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A Comparison of Strategies for Ameliorating Subsoil Acidity II. Long‐Term Soil Effects
Author(s) -
Farina M. P. W.,
Chan P.,
Thibaud G. R.
Publication year - 2000
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2000.642652x
Subject(s) - lime , subsoil , gypsum , soil ph , saturation (graph theory) , soil water , chemistry , sorption , soil horizon , environmental chemistry , soil acidification , dissolution , soil science , mineralogy , sulfate , cation exchange capacity , geology , adsorption , mathematics , paleontology , organic chemistry , combinatorics
Acid‐subsoil amelioration is complicated by differences in the efficacy of lime and gypsum across the diverse soil environments in which the problem occurs. This study was conducted to explain long‐term growth responses to lime and gypsum on a Plinthic Paleudult of mixed clay mineralogy. In a 10‐season experiment that monitored treatment effects on profile chemical properties, we compared the effects of (i) incorporating 15 Mg ha −1 of lime to different depths, (ii) incorporating 25 Mg ha −1 of lime to about 0.5 m, and (iii) conventionally incorporating 15 Mg ha −1 of lime plus 10 Mg ha −1 of gypsum. Even at the highest application rate, lime had minimal effects on acidity below the depth of incorporation. Gypsum, however, markedly improved the rooting environment to a depth of 0.75 m. Sulfate sorption against extraction with dilute CaCl 2 was accompanied by pH w increases of ≈0.4 units, by similar increases in ΔpH (pH w − pH s ), by depressions in exchangeable acidity of as much as 1.5 cmol c L −1 , and by decreases in acid saturation of more than 30%. The rate of subsoil amelioration was, however, much slower than that reported in more intensely weathered soils of similar texture. Only in the sixth season were benefits evident in the 0.60‐ to 0.75‐m horizon, and acidity in the 0.75‐ to 0.90‐m horizon actually increased significantly. It is speculated that this resulted from NO 3 accumulation and ionic strength–induced dissolution of interlayer Al. These findings indicate that acid‐subsoil amelioration in soils with Al‐hydroxy–interlayer minerals requires greater quantities of gypsum than soils that are dominantly kaolinitic.