Chemical composition of saturation paste extracts of a Fijian Oxisol after liming and repeated wetting and drying. (29)


  • R. Naidu School of Pure and Applied Sciences, University of the South Paciifc, Box 1168 Suva, Fiji
  • R.J. Haynes New Zealand Institute for Crop & Food Research, Canterbury Agriculture and Science Centre, Private Bag 4704, Christchurch, New Zealand


Aluminium, Anions, Cations, Calcium, Lime· Manganese, Phosphorus, Potassium, Soil acidity, Soil solution


The effects of liming and incubating an Oxisol, either in a continuously moist state or subject to periodic drying and rewetting, on the nutrient composition of saturation paste extracts was investigated. The soil used was acid (pHH2O 4.5), had a relatively high soil organic matter content (9.6% organic C), and was typical of soils presently being cleared for sugar cane production. Liming resulted in an increase in the concentration of solution Ca2+ and a decrease in solution Mg2+ as the net negative charge on variable charge colloids increased. Concentrations of solution K+ decreased between pH 5 and 6 but then increased again. Liming markedly decreased concentrations of solution Al, Mn2 +, and SiO32-. Concentrations of solution phosphate increased between pH 5 and 5.8, then decreased as pH approached 6 before increasing again above pH 6.6. Levels of NO3- and SO4 2- in soil solution were raised as soil pH increased. Addition of phosphate to the soil increased concentrations of NO3, SO42-, and SiO32- in soil solution but reduced those of Al. Drying and rewetting increased pH by about 0.1 pH unit, decreased concentrations of solution Ca2+, Mg2+, Al, and SiO32-, and increased those of Mn2+, NO3-, and SO42-. The results demonstrated the complex pattern of change in nutrient concentrations in soil solution that can occur when a highly weathered tropical soil is limed. It is evident, however, that when soils such as this Oxisol are brought under cultivation, the major factors limiting production are Al toxicity and P and Ca deficiencies.



Research Papers