Iron plaque on root surface (DCB-Fe) (p < 0.01) increased as a result of biochar amendments. The maximum increase was a factor
2.1 when using fine straw-char (Table 1). Fine straw-char application resulted in more DCB-Fe (1.6 vs 1.2 mg g 1) than the coarse
fraction, though for bran-char the fine fraction produced less than
the coarse fraction (0.8 vs 1.0 mg g 1)