Interrelationships between nitrogen rate and wild oat density on oilseed rape yield components

Abstract

In order to evaluate the effect of nitrogen on oilseed rape yield and yield component under wild oat densities, a field experiment was conducted in Shiraz University, Iran, during 2008-2009 and 2009-2010 growing seasons. The experimental design was split plot with three replications. Treatments included four nitrogen levels (zero, 50, 100, and 150 kg ha-1 ) and four densities of wild oat (zero, 15, 30, and 45 plants m 2 ). The result showed that number of pods per main stem and secondary branches, number of seeds per main and secondary pods, 1000-seed weight, grain and biological yield was significantly increased by enhancement of nitrogen levels from zero to 150 kg ha-1 at weed-free treatments. Also, weed interference significantly reduced grain yield up to 41% under 50 and 100 kg ha-1 nitrogen application in comparison 150 kg ha-1 . Regardless of oilseed rape yield, weed dry weight was significantly increased with increasing the nitrogen levels, suggesting that high levels of nitrogen favor the crop over the weeds. This experiment suggested that oilseed rape grain and biological yield was affected more by high nitrogen levels at maximum weed density.