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Date Last Edited:  08/27/2001


N. V. Hue* and D. L. Licudine
* Dep. of Agronomy and Soil Science, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, Honolulu, Hawaii 96822

Journal of Environmental Quality. Volume 28, no. 2, Mar.-Apr.1999.

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-l, with CaSO4 and CaCO3, each at 5.56 cmol (1/2 Ca2+) kg-l, on Al and Ca concentrations in the subsoil of an Ultisol having pH 4.4, 80% Al saturation and 2.78 cmol, kg-l exchangeable Al. Treatments were incubated moist for 14 d with the top 5 cm soil of 50 cm long soil columns, then leached with 37.8 cm of water in 5 d. The soil columns were then cut into four equal segments for chemical analysis. Results showed that the manures were effective in increasing soil-solution pH and Ca, and decreasing soil-solution AI and percentage of AI saturation in the subsoil, particularly below the 15 cm depth. Soil-solution C, nearly constant through the soil profile, averaged 2.8 mM in the CaSO4 treatment and 7.6 mM in the chicken manure treatment. A subsequent solution experiment on the competitive complexation of Al and Ca with model organic ligands supported the contention that (i) manure-derived organic molecules facilitated the downward movement of Ca as Ca complexes, and (ii) along their downward path, these Ca complexes reacted with AI, releasing Ca that would become plant-available, and forming complexed AI that may be nonphytotoxic.

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

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