In NW Europe, autumn-grown oilseed rape normally receives
nitrogen (N) in autumn as seedbed N
and in the spring as a split application at the beginning of
growth and at stem elongation. In the
growing seasons 1990/91 to 1992/93, the effects of
slurry and mineral N fertilization on yield, N
uptake by the seed and apparent N-use efficiency (NUE) by
oilseed rape (Brassica napus) were
investigated in a factorial field experiment at Hohenschulen
Experimental Station near Kiel, NW
Germany. The crop rotation was oilseed rape–winter
wheat–winter barley, and soil tillage
(conservation tillage without ploughing, conventional tillage),
application of pig slurry (none,
autumn, spring, autumn+spring) and mineral N fertilization
(0 to 200 kg N ha−1) were all varied.
Each year, the treatments were applied to all three crops of
the rotation and were located on the same
plots.Between the years, average seed yield ranged from 3·04
to 3·78 t ha−1, while the corresponding N
uptake by the seed varied from 107 to 131 kg N
ha−1. Slurry application in spring increased
the seed yield and N uptake by the seed in all years, whereas
the effect of autumn slurry alone or in
combination with spring slurry was negligible. Mineral N
fertilizer increased seed yield and N uptake
by the seeds except in 1991/92, when N amounts exceeded
160 kg N ha−1. No significant
slurry×mineral N interaction occurred. Apparent NUE of
mineral N was larger than that of slurry
N, but decreased with increasing mineral fertilizer N rates.
Only 5% of the autumn slurry N was
apparently utilized by the seeds, compared with 24% of the
spring slurry N.Despite its ability to take up substantial quantities of N
before the winter, oilseed rape utilized very
little autumn slurry N for seed production. To minimize
environmental impacts, slurry should be
applied in the spring, when plants are more able to use N for
yield formation, even if NUE of slurry
N is lower than that of mineral N. However, since NUE changes
with the amount of applied N, it
is difficult to find the best combination of slurry and
mineral N fertilization to avoid negative
environmental effects.
Effects of Plant Residue, Root Exudate and Juvenile Plants of Rapeseed (Brassica napus L.) on the Germination, Growth, Yield, and Quality of Subsequent Crops in Successive and Rotational Cropping Systems
