Effect of nitrogen source and calcitic lime on soil pH and potato yield, leaf chemical composition, and tuber cadmium concentrations

Three glasshouse experiments, using light textured soils, were conducted to investigate the effects of nitrogen (N) source and calcitic lime on i) soil pH(W) (soil pH in water), ii) tuber yield, iii) leaf chemical composition, and iv) cadmium (Cd) accumulation in tubers of the potato (Solanum tuberosum L.) cultivars Russet Burbank and Atlantic. The N sources applied were calcium nitrate, ammonium nitrate, urea, and ammonium sulfate. Rates of calcitic lime ranged from 0 to 20 tha(-1). Liming increased soil pH(W) values up to 2.8 units, and depending on sampling time, differences in soil pH(W) of up to 1.8 units occurred between the N sources. In 2 of the 3 experiments there was a significant interaction between lime and N source in their effects on tuber yield. When calcium nitrate was the N source, timing decreased tuber yields. In contrast, with ammonium sulfate yield increased. The effects of liming and N source on the chemical composition of the 5th leaf were not consistent between experiments. Liming significantly decreased potassium (K), sulfur (S), boron (B), and manganese (Mn) concentrations and increased calcium (Ca) and magnesium (Mg) concentrations. The application of ammonium sulfate consistently decreased Ca and Mg concentrations in the 5th leaf compared with calcium nitrate. Liming significantly decreased tuber Cd concentrations in all experiments. The use of calcium nitrate as the N source resulted in significantly higher Cd concentrations in tubers compared with ammonium sulfate when no calcitic lime was applied. It is possible that Ca added in this fertilizer enhanced Cd uptake through displacement of Cd from soil surfaces.