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Table 4 Fe recovered (%) from iron–humate complexes formed with HA2, after a first (I) and a second (II)a extraction at different hours of shaking (h), with a solution of the siderophore DFOM and a mixture of four organic acids: citric, oxalic, tartaric and ketoglutaric acids (Mix) at different concentrations

From: Potential alteration of iron–humate complexes by plant root exudates and microbial siderophores

Extractant h Concentration
0.01 M 0.001 M 0.0001 M
I II I II I II
DFOM 1 1.3 a 1.8 a 1.0 a 0.8 a 0.7 a 0.9 ab
2 3.1 a 2.4 a 2.2 ab 1.1 a 1.1 abc 0.7 a
4 4.0 a 2.7 a 2.6 ab 1.1 a 1.3 bcde 1.2 bcd
16 9.2 a 7.4 a 3.8 bc 3.3 bc 1.8 f 1.7 ef
Mix 1 26.6 b 25.4 b 5.4 cd 6.5 de 1.1 abc 1.5 cdef
2 42.0 c 38.1 c 6.9 de 7.7 e 1.5 cdef 2.3 g
4 53.5 d 37.9 c 7.0 de 10.3 f 1.6 def 2.5 gh
16 66.7 e 23.3 b 15.8 g 15.5 g 2.8 ih 3.1 i
  1. All values are average of three replications. Values followed by the same letter within columns are not significantly different by Tukey’s test at the level of P ≤ 0.05
  2. aFe recovered after the second extraction was calculated on the amount of iron left in the complexes after the first extraction