Fate of urea nitrogen (N) applied to rape grown on a
red soil was investigated by the ￣(15)N mass balancetechnique,
and efficiency of urea and
effect of nutrients balance in raising
rape yield were investigated ina field plot experiment. One
hundred and thirty-eight kg N/ha, 86 kg N/ha as basal dressing and 52 kgN/ha as top dressing,
was
applied with band application technique. The experiment was conducted in thesoutheast of
China, near Yingtan City, Jianxi Province.Results from is￣(15)N mass balance study showed
that when urea was applied as basal dressing the plantrecovery was 44.0% of the applied N for
Theatment T (with application of N, P, K, B and lime). Plantrecoveries were 38.0%-40.5% for
Treatments -K, -B, -lime and +RS (without application of K, B or limeas well as with additional
rice straw compared with Theatment T), which were not significantly differentfrom Treatment T.
In contrast, plant recovery was only 5.1% for Treatment-P (without application of P),indicating
that P was the factor limiting N uptake by rape. However, N remaining in 0-0.30 m soil was
highup to 71.6% for Theatment -P, while the corresponding data were 33.0%-42.6% for the other
treatments.The total recovery of applied N (including plant recovery and N remaining in 0-0.60
m soil) was 91.5% forTreatment T when urea was applied as basal dressing, while almost all
the applied N was recovered when ureawas applied as top dressing. It was suggested that N
loss was greatly controlled by using band applicationmethod in this experiment.Results from
the field plot experiment showed that N supply capacity of this red soil was very low, andthe
efficiency of the applied N was quite high, 7.1 kg rape seed was increased by application of
one kg N forTreatmentT. Nitrogen and phosphorus were the key factors limiting rape yield, and
the yield was very lowwhen neither of them was applied. The yield in TreatmentK was
significantly lower than that in TYeatmentT, with the former accounting for 77% of the later.