INFLUENCE OF FORM AND MODE OF NITROGEN FERTILIZER APPLICATION ON THE AVAILABILITY OF SOIL AND FERTILIZER POTASSIUM

Abstract

Ammonium applied alone or after addition of K depressed the uptake of K by oats grown in a sandy loam soil in the greenhouse. When NH4 was added first and K later at seeding, however, NH4 increased K-uptake.In the absence of K fertilizer, NH4 reduced the release of non-exchangeable K to the plants. When added prior to or at the same time as K at seeding, NH4 reduced K-fixation. This inhibitory effect of NH4 on fixation of added K was reflected in higher amounts of K in solution as shown by lower [Formula: see text] ratios. These results of chemical extraction of the soil indicated that the effects of NH4 on K-uptake by the oat crop arose from reactions in the soil.