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Table 6 Concentrations and percentages of organic P compounds in extracts of whole soil or residues, determined by solution P-NMR spectroscopy

From: Characterizing the phosphorus forms extracted from soil by the Mehlich III soil test

 

Extractant

 

AR-control

AR-N

AR-PL

AR-PL-alum

SK

PEI

Till Ref

Phosphonates

Mehlich III

Soil

1 (2)

2 (2)

5 (1)

5 (1)

1 (1)

2 (1)

0 (1)

 

NaOH-EDTA

Residue

2 (2)

2 (1)

4 (1)

8 (1)

3 (2)

3 (1)

2 (1)

 

NaOH-EDTA

Soil

2 (1)

5 (1)

5 (1)

8 (1)

5 (1)

5 (1)

3 (1)

Glucose 6-phosphate

Mehlich III

Soil

1 (1)

1 (1)

0 (0)

5 (1)

1 (1)

2 (1)

0 (1)

 

NaOH-EDTA

Residue

2 (1)

2 (1)

4 (1)

8 (1)

1 (1)

3 (1)

2 (1)

 

NaOH-EDTA

Soil

2 (1)

2 (1)

5 (1)

8 (1)

5 (1)

5 (1)

3 (1)

Choline phosphate

Mehlich III

Soil

1 (1)

1 (1)

0 (0)

5 (1)

1 (1)

0 (0)

0 (1)

 

NaOH-EDTA

Residue

4 (1)

5 (2)

4 (1)

8 (1)

3 (1)

3 (1)

4 (1)

 

NaOH-EDTA

Soil

5 (1)

4 (1)

5 (1)

8 (1)

2 (1)

5 (1)

3 (1)

Unknown 5.1 ppm

Mehlich III

Soil

1 (1)

1 (1)

3 (1)

5 (1)

2 (2)

0 (0)

0 (1)

 

NaOH-EDTA

Residue

4 (1)

5 (2)

8 (1)

8 (1)

8 (4)

6 (1)

28 (9)

 

NaOH-EDTA

Soil

11 (4)

9 (3)

10 (1)

25 (2)

15 (4)

11 (1)

10 (3)

Monoester 1

Mehlich III

Soil

1 (1)

1 (1)

3 (1)

5 (1)

1 (1)

2 (1)

0 (1)

 

NaOH-EDTA

Residue

2 (1)

2 (1)

4 (1)

8 (1)

1 (1)

3 (1)

2 (1)

 

NaOH-EDTA

Soil

2 (1)

4 (1)

5 (1)

8 (1)

5 (1)

5 (1)

3 (1)

Monoester 2

Mehlich III

Soil

2 (4)

3 (4)

8 (2)

30 (4)

6 (6)

3 (1)

2 (5)

 

NaOH-EDTA

Residue

9 (4)

18 (6)

12 (2)

91 (8)

11 (5)

6 (1)

32 (10)

 

NaOH-EDTA

Soil

21 (8)

18 (5)

14 (1)

41 (4)

25 (7)

16 (2)

25 (7)

Monoester 3

Mehlich III

Soil

2 (3)

2 (2)

3 (1)

5 (1)

2 (2)

2 (1)

0 (1)

 

NaOH-EDTA

Residue

2 (1)

5 (1)

4 (1)

8 (1)

3 (1)

11 (3)

4 (1)

 

NaOH-EDTA

Soil

5 (2)

7 (2)

10 (1)

8 (1)

5 (1)

5 (1)

5 (1)

Degradation

Mehlich III

Soil

3 (4)

3 (3)

3 (1)

15 (2)

5 (5)

3 (1)

1 (4)

 

NaOH-EDTA

Residue

23 (9)

27 (9)

20 (3)

54 (5)

17 (8)

17 (4)

68 (21)

 

NaOH-EDTA

Soil

25 (9)

24 (7)

26 (4)

58 (5)

45 (13)

27 (4)

27 (8)

DNA

Mehlich III

Soil

0 (0)

0 (0)

0 (0)

1 (1)

0 (0)

0 (0)

0 (0)

 

NaOH-EDTA

Residue

2 (1)

2 (1)

8 (1)

1 (0)

6 (3)

4 (1)

8 (2)

 

NaOH-EDTA

Soil

3 (1)

7 (2)

2 (1)

11 (1)

3 (1)

3 (0)

3 (1)

Other orthophosphate diesters

Mehlich III

Soil

1 (1)

1 (1)

2 (1)

4 (1)

1 (1)

1 (1)

1 (2)

NaOH-EDTA

Residue

3 (1)

4 (1)

17 (3)

7 (1)

6 (3)

5 (1)

21 (6)

 

NaOH-EDTA

Soil

11 (4)

10 (3)

16 (2)

21 (2)

9 (3)

8 (1)

5 (1)

Total orthophosphate monoesters

Mehlich III

Soil

27 (42)

29 (34)

37 (10)

308 (46)

21 (21)

22 (9)

6 (19)

NaOH-EDTA

Residue

70 (27)

99 (32)

117 (20)

520 (47)

60 (30)

84 (21)

117 (36)

 

NaOH-EDTA

Soil

103 (36)

129 (40)

109 (15)

385 (33)

116 (34)

133 (18)

102 (28)

 

NaOH-EDTA

Difference

33 (9)

31 (7)

− 7 (− 5)

− 134 (− 15)

55 (5)

48 (− 4)

16 (− 8)

Total orthophosphate diesters

Mehlich III

Soil

4 (6)

4 (5)

5 (1)

20 (3)

6 (6)

5 (2)

2 (6)

NaOH-EDTA

Residue

29 11)

33 (11)

45 (8)

62 (6)

29 (14)

25 (6)

96 (29)

 

NaOH-EDTA

Soil

39 (14)

42 (13)

49 (7)

90 (8)

57 (17)

37 (5)

35 (10)

 

NaOH-EDTA

Difference

10 (3)

9 (2)

5 (− 1)

28 (2)

28 (3)

12 (− 2)

− 61 (− 20)

Mono:Diester ratio

Mehlich III

Soil

7.2

7.1

7.0

15.7

3.3

4.4

3.0

 

NaOH-EDTA

Residue

2.4

3.0

2.6

8.4

2.1

3.3

1.2

 

NaOH-EDTA

Soil

2.6

3.1

2.2

4.3

2.0

3.6

2.9

  1. Values are concentration in mg kg−1 (percentage of extract P). Degradation is the sum of compounds in the orthophosphate monoester region known to be products of diester degradation during analysis. Monoester 1, 2 and 3 are the sum of peak areas in these regions after subtracting the peak areas for identified P forms. Mono:Diester ratio: the ratio of orthophosphate monoesters to orthophosphate diesters. Total orthophosphate monoesters, total orthophosphate diesters, and the monoester:diester ratio were corrected for degradation. Residue is the residual soil after Mehlich III extraction. Difference is the difference in between the NaOH-EDTA extracts of whole soils and the NaOH-EDTA extracts of the residue after Mehlich III extraction