EFFECT OF CURRENT-SEASON APPLICATION OF CALCITIC LIME ON SOIL-PH, YIELD AND CADMIUM CONCENTRATION IN POTATO (SOLANUM-TUBEROSUM L) TUBERS

Cadmium (Cd) has accumulated in many agricultural soils in Australia d ue to fertilization with phosphatic fertilizers that contained Cd as a n impurity. Nine field and seven glasshouse experiments using light-te xtured soils were conducted to investigate the effect of current-seaso n applications of calcitic lime on i) soil pH(w), ii) tuber yield, and iii) Cd accumulation in tubers of a range of processing (Russet Burba nk, Atlantic, Shepody and Kennebec) and fresh market (Crystal, Pontiac and Desiree) potato cultivars. Liming increased soil pH values by up to 2 units. Yields of potato tubers were generally unaffected by limin g. Under glasshouse conditions, significant reductions in tuber Cd con centrations were found after liming of soils. In contrast, in the fiel d, application of calcitic lime at rates up to 20 t ha(-1) had either no effect or significantly (p < 0.05) increased tuber Cd concentration s. Concentrations of Cd in tubers were closely correlated (R-2=0.74, p < 0.001) with concentrations of chloride (Cl). The lack of any benefi cial effect of lime application in reducing tuber Cd concentrations un der field conditions is attributed to a combination of ineffective mix ing of lime throughout the whole root zone, inadequate time of reactio n of lime with soil, competitive desorption of Cd2+ by Ca2+ and low so il moisture inhibiting lime dissolution under field conditions. Furthe r work is required to resolve which mechanisms are most important.