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Table 1 Yield, ash content, and elemental composition of the humic fractions

From: Chemical and spectroscopic characterization of insoluble and soluble humic acid fractions at different pH values

Fraction

Yield (g kg−1soil)

Asha(g kg−1humic fraction)

Elemental compositionb(g kg−1humic fraction)

Molar ratio

   

C

H

N

O

O/C

pH 1

Insoluble

83.9

247

541a

42a

43a

374a

0.5

Soluble

2.3

196

478bd

44a

43a

434bc

0.7

pH 3

Insoluble

88.0

267

525a

45a

42a

388ab

0.5

Soluble

7.2

127

493bc

41a

45a

421abc

0.6

pH 5

Insoluble

22.2

542

478bd

55b

40a

427bc

0.7

Soluble

60.3

225

518ac

49b

41a

392ab

0.6

pH 7

Insoluble

7.4

609

451d

52b

39a

459c

0.8

Soluble

67.3

283

534a

49b

42a

375a

0.5

  1. aValues are the means of three replicates, and the standard error values are < 10%; bon a moisture and ash-free basis. Within columns, values followed by the same letter are not significantly different (P < 0.05).