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Although chlorites are an important source of Mg and micronutrients in soils, little is known about their weathering behavior in acidic environments. The effect of organic (acetic, oxalic, citric) and inorganic (hydrochloric, nitric, sulfuric) acids on the dissolution of ripidolite was studied at 25[degrees]C over an acid concentration range of 0.03 to 10 mM. The increasing ripidolite dissolution with increasing acid concentration can be described by the same empirical equation for all six acids used in this study. Because proton and ligand promoted dissolution mechanisms are additive, the influence of ligands can be calculated by subtracting the influence of protons from the total dissolution of ripidolite. We assume that the influence of [Cl.sup.-] in HCl systems can be neglected. Greater dissolution of ripidolite in the presence of the other acids at the same pH is attributed to the accompanying anion. At pH 3.5 and an anion concentration of [10.sup.-3.5] mol [L.sup.-1], the relative effectiveness of the acids used in this experiment in promoting dissolution was nitric (enhancement factor: 0.97) [congruent to] hydrochloric (1.00) [congruent to] acetic (1.01) < sulfuric (1.19) < citric (2.70) < oxalic acid (3.27). The dissolution of ripidolite was nonstoichiometric with a preferential release of Si relative to Al, Fe, and, in some cases, Mg at low proton and ligand concentrations for all six acids. At higher acid concentrations the dissolution becomes almost stoichiometric in the presence of inorganic acids, whereas in the presence of oxalic acid Al, Fe, and Mg were released preferentially relative to Si. In the presence of citric acid, Fe is released preferentially relative to Si. The alteration of chlorites in soils and the amount of released elements into the soil solution therefore depends on the composition of acidifying agents in soils.

The effects of soil acidity on rates of nitrogen release from various ureaform fractions are discussed. The cold water soluble, hot water soluble and the soluble in hotwater but not cold water fractions of a ureaform were analyzed of nitrogen content. Fitting linear increase and plateau models estimated the rate of nitrogen release. Adjustments in rates of applications were found to be necessary for the successful use of ureaform fertilizers.

A test experiment involving the the relative effects of acidity and ionic strength on the chemistry of leachates from fresh, intact forest floor covers is discussed. Acidic and nonacidic treatments were conducted at each concentration. The chemical composition of field-extracted soil solutions were compared with laboratory leachates. Results indicate that the ionic strength ofincoming leaching water determined the downward movement of acidity in soils.

The influence of solution acidity and concentration on ion transport in an allophanic Andisol under saturated and unsaturated conditions is discussed. Anion-exchange capacity, cation-exchange capacity and the exchange isotherms were measured under different acidity conditions and concentrations. The resulting measurements were compared with breakthrough curves. The effect of both solution parameters were found to be significant.

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.sup.-1] of lime to different depths, (ii) incorporating 25 Mg [ha.sup.-1] of lime to about 0.5 m, and (iii) conventionally incorporating 15 Mg [ha.sup.-1] of lime plus 10 Mg [ha.sup.-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 Ca[Cl.sub.2] was accompanied by [pH.sub.w] increases of [approximately equals] 0.4 units, by similar increases in [Delta]pH ([pH.sub.w] - [pH.sub.s]), by depressions in exchangeable acidity of as much as 1.5 [cmol.sub.c] [L.sup.-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 N[O.sub.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.