Transport and transformations of fertilizer nitrogen in a sandy field plot using tracer techniques
1980
KOWALENKO, C. G.
In a field study utilizing N on Manotick sand, leaching, denitrification, clay fixation of NH4, mineralization, and immobilization all played a significant role in the transport and transformation of fertilizer NH4. Fertilizer NH4 applied 24 June was distributed throughout the 75-cm profile by 29 July. The relatively small amount (0.5% of the total N recovered) found in the deepest sample (60 to 75 cm) suggested that a larger portion of the 27% unrecovered N was denitrified rather than leached. Denitrification, then, was assumed to be more prevalent early, rather than late, in the season. On 4 October, a much larger proportion of the N was found deep in the profile, showing that leaching losses after 29 July became more important. Four percent of the fertilizer NH4-N was immediately clay-fixed. By 29 July, 9% of the initially fixed NH4-N was released, but by 4 October, 77% of the initially fixed NH4-N was released. The total amount of immobilized N was similar on both 29 July and 4 October samplings. The relatively constant amount of organic N during the field season showed that immobilization was more active between 24 June and 29 July than between 29 July and 4 October. Immobilized N accounted for 19 to 20% of the applied fertilizer N. The dynamics of N transformations were compared with a previously studied adjacent clay loam soil.
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