摘要
Four testing methods using canon exchange membrane (CEM), ammonium acetate, ASI (0.25 mol L-1 NaHCO3+0.01 mol L-1 EDTA +0.01 mol L-1 NH4P) and 1.0 mol L-1 boiling nitric acid, respectively, were used to evaluate soil available K. The soil K tested by CEM was significantly correlated with that by the other (conventional) methods (r2=0.43**~0.95***). The soil K tested by CEM saturated with NH4HCO3 (15 min extraction) was most closely correlated with that by the other methods (2 =0. 60***~0.95***). Potassium availability, as predicted by soil test, was comparable to actual K uptake by canola and wheat grown on the soils in growth chamber. Regression analyses showed that plant K uptake was more closely correlated with K extracted by CEM (r2=0.56***~0.81***) than that by the conventional methods (r2=0.46***~;0.81***), most closely correlsted with that by NH4HCO3-saturated CEM for 15 min (r2=0.81***), and worst correlated with that by HNO3 (r2=0.45**~0.72***).
Four testing methods using cation exchange membrane (CEM),ammonium acetate,ASI(0.25mol L^-1 NaHCO3+0.01mol L^-1 EDTA +0.01 molL^-1 NH4F) and 1.0molL^-1 boiling nitric acid,respectively,were used to evaluate soil available K.The soil K tested by CEM was significantly correlated with that by the other (conventional)methods(r^2=0.43^**-0.95^***).The soil K tested by CEM saturated with NH4HCO3(15min extraction)was most closely correlated with that by the other methods(r^2=0.60^**-0.95^***),Potassium availability,as predicted by soil test,was comparable to actual K uptake by canola and wheat grown on the soils in growth chamber.Regression analyses showed that plant K uptake was more closely correlated wiht K extracted by CEM(r^2=0.56^**-0.81^***)than that by the conventional methods(r^2=0.46^***-0.81^***),most colsely correlated with that by NH4HCO3-saturated CEM for 15 min (r^2=0.81^***).and worst correlated with that by HNO3(r^2=0.45^**-0.72^***)
