FIG. 3.

Effects of different microbial inocula on extractable NH₄⁺ levels in the upper layer (0 to 3 mm) (A) and the lower layer (10 to 13 mm) (B). Open bars, sterilized soil inoculated with protists and bacteria (treatment P+B); solid bars, sterilized soil inoculated with bacteria (treatment B); cross-hatched bars, control. The values are means ± standard errors (n = 3). Columns marked with different letters are significantly different (P < 0.05, as determined by Tukey's honestly significant difference test). dw, dry weight.