Fixation of Potassium in Soils.

That some of the potassium added in the form of fertilizers or otherwise becomes fixed in the soil had been known for a long time. With the clarification of the phenomena of base exchange in soils by Gedroiz it was revealed that the K-ion is fixed in the exchange complex not only in replaceable but also in non-replaceable form. A review of the work in this connection may be found in the paper by Voile (7) . The latter made the important observation that drying of the soil is conducive to the non-replaceable type of K-fixation. His work advanced the problem of K-fixation, but offered no satisfactory solution of this peculiar phenomenon. Volk suggested that the potassium added to a soil reacts "with the so-called silicates and becomes fixed in the form of muscovite, thus converting added available potassium into difficultly available form." He based his conclusion primarily on X-ray analyses of two soils from the Pennsylvania Experiment Station fertility plots. The evidence, however, is not conclusive. The muscovite lines of the X-ray pattern noted in the treated plot might have formed because of its inherent mineralogical composition, having had at the start of the experiment 6678.pounds of K more than the check plot. Why ascribe the. muscovite lines to the K added in the course of the history of these plots? It seems somewhat far-fetched to think of the formation of silicate minerals of K, like muscovite, under the conditions of temperature and pressure prevailing in the soil. The work of Volk was repeated, with slight modifications, by Gorbunov (3). He saturated the soils of several soil zonal types with K by treating them with KC1. After removing the excess of KC1 the soils were dried for eighteen hours, moistened with water and kept moist for seventy-two hours, and dried again for eighteen hours. Such treatment was repeated three times. Three sets of samples were prepared each one having a different temperature of drying: 40, 75, and 105°C. After the last drying the soils were electrodialized and the quantity of K determined by titration. The results of Gorbunov are very similar to those of Volk. The X-ray photographs made by Gorbunov do not indicate any differences between the treated and untreated soils. His explanation of the fixation phenomenon is associated with the aging of the soil gels during the intermittent wetting and drying of the soils. To quote Gorbunov: