Development and Validation of a New Soil Universal Extractant: 0.02 Molar Strontium Chloride

In this experiment, when the strontium chloride–citrate acid extractant (0.02 M SrCl2–0.05 M citrate) was used for extraction of calcareous soils with calcium carbonate greater than 70 g kg−1, the filtrate was turbid. Furthermore, white precipitation appeared when this extract was used for phosphorus determination with the Murphy and Riley method. As the concentration of citrate in strontium chloride–citrate acid extractant decreased to 0.025 or 0 M, the filtrate became clean. Further experiments indicated that the 0.02 M SrCl2 extractant could be used as a universal extractant for soil nitrate+nitrite and potassium; the extracted nitrate+nitrite and potassium significantly correlated with nitrogen and potassium phytoavailability, respectively, determined with ryegrass pot experiment (P<0.05). Thus, the 0.02 M SrCl2 was recommended as a universal extractant for soil nitrate+nitrite and potassium.