Evaluation of several methods for determining the potassium content in diverse plant materials

Abstract

Different plant analysis methods including varied incubation times with 0.5N and IN hydrochloric acid (HCl), diacid nitric (HNO₃) and perchloric (HClO₄) acids], triacid HNO₃, sulfuric acid (H₂SO₄) and HClO₄], H₂SO₄+hydrogen peroxide (H₂O₂) (Wolf method), and 0.5N and lN ammonium acetate (NH₄OAc) were evaluated for measuring the potassium (K) concentration in straw and grain samples of cereal, legumes, oilseed crops, and fruit‐tree leaves. The average K concentration in nine plant materials indicated that K extracted by 0.5N and lN HCl for 5 minutes, 1 hour, and 17 hours contact periods did not differ significantly. But the amount of K extracted by these acidic solutions gradually decreased during incubation, possibly due to reabsorption of released K by the plant material. The amount of K released in to the 0.5N HCl and IN HCl extractants was in close agreement with that obtained with the standard triacid method. The IN NH₄OAc extraction method slightly overestimated the K concentration in the materials compared to the other methods. Differences were observed among the methods in extracting K from different plant materials. In case of grain samples, the triacid method gave slightly higher values than that obtained by IN NH₄OAc extraction. The results suggest that the 0.5N HCl and lN NH₄OAc extraction methods can be used for the determination of K in plant tissues as these methods gave lower standard deviation and coefficient of variation values compared to the triacid method.