’N-Serve’ has been shown to reduce losses of applied N-fertilizer and thereby increase fertilizer N-utilization by plants. This study was undertaken to test the effects of ’N-Serve’ on fertilizer N efficiency in oilseed rape production and quality. Field experiments were conducted on two chernozemic soils over 4 yr in Manitoba. The oilseed rape cultivars Tower (Brassica napus L.) and Torch (B. campestris) were used in the study. Spring and fall applied ammonium nitrate, urea and fluid-N, with and without ’N-Serve’ delayed flowering and increased the herbage yield of both oilseed rape cultivars. The number of days from full pod to maturity was increased with application of N fertilizers, but the number of days from flowering to full pod was constant. Increased herbage yield and total plant N at flowering was reflected in increased seed yield and meal protein content, but decreased oil content. ’N-Serve’ applied with and without N fertilizer reduced oil content and oil yield. However, when ’N-Serve’ was applied in the fall with urea and fluid-N it improved their efficiency, resulting in higher seed yields and meal protein content equivalent to that of spring applications. ’N-Serve’ used with fall applied ammonium nitrate or with all three sources of spring applied N had no similar effect. It is concluded that ’N-Serve’ should not be applied to oilseed rape, mainly because of its negative effect on seed oil content.
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L. D. Bailey (1990) studied this question.