The transformation of potassium and ammonium forms in the soilagrocenoses

The sustainability of the ratio of potassium forms as well as the variability of ammoniumforms were shown in soils of agrocenosis under conditions of long-term field trial.The ratio between ammonium forms varies in soils of agrocenosis within wide limits; atthe same time the change of content of various soil ammonium forms can occur in differentdirections. Ammonium fixation depends to a great extent on soil potassium state. Inagrocenosis with exhausted soil potassium fund the soil does not fix practically the ammoniumof applied fertilizers; its level in soil is reduced below that of virgin, even at selfsupportingnitrogen balance. As it was evidenced by laboratory trials, if there is nocation removal by plants the soil having low content of nonexchangeable potassium andammonium fixes no more than 2-2,5% of applied ammonium nitrogen. The fixing capacityof soil in respect of ammonium increases considerably (up to 8-10% of applied dose)when potassium level in soil is high, independently if this background was formed earlieror potassium is received simultaneously with nitrogenous fertilizers. Potassium fixationin the soil amounts to 70% of applied dose and practically does not depend on nitrogenbalance in agrocenosis and ammonium content in the soil; joint application of potassicand ammonium fertilizers has a weak effect on nonexchangeable adsorption of potassiumby soil.

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