Isotope Methods for Assessing Plant Available Phosphorus in Acid Tropical Soils
| Author | S. Bühler | |
| Author | Astrid Oberson | |
| Author | S. Sinaj | |
| Author | Dennis K. Friesen | |
| Author | Emmanuel Frossard | |
| Date of acession | 2024-03-14T12:36:23Z | |
| Date of availability | 2024-03-14T12:36:23Z | |
| Date of issue | 2003 | |
| Abstract | Use of isotope methods to measure the availability of phosphorus (P) in soils that are well supplied with P is well established. We have evaluated such methods for acid tropical soils with very small P contents, which are less well studied. The isotopically exchangeable P in soil suspensions (E value) and that in plant growth experiments (L value) were measured in soils that had received varying amounts of P fertilizer in two field experiments in Colombia. We determined the E values over 4–5 weeks of equilibration allowing for the kinetics of isotope exchange. The decrease in radioactivity in the soil solution at a particular time, t, divided by that at the start (rt/R) was described by three parameters (r1/R, r1/R, and a coefficient n) derived from the time course of isotopic exchange over 100 minutes. Values of Et were calculated either from measured values of rt/R or those extrapolated until 12 weeks. Agrostis capillaris was grown on the same soils labelled with carrier-free 33P-orthophosphate ions to obtain L values. Agreement between E values derived from measured and extrapolated values of rt/R was satisfactory, but errors in n and r1/R limited the precision with which we could estimate E values. For most soils, the P concentrations in the soil solution were greater than the detection limit of the malachite green method (0.9 g l 1 ) but smaller than its quantification limit (3.6 g l 1 ). In the soils with the least available P, the P content of the seed limited the determination of the L value. The E values were strongly correlated, but not identical, with the L values measured for the same time of isotopic exchange. We conclude that these approaches are not precise enough to detect in these soils the ability of a plant to access slowly exchangeable forms of P or to quantify the mineralization of organic P. However, these isotope techniques can be used to estimate the total fraction of added fertilizer P that remains available to the plants. | |
| Citation | Buhler, A., A. Oberson, S. Sinaj, D.K. Friesen, and E. Froussard. 2003. “Isotope Methods for Assessing Plant Available Phosphorus in Acid Tropical Soils,” European Journal of Soil Science, 54:605-616. | |
| URL | https://hub.ifdc.org/handle/20.500.14297/2897 | |
| Language | en | |
| Subject | Soil | |
| Subject | Plants | |
| Title | Isotope Methods for Assessing Plant Available Phosphorus in Acid Tropical Soils | |
| Type | Article |