Correlation between root nodule bacteria and total nitrogen (TN), pH value and moisture in TP soil samples. Burk, Burkholderia; Brady, Bradyrhizobium; Meso, Mesorhizobium; Rhi, Rhizobium; Sino, Sinorhizobium; Azo, Azorhizobium. Blue curves show normal distribution of values in each sample. Pearson index was used to evaluate the level of correlation. Backslash lines indicate negative correlation (r = 0.45 ~ 0.79, P < 0.05).