Chemical speciation and fate of tripolyphosphate after application to a calcareous soil

Table 1 Bulk soil chemical analysis and XAS linear combination fitting results for the first application of TPP

Label	Depth (m)	Soil^a pH	Total elemental concentrations^b				Ca:Mg ratio	Labile^c extractable P (mg P/kg soil)	LCF analysis results^d,e		Reduced chi²
Label	Depth (m)	Soil^a pH	Ca (mg/kg soil)	Mg (mg/kg soil)	P (mg/kg soil)	Fe (mg/kg soil)	Ca:Mg ratio	Labile^c extractable P (mg P/kg soil)	Adsorbed P (%)	Ca-P species (%)^f	Reduced chi²
1a	1.82	7.7	23,800	14,900	950	24,500	1.6:1	10	38	70	0.00141
2a	3.66	7.7	36,000	16,000	910	26,500	2.25:1	10	33	70	0.00131
3a	1.82	7.8	25,400	16,900	880	26,700	1.5:1	23	48	56	0.00310
4a	3.66	7.5	32,400	21,800	1050	19,000	1.5:1	21	48	59	0.00127
5a	1.82	7.7	28,000	15,400	880	24,500	1.8:1	5	46	58	0.00142
6a	3.04	7.7	30,300	18,000	940	29,000	1.7:1	25	42	65	0.00110
7a	3.66	7.6	10,900	9100	1080	8100	1.2:1	75	45	52	0.00127
8a	1.82	7.7	28,300	18,600	1010	28,300	1.5:1	15	42	65	0.00123
9a	3.66	7.8	28,000	17,900	950	28,000	1.6:1	15	44	58	0.00149
10a	1.82	7.7	25,700	13,400	915	25,700	1.7:1	10	24	80	0.00219
11a	3.66	7.8	28,900	17,300	950	28,900	1.6:1	20	40	62	0.00054

^aSoil pH accurate to ± 0.1
^bVia total XRF elemental analysis, concentrations are accurate to ± 10%
^cCombination of H₂O and NaHCO₃ extractable P
^dEo Shift constrained to zero
^e% Relative contribution to XAS signal; models are unconstrained and not equal to 100%
^fRelative sum of the contribution from calcium phosphate mineral species

ISSN: 1467-4866