engleski

Potassium fixation in heavy soils of east Croatia

Bioavailability of potassium is strongly affected by present alkaline earth ions Ca and Mg and fixation of potassium into interlayer zones of some clay minerals. Soil fixation ability strongly affects the efficiency of fertilization. The research has been conducted on 6 hydromorphic and gleysoils in eastern Croatia. Soil fertilization with 450-4500 kg ha-1 K2O was simulated in lab-conditions. After one day the samples were extracted with NH4OAc 6 times, shaked, centrifuged and transferred into flasks. Fixation of potassium was calculated according to the formula: Kf = Ka – Ke + Ko, in which Kf is fixated K2O in mg 100g- 1 soil ; Ka is K2O added as fertilizer in mg 100g-1 ; Ke is K2O determined in the eluate and Ko is K2O in the sample without fertilization. Fertilizing simulation of heavy soils in eastern Croatia with medium or very high dosages of potassium (450-4500 kg ha-¹ ; ; ), deducted in lab-conditions, showed that AL method of potassium extraction gives relatively high values of available potassium (two times higher than extraction in NH4OAc). Also, highest relative amount of potassium is fixated at lower fertilizing dosages (approximately 76%), the increase in fertilization increases absolute, but reduces relative fixation. Some heavy soils have high ability of fixation (above 70-90%) and very low desorption, and require special attention when establishing dosages for fertilization and ameliorative fertilization with potassium. Results obtained by soil analyses show connection between high fixation of potassium added by fertilization and higher amount of clay in the soil as well as lower level of available potassium before fertilization.

potassium ; fixation ; desorption ; fertilization ; extraction ; ammonium-acetate

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