The effects of a compost (produced from by-products of the olive oil industry) and a poultry manure on mineral ion solubility and exchangeability in a highly saline agricultural soil (electrical conductivity for a 1:5 soil:water extract=1.85 dS m(-1)) from Murcia (SE Spain) were studied. The organic amendments did not change significantly the soil electrical conductivity or the soluble Na(+), Ca(2+) or Mg(2+). Only soluble K(+) increased, due to the K(+) supplied by the amendments. The cation exchange capacity increased in treated soils, the exchange complex being mainly saturated with Ca(2+), Mg(2+) and K(+). However, Na(+) was not retained in the exchange sites, and the sodium absorption ratio remained low. The compost and manure increased markedly the shoot growth of the salt-tolerant Beta maritima L. (sea beet) and Beta vulgaris L. (sugar beet). For B. maritima, this seemed to be related to decreases in the shoot concentrations of Na(+) and Cl(-) and increases in K(+) and H(2)PO(4)(-). In the case of B. vulgaris, increases in shoot H(2)PO(4)(-) and B and, for manure-treated soil, a decrease in shoot Na(+) may have been involved. Cultivation of tomato (Lycopersicon esculentum Mill. cv. Moneymaker) in the soil used previously for B. vulgaris indicated that the effects of the manure on tissue cation concentrations were longer-lasting than those of the compost.