TRANSFORMATION AND MOVEMENT OF BAND-APPLIED UREA, AMMONIUM SULFATE, AND AMMONIUM HYDROXIDE DURING INCUBATION IN SEVERAL MANITOBA SOILS

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Abstract
The transformation, effect on soil pH, and movement of nitrogen from banded fertilizer materials (urea, ammonium sulfate, and ammonium hydroxide) were studied in three Manitoba soils of different initial pH values. The greatest effect on soil pH took place near the fertilizer zone but the magnitude of pH change varied greatly depending on soil characteristics and on the fertilizer material added. The oxidation of ammonium nitrogen was inhibited near the zone of fertilizer application during the early stage of incubation in all soils. The oxidation of ammonium form of nitrogen was found to be very slow in the acidic Keld soil (pH 5.4), irrespective of the carriers. The majority of applied nitrogen stayed near the zone of application as the ammonium form even after 8 wk. With the neutral Wellwood soil (pH 6.6), the oxidation of the ammonium form of nitrogen was rapid with a high production or accumulation, or both, of nitrite during incubation when urea or ammonium hydroxide were the nitrogen carriers. The rate of oxidation, as well as nitrite production, was slower with ammonium sulfate. With alkaline Morton soil (pH 8.2), the conversion of the ammonium form of nitrogen to nitrate was rapid without accumulation of nitrite during the transformation, irrespective of the nitrogen carrier used. Diffusion coefficients of ammonium in the soils were dependent upon the types of soil or the fertilizer materials. Generally, the smaller diffusion coefficient restricted movement of ammonium away from the zone of application and eventually retarded the transformation.

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