15N tracer technique analysis of the absorption and utilisation of nitrogen fertiliser by potatoes

Field experiments using the potato variety Kexin No. 13 were carried out on calcic chernozem soils in western Songnen Plain, China. The accumulation, absorption ratio and distribution of nitrogen-15 isotope (N-15), as well as the nitrogen (N) fertiliser utilisation rate in the potato plants were examined by the N-15 tracer technique. The results revealed that the N contents of the aboveground parts, tuber and roots of the potatoes increased with increased N fertiliser application. The potato yield also gradually increased with increased N application. In the N-15 micro-plot experiment with 90 kg hm(-2) pure N treatment, the N fertiliser and soil N absorbed by the potato plants accounted for 17-29 and 71-83 % of the total N, respectively. The N fertiliser and soil N absorbed by the potato plants were 0.19-0.58 and 0.45-2.74 g plant(-1), respectively. The N-15 fertiliser utilisation rate of whole potato plant was 10-32 % and was relatively low at the early stage. Soil N was an important N source at both early and late growth stages of the potato plants.