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 due to fertilization with phosphatic fertilizers that contained Cd as an impurity. Nine field and seven glasshouse experiments using light-textured soils were conducted to investigate the effect of current-season applications of calcitic lime on i) soil pH(w), ii) tuber yield, and iii) Cd accumulation in tubers of a range of processing (Russet Burbank, 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 liming. Under glasshouse conditions, significant reductions in tuber Cd concentrations were found after liming of soils. In contrast, in the field, application of calcitic lime at rates up to 20 t ha(-1) had either no effect or significantly (p < 0.05) increased tuber Cd concentrations. Concentrations of Cd in tubers were closely correlated (R-2=0.74, p < 0.001) with concentrations of chloride (Cl). The lack of any beneficial effect of lime application in reducing tuber Cd concentrations under field conditions is attributed to a combination of ineffective mixing of lime throughout the whole root zone, inadequate time of reaction of lime with soil, competitive desorption of Cd2+ by Ca2+ and low soil moisture inhibiting lime dissolution under field conditions. Further work is required to resolve which mechanisms are most important.