Comparison of plant response and phosphorus uptake by ion exchange desorption and chemical extraction for soils under different land uses

Abstract Aims We quantified the relative significance of phosphorus (P) availability quantity and rate of P desorbed to plant growth using ion exchange membranes on three soils (0–10 cm), initially under native vegetation and converted to either cropping, pasture, or plantation for up to 115 years. Methods Soil P availability parameters were measured by the widely used sodium bicarbonate test (Colwell P), anion exchange membranes and anion + cation exchange membranes either saturated by NaHCO 3 or KCl solution. Plant P parameters measured were dry matter yield, relative yield, and P uptake by Rhodes grass ( Chloris gayana ). Results We found that the quantity of soil P measured by the HCO 3 -anion exchange membrane accounted for up to 90% variability in dry matter yield and P uptake, and the rate of P desorbed by HCO 3 - anion exchange membrane accounted for 81% variability in yield response, while Colwell P was unsuccessful. Conclusion Anion exchange membrane saturated with NaHCO 3 provided superior performance in predicting the availability of soil P to plants compared to the routinely used soil test under different land uses. Thus, wider use of these ion exchange membranes is recommended to provide a more accurate assessment of the amount of plant available P present in soils. This will be beneficial for improving fertiliser P management practices to increase P use efficiency in the face of decreasing P reserves. Moreover, HCO 3 -anion exchange membrane technique will be useful in monitoring excess P applications, and thereby devising practices to reduce environmental P pollution.