Phosphorus uptake by Zea mays L. is quantitatively predicted by infinite sink extraction of soil P

BACKGROUND AND AIMS: Sink extraction of phosphorus from soils has been utilised to study soil P desorption kinetics and as index of plant availability, but not for quantitative prediction of P uptake by plants. Here we investigate the potential of a modified sink extraction method for determining P desorption kinetics and for quantifying plant available soil P. METHODS: Modified diffusive gradients in thin films samplers were immersed in shaken soil suspensions for long-term extraction of soil P. Results were evaluated in terms of P desorption kinetics and compared to the P uptake of Zea mays L. and standard soil extracts. RESULTS: In contrast to literature reports, four of the six studied soils only showed a rapid, but not a slowly desorbing P fraction. The quantity of P desorbed by long-term sink extraction not only showed the highest correlation to plant P uptake, but also matched plant P uptake quantitatively. CONCLUSIONS: Our data indicates that soils with only a fast desorbing P fraction might exist. Sink extraction methods have the potential to quantitatively predict plant P uptake. Furthermore, they could become valuable research tools for understanding P acquisition and might serve as a benchmark for calibrating soil P tests.