Quantitative prediction of plant uptake by infinite sink extraction

Wien

2014

S. 33

Artikel aus einer ZeitschriftUnselbständiges Werk

200190225

Besides batch extraction methods, infinite sink extraction techniques like Fe-oxide papers, anion resin methods and diffusive gradients in thin films have been applied to estimate soil phosphorus availability to plants. These methods selectively sample the reversibly adsorbed inorganic soil P fraction by the continuous removal of porewater P, which induces P desorption from soil surfaces. To date, the application of these methods for bioavailability estimation is confined to the use as P indices. In this work we explored infinite sink extraction for quantitative prediction of the P uptake in plants from soil. We used a modified infinite sink extraction protocol to exclude release of P from organic compounds through microbial degradation and P solubilisation by reductive dissolution of P sorption sites such as Fe (oxy)hydroxides. The extracted P quantities were compared to the P uptake of Zea mays L. in a pot experiment and to the amounts extracted by several standard soil P tests (CAL P, Colwell P, Ca(NO3)2 P, cDGT P). Plant P uptake was correlated with the P amounts extracted by all extraction techniques. The strongest correlation was found with the infinite sink approach (Pmax). More importantly, the absolute amounts of P taken up by plant roots quantitatively matched Pmax almost quantitatively, with the deviation of Pplant to Pmax being ≤ 30%. We conclude that plant P uptake may quantitatively be assessed by suitable infinite sink methods. Although this approach may be too tedious for routine use it can be employed as a research tool and as a benchmark test for calibrating routine soil P tests.