Extraction of Potassium from Soils with Sodium Tetraphenylboron

Abstract

The amounts of K extracted from several soils of different K supplying power with solutions containing NaTPB were compared with the amounts taken up by intensive greenhouse cropping and with the amounts extracted with 1N NH₄OAc (exchangeable K). The best estimate of plant available K was the amount of K extracted from 2‐g samples of nondried soil with 10 ml of 0.3N NaTPB in 15 min (r = 0.991). The decrease in the amount of K extracted by the same reagent in 16 hours, as a result of cropping, likewise was closely correlated with available K (r = 0.984). Exchangeable K determined in nondried soil samples was more closely correlated with available K (r = 0.971) than was exchangeable K determined in dried soil samples (r = 0.788).