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Optimum Application Parameters for Point Injection of Nitrogen in Winter Wheat
Author(s) -
Janzen H. H.,
Lindwall C. W.
Publication year - 1989
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1989.03615995005300060044x
Subject(s) - fertilizer , nitrogen , urea , mathematics , field experiment , agronomy , zoology , ammonium nitrate , crop , yield (engineering) , tracer , environmental science , chemistry , materials science , statistics , biology , organic chemistry , nuclear physics , metallurgy , physics
Point injection may enhance N fertilizer use efficiency in winter wheat but optimum application parameters have not been identified. Three field experiments, employing 15 N tracer techniques and manual injections on small plots, were established at two sites in southern Alberta, Canada, to identify optimum injection intervals and injection depth for spring point‐injection of urea‐ammonium nitrate solution (UAN). The optimum lateral (across‐row) injection interval was found to be the equivalent of two row spacings (40 cm). Higher intervals resulted in unacceptable variability in N availability because wheat in rows not directly adjacent to injections assimilated comparatively little fertilizer‐derived N. The optimum longitudinal injection interval was also approximately 40 cm. Analysis of fertilizer N distribution from the injection point demonstrated unacceptable variability when this interval was exceeded. Crop uptake of fertilizer N was reduced when the injection interval was increased from 40 to 60 cm. Adoption of smaller injection intervals in both dimensions, while not jeopardizing fertilizer use efficiency, would increase the cost of fertilizer application. The optimum injection depth was observed to be approximately 10 cm. Grain yield response and fertilizer N recovery in the crop increased four‐ and three‐fold, respectively, when injection depth was increased from 2.5 to 10 cm. This effect was attributed to the inaccessibility of fertilizer N residing in dry surface soil. Injection of fertilizer at 15 cm rather than 10 cm demonstrated no additional advantage.