Soil NO3−-N concentrations (mg kg−1) at the soil depths of 0–10, 10–20 and 20–30 cm in spring (May 9), summer (July 19) and autumn (September 14) of 2004 for control and rhizome severing treatments.

Values shown in the table are the mean ± SE of five independent replicates. In each horizontal row, the values with the same superscript letters are not significantly different from each other at P = 0.05.

表格中所示数值为五次独立重复实验的平均值±标准误（Standard Error，SE）。在每一行中，带有相同上标字母的数值在P=0.05显著性水平下彼此无显著差异。