Effects of organic and inorganic calcium compounds on soil-solution pH and aluminium concentration

Berlin

1995

S. 53-63

5 Abb., 1 Tab., 39 Lit. Ang.

Artikel aus einer ZeitschriftUnselbständiges Werk

200151985

The reactions of two organic (citrate and fulvate) and two inorganic (chloride and phosphogypsum) calcium compounds were studied during leaching of columns of unsaturated acidic soil. The potential of these compounds to decrease the aluminium concentration in the soil solution and remove exchangeable aluminium, and their effects on soil acidity are described. The calcium citrate solution increased the soil solution pH from 5 to a maximum value of 7 in the upper portion of the column. In contrast, the fulvate, calcium chloride and phosphogypsum solutions had little effect on soil-solution pH. Treatment with calcium citrate, or fulvate solution that contained 51 mm Na, removed most of the exchangeable aluminium from the column. The cation exchange sites in the upper portion of the column were saturated with calcium, and the cation exchange capacity of the soil was increased from 35 to c. 80 mmolc kg−1 in the calcium citrate treatment. Leachate from this treatment contained low (< 2 mm) calcium concentrations and high aluminium concentrations. In contrast, the above changes were not shown by the calcium chloride and phosphogypsum treatments. In these treatments the calcium concentration in the leachate was equal to that in the inflowing solution, which indicated that calcium was transported through the entire column. These results suggest that calcium alone was ineffective in displacing aluminium from the cation exchange sites and a strong complexing agent such as citrate or fulvate is needed to mobilize the exchangeable aluminium.