Nitrogen Transformations and Transport over 17 Months in Field Fallow Microplots using 15 N

Kowalenko, C.G.

Canadian Journal of Soil Science 58(1): 69-76

1978


ISSN/ISBN: 0008-4271
DOI: 10.4141/cjss78-007
Accession: 068494897

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Abstract
A field experiment with an Ottawa area clay loam soil utilizing open-ended microplots and 15N-labelled fertilizer showed the relative importance of seasons on transformation and transport of nitrogen. Denitrification appeared to be appreciable during the growing season; about 39% of the fertilizer N was denitrified in 86 days (May–Sept.) and 65% was lost after 511 days but leaching losses were included in the latter period. Nitrification of fertilizer N was very rapid with extractable NH4+-N approximating background level within the first 43 days. Immobilization of fertilizer N was negligible in the first 159 days and only a small amount was immobilized during the remainder of the experiment. Mineralization of soil N averaged 0.77 and 1.10 kg N/ha/day in the first two sampling periods. Clay fixation of NH4+-N was significant in this soil with 59% of the 152 kg N/ha applied being immediately fixed. Over one-half (66%) of this recently fixed NH4+-N was released in the first 86 days of the experiment with the remainder held tightly through the sampling period. Movement of fertilizer N was greatest in the late fall and early spring, i. e. periods of high precipitation and low evaporation.