Effects of lime additions on the availability of phosphorus and sulphur in some temperate and tropical acid soils
1991
Haynes, R.J. | Naidu, R.
The effects of lime additions on phosphate adsorption and availability in acid soils from both New Zealand and Fiji were examined. In addition, the effects of both lime and phosphate additions on sulphate adsorption and S mineralization were studied. Liming caused decreases in phosphate adsorption in some soils, increases in others and had no significant influence on adsorption in still others. Decreased adsorption was explained in terms of the surface charge on soil colloids becoming more negative following liming. Where phosphate adsorption was increased, this was attributed to polymerization of exchangeable Al, and Al associated with organic matter, to from hydroxy-Al species as the pH was raised. The hydroxy-Al represents new, highly active, adsorption surfaces in limed soils. The effects of liming on phosphate adsorption and extractability were not great and the major agronomic effect of liming was to alleviate Al toxicity and allow the plants to make effective use of available soil phosphate. Additions of both lime and phosphate reduced the sulphate adsorption capacity of all the soils and therefore their ability to retain sulphate against leaching. Additions of lime and phosphate, however, also resulted in net mineralization of soil organic S and the accumulation of sulphate in the soil. Thus, avoidance of overliming and timing of lime and phosphate applications to avoid leaching will result in maximum benefit to the S nutrition of crops.
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