A Comparison of Strategies for Ameliorating Subsoil Acidity II. Long‐Term Soil Effects

Abstract

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 CaCl2 was accompanied by pHw increases of ≈0.4 units, by similar increases in ΔpH (pHw − pHs), by depressions in exchangeable acidity of as much as 1.5 cmolc 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 NO3 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.

Surface application of gypsum in low acidic Oxisol under no-till cropping system

“…In several field studies a gypsum application increased corn yields (Caires et al, 1999;Farina et al, 2000a;Caires et al, 2004), but not soybean yields (Quaggio et al, 1993;Oliveira and Pavan, 1996;Caires et al, 2003Caires et al, , 2006. Gypsum may increase crop yield due to increase of Ca and sulfate (SO 4 2-) available to the plants (Caires et al, 2002(Caires et al, , 2004.…”

High clay contents, dense soils, and spatial variability are the principal subsoil constraints to cropping the higher rainfall land in south-eastern Australia

“…Incorporation of gypsum at depth (MacEwan et al 1992) and gypsum analogues (Jagadeeswaran et al 2002) have been used to stabilise sodic subsoils. Surface application of gypsum has also been demonstrated to increase the benefits of liming on acidity (Farina et al 2000a(Farina et al , 2000b. Gypsum also has a role in dealing with transient salinity by enhancing leaching of salts from the subsoil (Kelly and Rengasamy 2006).…”

“…Rates of gypsum commonly applied range from 1 to 5 Mg/ha, with the higher rates usually confined to research trials. Much higher rates may be needed to fully ameliorate the soil profile as experiments overseas have demonstrated (for example, Toma et al 1999;Farina et al 2000b).…”

“…Research into the combined effects of lime and gypsum has been conducted overseas and in Australia, often in combination with tillage treatments such as ripping and slotting to overcome physical constraints and to facilitate lime distribution through the profile. Subsurface incorporation of lime and gypsum have been demonstrated to be effective for amelioration of subsoil acidity (Coventry 1991;Farina et al 2000b). Differences in responses between soil types in the same region have been found (Ellington 1986) and so management prescriptions are not simple or predictable at present.…”

High-Yielding Performance of A New Rice Variety, Ir53650In Mildly Improved Acid Sulfate Soil Conditions

“…Acid sulfate soil is one of the problem soils in the tropical Asia and Africa, which is formed by oxidation of upcoming iron sulfate and pyrite from the bottom of ancient seas or lagoons (Suthipradit et al, 1995;Farina et al, 2000). In most cases, pH of acid sulfate soil becomes as low as nearly 3.0, and it causes low productivity in many kinds of the crops (Attanandana et al, 1999).…”