Table 1.
Properties of the three tropical soils on which the organic acid extraction method was developed, and the five tropical soils on which bioavailable P was determined.
| Soil | Common site namea | Soil taxonomy | Topsoil texture; subsoil mineralogy | Total P |
Organic P |
pH |
Alox |
Feox |
Mnox |
Pox |
Carbon |
|---|---|---|---|---|---|---|---|---|---|---|---|
| mg P kg− 1 | mg P kg− 1 | g kg− 1 | g kg− 1 | g kg− 1 | g kg− 1 | % | |||||
| Method development | |||||||||||
| Ultisol | Albrook | Ultisol (Humic Hapludults) | Clay; Kaolinitic | 402.7 | 58.9 (14.6)b | 4.9 | 1.81 | 2.93 | 0.03 | 49.50 | 1.98 |
| Oxisol | BCI 50 ha | Oxisol (Kandiudalfic Eutrudox) | Clay; Kaolinitic | 764.0 | 233.1 (30.5) | 5.7 | 2.94 | 4.72 | 2.50 | 70.96 | 4.25 |
| Alfisol | Campo Chagres | Alfisol (Mollic Hapludalfs) | Clay; Smectitic | 1542.1 | 726.8 (47.1) | 7.4 | 3.23 | 5.05 | 0.89 | 590.50 | 4.07 |
| Determination of bioavailable P | |||||||||||
| A | Plot 6 | Ultisol (Typic Kandiudults) | Sandy clay loam; Kaolinitic | 183.0 | 74.7 (40.8) | 4.4 | 0.91 | 2.65 | 0.40 | 34.09 | 2.38 |
| B | Plot 16 | Inceptisol (Dystric Eutrudepts) | Clay; Mixed | 304.9 | 107.5 (35.3) | 6 | 1.47 | 4.89 | 1.11 | 32.09 | 3.22 |
| C | Plot 18 | Alfisol (Aquic Paleudalfs) | Clay; Smectitic | 434.7 | 116.5 (26.8) | 6.1 | 1.76 | 8.49 | 1.51 | 60.06 | 3.04 |
| D | Plot 25 | Ultisol (Typic Kanhapludults) | Silty clay loam; Kaolinitic | 77.4 | 21.1 (27.3) | 4.6 | 1.40 | 1.99 | 0.09 | 22.82 | 2.96 |
| E | Gigante 1 | Oxisol (Typic Eutrudox) | Clay; Kaolinitic | 255.3 | 82.4 (32.3) | 5.3 | 3.59 | 5.01 | 1.58 | 50.87 | 4.21 |
a
For comparison with previously published studies on these plots, e.g. Turner and Engelbrecht (2011); Condit et al. (2013).
b
Value in parentheses indicates organic P as a percentage of total P.