correct by conventional liming practices. Thus, a different approach to ameliorating acid subsoils was evaluated. Subsoil material of an acid Ultisol (pH 4.4) was packed into 50-cm long columns, then leached with solutions of CaCl2, CaCO3 (suspension) or Ca fulvates prepared from chicken manure, cowpea green manure, or sewage sludge. The total water applied was 30.26 cm (or 800 ml) in 2 days. Thereafter, the columns were dismantled and cut into 5-cm segmanets for chemical analysis. The results indicated that only 2% of the added Ca from CaCO3 moved past the 15-cm depth, compared to 68% from CaCl2 and 35-75% from Ca fulvates. Correspondingly, CaCO3 precipitated all KCl-extractable A1 in the top 5 cm, but had no effect beyond the 10-cm depth. The CaC12 displaced a small but significant portion of extractable Al from the top 15 cm and redeposited some of the Al in lower depths. Similar to CaCO3, Ca fulvates from chicken manure and green manure only decreased extractable Al significantly in the top 10-cm layers, but had little effect eyond that depth. By contrast, the Ca fulvate from sewage sludge decreased Al down to the 45-cm depth. In terms of reducing Al saturation as a percentage of total extractable cations (effective cation exchange capacity), the Ca fulvates were as effective as CaCO3 in the 0- to 5-cm layer, and more effective than CaCl2 in any soil layer because of the increased exchangeable Ca and/or decreased Al. In general, surface application of common organic material-derived Ca fulvates can increase subsoil Ca and decrease the Al saturation percentage. However, Mg depletion and enrichment of unwanted metals (e.g., Na or heavy metals) may be a problem when leaching with these organic sources.

Amelioration of Subsoil Acidity through Surface Application of Animal Manures


Agronomy Abstract, p. 242, 1996.

Subsoil acidity is a serious constraint to crop production, and is difficult to correct by conventional liming practices. Thus, different approaches to ameliorating acid subsoils are needed. A column leaching study was conducted to compare the effects of chicken manure and sewage sludge amendments, each at 20 g kg-1, with gypsum and CaCO3, each at 5.56 cmolc kg-1, on increasing Ca and decreasing Al concentrations in the subsoil of an Ultisol having pH 4.3, 80% Al saturation and 2.78 cmolc kg-1 exchangeable Al. Treatments were mixed with the top 5-cm soil of 50- cm long soil columns, then leached with 37.8 cm of water in 5 d. Results showed that the manures were more effective than lime or gypsum in increasing soil-solution pH and Ca, and decreasing soil-solution Al and percentage of Al saturation in the subsoil, particularly below the 15-cm depth. Soil-solution C, nearly constant across the soil profile, averaged 2.8 mM in the CaSO4 treatment and 7.6 mM in the chicken manure treatment. Apparently organic molecules produced by the manure decomposion helped facilitate the downward movement of Ca as Ca chelates.

For more information regarding this page, please send e-mail to nvhue@hawaii.edu.

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