Effect of plant density and row spacing on winter oilseed rape yield in the mediterranean area.

Two experimental field research-studies were carried out in 1988-90 to evaluate the optimal seeding pattern for winter oilseed rape (cv. Santana). This crop showed extreme plasticity in size and form that gave it the ability to adjust to different planting patterns without remarkable yield reductions. However, in order to achieve the highest yield it was necessary to establish winter populations of 80-100 plants m-2, which also gave the crop more chances to recover from possible frost or hail injuries. Conversely, low density levels before winter (less than 40 plants m-2) always led to lower yields. Row spacing did not exert a big influence on crop yield, but 0.5 m wide rows were always the lowest yielding arrangement. The reduction of row distance to less than 0.25 m, aiming at a more regular plant disposition, did not seem to positively affect yield. The remarkable compensating ability of oilseed rape to low density levels was due to an increase in the number of lateral racemes and, above all, to an increase in the number of pods on lateral racemes.